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Parasitism of Barley by Ustilago Hordei (Pers.) Lagerh. : some quantitative aspects of Disease expression Groth, James Vernon 1974

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PARASITISM  OF BARLEY  LAGERH•t  SOME  BY  USTILAGO  QUANTITATIVE  DISEASE  HORDEI ASPECTS  (PERS.) OF  EXPRESSION  by JAMES  VERNON  GROTH  B«Sc«,  University of  Minnesota,  196?  M.Sci,  University of  Minnesota,  1969  A THESIS  SUBMITTED  IN  THE REQUIREMENTS DOCTOR in  OF  the  PARTIAL  FOR  FULFILMENT  THE DEGREE  OF  OF  PHILOSOPHY Department of  Botany  We a c c e p t standard  THE  this  thesis  UNIVERSITY  as  conforming  OF B R I T I S H  October,  197^  to  the  COLUMBIA  required  In  presenting this  thesis  an a d v a n c e d  degree at  the L i b r a r y  s h a l l make  I  the U n i v e r s i t y it  freely  fulfilment of of  British  available  for  f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e  for  the  requirements  Columbia, reference  copying of  I agree and this  this  written  representatives. thesis  for  It  financial  is understood that gain shall  permission.  Department  of  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8 , Canada  Columbia  not  for  that  study. thesis  s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t  by h i s of  in p a r t i a l  or  copying or p u b l i c a t i o n  be a l l o w e d w i t h o u t my  i ABSTRACT Quantitative the  barley-Ustilago  volving one  of  a  form  in  at  dikaryons  influenced which  are  by  aspects  ivar  and  smut  of  the  correlated  cultivars  and  over  21  U.  for  parasite, in  being  the  in  i n in  relation  which  to  the  method  available which  inoculated  to  can  be  plants  of  smutted  heads  within  smutted  When most  often  remained  age-frequency  to  families were  were  of  plants  the  of  t i l l e r i n g  t i l l e r s  at  virulent  plants  either  The  higher  so  not  of  reduction that  nodes  the of  of  the  smutted, older  Distribution  did  principal  or  entirely  the  not  t i l l e r i n g plants  Nodal  older  families  occurrence  inoculated  the  random.  smutted  culm  dikaryon,  and  was  principal  combinations  pathogen  smutting.  Entire  the  found.  and  d i f f e r e n t i a l l y  and  Within-cult-  patterns  entirely  nonsmutted.  caused  also  smutting  Regardless  inoculation pattern  be  determined,  dikaryons.  were  inoculation  nonsmutted. pattern.  genetically  reaction  disease-producing  a  within-plant  tended  within-plant  hordei  using  growth  lateral  studies  Resistance,  correlations  plant  families  of  a l l  on  often  made  in  plants,  500  being  effects  members  reactions  inoculation  seed  existt  were  healthy.  per  accounts  studies  t i l l e r  and  diluted  plant.  Both  within-dikaryon In  of  host  greatly  disease  reaction.  closely  barley  12  which  disease  Inoculation  of  sporidia  100  of  partial-vacuum  environemnt,  between-plant were  system.  was  the  made  nonsmutted.  Two  two  that  least  were  combination  mating-types  indicated  results  hordei  compatible  the  other,  of  studies  of and  f i t  most this  smut, changed  produced c u l i v — \  i i  TABLE  OF  CONTENTS PAGE  GENERAL  INTRODUCTION  LITERATURE A.  Early  6  Development  B.  The  Expression  The  Effect  EFFICIENCY  * HANNCHEN*  of OF  Introduction M a t e r i a l s and Results Discussion  DISEASE  the  Susceptible  Host  Resistance  Environment WITH USTILAGO  B. C. D.  RELATIONSHIP  of  Within  Covered  INOCULATION  Smut.  Introduction  B.  Materials  22 Methods 29 31  BETWEEN W O  ASPECTS  OF 39 39  and  hS  Methods  50-  Discussion  THE PATTERN BY USTILAGO  *  OF SMUTTING AND E F F E C T ON PLANT HORDE I I N ' H A N N C H E N ' B A R L E Y  A. I n t r o d u c t i o n B. M a t e r i a l s a n d EwsRe s u i t s 1.  The  2.  The  in  Smutted  Effect  Plant D.  Methods  D i s t r i b u t i o n of  Heads  of  59 GROWTH  • Smutted  and  Healthy  Plants  Inoculation  The  75 and  Smutting  on  Growth  83  2.  The  88  D i s t r i b u t i o n of  Heads  in  Smutted  Effect  Plant  , °7 67 6$ ?1*  Discussion 1.  11 18 22  CsiS.Befc.aLts*.... D.  6  OF  HORDE I  EXPRESSION  A.  ... •  on B a r l e y  PARTIAL-VACUUM  BARLEY  A.  THE  1  REVIEW  C. THE  .'  of  Growth  Smutted  and  Healthy  Plants  Inoculation  89 and  Smutting  on 95  i i i  T A B L E O F CONTENTS  (continued) PAGE  GENERAL  CONCLUSIONS  1  0  0  BIBLIOGRAPHY: APPENDIX A  113  APPENDIX B  115  iv LIST  OF  TABLES  TABLE l . i  1.2.  2.1  2.2  PAGE Three separate estimates o f the effective s p o r i d i a l number based on three sporidial r a t i o s and t h e i r r e s u l t i n g levels of smutting. ••••••«••«  32  The number o f m i n o r i t y o f m i n o r i t y s p o r i d i a over t o t a l c o l o n i e s , as shown by t h e i r mating r e a c t i o n s , o f two c u l t u r e s with unequal s p o r i d i a l r a t i o s sampled at four d i f f e r e n t times after m i x i n g . •  32  The b a s i s o f measurement o f smut reactions u s e d b y many p a t h o l o g i s t s a n d b r e e d e r s working w i t h smuts o f c e r e a l s . . . •  41  Combinations o f host c u l t i v a r and pathogen dikaryon, and disease reaction o b s e r v e d . . .  51  Some w i t h i n - c u l t i v a r a n d w i t h i n - d i k a r y o n . correlation analyses involving lowt i l l e r i n g p l a n t i n g s only.•••••••*•••••••»•»  58  Observed and expected numbers o f v a r i o u s l y s m u t t e d two., thr.ee and, f o u r o r more, t i l l e r f a m i l i e s , and the a p p l i c a t i o n o f a C h i square t e s t f o r randomness o f smutting among f a m i l i e s , u s i n g a b i n o m i a l e x p a n s i o n to calculate expected values.••••••••••••••  77„  Test f o r randomness o f p o s i t i o n o f smutted t i l l e r ( s ) within smutted t f a m i l i e s , i n terms o f age (order o appearance) of the t i l l e r s . . . . . . . .  78  0  2.3  3.1  3.2  3.3  noni l l e r f . . . . . . . . .  Test f o r randomness o f p o s i t i o n o f n o n smutted t i l l e r families within the smutted b a r l e y p l a n t , i n terms o f age (order of appearance) of the f a m i l i e s . . . . . . . . . . . . . . .  80  T h e p r o d u c t i o n "by s m u t t e d p l a n t s a n d f a t e s o f t i l l e r f a m i l i e s , a n a l y z e d "by n o d a l position......o.....»»..**.o...»••«••<>  81  9  3.4-  3.5  Mean numbers o f culms i n i t i a t e d p e r p l a n t , and t h e i r f a t e s (headed, smutted or dead), when p l a n t s were u n i n o c u l a t e d , inoculated b u t f a i l e d t o become s m u t t e d , o r inoculated and s m u t t e d . • . . . • 0  •  84  V  TABLE 3„6  PAGE Comparisons o f growth patterns plants attempting lateral t i l l e from d i f f e r e n t nodes o f the p r i o f 209 smutted, 194 nonsmutted a n d 83 n o n i n o c u l a t e d " H a n n c h e n 8  (percent o f r production ncipal culm) inoculated, barley  plants•»»»«»oo«oo»o9»»o«9»»»»»»e»»»»«»«»»«»»j  86  LIST  OF  FIGURES  vi  FIGURE 1,1  1.2  2,1.  2.2  3.1  3.2  3»3  PAGE D i s e a s e l e v e l , a s m e a s u r e d "by t h e p r o p o r - t i o n o f maximum p o s s i b l e p e r c e n t o f p l a n t s s m u t t e d b y U s t i l a g o h o r d e i (among t h e control plants—those inoculated with a 1«1 s p o r i d i a l m a t i n g - t y p e r a t i o ) , i n r e l a t i o n to mating-type ratio of the inoculum •*.... . . . . . . . . . . . . . » •  30  T h e o r e t i c a l r e l a t i o n s h i p between effective numbers and mating-type r a t i o s necessary t o r e a l i z e 0,95. 0.50^and 0.05 o f t o t a l possible plants smutted, including p l o t t i n g o f three observed v a l u e s . . . . . . . . . .  35  C o r r e l a t i o n s c a t t e r d i a g r a m f o r 82 b a r l e y Ustilago hordei genotypic combinations planted under l o w - t i l l e r i n g c o n d i t i o n s . . . . .  $6  C o r r e l a t i o n s c a t t e r diagram f o r 29 b a r l e y Ustilago hordei genotypic combinations planted under h i g h - t i l l e r i n g c o n d i t i o n s . . • •  57  I l l u s t r a t i o n o f the pattern o f early t i l l e r p r o l i f e r a t i o n i n a one-month o l d p l a n t o f ' H a n n c h e n * b a r l e y . . . « • • • • • • • . . . . . • » • • • . • • ...  73  F r e q u e n c y o f c o v e r e d s m u t o c c u r r e n c e i n Irl t i l l e r families of barley plants i n r e l a t i o n to r e l a t i v e age o f the t i l l e r fami l y (as i n d i c a t e d by position)••»•••••*•••»  82  The p e r c e n t o f smutted, nonsmutted inocu-ats^ l a t e d and noninoculated barley plants i n i t i a t i n g l a t e r a l t i l l e r p r o d u c t i o n accord*? ing to nodal p o s i t i o n on the p r i n c i p a l culm  :  87  vii  ACKNOWLEDGEMENTS I Clayton always  would Person  been  especially  l i k e  who,  advisor  as  readily  an  available  to  thank and  for  Professor  friend,  guidance  has  and  support.  Thanks sound  and  providing Rolando  l o g i c a l  advice;  help;  and  to  to Dr.  University,  despite  remained  two  patient  I  Dr.  advice; and  who  F i n a l l y , who,  to  cultures  Robillo  technical  State  also  R. for  to  Tadessa  R.  the  figures  Kiesllng, samples  for  of  of  thank  never-ending  for  Ebba  and  provided  Dakota  races  my w i f e ,  distractions,  understanding.  to  mycological  North  the  his  for  information;  Bandonl  sincerely  and  G r i f f i t h s  frequent  drew Dr.  Tony  used. Jo  Ann, has  1  GENERAL  The vulgare  covered  L.)  Is  Lagerh..which on  growth  cycle).  caused Is  within The  mature  barley  by  masses  of  to  of  learn  disease  standing  of  the  long-term  control  selection  pressure  appear of a of  1967)0  to  be  population greater what  is  a  the  of  effects  disease  favoring  at  by  studies  understanding in  of  avoiding  thesis  a  at,  far,  been  the  either  large  allows  in  the  general  greater  use  by  been has  in  no  effects under-  smutting  " p a r t i a l "  more  effective  intense  genotypes  for  among  this the  would i n i t i a t i o n  other  coevolution.  concerning  in  of  the  reasons,  host-parasite  this  has  genes,  pathogen  system  shown  replaced  Thus  the  result  several  aimed  which  is  intent  time  l i f e  produced  r e l a t i v e l y  since  may  its  are  system  single  this  that  v i r u l e n t for  been  system. of  dependent  disease  whose  have  host-psrasite  genetios  with  which  resistance  the  useful  single  than  of  relationships  desirable,  Moreover,  dealt  a  other  "complete"  have  (Pers.)  t o t a l l y  (caryopses)  which  However,  especially  the  investigation  parasite,  resistance  than  (Person,  on  of  (Hordeurn  hordei  ( i . e . ,  host-parasite  studying  centered  Is  (sori)  barley  completion  f r u i t s  host-parasite  expression.  whatsoever rather  whose  genetic  have  for  manifestation  particular  studies  on  l i v i n g  plants  about  in  Ustllago  host  recent  or  fungus,  the  intensively  host  cultivated  p a r a s i t i c  This  more  of  obllgately  through  the  a  teliospores  fungus.  subject  disease  by  p r i n c i p a l  by  the  smut  INTRODUCTION  things, Much  intermediate  2  disease  expression w i l l  i f  studies  such  are  to  be be  When c o n s i d e r i n g population relative It  is  genetics,  ductive  success  system,  rather  Logically,  of  the  than  each  affect  sidered  along  with  studies  Regardless of  this  they  kind  are  of  parasite  are the  a as  the  reproductive w e l l .  That  host-pathogen by  Person  to  or  of  be  In  so  on  terms  the  to  the  must  pathogen  each order  In  such  the  its host con-  In  the  the  as  for host  neither  elimination.of  that  the  the, pathogen.  limiting,  order  studies  much  a  the  and  pathogen  can the  discussed  might  end more  as  host-  become other.  organism must other  the  organisms.  be  systems  that  component  been  of  increase  involve is  the  repro-  success  i t s e l f .  e q u i l i b r i u m of  cause  of  selective, force, f o r  host-parasite  an  of  however,  parasite  of  organisms*'  c o m p a t i b i l i t y must  the  has  in  terms  component  as  e q u i l i b r i a represent  coevolutlon  in  extremes  parasite,  reached,  and  of  the  organisms.  succeed,  such  of  major,  not  system think  pathogen  reproductivity  decrease  (I967).  a  survive,  must  Information  interacting  change  In  is  component  successful  system  and  obligate  v a l i d l y  to  two  success  changes  host  reproduotlvltles  For  an  to  effects  parasitic  whether  system  completely  the  the  pathogen of  of  the  organism w i l l With  the  convenient  host  on  which  where  host-parasite  of  examine  changes  host,  is  to  reproductivity.  case  any  i t  preliminary  undertaken.  reproductivitles  necessary  essential  suffer  reproduce  result  of  completely  3  The well  to  the  t o t a l l y  host  spore and  and  U.  matches  that  is  probably  agricultural  of  past,  system  production  it)  It  that  the  barley  can  avoid  expense  where  pathogen  disease  can  related:  of  are  seed  also  obligate the  the  the  reproductivlties  host,  i t of  t e l l o -  shown by  pathogens,  that  is  production  generation  time  the  many it  of  is the  features  the host,  there t o t a l l y  existence  more, or, l e s s The  in  the  and  terms  this  of  of  dependent  barley-U.  is are  natural  mechanisms  some  this  thesis  the  the  barley-  o n , man,,and  horde1 system  is  point  kept  must  evolutionary in  be  not  concepts-  order  to  avoid  conclusions.  when  both  with  that  reproductivlty),  existed,  of  is  being  i t  (relative  oversimplified  hordei  causing  features  parasitism,  mind when d i s c u s s i n g fitness  here  practices.  system  the  the  of  (1)  especially  clearly.  system  assured. of  smuts,  hordei  as  at  applies  reciprocally  involving  noted  In  the  systems  by  relative  these  be  drawing  U.  occurs  because  only  clearly  should  such  system  the  It  "natural"  in  (2)  Although  most  reproductivlty  host:  are  only  exactly  shown  his a  the  head-infecting  parasite are  hordei  and  host-parasite the  relative  pathogen  vice-versa.  with  on  sexually;  production  other  of  barley-U.  dependent  reproduce the  concept  seed  aspect  and of  smutted.  of  the  barley-  evolved  whereby  must  have  some  tellospores  the  concerned. several  progenitor  system  From  ways F i r s t ,  in  the  (or  the  was remnants  standpoint  which  although  the  of  plants  susceptible,  4  a  plant  can simply  doubtedly  escape  an important  systemsj  It  possible  alternative  Second,  a plant  disease. hand,  of  This  i t  plants  w i l l  i s  In  resistance  to develop  the monogenic  cultlvsrs  spikes  are not found. smut  combinations the  most  way  i n which  of  form  other  t o t a l  disease  spikes.  smut  1974;  It  might  systems  the two types  On one  by  where  to  Another  through Is  production  known  1973). plants)  are neither  and within-plant  found  This  type  results  in  devastating  t o the pathogen. w i l l  about  somewhat  or "tolerance"  of resistance  smutted  Incompatible  1972).  L i t t l e  of diseased  some  as low as \ $ % f o r  Sidhu, i s  of  case  f a l l i n g  be considered  detrimental  to a s b e t w e e n - p l a n t  respectively.  expressed  of plants  (Robinson,  which  to the  proportion  genotypes,  can be expressed plants.  thesis.  The extreme  and sometimes  (Ebba,  a  one form.  100^ f o r t h e " t o t a l l y "  levels  nor c r i t i c a l l y  than  resistance,  certain  (partial-smutting  convenience, referred  of a certain  terms  as  of resistance  In  on smutted  host-paxasite  Intermediate host  ones  of the  more  to the horizontal resistance  resistance  the  sort  Is u n -  except  can take  t o a b o u t . 30%  resistance  t i l l e r s  section  smutted  of r e s i s t a n c e .  analogous in  down  some  This  host-parasite  further,  The percentage  from  compatible  healthy  this  against  ranges  with  the f i r s t  can express  infected.  of natural  not be dealt  barley  develop  feature  can be expressed  f a l l i n g  this  becoming  For  hereafter  be  resistance,  to  of  5  The  purpose  of  these  studies  understanding  of  the  disease  the  hordei  system.  barley-U. 1)  examining to  the  determine  disease  in  was  to  further  expression  of  resistance  This  basis  plants  of  inoculation  of  an  In  includest  a r t i f i c i a l the  our  phenomenon  non-expression  inoculated,  of  susceptible  c u l t i v a r ; 2)  determining is  3)  whether  correlated  establishing barley smut  with the  or  not  wlthin-plant  between-plant  pattern  of  some  plant,  as  well  presence  on  plant  as  resistance  resistance;  smutting within  growth.  of  the  effects  and the of  6  LITERATURE  A.  EARLY DEVELOPMENT WITHIN T H E S U S C E P T I B L E HOST  A of  number  various  opposed l i g h t the of  REVIEW  l a t t e r  are  i n i t i a l  Both,  l i k e  Infection for  tion  Is  and  U.  U.  type  and  of  accurately location which  are as  been  minimized  l a t i o n  U.  hordei  so  the  timing  Intensive  of  studies  covered  smuts  Is,  Is,  however,  therefore,  Infection on  of  of  k o l l e r l .  techniques.  An  fungus  s i m i l a r  source  of  rather  the  caryopsls.  a  the  an of  or  In  in  Inoculated  seed  the  any  seedling  using  f l o r a l  (1948)  for  by  the  germina(Fisher  proliferates  of  work  on  teliospores  Tapke  between  and  intermediate  location  difference  (1930)  on  f a i l u r e .  true  of  Infecting  some  time  seed by  made  means  Ustllago  of  avenae  dormant  was  to  U.  their  respectively.  be  the  than  attempt  experimental Kolk  of  infection  This  at  to  shed  although  seedling  capable  embryos  mycelium  h u l l  the  also  oats,  be  as  events  been  W i l l i e ,  considered  mycelium The  Inner  In  k o l l e r l  in  early  have of  to  barley,  except  the  development  l i k e l y  In  different  considered- to  rather  such  U.  the  Seedling,  more  are  the  the  with  are  horde1.  locate  Is  smuts  of  hosts.  U.  1957)•  the  their  not  and  made  and  dependent  in  been  Rostr.  which  pericarp  in  loose  avenae  Holton,  either  and  i n f e c t i o n .  (Pers.)  smuts.  infecting  probably  of  have  within  occurring  entry  development avenae  smuts  f l o r a l ,  events  following  studies  cereal  to  on  of  outer to  case,  more the  teliospores  the  two  infectors smuts  Identical  dehulled  has  inocu-  seeds  of  a  7  susceptible of  U.  oat c u l t l v a r  avenae.  The seeds  smut  mycelium  that  the fungus  after  Gage in  leaf  t h e same  seedlings  which  were  old  and  Kolk  t i l l e r  growing  (1910), a  13-day-old  the  some  f i r s t  leaf  penetration old,  mycelium  was a l i k e l y  she observed  point  with  than  d i s t r i b u t i o n k o l l e r l  The d i f f e -  days  be d u e t o t h e d i f f e r e n t  i n a l l parts  susceptible  node,  t h e same t i l l e r  that  13-day-  of the  a l l leaf  axils  i n the main  growing  between  In a  system,  he bxamlned.  Lutman  point  Because  invaded  she had  the coleoptile and  sheath-to-sheath  In seedlings, o f t h e cone  13  Inward  t o 30  d i s t r i b u t i o n of the  (1933)  found  days  of the growing  a t t h e t i p o f t h e cone  Sampson  and chronology  on a  o l d .  random l a t e r a l  at the base.  vege-  no mycelium  with  f e l t  days  found  None w a s s e e n  invasion  concentration  the f i r s t  i n the two studies.  pathway.  general  apparently  mycelial  lower  Kolk  three  and host,  i n the space  sheath,  u n t i l  planting.  the coleoptile  seedling which  She found  after  could  t h e main  of  days  mycelium  Working  d i d f i n d  either  seven  a x i l l a r y bud.  point.  however,  observed  used  the mesocotyl,  the coleoptile  than  observations  observed  planting.  four  fungus  d r y tellospores  f o r the presence  the coleoptile  u n t i l  less  and techniques  coleoptile,  U.  these  seedling,  after  and i t d i d not reach  using  materials  The  d i d not reach  or the mesocotyl  between  them w i t h  examined  stages  (1927),  rence  in  were  a t various  planting,  tative  by dusting  a  was  somewhat  similar  of penetration  when  oat cultlvar.  On t h e b a s i s  hyphae.  mycelial  studying of  8  negative f i r s t than  evidence,  vegetative direct.  stage  present  and  that  M i l l s  at  observed  after  planting) point  sheath.  f i r s t  leaf,  coleoptile  v i a the nodes,  that  of susceptible  buds  and second  In  the a x i l s were  When M i l l s  the fourth,  f i f t h  and s i x t h  stages,  within  o f U.  21  common b u n t  leaf  saw  avenae  In  useful  sheath  that  i n t e r c e l l u l a r  find  were  seedlings,  from the of the after  examined  he found  Western  oat apical  of a  hyphae  n o t occur o f bunt  In  a  plants  that  most  found  (1936) growing  o l d .  u n t i l  Swinburne  Invaded  u n t i l  31  (I963) days  some  days.  leaf  General  cultlvar. sheath  points  after  planting  by  seven  (1958)  8-day-old  the  however,  seedlings  of a l l growing o l d .  i n two d i f f e r e n t crown  Woolman  He f a i l e d ,  50 d a y s  that  using  coleoptile  plants  of  until  Invasion  were  made  Hansen  In coleoptlles  wheat  found  been  cultlvar,  In  by twelve  seedlings  development  t i v a r s ,  susceptible  hyphae  the f i r s t  have  T u l . ) and wheat.  had occurred  susceptible In  studies  (De C . )  invasion  bunt  30 t o 50 d a y s  study  susceptible  carles  Invasion  and primordial  seedlings  invaded.  h i s t o l o g i c a l  ( T l l l e t l a  determined  (1930)  days  had been  U.avenae  days.  Some  and  points  leaf  infected  respectively.  growing  oat  by mycelium  leaf  leaf  of  to rather  a t t h e second  the mycelium  Invaded  T i l l e r  from  days,  mycelium  did  be I n d i r e c t ,  p r i m o r d i a were  leaf  passage  a n d 21  apical  to  that  (1966)  days  t i l l e r  coleoptlles, I?,  must  i n the growing  subtending  14,  leaf  ( 1 4 t o 17  was  she f e l t  In a  points  thorough  susceptible c u l nodes  ( f i f t h  d i d n o t become  leaff  stage).  His  9  diagrams bud  indicated that,  invasion  plumule  appears  essentially smuts.  had  from  not  conditions  the  showed  that  scutellum,  Batts  and  dormant  They  mycelium  the  in  seed  by  l i t t l e  of  the  development  (1930)  for  sheaths  were  that  his  in  mycelium  atypical  t i l l e r  mycelium within  Kolk  50 days  of  at  wheat  of  are  the  oat  invaded  by  cultlvars  from  since  because  lower  the  fourth  the  plants  the  growth  nodes  plumule,  growing  seeds  (1958),  that  that  there  as  consisting  into (1)  and a l l that  the  of  is  the the  t i l l e r parts  mycelium l i t t l e  crown  the  elongation  of  node  of  the  (Us. t .11a g o  seeds  is  in  rapid  such  stem  develops and  They  internodes  is  the  also  is  not  According  to  position  in  a  of  in  its  being  elongation.  to  form  the  corresponding  mycelium  crown.  tr.lt l e i  but  radicle.  more  (1955)  It  internodes,  is  much  abundant  coleorhiza.  or  is  Batts  probability  branches  crowns, of  and  point,  period  t i l l e r  the  mycelium  time.  smut  wheat  and  the  Jeater  loose  embryo, young  the  planting  susceptible  permeate  Internodes,  points:  at  the  and  invaded  to  showed  grow  leaf  somewhat  t i l l e r  the  b e h i n d " d u r i n g  region  to  in  Bostr.)  in  the  f l o r a l - i n f e c t i n g smuts  embedded  found  to  by  leaf,  date,  details  found  that  f i r s t  of  Other  those  is  late  Location  oldest  work  begun  deeply  beginning  was  this  employed.  For  (Pers.)  as  next  His  at  random.  thought  point  yet  be  same  the  sheath.  " l e f t  to  the  growing  leaf  occurred.  Swinburne  mycelium the  had  even  generally also  noted  proceeds  crown nodes,  is  able  two  from  other  the  10  base  upward  (the lowermost  that  no mycelium  was present  observed  a general  seedling  22 d a y s  mycelium  could  Malik  invasion  o l d ,with  be found  mycelium  of barley  Infected  susceptible  locatlon  o f wheat  in  barley  have  Information seedlings Odessa that  Is  pericarp  germination. the  Long,  lnternodal smuts,  occurred region  from  In  Kozar  wheat  that  no  nuda  the location  (Jens.)  was not d i f f e r e n t  mycelium  (I967)  In wheat  of  Rostr.)  r e l a t i v e l y  Inoculated  occurred  of the  In  summary,  based  other  than  i n  with  No  development  unbranched  areas  In  barley  susceptible teliospores,  as 48 hours  after  and, s p e c i f i c a l l y ,  p r i m o r d i a was seen  concentrations  the base  hordei  as early  o f an elongated  at  o f U.  hyphae  t i l l e r .  after were  o f mycelium  of the spike  found  In the  a l l  In older and In  of  hours.  100  As with  other plants  the  crown  plant.  on r e s u l t s  which  f o r differences  are admittedly i n timing,  i n  f r o m the-  seeds.  loose-smut  observed  o f t h e embryos  the subaplcal  complete,  seeds  had been  a n d node  the highest  (Ustllago  that  of post-germlnatlon  penetration  regions  established  smut  barley  Invasion  slender,  susceptible  the surprising exception  on the development  which  coleoptlles  (193*0  made...  scant.  barley,  a n d (2)  Ruttle  of an Inoculated  loose-smut  been  to elongate),  i n internodes.  (i960)  loose  studies  f i r s t  i n the plumule.  and Batts  h i s t o l o g i c a l  being  no  f a r  11  Important of  the  differences  various  This  seems  mode  of  to  B.  THE  the  the  in  reviewed  cultlvars  which  any  old  the  (1936) both  oat  fungus  smuts  including  large  infecting  f i r s t  the  by  was  the  can  be  shown.  difference smuts  U.  and  resistant  epidermis. other  loose  in f l o r a l  the  Its  also  cultlvar The A l l  races  tested  by  w i l l  Kolk  (1930) of  for  •Markton' were  observed  k o l l e r l  In  after  Western  single did  stopped  resistant  and  seedlings  (1933) U.  resistant invasion  cultlvar,  that  on  cul-  oats,  development.  fungi  other  In  i n i t i a l  Sampson  found  comparing  smuts  invasion  resistant  In  for  studies.  fungus.  Invasion  a  made  cereal  the  the  provided  susceptible  smuts  to  avenae.  checked  been  and  was  seedlings  different  notice  of  view  macroscopic  by  to  but  also  barrier  whatsoever.  several  of  coleoptile  t h i s ,  general  smut)  and  no  seedlings  confirmed  of  covered  cultivars  penetration  c u t i c l e  the  have  by  seedlings  the  a  no  studies  present  (susceptible)  day  of  hosts  susceptible  Studies  followed  young were  in  (showing  the  usually  resistant  five  of  both  and  section,  smuts.  f i r s t ,  (1931)  normal  their  seedling  infection  resistant  With  of  within  development  RESISTANCE  Histological  seeds  post-germination  regardless  between  of  cereal  t l v a r s .  Zade  true  previous  pathway  events  of  smuts  E X P R E S S I O N OF  several  be  be  early  smuts.  In of  cereal  infection  Infecting  in  not at  races allow the  combinations,  'Karkton , 1  allowed  12  invasion  of coleoptiles  combinations  differed  the  could  mycelium  guishable cases, host  tissue  invasion  choice  a l .  t i b l e  wheat  hyphal et  a l . observed  both of  cases.  deeper into found  nodes, that  et  internodes stage  (1)  no delay)  a l . (1955)  and growing  was always  stage  (2)  and stage  confirmed  a n d smut  this  races.  In  most of  with  indicates be  wheat  (1923)  that  observed. cultivars  and Crepin  of resistant  et  and suscep-  i n extent, o f  of growth. leaf  Crepin  sheath  three"distinct  i n  phases  and development  within  development  within  (2)  sheaths; points  attained  was attained  (3)  i n d i s t i n -  coleoptile  what w i l l  the second  and leaf  which  working  This  two weeks  into  was  observed  discerned  entrance  tissues  material,  cultivars  (1930)  during  by any type  showed, no. d i f f e r e n c e  into  These  combination.  i n resistant  of the coleoptile;  coleoptile  sistant (with  cells  (1)  oats,  seedlings  penetration  Woolman  which  (1937)t  Gaines  f o r the f i r s t  pathogenesist  epidermal  that  cultivars.  invasion  carles  picture.  reported  (1937)  Brandweln  can determine  by T.  similar  state  t o be general.  of material  a  of time  susceptible  of resistant smuts  Infection  i n a  tissues).  was n o t accompanied  alteration.  by both  presented  of a  arrest  cultivars  deeper  i n the length  persist  that  pathogen  several  the  from  ( o r even  was never observation  a n d (3)  entrance  o f t h e embryo. but that, only  using  i n r e -  i n some  attained.  He  plants  G r i f f i t h  different  13  With  Ustllago  nigra  barley,  Tisdale  tration  of the coleoptile  reactions  and Tapke  of resistant  Tapke,  the semi-loose found  (1924)  that  and the f i r s t  and susceptible  smut  prior  leaf  of  to  base  pene-  the  cultivars  were  indis-  tinguishable. The although Embryo  resistance  similar,  invasion  leading  to a  must  (1941)  resistant  wheat  o f the dormant  where- i n t h e s e e d s . i n which  however. found  frequently thorough 1959)  wheat  Invaded  barley.  investigation  and adult He f o u n d  high  percentage  ving  the plumular  seedling a  Ruttle  i t was often  (193*0> i n  found  one r e s i s t a n t ,  and Batts  were  elsewheat  (1958)  t h e embryos  of susceptible  cultivars.  o u t b y Popp  (1951  Infection,  plant  Infection  In both wheat and  o f embryo apex),  infection  they  plant  and  high Thus  a  Invol-  percentage  infection.  A  showed  (not generally  possessed  as  seedling  cultivars  an intermediate  and (If  of adult  most  also  were  o f embryo  f o r wheat,  some  infected,  and Jeater  In which  was c a r r i e d  condition  the mycelium was not  o f t h e embryos  cultivars  context.  shoi<red t h a t  (1946)  found  smuts,  levels  that  infection,  low percentage  (1942)  as those  who compared  Infection  reaction.  although  a minority  infecting  i s the normal  cultivars,  Bubentzov  Vanderwalle  tesistant  seed  disease  and barley  f l o r a l  i n a different  and Vanderwalle  i n t h e embryos,  cultlvar  toward  be viewed  susceptible  Bubentzov  present  shown  of  resistance) resistance  14  appears  t o be expressed  throughout  Other  wheat  cultivars  other  races  of the pathogen),  cultivars embryo U.  in  adult  respectively.  be a r e l a t i v e l y barley,  frequently wheat  embryos  Invaded  cultivars  t r l t l c l . five  that  resistant  inoculated  resistance  occurred  the  c u l t l v a r ,  f i f t h  a f t e r  Convincing showing  that  plants. found  smut  Hubbard  that  when  k o l l e r l .  reduced  resulted  even  Brandweln studies  with  after  often  stands  same  o f U. examined  o f  U . t r l t l c l  inoculation.  In  four  a n d , occa-  hadbeen  Is also  invaded.  were  were this  i n  available resistant  and Stevens  (1936)  Inoculated  (the proportion  d i d n o t observe these  two winter  races  present  (1934),  the plants  as  d i dnot occur.  mycelium  though  involving  apex,  evidence  two oat cultivars  (195^ a n d  were  when  t h e embryo,  macroscopic  and Stanton  (1937)  three  Infection  Is  resistance  andBever  f o r the presence  the plumular embryo  to  cultivars  following  percent  exclusion  h i s t o l o g i c a l l y  (I962)  cultivars  of  even  contributor Ohms  with  barley  between  embryo  o f susceptible  intervals  Inoculated  b y U. t r l t l c l a n d  that  of resistant  a t various  sionally,  Infection  wheat.  mycelium them,  correlation  implies  and Schafer  wheat  cultivars  important  as those  were  Gaskln  plant  with  of the plant.  anda l l of the several  a good  This  more  as compared  found  1955)  ( o r t h e same  showed  andpercent  nuda,  may  examined  the l i f e  with  of plants  apparently effect  two cultivars.  i n  U.  emerging) healthy.  greenhouse  He c o u l d ,  In  15  however, produce t h e e f f e c t b y p l a n t i n g l o o s e and c o v e r e d smut I n o c u l a t e d seeds o f r e s i s t a n t and s u s c e p t i b l e c u l t i v a r s i n 1938).  s o i l w h i c h was a f t e r w a r d s e v e r e l y compacted ( B r a n d w e l n ,  He c o n c l u d e d t h a t an i n t e r a c t i o n between i n f e c t i o n and d e h u l l i n g ( w h i c h was commonly done t o o b t a i n h i g h e r l e v e l s o f s m u t t i n g ) c a n s i g n i f i c a n t l y weaken t h e c o l e o p t i l e s , r e s u l t i n g i n r e d u c e d emergence. and S t a n t o n  (193*0  Zade  (193D»  Welsh  (1932)  and Hubbard  a l l observed r e s i s t a n t o a t c u l t i v a r s which  e x h i b i t e d r e d u c e d h e i g h t , r e d u c e d y i e l d and d e l a y e d h e a d i n g when I n o c u l a t e d w i t h U. k o l l e r l and/or U„ avenae.  Similarly,  w i t h f l a g smut o f wheat, U r o c y s t l s t r l t i c l K o r n i k e , Churchward (1937-8)  o b s e r v e d s t u n t i n g and c h l o r o s i s o f i n o c u l a t e d p l a n t s  w h i c h remained unsmutted, and were c l a s s i f i e d a s r e s i s t a n t . B l a s t i n g (= s t e r i l i t y ) o f heads o f r e s i s t a n t o a t c u l t i v a r s has been o b s e r v e d a f t e r i n o c u l a t i o n w i t h b o t h U . k o l l e r l and U. avenae (Reed and S t a n t o n , 1 9 3 8 ) and w i t h U. avenae (Halisky,  195&;  Holton,  1966).  Reed and S t a n t o n a l s o f o u n d  a few t e l i o s p o r e s i n some o f t h e b l a s t e d  heads*  On o c c a s i o n , w o r k e r s were a b l e t o m o d i f y r e s i s t a n c e t h r o u g h c u l t u r a l methods.  Some s m u t t i n g was o b t a i n e d I n  o t h e r w i s e " t o t a l l y r e s i s t a n t " 'Markton* o a t s when S m i t h and Bressman  (1931)  after planting.  c u t back t h e p l a n t s a t s i x t o seven Drought c o n d i t i o n s produced t h e sane  the f o l l o w i n g year.  However, Woodward and T i n g e y  weeks effect  (19^1)  c u t back b a r l e y p l a n t s a t t h e b o o t s t a g e and saw no  effect  16  on s m u t t i n g by U. h o r d e i , (1937)  Stevens ( I 9 3 6 ) and  Brandweln  c o u l d f i n d no e f f e c t on y i e l d , h e i g h t , d a t e o f  m a t u r i t y , o r amount o f t i l l e r i n g when t h e y i n o c u l a t e d s e v e r a l t o t a l l y r e s i s t a n t oat c u l t i v a r s w i t h U. k o l l e r l  and  U. avenae, Griffith  e t a l . ( 1 9 5 5 ) observed an e f f e c t on e a r l y  g r o w t h o f b o t h r e s i s t a n t and  s u s c e p t i b l e wheat c u l t i v a r s  f o l l o w i n g i n o c u l a t i o n w i t h T. c a r l e s .  The  g e n e r a l l y s m a l l e r than the uninoculated  p l a n t s were  controls.  The  d i f f e r e n c e soon d i s a p p e a r e d i n the r e s i s t a n t c u l t l v a r . o b s e r v e d a few  They  t e l i o s p o r e s i n the c e n t r e of seeds of some  l a t e t i l l e r s o f p l a n t s o f t h e r e s i s t a n t c u l t l v a r , however, so i t would appear t h a t the fungus.was s t i l l p r e s e n t even a t C r e p i n e t a l . ( 1 9 3 7 ) a l s o saw  maturity.  s i m i l a r e f f e c t s on  p l a n t g r o w t h i n o t h e r . r e s i s t a n t wheat c u l t i v a r s .  U.  nigra  a l s o caused d i s t o r t i o n of s e e d l i n g s developed from d e h u l l e d seed o f b o t h s u s c e p t i b l e and r e s i s t a n t b a r l e y according  cultivars  t o T i s d a l e and Tapke (192'J-).  L i t t l e has been r e c o r d e d c o n c e r n i n g the e f f e c t s o f floral  I n f e c t i n g smuts on r e s i s t a n t c u l t i v a r s of the  host,  T i n g e y and Tolman ( 1 9 3 * 0 c o u l d f i n d no c o r r e l a t i o n between p e r c e n t of wheat s t a n d  ( s e e d l i n g s u r v i v a l ) and  l o o s e smut  s u s c e p t i b i l i t y , i n d i c a t i n g t h a t i f t h e mycelium were p r e s e n t i n non-smutted p l a n t s i t s e f f e c t s were too to  detect.  small  17  An u n u s u a l t y p e o f r e s i s t a n c e i n v o l v i n g an a p p a r e n t h y p e r s e n s i t i v e r e a c t i o n has been r e p o r t e d i n wheat a g a i n s t  JJ.  t r l t l c l by Oort ( 1 9 ^ 7 ) and by Ohms and  Bever ( 1 9 5 5 ) , and i n o a t s a g a i n s t b o t h o a t smuts b y Western  (1936).  Ohms and Bever observed t h a t , because o f  I n f e c t e d seeds and s e e d l i n g s , stands were r e d u c e d . mentioned  Earlier  s t a n d r e d u c t i o n s may have been caused by t h i s  form o f r e s i s t a n c e , w i t h d e h u l l l n g b e i n g a n e c e s s a r y p r e r e q u i s i t e , however.  W i t h f l o r a l l n f e c t o r s , d e h u l l l n g was  not p a r t o f t h e i n o c u l a t i o n p r o c e d u r e . f u l l y described  Oort ( 1 9 4 7 ) most  t h e h y p e r s e n s i t i v i t y w h i c h he observed.  It  r e s u l t e d I n d e a t h o f e i t h e r e n t i r e p l a n t s o r o f culms. Thus when heading o c c u r r e d ,  a strong s e l e c t i o n f o r healthy  p l a n t s o r p l a n t p a r t s had t a k e n p l a c e . i n t h e case d e s c r i b e d by Western  (I936).  Details are lacking Death o f e n t i r e  i n f e c t e d p l a n t s i s n o t mentioned, b u t i n f e c t e d culms were seen t o d i e . P r a c t i c a l l y nothing  I s known about t h e presence o r  absence o f U. h o r d e i mycelium  In i n o c u l a t e d p l a n t s of  highly resistant barley cultivars. o f s u c h m a t e r i a l have been made.  No h i s t o l o g i c a l  studies  Faris (1924a) stated that  p l a n t s w h i c h were i n f e c t e d w i t h t h e fungus were n o t d i s t i n g u i s h a b l e from h e a l t h y p l a n t s u n t i l near matttSi^y* Johnston (193*0  observed r e d u c e d emergence o f G l a b r o n ,  a  t o t a l l y s m u t - f r e e c u l t l v a r , when b o t h h u l l e d and d e h u l l e d  18  seeds were I n o c u l a t e d . severely affected.  The d e h u l l e d seeds seemed t o be more  Reduced s t a n d s were a l s o noted I n two  r e s i s t a n t b a r l e y c u l t i v a r s by S c h a f e r e t a l . ( 1 9 6 2 a ) .  In  t h i s c a s e , r e d u c e d emergence o c c u r r e d o n l y when seeds were d e h u l l e d and p l a n t e d d e e p l y .  I t Is possible that In t h i s  and o t h e r c a s e s o f s t a n d r e d u c t i o n r e v i e w e d ,  s o i l pathogens  were i n v o l v e d . C.  THE EFFECTS OF ENVTRONMEOT ON BARLEY COVERED SMUT . Most o f t h e p u b l i s h e d i n f o r m a t i o n on t h e e f f e c t s o f  environment on c e r e a l smuts has been r e v i e w e d  by Tapke  The p u r p o s e o f t h i s s e c t i o n I s n o t t o g i v e a com-  (1948).  prehensive  p i c t u r e o f w h a t , i s known, but r a t h e r t o p r e s e n t  i n f o r m a t i o n on e n v i r o n m e n t a l results of this thesis. environmental  e f f e c t s w h i c h may r e l a t e t o t h e  As B a t t s and J e a t e r ( 1 9 5 8 ) s t a t e ,  e f f e c t s on one s p e c i f i c smut d i s e a s e cannot  be g e n e r a l i z e d t o I n c l u d e o t h e r smuts.  One e s p e c i a l l y cannot  a p p l y what I s l e a r n e d f r o m f l o r a l - i n f e c t i n g t o s e e d l i n g I n f e c t i n g smuts, and v i c e - v e r s a .  Here f l o r a l  infectors w i l l  not be c o n s i d e r e d and, e x c e p t f o r U. h o r d e i . t h e s e e d l i n g i n f e c t o r s w i l l be mentioned o n l y b r i e f l y . F a r l s (1924a) d e m o n s t r a t e d t h a t , f o r s u s c e p t i b l e genotypic  combinations,  c o u l d be o b t a i n e d  uniformly high infection levels  I n t h e greenhouse over wide ranges o f  t e m p e r a t u r e , s o l i a c i d i t y and s o l i m o i s t u r e .  He  concluded  19  t h a t f i e l d and greenhouse c o n d i t i o n s n e a r l y always i n t o t h e f a v o r a b l e ranges o f these v a r i a b l e s .  fall  H i s method  o f i n o c u l a t i o n was t o d u s t seeds w i t h d r y t e l l o s p o r e s . Aamodt and J o h n s t o n had  little  (1935)  determined t h a t s o i l  e f f e c t on l e v e l o f smut i n 1 3 8 b a r l e y  heterogeneity cultivars.  Other s t u d i e s i n d i c a t e , however, t h a t environment can be important.  Briggs  (1927)  was unable t o o b t a i n h i g h smut  l e v e l s using the d r y t e l i o s p o r e i n o c u l a t i o n technique f o l l o w e d by p l a n t i n g i n t h e f i e l d .  Tapke  (1938)  clearly  d e t e r m i n e d t h a t t h e post-emergence environment c o u l d be important.  He g e r m i n a t e d seeds i n t h e greenhouse and, a t  v a r i o u s times a f t e r germination, field.  transferred plants to the  When seeds were d r y d u s t e d w i t h t e l l o s p o r e s , t h e -  amount o f smut was p r o p o r t i o n a l t o t h e l e n g t h o f time t h e seeds remained i n t h e greenhouse.  When, however, i n o c u l a -  t i o n was w i t h an aqueous s u s p e n s i o n o f t e l l o s p o r e s ( w h i c h was a l l o w e d  t o r e m a i n on t h e seeds f o r 2k hours  d r y i n g ) , no v a r i a t i o n i n s m u t t i n g o c c u r r e d d i f f e r e n t treatments.  before  among t h e  The s t u d y emphasized t h e importance  of i n o c u l a t i o n t e c h n i q u e on t h e degree o f e n v i r o n m e n t a l s e n s i t i v i t y of inoculated seedlings.  The e f f e c t o f d e p t h  of p l a n t i n g on smut l e v e l has been i n v e s t i g a t e d by T a y l o r and  Zehner  (1931)  and by Jones and S e l f E l - N a s r  (19^0).  They found t h a t , I n g e n e r a l , t h e deeper t h e seeds were planted  (up t o 1 2 cm) t h e h i g h e r was t h e p e r c e n t o f p l a n t s  20  or heads smutted.  The  r e l a t i o n s h i p was  so t h a t the most n o t a b l e plantings.  e f f e c t occurred  not a l i n e a r  one,  a t the d e e p e s t  B o t h groups found t h a t of a l l the smuts t h e y  s t u d i e d , U. h o r d e i was Woodward and  l e a s t a f f e c t e d by d e p t h of p l a n t i n g .  T l n g e y (194-1) f a i l e d t o f i n d any e f f e c t whatso-  e v e r when p l a n t i n g s 1 . 5  3.0  and  inches deep were compared.  Perhaps the most extreme case of an e n v i r o n m e n t a l e f f e c t on d i s e a s e  l e v e l s of c o v e r e d smut of b a r l e y  r e p o r t e d by Ebba ( 1 9 7 3 ) . smut genotype and  was  He observed an i n t e r a c t i o n between  environment when i d e n t i c a l p l a n t i n g s were  made i n B r i t i s h C o l u m b i a and  California.  On one  barley  c u l t l v a r a smut d l k a r y o n w h i c h caused some smut i n B.C. avtrulehS  was  i n C a l i f o r n i a , w h i l e a n o t h e r d l k a r y o n , w h i c h caused  a r a t h e r low l e v e l of s m u t t i n g on a n o t h e r c u l t l v a r i n gave a much h i g h e r l e v e l i n C a l i f o r n i a .  B.C., to  I t i s impossible  say w h i c h e n v i r o n m e n t a l components are r e s p o n s i b l e .  From  t h e l a r g e number of o t h e r h o s t and pathogen genotypes combined and  s t u d i e d a t t h e s e two  l o c a t i o n s , i t would p r o b a b l y be  t o say t h a t t h i s o b s e r v a t i o n was  exceptional.  The  only  safe other  r e p o r t of such an i n t e r a c t i o n concerned T. c a r l e s and wheat. E e i c h e r t ( 1 9 3 0 ) found a s i t u a t i o n a l m o s t i d e n t i c a l t o the described  above, w i t h the two  S t a t e and  Germany.  I t was  l o c a t i o n s b e i n g Washington  of i n t e r e s t t o note t h a t , i n each  c a s e , t h e l o c a l bunt genotype was the two.  one  the more s u c c e s s f u l o f  Relchert also indicates that t h i s i n t e r a c t i o n  21  was,  in  his  experience,  an  That  environment  affects  between Tapke into  barley  (1952) three  subdivided  method (2)  post-emergence Thomas  (I965)  however,  covered  convenient  lation—the important;  and  the  exceptional  of  smut  the  been  done  them  In  to  terms  of  the  inoculation  i t  In  effects..  no  et  roughly the  because  qualitative  a l .  the  pre-  doubt.  period  and  not  inocubeing  (3)  (I962)  same and  of  chosen  environment,  Schafer  probably any  the  reaction  environment  a r t i f i c i a l  summarize  indicate  of  be  (1)  environment.  is  can  of  intervals:  pre-emergence  This  degree  there  effects  d i s t i n g u i s h i n g between  environments.  the  situation.  the  and  way,  not,  post-emergence enough work  difference  between  has  22  PART I THE EFFICIENCY OF PARTIAL-VACUUM INOCULATION OF HANNCHEN BARLEY WITH USTILAGO HORDEI A.  INTRODUCTION As s t a t e d i n t h e i n t r o d u c t i o n t h e smut d i s e a s e ,  when i t i s e x p r e s s e d  i n i n d i v i d u a l p l a n t s , may be shown  by one o r more, and f r e q u e n t l y by a l l , s p i k e s o f t h e Infected plant.  W i t h one o r more d i s e a s e d s p i k e s  taken  as t h e c r i t e r i o n f o r r e c o g n i z i n g t h e p r e s e n c e o f d i s e a s e In I n d i v i d u a l p l a n t s , the highest disease l e v e l s u s u a l l y r e s u l t i n about 5 0 t o 6 0 p e r c e n t o f the p l a n t s showing t h e disease.  A l t h o u g h Thomas  s i o n a l l y observed c e n t , Ebba  ( 1 9 7 4 ) ,  (I965)  and S i d h u  (1972)  occa-  d i s e a s e l e v e l s as h i g h as 80 t o 8 5 p e r who worked w i t h a range of smut genotypes  and b a r l e y c u l t i v a r s I n t e r a c t i n g under w i d e l y v a r i e d e n v i r o n mental c o n d i t i o n s , d i d not r e p o r t disease l e v e l s higher  than  6 0 per cent. For any p l a n t w h i c h shows a t l e a s t one smutted s p i k e I t I s evident t h a t the i n f e c t i o n process ful.  A question a r i s e s concerning  has been s u c c e s s -  those p l a n t s w h i c h ,  f o l l o w i n g i n o c u l a t i o n , show no e x t e r n a l e v i d e n c e  of s m u t t i n g .  T h i s c o u l d r e p r e s e n t t h e extreme case i n w h i c h , f o l l o w i n g s u c c e s s f u l i n f e c t i o n , none o f t h e s p i k e s became smutted. I t c o u l d a l s o r e p r e s e n t those cases i n w h i c h i n f e c t i o n had n o t been  accomplished.  23  T h i s s t u d y was, t h e r e f o r e , d i r e c t e d t o t h e q u e s t i o n of whether, i n s u s c e p t i b l e combinations, the f a i l u r e t o e x p r e s s t h e d i s e a s e f o l l o w i n g I n o c u l a t i o n was caused by the f a i l u r e o f t h e i n f e c t i o n p r o c e s s , perhaps because o f an i n e f f i c i e n t i n o c u l a t i o n technique, o r t o other causes. The a p p r o a c h chosen t o answer t h i s q u e s t i o n was q u i t e simple.  The s t a n d a r d method o f i n o c u l a t i o n has, i n t h e p a s t ,  i n v o l v e d i n o c u l u m made up o f s p o r i d i a o f t h e two n e c e s s a r y mating-types, A  and a , w h i c h were mixed and shaken t o g e t h e r  f o r a t l e a s t 24 hours I n l i q u i d b r o t h (Thomas 1 9 6 5 ) .  More  r e c e n t l y , Ebba ( p e r s o n a l communication) found t h a t Inoculum w h i c h has been mixed and. a l l o w e d t o s t a n d f o r one o r two days i s no;: more e f f e c t i v e t h a n Inoculum w h i c h has been mixed J u s t prior to inoculation.  From t h i s , I t mey be I n f e r r e d t h a t t h e  d i k a r y o n s , w h i c h u l t i m a t e l y r e s u l t I n I n f e c t i o n and s m u t t i n g , can be formed a f t e r t h e seed has been i n o c u l a t e d ; t h e y need not e x i s t p r i o r t o t h e time o f i n o c u l a t i o n .  I t was thought  t h a t by c a r e f u l l y a d j u s t i n g t h e r e l a t i v e amounts o f A and a s p o r i d i a and o b s e r v i n g t h e e f f e c t on l e v e l o f s m u t t i n g , a n i n d i c a t i o n of t h e e f f i c i e n c y of t h e i n o c u l a t i o n procedure would be o b t a i n e d .  Moreover, t h e b e s t e x p r e s s i o n o f t h i s  e f f i c i e n c y would be i n terms o f an " e f f e c t i v e number" o f sporidia.  T h i s would r e p r e s e n t t h e average number o f  s p o r i d i a w h i c h , f o r each i n o c u l a t e d s e e d , would be p o t e n t i a l l y capable of t a k i n g p a r t In a " s u c c e s s f u l " I n f e c t i o n  24  ( I . e . , I n an I n f e c t i o n w h i c h a c t u a l l y r e s u l t s I n d i s e a s e expression).  The e f f e c t i v e number would t h u s r e l a t e t o  e x p r e s s i o n o f t h e d i s e a s e by i n d i v i d u a l p l a n t s , and would be a measure o f t h e number o f s p o r i d i a p o t e n t i a l l y c a p a b l e of t a k i n g p a r t i n t h e i n f e c t i o n p r o c e s s .  I t would, of  c o u r s e , g i v e no i n d i c a t i o n o f t h e a c t u a l p h y s i c a l l o c a t i o n of these s p o r i d i a .  The above a p p r o a c h i s o n l y one p o s s i -  F o r i n s t a n c e , d i l u t i o n o f normal 1 : 1 m a t i n g - t y p e  bility.  i n o c u l u m would a l s o undoubtedly work.  I t was f e l t t h a t t h e  mathematics and l o g i c o f t h e approach chosen were s i m p l e r , however. The purpose o f t h i s s t u d y was t o d e t e r m i n e t h e e f f e c t i v e number for. a r e p r e s e n t a t i v e h o s t - p a r a s i t e genotype c o m b i n a t i o n and, I n so. d o i n g , t o a s s e s s t h e e f f i c i e n c y of the i n o c u l a t i o n procedure i n e s t a b l i s h i n g e f f e c t i v e hostpathogen  contact.  A s h o r t s t u d y was a l s o made t o d e t e r m i n e whether known s p o r i d i a l m i x t u r e s r e m a i n c o n s t a n t over t i m e , o r whether t h e i n i t i a l r a t i o s a r e brought c l o s e r t o u n i t y b y f a s t e r growth o f t h e m i n o r i t y t y p e component o f t h e m i x t u r e . B. MATERIALS AND METHODS A s i n g l e smut d l k a r y o n and a s i n g l e b a r l e y were used i n t h i s s t u d y .  cultlvar  The two smut h a p l o l d s w h i c h made  up t h e d l k a r y o n were o r i g i n a l l y i s o l a t e d by Thomas ( I 9 6 5 )  25  f r o m s e p a r a t e smutted b a r l e y p l a n t s found near W i n n i p e g , Manitoba.  They have been s i n c e used e x t e n s i v e l y as t h e  s t a n d a r d h a p l o l d c u l t u r e s i n t h e l a b o r a t o r y of Dr. P e r s o n , and a r e d e s i g n a t e d E 3 a and JAA. cultlvar  The two-rowed b a r l e y  'Hannchen' was chosen f o r two r e a s o n s : ( 1 )  n o r m a l c o n d i t i o n s a h i g h p e r c e n t a g e o f p l a n t s show  under infec-  t i o n when 'Hannchen* seeds a r e i n o c u l a t e d w i t h t h e s t a n d a r d d l k a r y o n mentioned above; and ( 2 ) i n t h e greenhouse, where m a i n l y t h i s s t u d y was c a r r i e d o u t , more p l a n t s of t h i s c u l t l v a r can be b r o u g h t t o m a t u r i t y i n a g i v e n amount o f space t h a n when o t h e r c u l t i v a r s a r e used. Seeds were t r e a t e d w i t h a d i l u t e s o l u t i o n of f o r m a l i n (one p a r t , f o r m a l i n ^ to*.3.2,0V p a r t s water), p r i o r t o i n o c u l a t i o n , i n o r d e r t o k i l l any c o n t a m i n a t i n g smuts and t o l o o s e n t h e seed h u l l s .  They were soaked i n t h e s o l u t i o n f o r one hour^  r i n s e d f o r 3 0 m i n u t e s i n r u n n i n g t a p w a t e r , and t h o r o u g h l y dried before inoculation., Seeds were I n o c u l a t e d u s i n g t h e p a r t i a l - v a c u u m t e c h n i q u e d e s c r i b e d by Tapke and Bever ( 1 9 ^ 2 ) .  Smut c u l t u r e s  were m a i n t a i n e d f o r up t o t h r e e weeks on m o d i f i e d V o g e l ' s (1956)  complete a g a r medium i n p e t r i d i s h e s .  These were  s t o r e d e i t h e r i n an I n c u b a t o r a t 22°C o r , more commonly, i n a r e f r i g e r a t o r a t 4°C.  S p o r i d i a from each c u l t u r e were  t r a n s f e r r e d , s e p a r a t e l y , t o 1 2 5 tnl Erlenmeyer f l a s k s cont a i n i n g 5 0 m l o f complete b r o t h .  A drop o r two of aqueous  26  a c h r o m y c i n s u s p e n s i o n (10 mg/ml) was added t o i n h i b i t p o s s i b l e b a c t e r i a l growth, and t h e f l a s k s were shaken i n a 22°C i n c u b a t o r f o r 3 t o 4 d a y s , by w h i c h time s p o r i d i a l s u s p e n s i o n s o f maximum d e n s i t y were o b t a i n e d . seeds were p u t I n t o a dram v i a l .  F o r normal  About 100 inoculation,  e q u a l q u a n t i t i e s o f t h e two h a p l o l d s ( o f o p p o s i t e m a t i n g - t y p e ) were mixed and t h e m i x t u r e was p i p e t t e d onto t h e seed a t a r a t e o f 8 t o 10 m l o f Inoculum p e r v i a l .  The v i a l s were then  p l a c e d i n a vacuum d e s s i c a t o r , w i t h o u t d e s s i c a n t , and subj e c t e d t o a p a r t i a l vacuum ( r e s u l t i n g i n b o i l i n g ) f o r 3 0 minutes.  Upon r a p i d r e l e a s e o f t h e vacuum, s p o r i d i a a r e drawn  under t h e seed h u l l s .  The e x c e s s l i q u i d was t h e n poured o f f ,  and t h e seeds were p u t I n t o s m a l l c o i n e n v e l o p e s .  Seeds were  a l l o w e d t o d r y f o r a t l e a s t 2k hours i n t h e opened envelopes^ w e l l spaced on m e t a l r a c k s o v e r paper t o w e l s . p l a c e w i t h i n t h r e e days a f t e r  P l a n t i n g took  Inoculation.  In o r d e r t o m a n i p u l a t e t h e r a t i o s o f t h e two smut h a p l o l d s , t h e a b s o l u t e c o n c e n t r a t i o n s o f t h e 3 t o 4 day o l d s p o r i d i a l s u s p e n s i o n s were f i r s t determined by d i l u t i n g each 1:100 w i t h s t e r i l e w a t e r and c o u n t i n g t h e s p o r i d i a l concent r a t i o n s w i t h t h e a i d o f a hemocytometer. Where n e c e s s a r y , the  more c o n c e n t r a t e d s u s p e n s i o n was a d j u s t e d by a d d i n g  s t e r i l e water t o o b t a i n equal concentrations of s p o r i d i a f o r the  two c u l t u r e s .  The s p o r i d i a l r a t i o s were t h e n r e a l i z e d  by m i x i n g unequal amounts o f t h e s t a n d a r d i z e d c u l t u r e s i n  :  27  the r a t i o s d e s i r e d t o g i v e a t o t a l o f 8 t o 10 ml of inoculum per v i a l . (and  Ratios of 1:1,  100:1,  500:1,  t h e i r r e c i p r o c a l s ) were used.  1:10,000  1,000:1,  by u s i n g a  inoculum.  Rows were  The p l a n t s were g i v e n 16 hours per day s u p p l e m e n t a l  fluorescent lighting.  I n t h e f i e l d , where some t r e a t m e n t s were  a l s o p l a n t e d , seeds were sown a t a r a t e of 1 2 5 seeds f o o t row.  1:100  i n s o i l benches i n t h e greenhouse.  About 5 0 seeds were sown i n each f o u r f o o t row. randomized.  and  This r e s u l t e d i n a very  s l i g h t d e c r e a s e i n t h e s p o r i d i a l d e n s i t y of t h e f i n a l Seeds were p l a n t e d  10,000:1  The extreme 1 0 , 0 0 0 : 1  r a t i o s were n e c e s s a r i l y o b t a i n e d  d i l u t i o n o f the m i n o r i t y c u l t u r e .  and  per 1 5 -  D i s e a s e l e v e l s , a s s e s s e d i n terms o f t h e percentage  o f p l a n t s showing a t l e a s t one smutted head, were r e c o r d e d about t h r e e months a f t e r seeds were sown, when t h e p l a n t s had reached maturity.  Readings were made w i t h o u t knowledge o f  treatment. The e f f e c t i v e number of s p o r i d i a was d e t e r m i n e d by u s i n g t h e f o l l o w i n g r e l a t i o n s h i p (see d i s c u s s i o n ) : S- = where  1-P  n  S = t h e d i s e a s e l e v e l t a k e n as a p r o p o r t i o n o f t h e c o n t r o l p o p u l a t i o n ( w h i c h had been i n o c u l a t e d w i t h a 1:1 mixture)! P = t h e p r o p o r t i o n of m a j o r i t y , s p o r i d i a i n t h e inoculum m i x t u r e ; n = t h e e f f e c t i v e number o f s p o r i d i a .  28  In l o g a r i t h m i c form the r e l a t i o n s h i p becomes! log  (1-S)  =  n l o g (P)  H = l o g (1-5) l o g (P)  or  w h i c h I s much more e a s i l y s o l v e d f o r n. Standard d i l u t i o n p l a t i n g t e c h n i q u e s were used t o o b t a i n samples, as s i n g l e s p o r i d i a l c o l o n i e s , from 1 0 0 : 1 and 1 : 1 0 0 r a t i o m i x t u r e s o f t h e two h a p l o l d s i n complete b r o t h shake c u l t u r e .  From t h e d i l u t i o n p l a t e s , f i v e day o l d  c o l o n i e s were t r a n s f e r r e d t o f r e s h p e t r i p l a t e s o f complete medium t o form 2 5 - c o l o n y master p l a t e s . .  These were r e p l i c a -  p l a t e d , a c c o r d i n g t o t h e method o f D i n o o r and P e r s o n to  complete agar p l a t e s c o n t a i n i n g : s p o r i d i a l lawns of E 3 a and  I 4 A , t h e two s t a n d a r d m a t i n g - t y p e t e s t e r s . at  ( I 9 6 9 ) ,  0 , 7 , 24 and 7 2 hours a f t e r m i x i n g .  Samples were t a k e n  I n a d d i t i o n , a t 24  h o u r s , , 5 0 ml o f f r e s h medium was added t o the c u l t u r e s t o i n i t i a t e a n o t h e r b u r s t o f growth.  C o l o n y m a t i n g - t y p e s , based  on t h e p r e s e n c e o r absence o f i n f e c t i o n hyphae o r s u c h f a d e n M  (Bauch, 1 9 3 2 ) , were r e c o r d e d two d a y s a f t e r t r a n s f e r t o t h e t e s t e r lawns. D e t e r m i n a t i o n o f s i g n i f i c a n c e was c a r r i e d o u t , u s i n g a s t a t i s t i c a l technique which deals with the confidence i n t e r v a l about t h e d i f f e r e n c e between two p r o p o r t i o n s ( s e e appendix).  The 1 : 1  c o n t r o l was t h e s t a n d a r d a g a i n s t w h i c h  a l l o t h e r t r e a t m e n t s were compared.  M  29  C. RESULTS Figure 1.1  shows t h e r e l a t i o n s h i p between d i f f e r i n g  A:a r a t i o s i n t h e inoculum and disease.  The  h i g h e s t d i s e a s e l e v e l , 30 per c e n t ,  o b t a i n e d w i t h the 1:1 Figure 1.1  the r e s u l t i n g l e v e l s o f was  m i x t u r e o f A and a s p o r i d i a .  t h i s l e v e l i s set a r b i t r a r i l y at 1 . 0 ,  In  and  other  l e v e l s are shown as p r o p o r t i o n s o f t h i s maximal l e v e l . E x c e p t f o r t h e 1 0 , 0 0 0 : 1 and 1 : 1 0 , 0 0 0 r a t i o s , w h i c h are based on samples o f c a . 1 0 0 p l a n t s , each p o i n t on the Is based on a sample of a t l e a s t 150 more f o r t h e 1 : 1 ,  100:1  and  1:100  curve  p l a n t s , and on 250  ratios.  or  These numbers  r e p r e s e n t p l a n t s from a t l e a s t t h r e e , and i n some cases from f o u r , separate 1:100  r a t i o s one  field.  For the 1.1,1.,, 1 0 0 : 1 . . and.  of the e x p e r i m e n t s was  c a r r i e d out i n the  R e s u l t s from d i f f e r e n t experiments were c o n s i s t e n t . The  The  experiments.  curve shown In F i g u r e 1 . 1  i s not  skewness becomes e v i d e n t when the 1 0 0 : 1  of A:a  symmetrical. and 1 : 1 0 0  ratios 100:1  s p o r i d i a a r e compared w i t h each o t h e r ; when the  r a t i o f a v o r s m a t i n g type a, the d i s e a s e l e v e l i s s i g n i f i c a n t l y lower t h a n t h a t o f the c o n t r o l s , and when i t f a v o r s m a t i n g type A the d i f f e r e n c e i n d i s e a s e l e v e l s i s not ficant. and  1:500  compared.  The  skewness i s a l s o made e v i d e n t when the  r a t i o s and  the  1 , 0 0 0 : 1 and  1:1,000 ratios  signi500:1  are  I n a l l c a s e s i t I s the r a t i o w h i c h f a v o r s mating  t y p e a t h a t a s s o c i a t e s w i t h the l o w e r d i s e a s e  level.  FIGURE  1.1  A  A to a sporidial ratio FIGURE 1 . 1 . DISEASE LEVEL, AS MEASURED BY THE PROPORTION OF MAXIMUM POSSIBLE PERCENT OF BARLEY PLANTS SMUTTED BY USTILAGO HORDEI (AMONG THE CONTROL PLANTS— THOSE INOCULATED WITH A 1:1 SPORIDIAL MATING-TYPE RATIO) IN RELATION TO MATING-TYPE RATIO OF THE INOCULUM '  31  A l t h o u g h the p o i n t s i n t h i s f i g u r e r e p r e s e n t averages o f . t h r e e o r more e x p e r i m e n t s , the skewness was  shown con-  s i s t e n t l y i n a l l the s e p a r a t e e x p e r i m e n t s . At the extremes of t h e c u r v e , where A:a r a t i o s o f 10,000:1  p l a n t was  and 1 : 1 0 , 0 0 0 were t e s t e d , o n l y one d i s e a s e d found.  In accordance w i t h the skewness,  this  s i n g l e d i s e a s e d p l a n t r e s u l t e d from i n o c u l a t i o n w i t h t h e 1 0 , 0 0 0 : 1 i n m i x t u r e of A t o a. The number o f c o l o n i e s ( o v e r the t o t a l examined) w h i c h showed the m a t i n g - t y p e o f t h e m i n o r i t y c u l t u r e when 1 0 0 : 1 and 1 : 1 0 0  m a t i n g - t y p e m i x t u r e s were made and  sampled a t v a r i o u s times- i s presented" i n T a b l e 1 . 2 .  These  d a t a show t h a t when s p o r i d i a a r e mixed t o g e t h e r u n e q u a l l y and m a i n t a i n e d JLn v i t r o , the r a t i o s do not change a p p r e c i a b l y toward l e s s d i s p a r i t y o v e r a 3-day p e r i o d . D. DISCUSSION I n q u a l i t a t i v e t e r m s , one would expect t h a t i f t h e e f f e c t i v e number o f s p o r i d i a i s l a r g e , so t h a t r e l a t i v e l y many s p o r i d i a have the p o t e n t i a l of f o r m i n g d i k a r y o n s and of t a k i n g p a r t i n a s u c c e s s f u l i n f e c t i o n which r e s u l t s In s m u t t i n g , then a r e d u c t i o n i n the percentage o f d i s e a s e d p l a n t s s h o u l d n o t be r e a l i z e d u n t i l r a t h e r d i s p a r a t e r a t i o s of the two m a t i n g types a r e used.  Likewise, I f  t h e e f f e c t i v e number i s s m a l l , t h e number o f p l a n t s  showing  32  TABLE 1 . 1 THREE SEPARATE ESTIMATES OP THE EFFECTIVE SPORIDIAL NUMBER BASED ON THREE SPORIDIAL RATIOS AND THEIR RESULTING LEVELS OF INFECTION  Sporldial r a t i o used*  Infection Level (proportion of control)  100:1  Calculated E f f e c t i v e Number .  0.643  500:1 1,000:1  103  0.331 0.175  201 195  *A c o m b i n a t i o n o f t h e r e c i p r o c a l r a t i o s o f A and a s p o r i d i a  TABLE 1 . 2 THE NUMBER OF MINORITY SPORIDIA OVER TOTAL COLONIES, AS SHOWN BY THEIR MATING-REACTIONS, OF TWO CULTURES WITH UNEQUAL SPORIDIAL RATIOS SAMPLED AT FOUR DIFFERENT TIMES AFTER M I X I N G  Time o f Sampling (hrs.) 0 7 24 72*  1 E3a:100 . 1/54 0/54 2/54 0/55  14A  Sporldial  1  .  •Sampled 48 h r s . a f t e r 50 ml o f f r e s h medium was added t o each c u l t u r e .  Ratio I4A:100  1/55 0/54 0/55 0/54  E3a  33  showing smut s h o u l d drop o f f r e l a t i v e l y q u i c k l y as t h e r a t i o s increase.  T h i s i s because some of t h e seeds,  w h i c h would o t h e r w i s e become smutted p l a n t s i f I n o c u l a t e d w i t h t h e u s u a l 1*1 m a t i n g - t y p e m i x t u r e , w i l l , a t h i g h r a t i o s , f a i l t o r e c e i v e s p o r i d i a o f the m i n o r i t y m a t i n g type.  S i n c e a s i g n i f i c a n t d e c r e a s e i n t h e p e r c e n t of  smutted p l a n t s does n o t o c c u r u n t i l t h e r a t i o r e a c h e s 100 to  IkA t o 1 E 3 a s p o r i d i a on t h e one hand, and 5 0 0 E 3 a 1 IkA on t h e o t h e r , i t would seem t h a t the e f f e c t i v e  number must be r a t h e r l a r g e .  The r e l a t i o n s h i p used i n i t s  c a l c u l a t i o n i s an i n t u i t i v e one.  From t h e p e r c e n t a g e o f  smutted p l a n t s shown by t h e m a t e r i a l i n o c u l a t e d w i t h t h e 1 : 1 m a t i n g - t y p e m i x t u r e , one s u b t r a c t s t h e p r o b a b i l i t y p e r seed ( o n t h e average) o f m i s s i n g t h e m i n o r i t y m a t i n g t y p e , t h i s p r o b a b i l i t y b e i n g f i r s t t a k e n t o a power e q u a l t o t h e e f f e c t i v e number.  One w o u l d e x p e c t , t h e n , t h a t i f t h e  number o f a v a i l a b l e s p o r i d i a i s l a r g e r , t h e p r o b a b i l i t y o f n o t i n c l u d i n g t h e m i n o r i t y type w i l l be s m a l l e r f o r a g i v e n s p o r i d i a l r a t i o , and v i c e v e r s a .  The use o f average p r o -  b a b i l i t y i s v a l i d because l a r g e numbers o f p l a n t s arei n v o l v e d i n each c a s e . An a l t e r n a t e way to i l l u s t r a t e the e x p e c t a t i o n I n v o l v e d I s seen i n F i g u r e 1 . 2 , w h i c h d i s p l a y s the r e l a t i o n s h i p between s p o r i d i a l r a t i o and e f f e c t i v e number when three separate expectations ere considered.  When a l o g - l o g  34  p l o t I s used, t h e s i z e o f the e f f e c t i v e number n e c e s s a r y t o o b t a i n each o f t h r e e p r o p o r t i o n s o f maximum smut; 0 . 9 5 , 0 . 5 and 0 . 0 5 , I n c r e a s e s i n a l i n e a r f a s h i o n as t h e s p o r i d i a l r a t i o becomes more d i s p a r a t e .  The t h r e e observed  estimates  o f t h e e f f e c t i v e number a r e a l s o p l o t t e d a c c o r d i n g t o s p o r i d i a l r a t i o and p r o p o r t i o n o f t o t a l p o s s i b l e p l a n t s smutted.  The e f f e c t i v e number e s t i m a t e s a r e then o b t a i n a b l e  v i s u a l l y by o b s e r v i n g t h e a b s c i s s a l v a l u e s o f t h e t h r e e points. W h i l e I t i s p o s s i b l e t h a t o t h e r more complex approaches t o t h e d e t e r m i n a t i o n o f t h e e f f e c t i v e number might y i e l d more^ p r e c i s e e s t i m a t e s , f o r the purpose o f t h i s study t h e p r e c i s i o n a f f o r d e d by t h i s r a t h e r s i m p l e r e l a t i o n s h i p I s c o n s i d e r e d t o be adequate. One can o n l y s p e c u l a t e about t h e cause o f t h e asymmetry of decrease i n smutting f o r corresponding r e c i p r o c a l r a t i o s . . At r o u g h l y maximum asymmetry,, a s p o r i d i a l r a t i o o f around 2 5 0 E 3 a t o 1 I 4 A produces t h e same d i s e a s e r e d u c t i o n as a r a t i o of 100 I 4 A t o 1  E 3 a . The s i m p l e s t e x p l a n a t i o n f o r t h i s I s  t h a t , under p l a n t i n g c o n d i t i o n s , seedborne E 3 a s p o r i d i a do n o t s u r v i v e as w e l l as I 4 A s p o r i d i a .  There I s no r e a s o n t o con-  c l u d e t h a t t h i s I s m a t i n g - t y p e r e l a t e d , s i n c e t h e two h a p l o l d s a r e known t o be g e n e t i c a l l y d i f f e r e n t .  Another p o s s i b i l i t y  I s t h a t t h e two m a t i n g - t y p e s may n o t be p h y s i o l o g i c a l l y  PROPORTION OF MINORITY MATING-TYPE (1-P)  M O  a 3  3 2  i 11 miii  S  8  i 11 miii  Q  2  I  o  *  o  ^  iiniwr i i n i i i i r i i i n i n r i in  M o w  M  D >  t» 8*  36  equivalent.  If,  i n i t i a t o r  dikaryosis,  of  There mate  may  that  a  w i l l  as  be  low.  which  of  a  are  that  very  some  majority  make  the  actual  and  infection.  substances the  and  a  are  In  of  could  of,  be  these  of  As  fungi,  w e l l ,  by  two  explained  or  s e n s i t i v i t y  w i l l  eliminate  one  an for  to  some  of  as  many  nothing  the  that  the by  these  effect  the  minority  would the  would  be  underestimate  of  dlkaryon  formation  conjugation-inducing  unequal such  ratios  of  produced when  is  minority  While  mating-types,  by  to,  a  trigger  available  the  as  f a l l The  e s t i work  This  number  reciprocal  this  I965).  conjugate.  i f  In  suggests  (Bandoni,  skewness.  mating-type  with  substance(s)  effective  produced  work  the  number  r a t i o .  insufficient  sporidia  be  unequal  s p o r i d i a would to  made  conjugation  species,  related  is  is  the  effective  disparate  in  less  infrequent  could  lines  regarding  a  this  sporidia  number  curve  a c t i v i t i e s A  in  calculated  the  of  of  the  very  conjugation-inducing  sporidia  to  why  determine  assumption vfhlch  for  group  A mating-type  could  reason  occurs  mating-type  nearby  the  participate  minority  mean  this  sporidlum at  known  Tremellales, amount  An  frequently  actually  instance,  another  minority  sporidlum is  is  for  the  production  substances.  the  skewness  above  or  Isogenic  p o s s i b i l i t i e s  skewness.  order  to  make  use  of  the  corresponding reciprocal  the  effective  number.  ratios  observations  were  combined  as to  possible, calculate  37  The  two e f f e c t i v e number e s t i m a t e s from the  500:1  and 1 , 0 0 0 : 1 r a t i o s a r e i n good agreement, but the one the 1 0 0 : 1  r a t i o s i s somewhat l o w e r .  A weighted  the t h r e e g i v e s an o v e r a l l e s t i m a t e o f 1 5 5 t h i s i t can be s a f e l y c o n c l u d e d  from  average o f  sporidia.  From  t h a t the e f f e c t i v e number  100.  is at least  Sampling over time from the two shake c u l t u r e s o f reciprocal 100:1  s p o r i d i a l r a t i o s shows c l e a r l y t h a t the  r a t i o s do n o t d e c r e a s e  i n t h r e e days t i m e .  I f one assumes  t h a t something s i m i l a r o c c u r s I n I n o c u l a t e d and p l a n t e d t h e n t h e r a t i o s must r e m a i n unchanged d u r i n g the f i r s t days o f g e r m i n a t i o n .  three  T h i s i s the c r i t i c a l p e r i o d f o r i n f e c -  tIon- by U s t l l a g o h o r d e i ( A p p e l and Gassner, 1 9 0 7 ) . also indicate  seeds,  Results  t h a t t h i s i s t r u e even i f , a f t e r I n o c u l a t i o n ,  t h e s p o r i d i a a r e a b l e t o d i v i d e s e v e r a l times more. d a t a s u p p o r t t h e v a l i d i t y o f the concepts  These  here employed t o  e s t i m a t e t h e e f f e c t i v e number, f  The c o n c l u s i o n t o be drawn from these experiments  is  t h a t v i r t u a l l y a l l seeds a r e making e f f e c t i v e c o n t a c t w i t h the fungus when the inoculum mating-type  ratio.  i s composed of the normal  1:1  I f i t Is c o n s e r v a t i v e l y estimated that  1 0 0 s p o r i d i a a r e p o t e n t i a l l y c a p a b l e of t a k i n g p a r t i n d i k a r y o n f o r m a t i o n and i n f e c t i o n ( r e s u l t i n g i n d i s e a s e e x p r e s s i o n ) o f a s i n g l e b a r l e y seed, and a l l o w i n g f o r  38  variation  due  to  sampling  in  the  the  111  ratio  the  two  mating  extremely f a i l  to  small.  show  ciable.  is  not  inoculum  the  conclusion  and  when  such  or  "natural  In  out w  that  of  the  are  the  resistance  however,  of  numbers  of  plants  always  i t wild  quite  by  for  the  might  is  also  operate  Such resistance and  may  not  having  represent  barley  a  to How  indicated  appears bred  remnant to  of  points  not  been  ancestors  be  appre-  factor.  is  to  disease  and a  of  which  capacity  dikaryons,  from  one  expected  resistance  study.  of  is  determined  resistance  crop,  probability  potential  infective  host  this  the  deviation  absent  nearly  that  entirely  the  t o t a l l y  practice  mean  barley, of  being  produce  host  results  universal into  to  (accidental  inoculum),  disease  must  the  the  In  the  This  expression  by  types  error  U.  of  to  be  either the  hordei.  39  PART  II  T H E RELATIONSHIP BETWEEN TWO ASPECTS O P DISEASE EXPRESSION. A . INTRODUCTION A basio has  been  tenet  frequently  importance.  It  is  of  the  Ignored that  One  type  measured  the  percentage  least  one  culm.  It  in  s p o r u l a t i o n by  pointed  out  in  combinations s a r i l y  of  even  though  standpoint form  of  the of  fungus  resistance  at  one  maturity.  severity.  showing  smutted  smut  spike).  by  resistance  the  review, the  the  Yield  second  smutting within It  can  It  is  on  smutted  be  measured  called in  plants  is  loss but  this  is  type  of  plants  at  plants As  resistant"  not  neces-  seedlings  sporulate;  reproductivlty,  of  in  is  disease  " t o t a l l y  mycelium  plant.  The  smut  be  and  prevented.  in  minor  can  proportion of is  smuts  of  plants  showing  pathogen  not  cereal  considered  entire  from.entering  indeed.  infected  of  of  between-plant  than  smut,  does  pathogen  curtailment  culms  and  infected  involves  disease  called  the  either  the  least  plants  l i t e r a t u r e  host  prevented  growing within  of  be  process  aspects  n o t h i n g more  the  at  manifested  can  and  which  is  is  severity  or  two  discerned. as  disease  or  may  result,  from an  from  the  effective  resistance known  to  be  within-plant  terms  of  (plants  per with  cent at  of least  40  I n t h e p a s t , b r e e d e r s and p a t h o l o g i s t s have d i f f e r e d In t h e measure t h e y chose t o employ I n d e s c r i b i n g severity.  Table 2 . 1 presents  measure used by many w o r k e r s . but  disease  a summary o f t h e b a s i s o f The l i s t I s n o t e x h a u s t i v e ,  i t i s probably representative.  The p l a n t b a s i s , as t h e y  used I t , i s a d i r e c t measure o f t h e f i r s t type o f r e s i s t a n c e discussed  above.  The head b a s i s r e f e r r e d t o i n t h e t a b l e  Is n o t s i m p l y a measure o f t h e second t y p e , however.  Measured  as smutted heads over t o t a l heads on a l l p l a n t s , i t i s r e a l l y a compounding o f b o t h t y p e s o f r e s i s t a n c e .  Few w o r k e r s have  a t t e m p t e d t o l i m i t t h e i r measure o f p e r c e n t o f smutted heads t o p l a n t s w h i c h were known t o be smutted.  Some went so f a r  as t o count b o t h p e r c e n t o f p l a n t s and p e r c e n t o f heads smutted.  One c a n n o t s a f e l y assume, however, t h a t  simple  d i v i s i o n o f t h e p e r c e n t a g e based on heads by t h e p e r c e n t a g e based on p l a n t s w i l l g i v e an u n e q u i v o c a l plant severity.  measure o f w i t h i n -  T h i s would o n l y work i f i t were a c c u r a t e l y  known t h a t smutted p l a n t s produce as many culms as nonsmutted p l a n t s .  As P a r t I I I w i l l show, t h i s was u s u a l l y  not t h e c a s e . C o r r e l a t i o n s between p e r c e n t o f p l a n t s and p e r c e n t o f heads smutted have been shown. obtained  a high c o r r e l a t i o n ( r =  Clark et a l . 0.7^1)  (1933)  between t h e p e r -  c e n t a g e o f p l a n t s and o f heads w h i c h were b u n t e d , f o l l o w i n g l n o o u l a . t l o n o f wheat w i t h T. c a r l e s .  They c o n c l u d e d t h a t ,  41  TABLE  2.1  THE B A S I S OF MEASUREMENT OF SMUT REACTIONS USED BY MANY PATHOLOGISTS AND BREEDERS WORKING WITH CEREAL SMUTS Plant Reference  Basis  Aamodt a n d J o h n s o n ( 1 9 3 5 ) Batts (1955b) B a t t s and J e a t e r ( 1 9 5 8 ) Brandweln (1940) Brlggs (1926,1927) Cherewlck (1958) Churchward ( 1 9 3 7 - 8 ) Clark et a l . (1933) Ebba (1974) Faris  (1924a,  1924b)  F a r i s (1934) Gaines (1923) G a s k i n and S c h a f e r ( 1 9 6 2 ) G r i f f i t h e t a l . (1955) Hallsky (1956) Heald  (.19.21.).  Heyne a n d H a n s i n g ( 1 9 5 5 ) Holton (1964) H o l t o n and H a l i s k y ( i 9 6 0 ) H o l t o n and R o d e n h i s e r ( 1 9 4 2 ) Hubbard and S t a n t o n ( 1 9 3 4 ) Johnston (1934) Jones e t a l . (1940) K o l k (19307 Leukel (1936) Mather and H a n s i n g ( i 9 6 0 ) Metcalf (1962) M e t c a l f and H e l g a s o n ( 1 9 6 2 ) M i d d l e m a n a n d Chapman ( 1 9 4 1 ) Oort (1939) Oort (1947) P e r s o n and  Cherewlck ( 1 9 6 4 )  Poehlman ( 1 9 4 9 ) Poehlman and C l o n l n g e r ( 1 9 5 5 ) Popp ( 1 9 5 D Reed ( 1 9 2 9 , 1 9 3 8 ) Reed and F a r i s ( 1 9 2 4 ) Reed and S t a n t o n ( 1 9 3 8 ) Reichert (1930)  R o d e n h i s e r and  Ross e t a l .  Holton  (1948)  (1942)  Head a  Basis'  x  Both x x  x x x  3  c  x x°  x  x  x  x x x x x° x x x x x x x  x x x,  x x x  x x x x x x  x  x  x x  c  x x x  x  42  TABLE  2 . 1  (continued)  Plant Basis  Reference Ruttle (1934) Sampson e t a l . (1927) S c h a f e r e t a l . (1962b) S c h a l l e r e t a l . (I960) Shands (1956) Sldhu andPerson (1972) Smith ( 1 9 3 2 a ) Smith andBressman ( 1 9 3 Swinburne (I963) Tapke ( 1 9 2 9 , 1 9 3 1 ) Tapke ( 1 9 3 7 , 1 9 4 5 , 1 9 5 2 , 1 Tapke ( 1 9 3 8 ) Tapke andBever (1942) Taylor and Zehner ( 1 9 3 1 T e r v e t  Thomas  X  X X 1 )  9 5 5 )  )  ( 1 9 4 0 , 1 9 4 1 , 1 9 4 4 )  andPerson  Percent  ^Percent  Both x  o f plants o f heads  ©Different  x x x X  ( I 9 6 5 )  Tingey endTolman ( 1 9 3 4 ) T i s d a l e andTapke ( 1 9 2 4 ) Waud a n d M e t z g e r ( 1 9 7 0 ) W e l l s (1958) W e l s h (1932) W e s t e r n (1936) W i l l i a m s a n d Verma (1954) Woodward a n d T l n g e y (1941)  a  Head Basis  showing showing  measures  were  x  x  ;  * x  •  o n e o r more  smutted  head.  smut. used  i n different  sections  o f work.  as a s e l e c t i o n c r i t e r i o n I n p l a n t b r e e d i n g , head c o u n t s would be n e a r l y as r e l i a b l e as p l a n t c o u n t s , I n s p i t e o f t h e f a c t t h a t the f o r m e r was  c o n s i s t e n t l y lower than  l a t t e r In I d e n t i c a l m a t e r i a l .  E u t t l e (19 3*0  the  a l s o found a  s i m i l a r c o r r e l a t i o n I n a s i n g l e b a r l e y - U . h o r d e i combination.  Tapke ( I 9 2 9 , 1931)  r e c o r d e d b o t h head and p l a n t smut  p e r c e n t a g e s f o r b o t h f o u r wheat c u l t i v a r s I n o c u l a t e d w i t h U. t r l t l c l and two b a r l e y c u l t i v a r s I n o c u l a t e d w i t h U. nuda. The  d a t a show a s t r o n g c o r r e l a t i o n between p e r c e n t of p l a n t s  and p e r c e n t of heads s m u t t e d .  Tapke d i d not d i s c u s s t h i s  f i n d i n g , however, I n h i s p a p e r . percent  o f smutted heads was  among o t h e r r e a s o n s ,  Gaines ( 1 9 2 3 ) d e c i d e d  t h e p r e f e r a b l e measure b e c a u s e ,  I t gave a more r e a l i s t i c e s t i m a t e  the Impact w h i c h smut has on a c r o p . l a t e r , he was  that  of  As w i l l be mentioned  aware o f t h e c o r r e l a t i o n as w e l l .  Brlggs  ( 1 9 2 6 ) and Churchward (1932-3) argued t h a t f o r g e n e t i c s t u d i e s the p l a n t , not t h e c u l m , must be m a i n t a i n e d unit.  as  the  I n t h e i r g e n e t i c s t u d i e s , even though t h e y , t o o , were  aware o f the c o r r e l a t i o n , t h e y used the p l a n t b a s i s . t h a n c o u n t b o t h head and p l a n t s m u t t i n g p e r c e n t a g e s ,  Bather some  w o r k e r s t r i e d t o g e t an I n d i c a t o r o f w l t h l n - p l a n t d i s e a s e s e v e r i t y i n a n o t h e r way:  b y r e c o r d i n g p l a n t s as e i t h e r  diseased, p a r t i a l l y diseased, or healthy.  Gaines ( I 9 2 3 )  and Churchward d i d t h i s w i t h wheat-T. c a r l e s .  With oats  and b o t h smuts, W e l s h ( 1 9 3 2 ) used t h i s method t o e v a l u a t e  the  overall  the  above  of  resistance  works  diseased  plants. this  plants  Since  purpose  should  be  (1938)  used  Involving both  oat  l a t i o n  of  in  Is  percent  smutted  Is  to  plants  a  At  disease  in  not  r e a l l y  smutted  plants),  Independent  because  the  within-  those  even  Barring  be  percent  culms  i f  the  i f  a  smutted,  of  measure of  correlation of  smutted are  l o g i c a l l y  cannot  the  be  frequency  frequency  of  disease  correlation  severity, positive  variables,  of  scoring  within-plant  disease  ;of  corre-  numbers  They  negative  surprising  non-independent  and  a  a  higher  s h o u l d be  between-plant  would  the  plants,  vary.  and  It  higher  races  number  of  things  i960).  the  the  percent two  study  negative  large  Torrie,  not  smutted  these  Eeed  qualitative  establish and  five  type  for  results  extensive  and  and  on  does  to  abundant the  a  unless  plants  because  (Steel  plants,  culms  v a l i d  or  percent  diseased  of  of  this  In  negative.  total  best,  case  between  an  smutted  severity,  involved.  of  a  nonparametric  are  be  between  of  plants.  gives  a l l  unlikely,  plants  scoring  evidence  smutted  t i o n  than  presented  Independent  between  of  rather  He  (on  severity  sort  seen  however,  smuts.  percent  smutted  studies,  Inconclusive  no  particularly  and  It  of  not  In  p a r t i a l l y  cultivars  observations  expected  the  of  oat  within-plant  not  were  be  eight  severity  heads  cultivars.  frequency  of  same  between  between  s i x  correlation  data  any  the  a  and  the  Judged  p a r t i a l l y smut  could  of  that  was  not  which c o r r e l a -  i s ,  percent  found.  ^  There  Is  no a p r i o r i  percent  o f smutted  reason,  culms  should  n o t be Independent  Hence,  the empirical  between  these  l a t i o n  of within-  v a l i d l y  presented  presented and  no date  Jeater  (1958)  presumably, In  only  gated. bunted  called  of the  attention  to the possible disease  severity  evidence  of It.  Although  In  In favor  support  concluded  of  i t , Batts  from  earlier  which  that  plants,  of bunted  b,  heads  the overall  i t  c,  percent  of  i n v e s t i totally  the proportion  and a value, on p a r t i a l l y  they  exist3^  properly  the proportion  he c a l l e d  and  literature and,  determined  plants,  corre-  and Batts  (1955b)  own o b s e r v a t i o n s ,  (1923)  determined  relationship  and between-plant  fchelr  bunted  smutted.  valid.  Gaines wheat  plants  of plants  was t h e r e l a t i o n s h i p  proportion  the  from  Is  why t h e  diseased  of percent  Investigation  hand,  two Instances  p a r t i a l l y  then  on obviously  two variables  Some w o r k e r s  on the other  a, which bunted  o f bunted  of  was the  plants. heads,  He  d , by  relationship! d= a b + c  The  Important  was  lower  thing  on the four  four  susceptible  this  i s good  in  showed  that  cultivars, that  Oort what  he noted  resistant  evidence  h i s material.  t r l t l c l ,  i s  that  cultivars  the value than  ( O . 6 7v s . O . 2 5 ) . a positive  (1947),  appeared  It  t o be a very  a  was on t h e  Qualitatively,  correlation  working with  of  wheat close  existed and U, correlation  of  within-  which  and  Involved  rather  small  analysis. in  in  the  objective this  many  His  which  wheat  most was  the  in  a  disease  severity  c u l t i v a r s .  cases  and  only  correlation  and  study  was  manner  he  His  in  sample  Included  no  found  the  in  investigated  similar  to  a  sizes  are  s t a t i s t i c a l  as  that  study  literature  the  main  undertaken  in  thesis. The  as  between-plant  broad  a  possible, severity c a l l y  purpose  of  this  sampling of whether,  of  in  disease  variable,  study  barley this  (2)  and  to  U.  determine,  hordei  host-parasite  reaction  and  was  within  correlated  with  genotypes  system,  plants  using  is  as  the  (1)  geneti-  severity  between  hordei  dikaryons  plants. B.  MATERIALS  AND  Twelve were  used  which  METHODS  barley  i n  this  study.  showed  smut  in  plants  were  of  o r i g i n a l  13  These  were  the  (1942). North  Dakota  tained. of are  cultivars  smut from  The  used.  at  The  Only least  smut  genotypic  percent  obtained  as  eight i t  America  where  except  the  they  have  readily  three  inoculated representatives by  samples  represent  possible  combinations  described  teliospore  cultures  was  of  Included  physiological races  other  North  those  U.  dikaryons  University,  as  21  five  State  biotypes  and  Tapke from  been  main-  as  wide  a  to  obtain.  prefixed  n  Et",  range A l l which  4?  are  from  three  Of from I.  the For  were  the  the  both  four  products  petri  dish  Blocks s t e r i l e spores  cover were  suspensions per  ml  s l i p .  a  drop a  to  In  small  test  teliospores  were  included  agar  blocks  with  their  22°C  for  by  which  minated. with  a l l  section, and  an  time On four was  12 most  each  hours of  s p o r i d i a l selected.  upward-bent  fine  was  following complete  After  a  t e l i o -  to  these  tellospore  suspension  agar  block rate  so  drop  of  then  older  teliospores  deFonbrune  glass  needle,  the  was  PastoTas* teliospores  10-100 The  Incubated  for  accessible  a  a  the  from  germinated  Using  achromycin  transferred.  longer  suitably  with  that  (somewhat  viable  mg  at  samples), had  ger-  tellospore,  for  micro  d i s -  micromanipulator four  2  mm  22  (10  each  products  adding  wayi  agar.  suspension  adjusted  5-10  of  different-  tubes.  were  a  two  of  teliospores  the  block  each  of  20  of  20  the  layer  germination  In  These  from in  haplolds  suspensions  each  was  section  aqueous  of  concentration  in  on  centre the  used  placed  the  used,  about  thin  of  on  derived  "selflng"  derived  drop  Depending  was  constituent  derived  and  ml  Ethiopia.  tellbspore.  achromycin  pipette. the  a  cut  Five  of  the  with  were  prepared  HJJO),  transferred  2  one  through  were  In  were  the  tetrads  20  poured mm  15  which  single  tetrads  was  about  a  produced  of  The  I4A  made  used,  dikaryons,  from  thus  here  and  20  derived  teliospores. A  E3a  other  were  collections  dikaryons  21  haplolds  dikaryons the  separate  primary  48  sporidia of  the  were  four  mycelium edge.  drawn  sides  was  sporidia.  and,  after  Into  screw-cap  s i l i c a of  In  gel  each  which  were  were  used  selected  to  the the  the  size  amount  of  at  formed  singly  tested  for  of  the  pro-  near  from  to  each  the the  fresh  plates  mating-type  s p o r i d i a were  Two  of  the  random  to  form  were  as  very four  put  dry cultures  the  dikaryons  study.  combination  was  set  were  of  minimum number within-plant at  the  and  smutted  severity Only  30.  overall  space  of  described  each with  In  order  to  plants,  for  those  combinations  30  available  concerning  the  the  number  of  inoculated  seeds  determined  by  using  the  P  = the  percentage  n  = the  number of  of  amount  of  needed  smut for  time  which  would  genotyplo three  percent  99  in  or  more  certain  of  where  information  to  expected,  be  planting  was  relationship!  (1  certain  be  recording plants  i n  plants  experiment  Included.  was  where  had  to  on  s l i p ,  fine-textured,  f i e l d  for  obtaining  cover  Inoculation  examined  culms  position  amounts  the  and  one  I.  available, be  were  storage.  throughout  Considering relation  the  transferred  containing  treatment  section  on  Small  long-term  tetrad  Their  colonies  growth, I.  tubes  for  Seed in  were  Part  promycelium,  block.  v i s i b l e  They  the  d i r e c t l y  s u f f i c i e n t  described  from  the  days,  four  as  of  recorded  3-k  In  away  of  P)  n  =  plants  plants  obtaining  0.99 showing  needed at  to  least  be one  smut; 99  percent  smutted  plant.  49  The a  net  result  particular  the  was  genotypic  smutting  row,  The  of  seeding was  rate  depending  amount  the  in  where  the  samples  at  fewer  of  plants  smutted cally  was  was  in  when,  expected  of  the  f i e l d  for that  the  seed  during  except  a  on  given  In  C a l i -  winter  that  the  spikes  had  the  combination  each. the  15-ft. per  8nd  at  genotypic rows  in  seeds  cultlvar  several made  the  90-150  from  particular  identical  high  plants  were  one  and  given  wlthin-plant  recorded  percent  sere  carefully  plants  be  varied  of  planted  low.  v i a b i l i t y  blocks  least  adequate  Smutted  to  a  i t  planted  p l a n t i n g was  were  Generally,  with  be  exhibited by  were  were  rows  months, were  20  long. Data  were  were  percent  1-2 a  would  seeding  Usually  procedures  feet  on  rate.  fornia,  of  seeds  combination,  seeds  t i l l e r i n g  planted  more  percentage  Inoculated rows.  that  when  of  plants  available, enough  so  were  to  When  available,  40-50  they  were  severity.  be  not  sample  A l l  and  was  plants  used  few  cases of  Tbrrle, on a  not  were  in  determining a  where  plants  were  s t a t i s t i -  i960). t i l l e r  examined.  recorded,  in  on  basis  l i m i t i n g and  also  plants  emerged. based  sizes  examined  time  were  the  percentage  (Steel  pulled.  t i l l e r s  In  the  that  nonetheless  two  s m u t t e d was  plants.  300  which  a l l  but the  row were  the  Plants  for  reasons  degree pulled  of  50  and  recorded  avoid also  biased  going  sampling.  recorded When  been  before  on  a  head  the  to  the  Incomplete  single  smutted  calculated,  on  plant and  next  row, i n  smutting  of  order  to  spikes  was  basis.  smutted  correlation  plant  analyses  percentages were  done  had  by  computer. C.  RESULTS Table  21  smut  is  2.2  dikaryons,  a  matrix.of  showing  observed.  The  mine  combinations  which  Investigate. gave  less  basis)  work  As,shown  than  was  per  1.0  not  included  negative  and  low  eight  the  barley  of  of  the  by  his  in  readings  work  Also,  was  taken  where  there  cient  data  included. other tion  while  was were  as  5  less  with  cent  If  was no  on  work  or'Vantage*)  Per  Information  Ebba.  (his  practical  nonetheless  combinations  table  lower  plants per  obtained  expected  obtained  was  deter-  the  whioh  per  many  to  row  of  the  races  13  and  did  not  include,  are  the  findings  l i m i t  that  smutting  through  Information  Thus, for  were  genotypes  head  plants so  to  combination a  and  which  consulted  smutted,  cent  cultivars  reactions  used  study.  the  than. 5  any  (he  the  cultivars  ^s  barley  parasite  data,  this in  w  and  smut  ' C o n q u e s t , ' ' G a t e w a y J *Keystone? Tapke.  disease  host  cent  12  (19^5)  Tapke of  the  in In  the  present  three  cases  smutted, they for  personal available  of  s u f f i -  could  some  be  of  the  communicaabout  a  51  combination,  5-8  rows  planted.  the  table,  not  part  In of  different the  same  Thus  the  races haplold  their  (and  there  matrix. or  more  later  are  While  products  possible  as  genetic  necessary)  three  they  c o l l e c t i o n s ,  If  represent  they  shown  points  are  not  TABLE  is  which  are  crosses  of  crosses  elsewhere  significance  were  in not  of  the  table.  discussed.  2.2  COMBINATIONS OP HOST C U L T I V A R AND PATHOGEN D I K A R Y O N , AND D I S E A S E R E A C T I O N S OBSERVED  Barley Cultlvar Conquest  Ustilago HI  R2  -  -  B3  hordei R4  dlkaryon R5  3  Ro  2.0°  R7  „  19.0 Excelsior  -  L  53.2  L  50.6  87.4  L  -  20.7  -  -  Gateway Hannchen  —  83.3 Himalaya  -  L  -  66.3 -  L  45.8  89.8 Keystone  L  ;..... '.1  Lion Nepal  Odessa  b  -  -  27.0  34.6  . t .  71.2  80.8  -  55.5  57.5  95.5  96.7  91.9  47.1  59.5  42.3  37.2  22.9  72.6  94.6  69.0  75.2  70.4  39.9  -  -  31.5  b  -  L  22.1  -  64.4 Pannier  3.9  L  -  12.6  67.5 56.2  -  18.9  b  -  53.7 -  -  b  25.0 52.8 L  79.0 Trebi  7.6  L  L  30.6 Vantage  -  6.8  31.0 -  -  12.1  L  44.7 -  -  -  b  52  TABLE 2 . 2  (continued)  Barley Cultlvar  w  R9  Conquest  -  L  Excelsior  -  Gateway  -  Hannchen  •  26.6 70.8  -  -  28.2  78.3  Himalaya  6.0  Lion  -  Nepal  L  23.6 59.1  b  -  -  L  -  -  -  58.6  32.3 71.0  35.2 69.9  32.3 72.3  64.4  -  10.3  -  53.0 70.5  18.1  76.0  5.9 70.0  5^.1"  40.7  55.8  I7.^  18.1  48.4 82.5  81.0  27.0  -  5.3  b  -  24.2  4.6 65.3  24.1  30.7 56.0  49.3  53.** 96.6  53.5 71.9  5*U8 77.9  29.4  -  -  L  Trebi  -  -  Vantage  -  24.0  60.0  27.6  L  L  b  42.1  Pannier  Etl  L  6.8  86.1  Keystone  Odessa  Ustllego hordei d i k a r y o n HI 2 R13 R l l R10  73.1  26.7 71.^  61.5 93.*»  83.2  44.6 86.6 L  71.**  -  46.8  83.6  -  L  37.6  85.9  9.0  24.8  84.1  as.4  b  35.7  80.7  —  —  95.7  7.6  44.3 69.5  46.1  58.7 66.8  40.2  60.5  L  -  6.8 13.8 42.1 81.0  b  2.8  32.2  44.6  77.**  53 TABLE  2.2  Barley Cultlvar Conquest  (continued)  Et2  Et3  -  -  Ustila.aro hordei vlv2 Uh6 Uhl2  -  -  23.0  55.0 Excelsior  —  —  Gateway  7.9  -  Himalaya  -  -  Keystone  2.7  Hannchen  72.1  56.3  85.6  -  Nepal  L  30.3  Odessa  81.9  67.  l 81.4  b  Vantage  a  b  14.8  53.0  32.0  85.7 91.0  (V3XUh-6)  14.7  b  24.0  b  46.2  46.0  b  76.8  8.5 5 3 . 5 52.1  -  10.3  b  2 0 . 6 19.8 83.2 7 5 . 2  7.4  55.1 26.8 53.9  19.7  47.3  95.2  b  48.2  36.0 76.2  -  -  -  11.2 53.9  -  95.6  29.7  85.3 23.2  66.1  b  :8.0 42.4  (Uh-6xUh-12)  61.7  b  67.7  61.6 46.9 b  27.8 72.6  b  32.  8  b  48.1  -  b  10.8 50.2  I6.6  (R5xRll) b  4 8 . l  85.1 b  42.8  Numerlcal values indicate sufficient data f o r analysis. Upper value i s percent o f p l a n t s smutted; lower is p e r c e n t o f smutted culms on d i s e a s e d p l a n t s . - = no smut observed. L = l e s s t h a n 5% p l a n t s s m u t t e d ; insufficient data. High  t i l l e r i n g  plants  b  -  36.5 1 6 . 5  55.6  31.5  46.6  45.5 1 6 . 0 86.9 5 3 . 4  4 0 . 3 62.2  85.7  1 1 . l  •-  77.5  55.6  -  L  24.0 18*6  30.1  5.9  33.9  L  -  Pannier Trebl  b  13.4b 76.4  28.6  Lion  12.6  mm  •  L  Additional  d i k a r ?•on v3 EXI  b  5*  Before done,  a  to  the  average  be  smutted  of  f i r s t  culms  Columbia,  where  was  no  at  and  higher were  Yet  ditions  binations vealed  a  at the  the  was  land  44.3,  was  59*^  was  percent  that  of  or  a  smutted. plants  was  made  when  only  here  the  s i g n i f i c a n t l y  for  a  combination  C a l i f o r n i a was culms  on  of  a l l of  t i l l e r  111  largely  diseased con-  low-tlllerlng  regression  average  4.26  C a l i f o r n i a ,  h i g h - t l l l e r l n g 82  were  culms,  of  find  of  In  percent  smutted  the  there  were  in  under  planting  culms  data  Analysis  negative on  In  example,  B r i t i s h  12.8  locations;  the  of  percent.  plants  the  of  University  average  of  actually  Columbia  At  smutted.  similar  both  Whether  while  of  A  combinations  s i g n i f i c a n t  on d i s e a s e d  at  the  latter  an  between  For  conditions  average  difference  smutted  B r i t i s h mean  were  an  locations.  at  The  produced  culms  t i l l e r i n g  percent  t i l l e r i n g .  percent  71.1  the  both  other  high  plants  planted  29  and  plant  discovered.  C a l i f o r n i a .  the  C a l i f o r n i a .  for  in  was  properly  relationship  and  planted  produced  plants  obtained  plants  two  were  of  In  was  s i g n i f i c a n t  Uh6  random.  culms  lower  the  percentage  of  plant  be  In  Inverse  plants  Uh6  smutted  plants  s i g n i f i c a n t l y  Lion  per  extremely  percent  95.2  smutted  with  to  smutted  There  culms  f e r t i l i z e d  conducive  where  An  Columbia and  highly  culms,  of  could  variation  with.  smutted  inoculated  on  also  on  analysis  involving  dealt  number  B r i t i s h  was  correlation  complication  had  Nepal  the  com-  points  frequency production.  r e -  of When  55  low-  and  however,  h i g h - t l l l e r l n g plantings  were  there  regression  grouping,  (an  considered separate per  was  average  analyses with  this  variable  f e l t  to  be  of  nine  or  data  the  variation  only  thus  plants  with  three  mean  The  variation  the  h i g h - t l l l e r i n g plantings, not  often  average  In  plantings,  both  and  2.1  (expressed  as  the  effect This  to  culms  culms  were  three  of  was  avoid  was  this  planlow  considered.  culms  t i l l e r i n g was a  brought  In  the  out  variance  in  In  was  per  plant.  greater  regression was,  of  deviation  w i t h i n - and for  low-  determining  used  variances  the  the  diagrams  percentages'.).  standard  be  are  2.2  scatter  transformation  of  but  culms  the  way  of  than  of  two  l o w - t i l l e r i n g  more  higher  amount  respectively.  analyses,  units  average  severity  arcsin©  much  of  being  for  nonethe-  found.  Figures disease  not  into  severity.  number or  plant  average  effective  number  in  data of  either  per  minimizing  disease  most  large  of  separately,  in  culms  variation  set,  The  less,  was  the  simplest'and For  more  Division  on w i t h i n - p l a n t  the  the  reduced  each  complication.  because  s i g n i f i c a n t  h i g h - t l l l e r i n g ) .  plant  tings,  no  analyzed  of  (Steel x  and  Hence were  values,  Torrie,  were  scatter  r  h i g h - t l l l e r i n g  very  diagrams  a  strong  disease  genetic  severity  Is  the  i960).  In  close involving  t h o u g h t u n n e c e s s a r y . As  discussion,  within-plant  the  and y  and  between-plant  shall  component indicated.  56 FIGURE 2.1  3 U  to  2S  P©re©nt of  z^gj  Plates  615  Slutted  FIGURE 2.1. CORRELATION SCATTER DIAGRAM FOR 82 BARLEY-USTUAGO HORDEI GENOTYPIC COMBINATIONS PLANTED UNDER LOW-TILLERING CONDITIONS  57  FIGURE 2.2 90  J2 s <3  ?0  s © o  50  3  O  i  E  r  =  o.?6?  10  W  20  Percent  of plants  60  smutted  FIGURE 2.2. CORRELATION SCATTER DIAGRAM FOR 29 BARLEY-USTILAGO HORDEI GENOTYPIC COMBINATIONS PLANTED UNDER HIGHTILLERING CONDITIONS  58  S e p a r a t e w i t h i n - c u l t l v a r and w i t h i n - d i k a r y o n c o r r e l a t i o n s were made on l o w - t l l l e r l n g p l a n t i n g s o f f i v e c u l t i v a r s and t h r e e d i k a r y o n s .  Upon e x a m i n a t i o n , i t appeared t h a t t h e  other combinations d i d not possess s u f f i c i e n t i n f o r m a t i o n ( p o i n t s ) o r s u f f i c i e n t v a r i a t i o n o f one o r b o t h v a r i a b l e s t o w a r r a n t an a n a l y s i s .  The r e s u l t s a r e summarized i n T a b l e 2 . 3 . TABLE 2 . 3  SOME WITHTN-CULTIVAR AND WITHIN-DIKARYON CORRELATION ANALYSES INVOLVING LOW-TILLERING PLANTINGS ONLY  Common C u l t l v a r .. or D l k a r y o n  Number o f P o i n t s  Value of r  Hannchen  10  0.580  Lion  12  0.669*  Nepal  10  0*911*  Odessa  13  0.450  Trebl  10  0.815*  Race 9  7  0.758*  Race 1 3  8  0.762*  vlv2  9  0.500  * S i g n l f l e a n t c o r r e l a t i o n a t t h e 5% l e v e l .  59  Five  of  the  eight  three  which  small  sample  is  l i k e l y  were  correlations not,  vlv2  and  and  lack  or  size  that,  had  the  correlation  and  within-dikaryon  strong plant  would  among  have  be  Of  found In  plants,  as  by-  respectively.  in  a l l  severity measured  It  available,  within-cultlvar  conclusion,  disease  the  explained  information been  groupings.  barley  can  variance,  been  between  significant.  Odessa  s u f f i c i e n t  correlation and  were  there  within by  is  a  a  barley  amount  of  smutting. D.  DISCUSSION In  races  Interacting with  (19^5) was a  comparing  his  obtained.  plant  present were  Tapke.  This  the  while  gave would  different. races  terms  of  also  As had  reductions  virulence,  If  combinations  the  they which  good  present of  however.  were  changed. or  occurred, Tapke  study  A l l  losses  In went  found  qualitative were  on a  than  recorded  head  those the  revealed  gave  l i t t l e  There  er  two  lots  that  seed some  were  simply no  Inby  Gains  undetected  the  obtained  changes  virulence.  on  basis,  combinations  that  detected  Tapke  agreement  the  of  suspect  this  by  A l l  lead  w e l l ,  studied  much h i g h e r .  lower  to  o r i g i n a l  13  always  percentages one  the  results  Tapke  nearly  for  cultivars  f a i r l y  the  were  data  eight  a  those  exceptions,  Trebi  present  r e s u l t s ,  percentages  volving  were  with  Because  basis  some  the  of in  in because  smut  60  were  not  included  virulence either race at  race  least,  6  a  spores  in  lence  (two  second each  found  in  both  admittedly samples  are  in  of  races such  obtained  from  identified Detailed  In  the  long  two  studies.  In as  the  were  by  time,  in  different  between  by  study, Tapke,  end  this the  race  conclude of  that, smut  samples  similar  early  of  and  percent  those  1 9 4 0 s .  were of  to  not  made,  smutting  examination,  quite  used  maintaining  percent  was  that  race  measures  the  on  also  results  casual  v i r u -  consistently  of  the  the  in  i n s t a b i l i t y  remarkably  Tapke  under  can  t e l l o -  products  Based  d i f f i c u l t y  of  f i r s t  environment.  suggested One  quantitative  present  measured  be  the  generally  to  were  races.  uniform.  period  Even  measured  may  in  7 were  due  or  qualitatively  teliospore  heterogeneity  the  "correlation" the  i t  two  were,  differences  virulence  the  and  of  expected  smutted,  been  of  involving  from different  have  Dakota  of  and  could  collected  because  6  in  cultivars),  smutting  of  of  1 9 5 8 )  North  and  poor  sets  notorious  a  races  two  losses  comparisons  primarily  the  q u a l i t a t i v e l y  over  of  reductions  (three  quantitative  sampling,  (Cherewlck, races  Some  dikaryons  the  other  or  combinations  7  using products  these or  small  race  involving races  between  reductions  A l l  Because  test.  tests;  Losses  different  c u l t i v a r s ) ,  time,  Gross  view  seven  unchanged.  two  study.  c u l t i v a r s ) .  existed  the  this  in  combinations  tested  in  occurred  1 1 (two  test,  in  plants  used  the  smutted,  of  evident,  a l l  as  heads  however.  61  The severity plants  Inverse  and  has  the  and  smutting  were  s o i l  than  be  Tingey  assumed  in  average  observed to  disease  t i l l e r  that  influence  percent did  of  they  the  affect  explanation  infected  plant  many  tion the  them w i l l  amount  r e s u l t  are  of  that  some  heads  equal.  Unfortunately, and  concerning embryos.  than  Jeater both  a  become  smutted  Batts  Batts  Nonetheless,  others.  higher  s o i l ,  did  of  of  the  They  show  even  plant,  a  i f  other  a  and their  support  variable  is  smaller  A  Thus, propor-  provides  that  with  the  of are  presented  of  each  also  embryo,  their  but  that  conditions  amounts  hypothesis  the  t r l t l c l  frequency  h i s t o l o g i c a l work r e a l l y  expected  mycelium.  to  higher  ( 1 9 3 9 )  be  suggested  embryo  decrease  smutted,  amount  i t increased  the  by-U.  limited  the  the  affect  ( 1 9 5 8 )  w i l l  heads,  can  not  culms  this  Milan  also  of f e r t i l e  Since  observing  smutted  from  less  smutted  which  plants,  by  levels  on  Jeater  varies  limited  by  s o i l .  on  poorer  smutted.  not  mentioned  and  others,  does  the  accompanied  plants  produced  plants  which on  by  hordei  probably  percentage  by  mycelium  based  disease  produced  that  f e r t i l e  sowing,  wheat  contains  t i l l e r s  of  of  the  possible  i f  were  t i l l e r i n g of  inoculated  d i r e c t l y  was  severity  rate  culms  barley-U,  production  the  of  within-plant  d i r e c t l y  on more  disease  that  between  observed  with  obtained the  and  ( 1 9 4 1 )  obtained  of  within-plant  number  i n d i r e c t l y  were  measurement can  average  been  Woodward  relationship  by  hypothesis mycelium a  simple  In  62  and  p l a u s i b l e explanation  f o r b o t h M i l a n ' s and t h e p r e s e n t  d a t a ( d i f f e r e n c e s I n mode o f i n f e c t i o n o f the two smuts notwithstanding).  I f B a t t s had been a b l e t o s t u d y r e s i s -  t a n c e i n U. t r l t l c l  t  1958)  as was h i s i n t e n t i o n ( B a t t s and J e a t e r ,  he would u n d o u b t e d l y have p r o v i d e d  much a d d i t i o n a l  evidence e i t h e r f o r or against h i s hypothesis. R e g r e s s i o n a n a l y s i s f o r t h e e f f e c t o f average production  on w i t h i n - p l a n t d i s e a s e  tiller  s e v e r i t y was used i n t h i s  work o n l y as a means t o d e t e r m i n e whether t h e d a t a would e f f e c t i v e l y e l i m i n a t e v a r i a t i o n i n average t i l l e r i n g as a c o m p l i c a t i n g f a c t o r i n t h e between- and w i t h i n - p l a n t c o r r e l a tion analysis.  Some problems w h i c h d e t r a c t from t h e r e -  g r e s s i o n a n a l y s i s w i l l be d i s c u s s e d b r i e f l y .  For a r e -  g r e s s i o n a n a l y s i s , one o f t h e i m p o r t a n t i n i t i a l assumptions i s t h a t t h e independent v a r i a b l e i s n o r m a l l y d i s t r i b u t e d ( S t e e l and T o r r l e , i 9 6 0 ) .  The d i s t r i b u t i o n o f average  t i l l e r numbers was d e c i d e d l y b i m o d a l I n t h i s r e g r e s s i o n due t o t h e two v e r y d i f f e r e n t p l a n t i n g environments.  The p o s s i -  b i l i t y c a n be s u g g e s t e d t h a t some o t h e r e n v i r o n m e n t a l f a c t o r c o u l d be c o n t r i b u t i n g t o t h e r e g r e s s i o n . e a r l i e r work d i s c u s s e d  However, from t h e  above, w h i c h s u p p o r t s t h e i n v e r s e  cause and e f f e c t r e l a t i o n s h i p between t h e two v a r i a b l e s , I n s i t u a t i o n s where g r o s s e n v i r o n m e n t a l d i f f e r e n c e s a r e n o t present,  i t Is considered  as p r e s e n t e d .  l i k e l y t h a t the a n a l y s i s i s v a l i d  The second problem i s t h a t s i n c e a t l e a s t one  63  culm  of  each  not  free  to  vary.  By  and  denominators,  one  disease  percentage  cluded. the  As  slope  s l i g h t . large  smutted  the  of  simple  the  approach  r e l i a b l e  as  also  case  the  the in  Although t i o n ,  mostly  severity  which  although most the  d i f f e r e d of  the  conclusions  general hordei  combination  but  which  in  this  this Buttle  in  the  30  were  earlier  percent  of  intermediate  percentage  of  smutting  be  study.  In  On d i s e a s e d  healthy.  contributing  to  accordance  the  Indeed,  with  plants this  d i s p a r i t y  is  be.  0.00001), the  just This  was  heads  the a  as was  introducdisease  study,  r e l a t i v e l y studies one  were (of  the  by two  small,  are  i n  were  smutted  smutted.  plants)  correlation  found  and  barley-U.  plants  portion  between  the  this  mentioned  a l l  be  be  Hence,  in  in  of  would  decrease  than  within-plant  used  studies  (193*0  which  to  ex-  analysis.  those  and  were  s u f f i c i e n t l y  percentages  measuring  from  numerators  would  is  would  Is  within-plant  tend  n e g l i g i b l e .  workers, mentioned of  the  = less  1 7 percent  this  would  be  0  only  r e s u l t In  being  culm  they  decrease  approach  earlier  of  agreement.  regression  correlation  means  in  i f  the  unaltered  previous  chose  obtained  the  would  one  higher  but  slope  complex  the  be  culms  exclusion would  of  the  using  more  a  would  change  of  smutted,  s l i g h t l y  significance  that  be  obtains  e x i s t ,  of  to  these  regression,  (probability  however,  has  Including  than  data  the  The  plant  of  the  At  such derived culms  Buttle. measures  Also was  a  64  the  fact  that  smutted  plants  produced  presented  some  barley  and wheat  p a r t i a l  smutting  Is  perhaps  smut  barley.  In  Oort's  for  lated  covered  and  diseased  t o t a l l y  smutted.  and  4.0  percent  and  these  the  percentage  this the  were  would, present  p a r t i a l  Only of  of  of  was  the  high a l l  to  be  were  considered  a  the  inocu-  nearly wheat  always plants  healthy  culms,  Even  though  70  percent)  (over  high disease  of  frequent  study  had  high  smuts  less  minority.  was  of  combinations small  degree  general  most  I n i t i a l l y  at  undoubtedly  is  two  of  types  not  form  least,  studies  more  high  to  i n of  level  between-and  of  greatly  both to  however,  the  revealed  between-cultlvar  possess  d i s t i n c t  a  generally  can  easily  groups.  possessed  a  A  com-  high be  the  productive.  to  the  dlkaryon  r e l a t i v e l y  conclusion  inheritance  or  picked  disease-producing a b i l i t y  leads on  dikaryons,  analyses,  which  wlthin-plant This  a  resistance  such  instance,  the  contributed  limited which  for  be  not  cultivars  c u l t i v a r s .  would  of  within-cultlvar  do  and  any  possessed? l i t t l e  possessed  the  between-  which  in  While  found,  sistance  plants  to  The  dikaryons  or  the  loose  diseased  plants  resistance  correlation  level  not  have  resistance,  parisons.  out,  in  like- Odessa,  which  correlation.  low  always  plants of  barley  the  Oort  smutting,  Keystone,  that  diseased  for  barley  percent  3-9  smutted  study,  withln-plant  types  and  comparison with  Cultivars> or  wheat  nearly  in  of  that  t i l l e r s .  (1939)  than  evidence  fewer  of  host  on  that, r e -  65  The plant  v a r i a b i l i t y  disease  determined.  reaction  Earlier  of  close  less  are  I t s e l f  be  taken  within-plant attest at  to  planted  in  over  a  two  poor  s o i l ;  were  *5  be  reaction  ignored,  than  between-  for  played  but  genetic that  of  are  between-plant so  genetic  The  experimental environment.  which  were  planted  basis.  In  effects  percent)  into two on  when  the  of  types.  which In  which  of  two  or  more  sub-block  possesses  always  only there  for  withinand  genetic of  seems  high between-plant  and  dikaryons  Sometimes  at  UBC, (up  to  compared.  close,  one  very  minimal  were  rather  combinations  located  sub-blocks.  results  was  a  Yet,  was  in  cultivars  years.  were  smutted,  on b o t h  various  disease  p a r t i c u l a r , give  high  different  correlation  contrasting  each  combinations  Blocks  s p l i t  planted  always  of  Odessa,  Some b l o c k s  s m u t t i n g was  can  also  randomly  yet  the  results  less  period.  disease  determination  or  year  almost  reactions  the  more  percent.  that  were  which  5  determinants.  wlthln-plant  by  -  they  determined,  and  reaction. role  magnitude  blocks  that  found  the  within-  genetically  heavily  Because l i k e l y  be  extent,  in  consistently  environmental about  of  combinations  C o l u m b i a was  frequently  these  large  genetically  evidence  minor  between-plant were  of  as  a  established  disease  the  B r i t i s h  cannot  largely  correlation  111  is  Importance  have  for  to  error  effects  studies  reactions  i s ,  Sampling  Environmental certainly  shown  the to  be  It  Is  not  studies high a  reactions  w i l l  disease  lack and  of low  66  within-plant further  study:  reactions between d i f f e r For  reactions.  be  either give  be  crossed  reactions; in  example,  could  varieties  can  only  to  or  or  their  contrasting  to  In  within-plant  of and  R9, a n d  Trebl  the  In  progeny  be  Combinations reactions  are  non-identity  To  on  Alternatively, cultivars l i k e l y ,  these  in  and  proper  to  their the  be  in  because  they  may  the  types  be  an  experimental In  design  crossing  R l l  parents  give  reactions.  virulence on  Trebl.  within-plant  of  possible  resistance.  sensitivity  important,  polygenes  Lion  with  indicate  environmental  Background  p o s s i b i l i t i e s  two  their  d i f f e r  inheritance  disease  tested  Good  and  the  within-plant  only  could  the  Trebl  with  to  crossed  which  progeny  studied.  types.  seem  study  low-  cultivars  Keystone  d i f f e r  in  be  parent  wlthin-plant  governing  dikaryons  A  and  differences  explanation.  Important. between  or  could  Trebl,  which  genes  R4  and  which  tested  which  R6.  noteworthy of  cultivars  with  can  resistance  Lion  d i f f e r  crossed  both  for  resistance,  the  are  which  could  of  only  Rl  only,  for  varieties  progeny  genotypes  pathogen,  tested  the  l e f t  low-within  reactions  reactions  between-plant  Et2,  and  parent  and  the  involving  are  and'hlgh-between  with  inheritance  Nepal  contrasting and  those  the  potential  virulence  with  reactions  of  with  high-withln  which  examples their  with  within-plant  with  E t l ,  p o s s i b i l i t i e s  crosses  study  crossed  R4  Two  although  might  would  also  of less  be  distinguish  studies.  67  PART I I I THE PATTERN OF SMUTTING AND EFFECT ON PLANT GROWTH BY USTILAGO HORDEI IN 'HANNCHEN' BARLEY A.  INTRODUCTION F a r l s ( 1 9 2 4 ) and J o h n s t o n ( 1 9 3 4 ) ,  In t h e i r  of t h e b a r l e y - U. h o r d e i s y s t e m , b o t h r e p o r t e d  studies  that,  f o l l o w i n g I n o c u l a t i o n o f b a r l e y w i t h U. h o r d e i , t h e f i r s t heads t o appear i n a group o f p l a n t s were u s u a l l y and  that diseased  healthy,  heads u s u a l l y appear a t a l a t e r d a t e .  Johnston concluded that diseased  culms were s l o w e r t o  mature than h e a l t h y r e g a r d l e s s o f whether the l a t t e r were f r o m h e a l t h y o r smutted p l a n t s .  F a r l s r e p o r t e d t h a t i t was  culms from h e a l t h y p l a n t s w h i c h one observed f i r s t . n e i t h e r c a s e was t h e e x p l a n a t i o n data.  In  supported by o b s e r v a t i o n a l  An a l t e r n a t e , o r a t l e a s t c o n t r i b u t o r y , p o s s i b i l i t y  i s t h a t o l d e r culms o f smutted p l a n t s more f r e q u e n t l y remain healthy.  I n p a r t , t h i s work was undertaken t o t e s t  t h i s p o s s i b i l i t y — t h a t i s whether, w i t h i n a diseased p l a n t , the diseased  barley  and h e a l t h y t i l l e r s a r e produced  r a n d o m l y , o r i n an a g e - r e l a t e d  pattern.  The work a l s o  c o n c e r n s t h e development o f b a r l e y p l a n t s and how t h i s may be a f f e c t e d by U. h o r d e i .  Since p a r t i a l r e s i s t a n c e probably  i s , as p a r t s I and I I w o u l d i n d i c a t e , an Important c o n t r i b u t o r to host-parasite accord,  i t was f e l t t h a t s t u d i e s f u r t h e r i n g  68  our u n d e r s t a n d i n g be most  o f t h e d e t a i l s o f such r e s i s t a n c e would  worthwhile. Very l i t t l e  information i s a v a i l a b l e concerning the  e x a c t l o c a t i o n o f h e a l t h y and d i s e a s e d  culms i n p a r t i a l l y  smutted o r bunted c e r e a l s and p l a n t s .  Churchward  (1937-38)  found t h a t t h e r e s i s t a n t wheat c u l t l v a r Hope showed a low p e r c e n t a g e o f l a t e t i l l e r b u n t i n g when i n o c u l a t e d w i t h T. c a r l e s .  U s u a l l y t h e f i f t h o r s i x t h t i l l e r was d i s e a s e d .  Beed ( I 9 3 8 ) found t h a t t h e o a t s p e c i e s Avena b r e v l s , when i n o c u l a t e d w i t h r a c e 1 o f U. k o l l e r l . showed smutted l a t e r a l tillers  and h e a l t h y s p i k e s o f p r i n c i p a l culms i n n e a r l y a l l  of t h e 2 0 t o 3 0 p e r c e n t o f d i s e a s e d  plants.  Neither of these workers paid a t t e n t i o n t o exact t i l l e r r e l a t i o n s h i p s . A t b e s t they c a s u a l l y d i s t i n g u i s h e d t h e p r i n c i p a l culm from t h e s m a l l e r l a t e r a l culms. work was found w h i c h i n any way f u r t h e r showed  No o t h e r  smutting  patterns i n cereals. The p a t t e r n o f b a r l e y growth i s s i m i l a r t o t h a t o f t h e more t h o r o u g h l y (1936),  s t u d i e d wheat.  According  to Hector  t h e two a r e so s i m i l a r t h a t the i n f o r m a t i o n on  g r o w t h p a t t e r n s i n wheat a l s o a p p l i a s to barley. A briaf a c c o u n t o f t h e p a t t e r n o f growth i n b a r l e y , g i v e n b y -Sarvella et a l . (1962),  compares c l o s e l y w i t h t h e d e s c r i p -  t i o n f o r wheat g i v e n by P e r c l v a l ( 1 9 2 1 ) .  In general, the  69  p a t t e r n of t i l l e r i n g can be c a l l e d m o n o p o d i a l , w i t h a c e n t r a l unbranched culm ( t h e p r i n c i p a l or a p i c a l culm) f r o m s e v e r a l of whose l o w e r nodes l a t e r a l culms laterals) arise.  (primary  Each of the p r i m a r y l a t e r a l culms i s  i t s e l f c a p a b l e of p r o d u c i n g ( s e c o n d a r y ) l a t e r a l s . for  Except  the l i m i t e d number of nodes on each culm, the g r o w t h  p a t t e r n i s , t h e o r e t i c a l l y , Indeterminate.  Plants  produce 1 0 0 culms i f the environment i s u n u s u a l l y  can favorable.  I n r e a l i t y , however, p l a n t s u s u a l l y do not p r o l i f e r a t e t o t h i s extent.  A more d e t a i l e d d e s c r i p t i o n of growth  patterns  w i l l be p r e s e n t e d i n t h e r e s u l t s s e c t i o n . B. MATERIALS AND  METHODS:  T h i s work was The  c a r r i e d out e n t i r e l y i n the greenhouse.  b a r l e y c u l t l v a r *Hannchen' was  chosen because of I t s  h i g h t i l l e r i n g c a p a c i t y under greenhouse c o n d i t i o n s . s i n g l e smut d l k a r y o n used t h r o u g h o u t . described  composed o f h a p l o l d s E3a and  Seed t r e a t m e n t and  i n part I.  Uninoculated  Ik A  The was  I n o c u l a t i o n were as  seeds were t r e a t e d -  e x a c t l y as those i n o c u l a t e d , e x c e p t t h a t s t e r i l e complete b r o t h ( f o l l o w e d by a d i s t i l l e d w a t e r r i n s e ) was  substituted  D u r i n g the 3 t o k months o f growing t i m e , p o t s  for  inoculum.  and  f l a t s were r o t a t e d and r e a r r a n g e d r e g u l a r l y .  70  When 2 t o 3 culms had appeared on t h e p l a n t s , they were tagged I n o r d e r t o e s t a b l i s h a r e c o r d o f t h e t i l l e r relationships.  They were a g a i n tagged a t a l a t e r d a t e ,  when more culms had appeared.  W i t h o u t such t a g g i n g , I t  was n e a r l y I m p o s s i b l e t o d e t e r m i n e , w i t h c e r t a i n t y , t h e t i l l e r i n g p a t t e r n s o f mature p l a n t s .  One by 1 . 5 I n c h w h i t e  m a r k i n g t a g s w i t h s t r i n g s were used.  To p r e v e n t t a g s from  d e t e r i o r a t i n g , a f t e r t h e i n f o r m a t i o n on t i l l e r n o d a l o r i g i n and sequence o f appearance had been r e c o r d e d on them i n p e n c i l , t h e y were d i p p e d i n p a r a f f i n .  I t was found t h a t  even i f a tagged culm d i e d , i t s e x a c t p o s i t i o n c o u l d  still  be d e t e r m i n e d . When a l l culms had headed, t h e i r p o s i t i o n , and f a t e (headed, smutted o r dead) were r e c o r d e d .  sequence Informa-  t i o n r e l a t i n g t o s i n g l e p l a n t s was i n each case t r a n s f e r r e d t o a s c h e m a t i c p l a n t d i a g r a m t o a i d I n subsequent a n a l y s i s . P o t s , w h i c h were found t o be more s u i t a b l e , were used e x c l u s i v e l y i n t h e next three p l a n t i n g s . grown i n each p o t .  Three p l a n t s were  One o f t h e t h r e e p l a n t s i n each p o t was  u n i n o c u l a t e d i n two o f t h e p l a n t i n g s .  These p l a n t s s e r v e d  as c o n t r o l s when o b s e r v i n g p o s s i b l e e f f e c t s o f l a t e n t I n f e c t i o n i n nonsmutted b u t i n o c u l a t e d p l a n t s .  To o b t a i n  p r o f u s e l y t i l l e r i n g p l a n t s , i n the l a s t p l a n t i n g , inoculated seeds were p l a n t e d s i n g l y i n f o r t y p o t s and h i g h l y  fertilized.  71  S t a t i s t i c a l Included  the  proportions, Chl-square C.  labelled the  culms,  and  recorded.  a  mean cent,  test,  of  young  analyze  about the  the  paired  of  culms  5.73  were  these  data  difference  of  t  the  test  and  nonsmutted  culms a  grows.  barley  plant  of  a  rather  typical  Below  i t  normal  The  terminology  internodes excluded, in  cent  total  plant.  and  Of  were 83.  became  of  1,198  these,  can  the  study  927,  a  modified is  also of  been be  a  analyzing  line  3.1  the  plant  with  of  which  the  plant,  lengthened  data.  the  subtend  in  hypothetical  the  was a  introduced  In  in  shows  drawing  leaves  greatly  seen  to  understanding  Figure  is  was  distributed  month-old barley  sketch have  of  thorough  there  the  useful  a  plants  totalled  per  4-7.0  were  t h i s ,  a  were  per  objectives  how  are  plants  produced  do  A diagrammatic  leaves  barley  smutted.  the  the  528  or  209,  plants  how  t i l l e r s .  diagrams  plants,  smutted  To  of  Nonlnoculated  primary  naming  which  total  the  culms.  diagram.  a  of  plants.  photograph  plant,  studies,  209  per  77.4  needed  a l l  t  simple  The  for  smutted  In  the  inoculated  425  determine  the  interval  to  test.  One  six  confidence  these  smutted.  or  used  RESULTS In  Of  techniques  and  appendix. In  r e a l i t y ,  These the  72  r e g i o n o f t i l l e r i n g , commonly c a l l e d t h e crown r e g i o n , i s g r e a t l y compressed, as t h e photograph would Some q u a l i t a t i v e  Indicate.  s t a t e m e n t s can be made about t h e  g e n e r a l p a t t e r n o f growth o f 'Hannchen' b a r l e y under t h e e x p e r i m e n t a l c o n d i t i o n s t h a t were employed.  Plants  i n v a r i a b l y produced t h e p r i n c i p a l culm ( I S ) as t h e f i r s t and o l d e s t culm. the  I f , f o r some r e a s o n , I t d i e d v e r y e a r l y ,  n e x t o l d e s t culm assumed I t s r o l e .  I f a l a t e r a l culm  was s e p a r a t e d e a r l y from a p l a n t , I t a l s o a c t e d as a p r i n c i p a l c u l m , t h a t I s t o s a y , t h e l a t e r a l ' s l o w e r nodes p r o d u c e d l a t e r a l culms t o a much g r e a t e r e x t e n t than i t would have done had I t remained a t t a c h e d t o t h e o r i g i n a l plant.  Only one p r i m a r y l a t e r a l was produced from each node  in this cultlvar.  W i t h r a r e e x c e p t i o n t h e l a t e r a l culm  a r i s i n g i n t h e a x i l o f a l o w e r l e a f was o l d e r t h a n one a r i s i n g from t h e a x i l o f a h i g h e r l e a f , so t h a t , f o r example, t h e 2 L culm appeared b e f o r e t h e JL culm I n a l m o s t a l l plants.  T h i s c a n be seen i n t h e photograph ( F i g u r e 3 * 1 ) »  where t h e 1 L , 2 L and 3L l a t e r a l s a r e c l e a r l y i n o r d e r o f d e s c e n d i n g age.  In. l a b e l l i n g , t h e n u m e r i c a l s u b s c r i p t  indi-  c a t e d t h e o r d e r o f appearance o f p r i m a r y l a t e r a l culms ( a p r i m a r y l a t e r a l b e i n g d e f i n e d as t h e f i r s t l a t e r a l produced from a node o f t h e p r i n c i p a l c u l m ) .  The e x c e p t i o n s t o t h i s  o r d e r were o f t e n i n t h e f o r m o f l a t e p r i m a r y l a t e r a l s from l o w e r l e a v e s , u s u a l l y t h e CN o r 1 L nodes.  These n e a r l y  73 FIGURE  FIGURE 3 . 1 .  3.1  I L L U S T R A T I O N OF THE PATTERN OF E A R L Y T I L L E R PROLIFERATION I N A ONE-MONTH OLD PLANT OF 'HANNCHEN• BARLEY  FIGURE  coleoptile ( bud dormant this  in  plant)  FIGURE 3 . 1 .  CONTINUED  3.1  75  always d i e d b e f o r e heeding.  I n o n l y one case was an excep-  t i o n a l o r d e r o f appearance o f p r i m a r y l a t e r a l culms seen on a p a r t i a l l y smutted  (and hence i m p o r t a n t ) p l a n t .  Because  t h i s may n o t r e f l e c t r e l a t i v e t i l l e r bud age i n t h e v e r y young s e e d l i n g , t h i s p l a n t was n o t i n c l u d e d i n t h e a n a l y s e s . P l a n t s produced  l a t e r a l s from t h e c o l e o p t i l e node up t o as  h i g h a s t h e e i g h t h v e g e t a t i v e l e a f node.  In general,  however, about 3 t o 4 nodes were I n v o l v e d . The nodes most commonly employed were 1L t h r o u g h 5L. of  Throughout t h e r e s t  t h i s t h e s i s a primary l a t e r a l together w i t h a l l of i t s  l a t e r a l culms w i l l be r e f e r r e d t o as a t i l l e r  family.  A t t e n t i o n was p a i d t o t h e o r d e r o f appearance o f culms w i t h i n a t i l l e r f a m i l y , where t h e sequence d i d n o t v a r y from what would be e x p e c t e d f o l l o w e d by 2 L - 1 L ) . ages o f secondary  ( e . g . 2L f o l l o w e d by 2L-CN  No attempt was made t o compare r e l a t i v e  l a t e r a l s a r i s i n g from d i f f e r e n t p r i m a r y  l a t e r a l s ( f o r i n s t a n c e 1L-CN w i t h 2L-CN).  At a l l l e v e l s of  t i l l e r p r o d u c t i o n t h e r e was o c c a s i o n a l absence o f expected tillers  ( e . g . t h e 2L l a t e r a l d i d n o t a p p e a r ) .  I n many  c a s e s t h i s was p r o b a b l y due t o I n j u r y t o t h e young bud. Q u a n t i t a t i v e data r e l a t i n g to l a t e r a l t i l l e r production w i l l be p r e s e n t e d l a t e r f o r i n o c u l a t e d and n o n i n o c u l a t e d p l a n t s . 1. The D i s t r i b u t i o n o f Smutted and H e a l t h y Heads I n Smutted P l a n t s Some s i m p l e s t a t i s t i c a l t e s t s were d e v i s e d i n o r d e r to  a l l o w d e f i n i t i v e statements  t o be made r e g a r d i n g t h e  76 randomness h e a d s i n or  not  among  or  nonrandomness  smutted  the  (bulked)  separately,  for  two,  was  a l l  were  the  smutted values  group  of  f i t  number  of  that  of is  was  for  frequency  .  within  of  is  For  three  composition  with  both  t i l l e r  that  families  families.  frequency two  not  f i t  the  Is  or  to  readily  be  classes  was  applying  can  mixed  in  too  high.  is  whether  these  family culm  family  size.  ,  the of  where  with  which not  paid  the a  the  If  propor-  smutting n  is  two-tiller heads  some  results  that  of  whether  a  the  families,  smutted both  is  heads  number to  of  the  relationship  Chl-square  seen  expected.  families  to  or  in  those  By  i t  of  of  families  mixed  observed  n  of  the  do  + q ) for  and  The  degrees  Thus  those  plants.  case,  family.  attention  numbers  other  (p  more,  the  the  the  more  From  each  heads  or  culm  various  binomial  2pq,  goodness-of-fit,  the  for  or  observed  of  the  four  probability  obtained  whether  presents  according  a  d i s t r i b u t i o n were  in  3.1  and  (mixed).  the  showing--the  mixed q  were  q,  tested  healthy,  of  healthy  nonsmutted  smutted  were  probability and  and  family  of  these  Table  a l l  a l l  healthy  of  three,  each  or  expanded  culms  p ,  culms  the  smut  the  expected  culms  p,  smutted,  the  healthy  some  families  should  2  smutted,  and  of  from  c l a s s i f y  healthy,  randomness tions  to  of  being  remaining  smutted random.  families  location  f i r s t  was  procedure  were  the  families  t i l l e r  culms  The  d i s t r i b u t i o n of  t i l l e r  analyses,  plants.  of  that In  too Hence  test  the  each  low  of  case  while  there  is  the that  a  77 TABLE 3 . 1 OBSERVED AND EXPECTED NUMBERS OF VARIOUSLY SMUTTED TWO, THREE AND FOUR OR MORE T I L L E R F A M I L I E S , AND THE A P P L I C A T I O N OF A CHI-SQUARE TEST FOR RANDOMNESS OF SMUTTING AMONG F A M I L I E S , USING BINOMIAL EXPANSIONS TO CALCULATE EXPECTED VALUES A l l Smutted  Grouping Two  t i l l e r  Expected  ( i f  o f t  81  Probability  randomly that  9  (p )  smutted  heads  2  (2pq)  63  44  are  (q ) 2  8 =  oft  ( i f  randomly  Probability  5  (p )  (3P q 3PQ. )  21  34  that  smutted  heads  are  2  +  2  o r more  t i l l e r  Observed Calculated values p = O.65  families  (average  6.2  ( i f  randomly  (p ) 6  distributed) Probability  q  )  1 =  56  <0.001  5  9  that  4 smutted  heads  are  (l-p -q ) 6  6  43  47  (q ) 6  0  randomly  distributed p  3  t i l l e r s )  33  oft  U  0.35  Expected  a  56  randomly  distributed  =  14  37  3  distributed)  q  <0.001  0.29  Expected  Four  115  families  Observed Calculated values p = 0.71 =  115  randomly  distributed t i l l e r  25  a  distributed)  q  Total,  families  Observed Calculated values p = 0.74 q = 0.26  Three  A l l Healthy  Mixed  =  <0,001  = the p r o b a b i l i t y , based on the observed data, o f a s i n g l e culm being smutted, = t h e p r o b a b i l i t y o f a s i n g l e culm remaining healthy.  47  7 8  s t r o n g tendency f o r t i l l e r  f a m i l i e s t o be composed  e n t i r e l y o f e i t h e r smutted o r h e a l t h y  spikes.  A t t e n t i o n was n e x t p a i d o n l y t o the 1 9 t i l l e r f a m i l i e s w h i c h were mixed. t o whether t h e nonsmutted youngest, o r n e i t h e r .  They were c l a s s i f i e d  according  s p l k e ( s ) were t h e o l d e s t ,  I f s m u t t i n g i s randomly d i s t r i b u t e d  i n r e l a t i o n t o age, the r a t i o o f o l d e s t h e a l t h y t o youngest healthy 3.2.  tillers  s h o u l d be 1 : 1 ,  The t e s t i s shown i n T a b l e  Sample s i z e s were s m a l l , so t h e Yates c o r r e c t i o n  f a c t o r f o r c o n t i n u i t y was a p p l i e d i n c a r r y i n g out t h e C h i square t e s t ( S t a n s f i e l d ,  1 9 6 9 ) .  A significant difference  e x i s t s between t h e o b s e r v e d and t h e expected r a t i o s . conclusion  The  i s t h a t t h e r e i s a c l e a r tendency f o r o l d e r  s p i k e s w i t h i n mixed smutted f a m i l i e s t o remain  healthy.  TABLE 3 . 2 TEST FOR RANDOMNESS OF POSITION OF NONSMUTTED T I L L E R ( S ) WITHIN SMUTTED TILLER FAMILIES, IN TERMS OF AGE (ORDER OF APPEARANCE) OF THE TILLERS  ' Observed Expected ( i f randomly distributed)  P o s i t i o n o f nonsmutted Oldest Neither 1 8  5 .  t i l l e r or t i l l e r s Yo ungest  0 5  P r o b a b i l i t y that oldest:youngest r a t i o f i t s ^Applying  4 8 1 : 1  . =  5 0 . 0 1 5 *  Yates s m a l l sample c o r r e c t i o n f o r c o n t i n u i t y .  79  Also between b i l i t y  age of  (position)  being  explained A  investigated of  smutted.  above,  t i l l e r  was  family  was was  the  a  t i l l e r  A  test,  applied  to  considered  smutted.  plants  were  c l a s s i f i e d  according  families.  A  them) the or  could  family  thus or  neither,  families  depending  had  nonsmutted  family  on  the  family  results  are  IS  as  be  which  IS  counted  the  older  can part  no of  and  as  culm  is  between  1«1  that the  When longer Table  the be 3-3  IS seen  to  Is  using  shows.  a  a  the of  oldest  no  end  included, the  A more  simple  the  of  the  youngest  ratio  Two  different  culm,  one  t i l l e r  which  including  only  plants  families  the in  are  significant ratio  strong in  age,  relationship  highly  healthy  of  to  1»1  of  than  details  principal  a  series  laterals  oldest!youngest  there.is  to  intermediate  considering  Is  remain  culm  the  lateral  there  Thus  is  smutted  relative  (or  expected  family,  only  a l l  probability).  hence  actual  expected. familes  there  t i l l e r  When  clear  the  Its  of  gives ratio  of  younger  3.3  f i t s  (and  or  one  or  primary  the  that  family  the  ignoring  a  age  their  proba-  families.  any  to  older  Its  among  i f  any,  the  on  smut,  smutting  tested--one  t i l l e r  plants.  how w e l l  survived). i t  Table  position  age  oldest  difference and  of  regarded  the  on when  assumption  between  cannot  showing  appeared.  tests  as  to  families  nonsmutted  c l a s s i f i e d  families  Chi-square  (based  be  Nonsmutted  i f  and  similar  smutted  were  smutted  family  smutting  spikes  the  relationship,  obtained  tendency  p a r t i a l l y  for  smutted  however,  the  tendency  test,  the  second  complete  as  picture  can  be  80  TABLE 3.3 TEST FOR RANDOMNESS OF POSITION OF NONSMUTTED TILLER FAMILES WITHIN THE SMUTTED BARLEY PLANT, IN TERMS OF AGE (ORDER OF APPEARANCE) OF THE FAMILIES  P o s i t i o n o f nonsmutted f a m i l y o r f a m i l i e s Oldest Intermediate Youngest Later t i l l e r s  only 55  Observed Expected ( i f  8  26  randomly d i s t r i b u t e d ) 4 o . 5  40.5  P r o b a b i l i t y t h a t o l d e s t t y o u n g e s t r a t i o f i t s l t l = 0.001 P r i n c i p a l t i l l e r included (as o l d e s t t i l l e r ) 31  Observed Expected ( i f randomly distributed)  30 .  28  P r o b a b i l i t y that oldesttyoungest  seen i n T a b l e 3.4. c i p a l culm  9  Here t i l l e r  are presented  25 2  8  r a t i o f i t s 1»1 = 0.45  f a m i l i e s , along w i t h the p r i n -  by p o s i t i o n and f e t e .  The d a t a o f  t h i s T a b l e a r e shown g r a p h i c a l l y i n F i g u r e 3.2, where  tiller  f a m i l i e s a r e c l a s s i f i e d and t h e p e r c e n t a g e i n each c l a s s w h i c h showed smut a r e g i v e n .  The 13 culm i s t h e o n l y p l a n t p a r t  w h i c h does n o t f i t t h e p a t t e r n o f d e c r e a s i n g f r e q u e n c y o f smutting w i t h 8 g e .  Data f o r t h e I S culms and,  to a lesser  e x t e n t , f o r the CN and 1L f a m i l i e s , a r e e f f e c t e d by t h e r e l a t i v e l y h i g h d e a t h r a t e s ; had these culms a l l s u r v i v e d t o  81  h e a d i n g , t h e p e r c e n t a g e s o f smut may have been changed. g r a p h and t a b l e show t h a t t h e CN and 1 L p o s i t i o n s were smutted  The  (bulked)  s i g n i f i c a n t l y l e s s f r e q u e n t l y than t h e 2 L  p o s i t i o n , w h i c h was i n t u r n smutted  significantly  less  f r e q u e n t l y t h a n t h e 3 L , 4 L o r ( b u l k e d ) 5 D and up p o s i t i o n s . The l a t t e r t h r e e were n o t s i g n i f i c a n t l y d i f f e r e n t . One o t h e r n o t a b l e p o i n t emerges i n T a b l e 3.4.  The  f r e q u e n c y o f t i l l e r f a m i l y d e a t h seemed t o be d i r e c t l y p r o p o r t i o n a l t o t h e i r age.  T h i s f a c t was n o t i c e d c a s u a l l y d u r i n g  l a b e l l i n g and h a r v e s t i n g . " f a v o r e d " by t h e p l a n t .  L a t e r emerging culms seemed t o be  Not o n l y were t h e y more l i k e l y t o  s u r v i v e , b u t t h e y grew f a s t e r .  The v e r y l a t e culms, sometimes  s e e n , e s p e c i a l l y i n r e s p o n s e t o l a t e heavy w a t e r i n g , were the f a s t e s t growing of a l l .  Because t h e s e a r o s e s p u r i o u s l y ,  t h e y were n o t i n c l u d e d i n t h e a n a l y s e s . TABLE  3.4  THE PRODUCTION BY SMUTTED PLANTS AND FATES OF TILLER FAMILIES, ANALYZED BY NODAL POSITION  Nodal Position IS CN and 2L  3L 4L  1L  T i l l e r f a m i l y f a t e (%) Headed Smutted Dead 14.6  29.0  17.6 10.3 14.8  5 L and above 1 2 . 5  50.2  46.0 61.7  68.5 74.7 72.2  35.2  25.0 20.7 21.2  10.5  15.2  Percent of Surviving Fam. Smutted* 80.4 61.3 77.8° D  C  a  86.9° 83.40 85.3°  • V a l u e s not s h a r i n g t h e same l e t t e r a r e s i g n i f i c a n t l y d i f f e r e n t (p=0.05). S t a t i s t i c a l comparisons a r e made vertically.  Sample Size 213  124 188 184 162 184  FIGURE 3.2  100  Nodal  position  of tiller  100  family  FIGURE 3.2. FREQUENCY OF COVERED SMUT OCCURRENCE IN TILLER FAMILIES OF BARLEY PLANTS IN RELATION TO RELATIVE AGE OF THE TILLER FAMILY (AS INDICATED BY POSITION)  00  8  2.  The E f f e c t of I n o c u l a t i o n S m u t t i n g on P l a n t Growth  The plant and  main  growth  effects  effects  were on  Three  of  the  pattern  weeks  after  stunting, of  plant  planting,  greenhouse  experiment  season  Out  inoculated  seedlings,  of  206  stunting None  of  (plants 83  stunted sample  with  uninoculated  plants, is  short  too  16  small  were  for  that  related,  no  relationship  sequent  clear  s m u t t i n g was  always  observed  in  should  order  smutting  Table  3.5»  of  while  seen  rather  1972-3,  in  treatments  and  was  t i l l e r i n g ,  growth. of  for  exhibited dark  and  nine  stunting. some leaves).  Of did  the  between  This  One  probably  stunting  stunted  25  not.  treatment. is  1973-4  the  green  stunted.  stunting  ( i . e . ,  on  on  can,  smut-  and  plants  sub-  were  not  smutted).  Because  pot,  25  s t a t i s t i c a l  conclude  smutting  effects  examined  smutted  however,  and  seedlings  narrow,  plants  became  and  Inoculation  examined:  3  to on  it  be  large  was  thought  paired,  measure  the  t i l l e r i n g .  Whether  or  not  significant  reduction  in  plant,  both  Initiated  and  plants  were  compared  with  among-pot  each  pair  effects, The  plants being  If  analysis  plants  the  that  showed  number  surviving  of (to  uninoculated  variation different  from  any, is  of  of  the  inoculation  presented  smut,  t i l l e r s  there per  maturity), plants.  same  In was  a  inoculated when  There  such  was  no  84 TABLE  3.5  MEAN NUMBERS OF CULMS I N I T I A T E D PER P L A N T , AND T H E I R F A T E S ( H E A D E D , S M U T T E D OR D E A D ) , W H E N P L A N T S WERE UNINOCULATED, I N O C U L A T E D B U T F A I L E D TO B E C O M E SMUTTED, OR I N O C U L A T E D A N D S M U T T E D  Mean number of culms per plant* Headed Dead Total  Number o f paired Observations  Treatment Comparisons Noninoculated  68  Inoculated nonsmutted Inoculated nonsmutted Smutted  63  Noninoculated  48  Smutted  5.56  2.93  8.49  4.91  2.47  7.83  4.97  a  2.13  7.10  D  4.63  a  2.81  7.44  b  6.33  2.87  9.21  4.10  2.35  6.46  *Means n o t s h a r i n g t h e same s u p e r s c r i p t a r e s i g n i f i c a n t l y different (P=0.05, p a i r e d t a n a l y s i s ) . S t a t i s t i c a l c o m p a r i s o n s i n v o l v e d p a i r e d means only.  significant viving, The  between  situation  plants smutted a  difference,  had or  smutted  was  and  different  significantly nonsmutted  reflection  noninoculated dead  in  t i l l e r s  of  the  than  did  t i l l e r s  nonsmutted for  more  dead  dead  inoculated  overall  plants.  total  Smutted  t i l l e r s .  t i l l e r s  t i l l e r  plants  nonsmutted  inoculated  plants.  higher  initiated  had  or  sur-  plants.  Noninoculated  than This  either is  probably  production  of  s i g n i f i c a n t l y  Inoculated  plants.  more  85 To examine the e f f e c t o f I n o c u l a t i o n and s m u t t i n g  on  the p a t t e r n of p l a n t g r o w t h , smutted, nonsmutted i n o c u l a t e d and  noninoculated  p l a n t s were a n a l y z e d w i t h r e g a r d to the  p e r c e n t a g e s of p l a n t s a t t e m p t i n g from each node.  to produce t i l l e r f a m i l i e s  The d a t a , a l o n g w i t h the s t a t i s t i c a l  l y s e s , are p r e s e n t e d  i n Table 3.6.  ana-  The date a r e p l o t t e d , t o  show the d i f f e r e n c e s more c l e a r l y , i n F i g u r e 3.3.  Smutted  and nonsmutted i n o c u l a t e d p l a n t s d i f f e r e d In t h e i r growth p a t t e r n s o n l y i n s o f a r as smutted p l a n t s attempted  tiller  f a m i l y production w i t h a s i g n i f i c a n t l y higher frequency t h e CN a n d ' 6 L nodes.  T h i s may  at  r e l a t e to the h i g h e r d e a t h  r a t e of culms i n smutted p l a n t s , whereby dead culms a r e r e p l a c e d by new  ones.  A marked e f f e c t of s m u t t i n g and  l a t i o n on the p a t t e r n of plant- g r o w t h I s seen when the  inocunon-  i n o c u l a t e d p l a n t s were compared w i t h the o t h e r two g r o u p s . I n t h e f i g u r e , i t i s c l e a r t h a t the n o n i n o c u l a t e d  plants  produced l a t e r a l t i l l e r s from lower nodes t h a n e i t h e r nonsmutted i n o c u l a t e d or smutted p l a n t s .  I n o t h e r words,  I n o c u l a t i o n had the e f f e c t o f d e c r e a s i n g l a t e r a l p r o d u c t i o n a t the 1 L node and nodes.  tiller  I n c r e a s i n g i t a t the 5 L >and 6 L ^  The CN node d i d not conform t o t h i s e f f e c t ,  i t m i g h t have been e x p e c t e d t o do  although  so.  A f i n a l o b s e r v a t i o n s h o u l d be noted here.  Smutted  p l a n t s e x h i b i t e d a marked d e l a y i n emergence of heads. each p l a n t i n g the h e a l t h y p l a n t s were the f i r s t t o be  In  86 3.6  TABLE  COMPARISONS OF GROWTH PATTERNS (PERCENT OF LATERAL T I L L E R PRODUCTION FROM DIFFERENT NODES OF THE P R I N C I P A L CULM) OF 209 SMUTTED, 194 NONSMUTTED INOCULATED, AND 83 NONINOCULATED * HANNCHEN' BARLEY PLANTS P e r c e n t of p l a n t s attemutins: t i l l e r i n g from Nonsmutted Smutted Inoculated Noninoculated  Nodal  Position CN  25.8  a  13.4**  21.7  IL  35.9  b  44.8  90.4  2L  91.9**  93.3**  98.8**  3L  87.6**  93.3**  96.4**  4L  78.5°  84.0°  62.6  5L  56.0  46.4  13.2  6L  28.2  d  size  recorded  and  too  smutted  plants  not  did  inoculated  small  harvested,  invariably  for  horizontally. Values l e t t e r are significantly  those  Heads  noticeably  a  3.6**  s t a t i s t i c a l  while  plants.  emerge  plants.  d  12.9  * S t a t i s t i c a l c o m p a r i s o n s a r e made n o t s h a r i n g t h e same s u p e r s c r i p t different (p=0.05). **Sample  b  node*  of  analysis.  which  appeared  nonsmutted  later  than  those  last  were  Inoculated of  non-  FIGURE 3.3  100  80  e E «  s  a n -a „  1=  &. J_ tt>  —*  *0  C  to ~~  20  \  smutted  /  nonsmutted,  inoculated  noninoculated Cf4  1L  ZL position  \  \  \  3L  on  principal  culm  FIGURE 3.3. THE PERCENT OF SMUTTED, NONSMUTTED INOCULATED AND NONINOCULATED BARLEY PLANTS INITIATING LATERAL TILLER PRODUCTION ACCORDING TO NODAL POSITION ON THE PRINCIPAL CULM  00  88  D. DISCUSSION Since very l i t t l e  has been w r i t t e n c o n c e r n i n g  of the b a r l e y p l a n t , the I n f o r m a t i o n b a r l e y was vation.  growth  on growth o f •Hannchen'  learned almost e n t i r e l y through f i r s t - h a n d obser-  The  p a u c i t y of i n f o r m a t i o n about b a r l e y may  be  due  t o t h e b e l i e f t h a t g r o w t h of b a r l e y I s q u i t e s i m i l a r t o t h a t of wheat o r o a t s , two much more t h o r o u g h l y cereals.  The  studied  a s s u m p t i o n can a l s o be made t h a t p l u m u l a r  development i n t h e dormant seed o f b a r l e y I s s i m i l a r t o t h a t o f wheat, as H e c t o r  (I936)  s t a t e s In h i s chapter  I n wheat, b o t h P e r c l v a l (1921) and M c C a l l two  bud  prlmordia  are present  t h e s e I s the a p i c a l bud, and  on b a r l e y .  (193*0 found t h a t  i n the dormant seed.  One  w h i c h w i l l g i v e r i s e t o the IS culm,  the o t h e r i s i n the a x i l  d e v e l o p i n t o t h e CN culm.  of t h e c o l e o p t i l e and  B o n n e t t (1935) v e r y  will  briefly  described  the same c o n d i t i o n In seeds of b o t h 2- and  barleys.  P e r c l v a l found t h a t I t was  a f t e r germination  of  t h a t the bud  6-rowed  n o t u n t i l 10 t o 15 days  p r l m o r d i a i n the a x i l s o f  o l d e s t v e g e t a t i v e l e a v e s c o u l d be d e t e c t e d ,  lowermost  the  first.  I n c o n c l u s i o n , t h e above s t u d i e s i n d i c a t e t h a t t h e r e i s a c l e a r d i f f e r e n c e In development among bud t i m e o f I n i t i a t i o n of smut i n f e c t i o n .  prlmordia at  Whether t h i s  o f e a r l y development v a r i e s a p p r e c i a b l y has, n e v e r been d e t e r m i n e d .  the  pattern  unfortunately,  H i s t o l o g i c a l s t u d i e s have n e c e s s a r i l y  i n v o l v e d o n l y a s m a l l number o f embryos, so t h a t the r a r e  89  c a s e of a t y p i c a l development, i f i t e x i s t s , would have gone undetected.  As P e r c l v a l has p o i n t e d  o u t , however, one  e x p e c t normal b i o l o g i c a l v a r i a t i o n i n t h i s and,  can  i n d e e d , as  t h e p r e s e n t s t u d i e s show, i n e l l a s p e c t s of b a r l e y growth. 1 . The D i s t r i b u t i o n o f Smutted and H e a l t h y Heads i n Smutted P l a n t s Smutted heads d i d not o c c u r randomly i n p a r t i a l l y smutted p l a n t s .  Members of a t i l l e r f a m i l y tended to e i t h e r  be a l l h e a l t h y o r a l l smutted.  F u r t h e r , a t b o t h the w i t h i n ^  f a m i l y and b e t w e e n - f a m i l y l e v e l , o l d e r culms remained more f r e q u e n t l y t h a n d i d younger culms.  I t should  healthy  be  emphasized t h a t t h e s e were s t a t i s t i c a l t e n d e n c i e s o n l y . Exceptions  were not r a r e .  A phenomenon s i m i l a r t o t h e above o c c u r r e d individual spikes. contained  within  O c c a s i o n a l l y , s p i k e s were found w h i c h  b o t h smut t e l i o s p o r e s and  h e a l t h y seeds.  In-  v a r i a b l y , t h e h e a l t h y seeds were f o u n d on t h e upper p a r t t h e s p i k e and v a t i o n was (1971)  the smut on t h e l o w e r p a r t ,  r e c o r d e d by F a r i s  (1924a).  determined t h a t meiosls  The  of  same o b s e r -  Bennett and  Finch  i n b a r l e y b e g i n s a t the  top  o f t h e s p i k e and  proceeds downward, so t h a t upper seeds a r e  s l i g h t l y older..  Thus t h e w i t h i n - s p i k e s m u t t i n g p a t t e r n I s  t h e same as t h a t , seen a t t h e w i t h i n - and b e t w e e n - t i l l e r family level.  The  p a r t i a l d i s e a s e was  o n l y o t h e r r e p o r t found o f w l t h l n - s p l k e by H o l t o n and R o d e n h l s e r  (1942).  They  90  observed T.  p a r t i a l l y  carles  in  randomly  has  take  been  l i k e l y  does  the  tissues  same  pointing  to  in  for  not  any  is  older  culms of  the  This of  were culms  the  are in  the  the to  l o g i c a l  infected  balls  were  If  the  with  both  more  work  on  have  embryos  crown  from  part  of  does  both  It so  the  crown  the  smutted.  expect In  infection  the  the  more  upper.  the crown older  conclusion, and  sheaths  explanation  within  would  smut  is  the  On  one  the  leaf  ready  small  the  mycelium in  of  the  that  culms.  factor,  weak.  only  smutted hyphae  of  a  is  From  older  than  provide  the  tendency  that  appears  the  through  by  cases,  fact  that  the  evidence  the  examined.  the  pathway  that  d i s t r i b u t i o n  explain  of  frequently the  been  is  precisely  the in  that  d i s t r i b u t i o n of  so  crown  i t  crown,  and  not  too,  of  the  available  f i r s t ,  the  taken  In  from  below,  of  route,  would  have  pathway  Histological  healthy.  is  move  difference  stems  parts  Here,  to  parts  which  the  exists,  frequent  a  which  determining be  or  remain  location  various  seedling.  for  evidence  review,  v a r i a b i l i t y  crown  lower  observed  to  various  infected  available  contrary,  to  infected  enter  the  bunt  determined.  each  evidence  evidence  abundant  in  to  limited  nodes  wheat  literature  necessarily  the  of  and  of  and  spreading  evidence  numbers  hyphae  the  specific  within  weakness  in  spreading  weak  mycelium  in  considerable  mycelium  Also  seed  conclusively  that  fungus  sound  Indicated  smuts  not  which  heads  located.  As which  diseased  histo-  d i s t r i b u t i o n  91  o f smut mycelium does l i t t l e t o e x p l a i n the p a t t e r n s m u t t i n g w h i c h was most f r e q u e n t l y o b s e r v e d .  of  In the l e s s  f r e q u e n t c a s e s , where younger culms were nonsmutted, the i n f e c t i o n pathway and/or the d i s t r i b u t i o n p a t t e r n m y c e l i u m w i t h i n the crown i s a p o s s i b l e In a few lateral  p l a n t s , the o l d e s t and  culms were smutted w h i l e one  t i l l e r f a m i l i e s were h e a l t h y .  of  explanation. youngest p r i m a r y  or more  T h i s may  intermediate  be the r e s u l t of  m u l t i p l e i n f e c t i o n s ( i n f e c t i o n o f a seed by more t h a n dikaryon).  one  Such m u l t i p l e I n f e c t i o n s have been c o n c l u s i v e l y  d e m o n s t r a t e d i n o a t s i n f e c t e d w i t h U. k o l l e r l by P e r s o n Cherewick (1964).  A l t h o u g h not d e t e r m i n i n g s m u t t i n g  and  patterns  based on t i l l e r r e l a t i o n s h i p s , t h e y showed t h a t d i f f e r e n t d i k a r y o n s can o c c u r i n d i f f e r e n t culms of the same p l a n t . The  similarity  of U. k o l l e r l t o U. h o r d e i  i s such t h a t i t  would seem q u i t e l i k e l y t h a t such m u l t i p l e i n f e c t i o n s o c c u r i n the l a t t e r  also.  In U. k o l l e r l g e n o t y p i c mosaics i n d i c a t e  t h a t v a r i a t i o n i s p o s s i b l e i n how  and/or when smut hyphae  s p r e a d t h r o u g h o u t the crown r e g i o n .  A t h o r o u g h s t u d y of  t h e m u l t i p l e i n f e c t i o n phenomenon i n b a r l e y - U .  h o r d e i would  w e l l complement the p r e s e n t s t u d i e s . A p o s s i b l e b a s i s f o r the observed p a t t e r n of s m u t t i n g has been mentioned by o t h e r w o r k e r s . a b a r r i e r of l i g n i f i e d  cells  Sampson (1932) o b s e r v e d  between the n o d a l t i s s u e s  92  c o n t a i n i n g U. k o l l e r l mycelium and t h e a p i c a l growing p o i n t In r e s i s t a n t oat p l a n t s .  She c o n c l u d e d t h a t i f t h e p l a n t  c o u l d produce t h i s b a r r i e r b e f o r e t h e fungus reached t h e g r o w i n g p o i n t , t h e culm o r culms would not become smutted. She s u g g e s t e d t h a t s u s c e p t i b l e p l a n t s were unable t o l a y down t h i s b a r r i e r i n t i m e , because t h e fungus was g r o w i n g r a p i d l y , and t h a t g r o w t h o f t h e mycelium i n t o t a l l y r e s i s t a n t c u l t i v a r s was s t r o n g l y r e t a r d e d .  Regardless of  whether o r n o t l l g n l f I c a t I o n i s t h e c r i t i c a l e v e n t , t h e h y p o t h e s i s t h a t degree o f s m u t t i n g depends on r e l a t i v e r a t e s of g r o w t h o f t h e embryo and t h e smut mycelium I s p r o m i s i n g and p o p u l a r , p a r t i c u l a r l y i n e x p l a i n i n g t o t a l r e s i s t a n c e . Ohms and Bever (1955) f o u n d t h a t t h e mechanism o f r e s i s t a n c e t o U. t r l t l c l  i n one wheat c u l t l v a r seemed t o be s i m p l y t h a t  t h e s e e d l i n g s outgrew t h e smut mycelium.  The same can be  s a i d f o r o t h e r s t u d i e s , mentioned i n t h e l i t e r a t u r e r e v i e w , where e a r l y embryo i n f e c t i o n o f t o t a l l y r e s i s t a n t c u l t i v a r s was as h i g h as t h a t o f s u s c e p t i b l e c u l t i v a r s .  Swinburne  (I963) b e l i e v e d t h a t f o r wheat I n f e c t e d by T. c a r l e s , once t h e hyphae r e a c h e d a g r o w i n g p o i n t , smut was always e x p r e s s e d i n t h a t culm.  I n o t h e r words, r e s i s t a n c e c o u l d o c c u r any  t i m e b e f o r e . t h e smut had r e a c h e d t h e g r o w i n g p o i n t , b u t n o t after.  The c r i t i c a l p e r i o d , t h e n , appears t o be t h a t  period  o f g r o w t h p r i o r t o development o f some b a r r i e r t o h y p h a l g r o w t h , such as l l g n l f i c a t l o n o r e l o n g a t i o n o f t h e I n t e r n o d e s  93  of  a  culm.  If  the  barrier,  key  to  the  barrier culms, which  i t  w i l l  would  be  the  smut with  families  might  s i m i l a r i t y  be  a  pattern  mycelium younger  of  age  reach The  not  culms  pattern  the  the  IS  least  observation  group  of  as  special  could  the  to is  that  in  growing of  of  area to  the  The  the  older  during  point,  mixed of  of  be  observed.  combination  with  perhaps  be  the  when  t i l l e r  relative  primordia  of  smutting.  considered  is  occupies  lateral  smutting culms.  probably  crown  frequency  It  the  region. a  unique  on  any  appear  to  said  agei  by  same  and  there  culm  culms.  the  i t  culms  the  culms,  of  throughout that  oldest  is  into  While  smutted,  spreading here  f i t  lateral  plants  regard  not  them.  healthy  relationship  place  did  frequently  inoculated  smutting-age  with  appears  f i r s t  rarity  proximity  culm  that  the  a  the  germination  the  and  doubt  to  from  by  principal  frequency  point  This  produced  period  must  beyond  frequently  explained  apply  a  be  culms.  hypothesis" cannot  the  most  close  get  t i l l e r  members.  The  is  not  behind.  to  shorter  be  does  l e f t  expected  allowing  family  mycelium  smutting  compared  smut  the  can the  not  due  seems  to  of  most  when  no it  Hence,  smutted to  in  the  occupy  a  growing smut  that  position with  relationship,  above  plant,  apical  "target" The  be  means.  before  The  the  aget  hyphae can  be  regard  compared  94 Some workers  have t r i e d to r e l a t e s i z e o f seed and,  r a p i d i t y o f g e r m i n a t i o n t o smut s u s c e p t i b i l i t y i n d e t e r m i n i n g i f , from t h e s t a n d p o i n t o f t h e p l a n t , t h e l e n g t h o f t h e c r i t i c a l period i s important.  Results vary.  T e r v e t (1944)  f o u n d t h a t r a p i d , v i g o r o u s l y g e r m i n a t i n g o a t seeds were l e s s s u s c e p t i b l e t o l o o s e and covered smut than l e s s r a p i d l y g e r m i n a t i n g seeds o f each o f s e v e r a l c u l t i v a r s . (1924)  Reed and F a r i s  had found t h i s n o t t o be t h e c a s e , however,using t h e  same h o s t and pathogens.  Brandwein ( 1 9 3 3 )  c o u l d f i n d no  c o r r e l a t i o n between covered smut s u c e p t i b i l l t y and t h e g e r m i n a t i o n and g r o w t h r a t e o f s u s c e p t i b l e and r e s i s t a n t o a t cultivars.  F a r i s ( 1 9 3 * 0 a c t u a l l y found b u n t i n g  percentages  t o be h i g h e r on r a p i d l y g e r m i n a t i n g seeds o f s e v e r a l wheat c u l t i v a r s i n o c u l a t e d w i t h T l l l e t l a F o e t I d a ( W a l l . ) L i v o and T. c a r l e s ; b u t Smith ( 1 9 3 2 a )  c o u l d f i n d no r e l a t i o n between  g r o w t h r a t e and bunt s u s c e p t i b i l i t y i n t h e wheat c u l t i v a r s he examined.  These i n c o n s i s t e n c i e s m i g h t b e s t be e x p l a i n e d  by d i f f e r e n c e s i n e x p e r i m e n t a l procedures and by t h e f a c t t h a t v a r i a t i o n i n seed s i z e , v i g o r o f g e r m i n a t i o n o r g r o w t h r a t e s a r e complex phenomena about w h i c h g e n e r a l i z a t i o n i s r i s k y , p a r t i c u l a r l y when one t r i e s t o r e l a t e them t o a c o n c e p t e q u a l l y complex, such as smut s u s c e p t i b i l i t y . I n c r e a s e d smut s u s c e p t i b i l i t y caused by such ments as deep sowing and c o o l e r growing  treat-  temperatures,  which  t e n d t o slow g e r m i n a t i o n and p l a n t growth r a t e , can a l s o be  95 explained period.  on t h e b a s i s t h a t they a l l o w a l o n g e r  critical  Swinburne (1963) e x p r e s s e d t h i s i d e a f o r wheat-T.  c a r i e s , and Jones and S e i f - E l - N a s r (1939), w i t h r e g a r d t o p l a n t i n g d e p t h , f o r s e v e r a l c e r e a l smuts, i n c l u d i n g U . hordei. 2 . The E f f e c t o f I n o c u l a t i o n and S m u t t i n g on P l a n t Growth Seeds w h i c h had been i n o c u l a t e d grew i n t o p l a n t s w i t h fewer s u r v i v i n g culms than t h o s e w h i c h had n o t , regardless  o f whether o r n o t t h e s e p l a n t s became smutted.  This represents,  as f a r as t h e a u t h o r i s aware, t h e f i r s t  r e p o r t o f any e f f e c t o f i n o c u l a t i o n on nonsmutted p l a n t s when a c o m p a t i b l e host-pathogen c o m b i n a t i o n I s i n v o l v e d . It  i s a l s o t h e f i r s t r e p o r t , o f any k i n d , o f such an e f f e c t  in the barley-U.  hordei  system.  R e p o r t s o f e f f e c t s on g e r m i n a t i o n  o r growth o f non-  smutted i n o c u l a t e d p l a n t s when t h e host p o s s e s s e d t o t a l o r n e a r t o t a l r e s i s t a n c e t o s m u t t i n g were covered i n t h e l i t e r a t u r e review.  Rather s u r p r i s i n g l y , the e f f e c t s  o b s e r v e d i n t h i s work were much more s u b t l e t h a n any o f those reported.  Neither apparent b l a s t i n g , s e e d l i n g  r e d u c t i o n s , nor increased  stand  t i l l e r m o r t a l i t y were observed  i n nonsmutted i n o c u l a t e d p l a n t s i n t h e p r e s e n t work.  The  e a r l y f i n d i n g t h a t nonsmutted "Immune" c u l t i v a r s were I n r e a l i t y b e i n g r a t h e r s e v e r e l y a f f e c t e d by smut caused some  96  alarm.  Of  course,  cultivars large  were  lated  only  of  seedlings  of  these  space  and  In  the  plant  and  magnified  by  p l a n t s w»r©,  the  plant  maturity.  this  a  short  plants.  the  were  could  be  for  a  can  smut  combinations  of  host  investigated  the in  could  where  the  pericarp. these  have  a  as  of  t i l l e r i n g .  is  had  time, in  s i g n i f i c a n t  and  probably  is  inoculated  this  was  is  unable on  particular for  in  at  plants  least "healthy"  some In  to  doubtful  effect  in  to  ultimately found  plants,  present  (discussed  effects i t  space  perhaps  present  been  pathogen  to  noninoculated  of  smut  Due  root  were  A l l  being  stage. for  inocu-  stunting  nonsmutted  that  cases,  reproductivity.  mycelium  long  and  While  l a t t e r  had  the  seedlings  not  resistant  competition.  than  mycelium  Is  the  smut m y c e l i u m  shown- t h a t  situation  barring  infrequent  plant  conclude  such  nonsmutted  treatments  that  inoculated  review)  the  competing  r e l a t i v e l y  safely  on  pattern  vigorous  i f  low  seedling  tissue  beyond  the  between  less  of  at  premise  in  were  on  by  the  The  l i t e r a t u r e  pathogen  i t  combination,  resistant  trate  i f  smut  caused  support  period  would,  inter-treatment  o v e r a l l ,  One  genotyplc  plants  differences  Alternatively,  would  only  the  observed  in  be  that  virulence  plants  s h i f t  could  l i m i t a t i o n s ,  l i g h t ,  i t  the  realized  because  effects  barley  1  effects  present  toward  eliminated  other  *Hannchen  also  planted,  shifts  soon be  The  was  widely  population  c u l t i v a r s ,  It  the  penewere that  on p l a n t  not the  growth  97  when  e x c l u s i o n was  workers  who  cannot  generalize  combination,  by has  has  system  ( i . e . ,  been  to  be  present  strating  the  It  has- t h e  be  observed.  a l l  suffer  based  on  a  from  smutted  small,  and  and  of  upper  culms).  In  may  a  found  single  occur  in  a  In  the  exhibits than  that  U.  hordei  to  barley.  observation more  larger  studies  in  It  numbers  that  way  of  demon-  of  of  plants.  plants  smut  of  can  infection  conclusions  number would  seedlings,  nonsmutted  studies  Inadequate,  of  indirect  mycelium  exhibited  plants  occasional also  in  are  observations.  complement  the  vice-versa.  plants  plants  one  resistance  Resistance  c r i t i c i s m  h i s t o l o g i c a l  showed,  same  however.  smut  major  the  resistance  h i s t o l o g i c a l  often  inoculated  d i s t o r t i o n healthy  the  as  combination  of  seed  that" much  Detailed  studies,  t i l l e r i n g  the  admittedly  advantage  Smutted smutted  sort  studied.  of  of  that  h i s t o l o g i c a l  presence  Nevertheless, present  is  resistance  when  demonstrated,  work  course,  o n ttfhat w a s  partial)  from  Of  details  based  Compared w i t h the  the  commonly  near-exclusion yet  about  such  p a r t i c u l a r l y  different  which  effective.  demonstrated  host-parasite  a  so  did  other  not.  stunting  In of  exhibited  some  leaves  of  smutted  one  the  of  symptoms w h i c h addition  young  spring  reduced  seedlings,  chlorotic culms  to  non-  streaking (but  plantings,  never stripe  and of  98 s m u t t i n g was common i n the upper 1 t o 2 l e a v e s o f smutted culms.  High t e m p e r a t u r e p r o b a b l y induced t h i s symptom  (Schafer  et a l .  t  1962).  T h a t smutted p l a n t s s h o u l d be  a f f e c t e d i n ways o t h e r t h a n t h e s m u t t i n g o f f l o r e t s i s w e l l documented.  Here, t o o , g e n e r a l i z a t i o n i s i m p o s s i b l e .  R e p o r t s o f e f f e c t s on t i l l e r i n g , f o r example, a r e found f o r n e a r l y a l l c e r e a l smuts. i n t i l l e r i n g (Welsh, 1932; and  Manners, 1971).  Some w o r k e r s r e p o r t e d  reductions  Mather and Hansing, i960; Gaunt  Sampson (I927) and H o l t o n and R o d e n h i s e r  (19^2) found i n c r e a s e d t i l l e r i n g w i t h wheat-T. c a r l e s . A l t h o u g h no s u p p o r t i n g  d a t a were p r e s e n t e d , R u t t l e (193*0  o b s e r v e d r e d u c e d t i l l e r i n g b y smutted p l a n t s o f one b a r l e y c u l t l v a r i n o c u l a t e d w i t h U. h o r d e i .  I t must be remembered  t h a t i n a l l o f t h e s e e x p e r i m e n t s , nonsmutted p l a n t s were a l s o inoculated.  Whether t h e y were I n f e c t e d o r n o t one cannot s a y ,  since i n o c u l a t i o n techniques v a r i e d .  I n t h e p r e s e n t work,  however, t h e r e was no s i g n i f i c a n t d i f f e r e n c e i n number o f t i l l e r s p e r p l a n t r e a c h i n g m a t u r i t y when nonsmutted i n o c u l a t e d end  smutted p l a n t s were compared.  This contrasts with Ruttle's  findings. A l t h o u g h smutted p l a n t s produced an u n u s u a l l y number o f culms w h i c h l a t e r d i e d b e f o r e r e a c h i n g  high  maturity,  t h i s phenomenon i s n o t c o n f i n e d t o smutted, o r even t o i n o c u lated, plants. p l a n t growth.  I t seems t o be a normal c h a r a c t e r i s t i c o f Even under t h e b e s t o f c o n d i t i o n s i n t h e  99  f i e l d , such dead culms were commonly observed. (1921) n o t e d them i n wheat and  speculated  Perclval  t h a t they were  p r o b a b l y the r e s u l t of I n s u f f i c i e n t a d v e n t i t i o u s c o u p l e d w i t h d r y growing c o n d i t i o n s . smutting should frequency.  roots  I t i s not c l e a r  why  have the e f f e c t of i n c r e a s i n g t h e i r  P o s s i b l y i t represents  caused by the d e v e l o p i n g  a p h y s i o l o g i c change  s o r l , which deprives  some of  the  culms o f w a t e r o r n u t r i e n t s . One  can o n l y s p e c u l a t e  on t h e r e a s o n f o r the change  i n p a t t e r n of p l a n t development shown i n F i g u r e 30»  ' I t Is  f u r t h e r e v i d e n c e f o r t h e p r e s e n c e of smut mycelium i n nonsmutted i n o c u l a t e d p l a n t s , and  i t p o i n t s up how  much more  s i m i l a r smutted, and. nonsmutted i n o c u l a t e d , p l a n t s are when compared t o n o n i n o c u l a t e d  plants.  I t appears t h a t  p r e s e n c e of the smut i n h i b i t e d t i l l e r p r o d u c t i o n  the  at  the  lowermost nodes, w h i c h then caused the p l a n t s t o produce t h e i r l a t e r a l t i l l e r s from h i g h e r nodes. d e s p i t e the f a c t t h a t I n o c u l a t e d culms t h a n n o n i n o c u l a t e d i s due  plants.  T h i s Is c l e a r  p l a n t s i n i t i a t e d fewer Whether t h i s  inhibition  t o a c t u a l d e a t h of p r l m o r d i a or t o some o t h e r  s u b t l e ) f a c t o r i s not c l e a r .  (more  100  GENERAL CONCLUSIONS A huge l i t e r a t u r e has d e v e l o p e d over many y e a r s c o n c e r n i n g r e s i s t a n c e I n c e r e a l s to smuts and  bunts.  Because o f the o v e r r i d i n g economic c o n s i d e r a t i o n s ,  total  o r n e a r - t o t a l r e s i s t a n c e has been d e a l t w i t h a l m o s t e x c l u s i v e l y ; but from the s t a n d p o i n t  of h o s t - p a r a s i t e homeo-  s t a s i s , p a r t i a l o r I n c o m p l e t e r e s i s t a n c e , such as t h a t w i t h w h i c h t h i s t h e s i s d e a l s , I s a t l e a s t as i m p o r t a n t and b a b l y more so. considerable  One  pro-  must be c a r e f u l i n t r y i n g t o extend  the  knowledge about t o t a l r e s i s t a n c e t o i n c l u d e  p a r t i a l resistance.  T h i s work has not r e v e a l e d any  great  d i f f e r e n c e s , however. P a r t s I and  I I P g i v e two  separate l i n e s of evidence  w h i c h show t h a t i n •Hannchen' b a r l e y I n o c u l a t e d w i t h a dikaryon  to w h i c h I t I s , i n the s t a n d a r d  thinking,  " s u s c e p t i b l e , " nonsmutted I n o c u l a t e d p l a n t s have not escaped I n f e c t i o n b u t , r a t h e r , have remained unsmutted as the r e s u l t of a type of a c t i v e r e s i s t a n c e .  This i s shown  i n P a r t I , w h i c h d e m o n s t r a t e s t h e extreme e f f i c i e n c y w i t h w h i c h the i n o c u l a t i o n p r o c e d u r e i n s u r e s t h a t smut w i l l In contact w i t h the germinating  seed.  be  P a r t I I I shows t h a t ,  as I n t h e m a j o r i t y of t o t a l or n e a r - t o t a l t y p e s of r e s i s t a n c e w h i c h have been I n v e s t i g a t e d i n s e v e r a l host-smut s y s t e m s , U. h o r d e i a f f e c t s t h e growth of nonsmutted p l a n t s , i n d i c a t i n g t h a t t h e mycelium I s p r e s e n t i n a t l e a s t a  101  proportion of  of  cereal  II  genetics  studies,  accounted  from  for.  fitness  infected  for  an  undetermined  length  studies  Part  exclude  to  smut  f i r s t  resistance w i l l  where  Important  a l l  gene's  be  fitness  particular, the  in  inadequate  in  that  are  essential  this  the  past  since  i t  the  are  add  understood  on  two  population  which  Information based  of  closely  in  effects be  any there  which  must  measurement has  time  evidence  knowledge  II,  useful  the  p a r t i a l l y  and  III  the  p a r t i a l l y  and  indicate  curtailment  to  that  smutted  via  host  f i r s t  in  order  It  w i l l  This  event  to be is  given  Inoculated disease  consider  t o t a l l y  thresholds,  pass  reasons  withln-plant  be  d i s t i n c t  for  nonsmutted  of  would  plant.  the  s t a t i s t i c a l  which  be  f o r  and  shows  that  percentage  been  most  Ignores  to  of  often  wlthin-plant  reactions.  measure  the  In  w i l l  In  must  a  plants,  employed,  i t  This  subtract  disease  clear  components  correlated.  to  presents,  smuts,  separate  in  seedlings  time. Part  or  the  plants  them  plants,  stages,  produce able  to  There  again,  plants,  measured  in  some terms  Parts  as  to  well  If  be  the  I as  two fungus  i t  smutting of  with  disease  seem  tellospores.  a  point,  along  because  to  necessary  this  through which  cause  was  obtaining  At  plants,  contribute  resistance. or  once  nonsmutted  It  when  severity.  smutted  these  there,  gets in  between  past  the plant  102  disease fungus One  severity. w i l l  can  think  in  each  of  resistance  is  not  culm.  the  d e a r . in  the  were  those  This  continuous  these  plants and  binations  which  with  t o t a l l y  and  there  the  fungus  a l l ,  of  does  not  succeed surmount the  Is is  the  in  of  threshold.  were  and  the  the  ExI  reason  present  which  for  b a r r i e r ,  so  the  levels  these  a l l is  by  is  high.  be they  a  cannot,  time  In  In  plants  fungus  a l l Is  a  simi-  If  i t  com-  the  were  other  many  in  most  usually  the  findings  combinations, is  plants  I.e.,  which  also  the  succeeds are  stopped  resistance  for  clear  that  proportion, possibly  In  culms  smutted.  Here  then  threshold,  usually  that  a  classes  smooth f o r  Plants  to  with  between-plant  smutted.  applied  plants  plants  culms  and  extremes.  degree  thresholds  evidence  within-  t o t a l l y  high  infrequent  severity  or  a  nonsmutted  most  or  plant.  separately  two  not  f i r s t  of  the  the  the  place  is  two  of  display  the  seedlings.  i t  culms  followed  most  in  threshold  gradation  why  the  b a r r i e r ,  A l l  taking  can  sporulating.  culms  as  gradation  disease  beyond  this  event  having  inoculated  get  second  minority  no  a l l  smutted;  nonsmutted  *Hannchen'  or  involved  However,  either  many  frequency,  smooth  mechanisms  classes  second  combinations  culms  resistance.  frequent  this  the  d i s t i n c t i o n between  of  with  in  smut  highest  minority  crosses  combinations  For  a  of  of  For  only  l a r i t y  It  frequently  best  occurred  If  are  It  the  smut  smutted;  at  the  found  fungus  does  in  not  does  surmounting but  second and,  In  In  In  a  103  intermediate  combinations,  r e l a t i v e l y  more  nonsmutted  plants,  that  two  host,  one  separate after  the  separate can (but  defined  in  two  thresholds  even  not  in  events  think  seedling  and  work.  important.  of  the  Thus  occur.  the  terms  operate  not  of  They  hinted  incidence  as  in  having  remaining  are  How at  of  standpoint  culm  chances  b e c o m e s r?.  combinations,  the  individual  probability. is  high  From  Inoculated. of  the  threshold  high disease  independent) Is  second  both  and  of  the  two healthy  measured  where  this  shows  or  the previous  104  BIBLIOGRAPHY Aaraodt, O.S. and W.H. 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Hansing. i960. Root and shoot development o f w h e a t i n f e c t e d w i t h l o o s e smut U s t i l a g o t r i t i c i . P h y t o p a t h o l o g y 50:645 ( A b s t r . ) .  McCall,  M . A . 1 9 3 4 . D e v e l o p m e n t a l anatomy and h o m o l o g i e s i n wheat. J . A g . R e s . 48*283-321.  Metcalf, . Metcalf,  D.R. 1 9 6 2 . I n h e r i t a n c e o f r e s i s t a n c e t o l o o s e smut, c o v e r e d s m u t , a n d f a l s e l o o s e smut i n t h e b a r l e y v a r i e t y J e t . C a n . J . P I . S c i . 42:176-189. D.R. andS . B . Helgason. 1 9 6 2 , Inheritance o f resistance t o a T r e b i - a t t a c k i n g c u l t u r e o f U s t i l a g o nuda ( J e n s . ) Rostr. i n five barley varieties of Abyssinian origin.  C a n . J . PI. S c i . 42:472-480.  Middleman,  G . K . a n d W . H . Chapman. 1941. R e s i s t a n c e t o f l o r a l i n f e c t i n g l o o s e smut ( U s t i l a g o n u d a ) i n f a l l g r o w n barley v a r i e t i e s a t S t a t e s v i l l e , North Carolina. P h y t o p a t h o l o g y 31*351-353.  108 Milan,  A.  Mills,  J.T. 1966. The d e v e l o p m e n t o f l o o s e smut ( U s t i l a g o a v e n a e ) i n t h e o a t p l a n t w i t h o b s e r v a t i o n s on spore f o r m a t i o n . Trans. B r i t . Mycol. Soc. 49:659-663.  Ohms, R . E .  1939. [ O n l o o s e smut o f w h e a t i n r e l a t i o n t o tillering}. R e v . A p p l . M y c o l . 18:447 ( A b s t r , ) .  and W.M.\Bever. 1954. E f f e c t of U s t i l a g o t r i t i c i i n f e c t i o n on t h i r d i n t e r n o d e e l o n g a t i o n i n r e s i s t a n t and s u s c e p t i b l e w i n t e r wheat. Phytopathology 44:500 ( A b s t r . ) .  .  .  ;  1955.  Types o f s e e d l i n g r e a c t i o n s  of  K a w v a l e and Wabash w i n t e r w h e a t t o t h r e e p h y s i o l o g i c races of Ustilago t r i t i c i . P h y t o p a t h o l o g y 45:  513-516.  Oort, A.J.P. 1939. I n o c u l a t i o n e x p e r i m e n t s w i t h l o o s e smut wheat and b a r l e y . P h y t o p a t h o l o g y 29:717-728. '  S p e c i a l i s a t i o n o f l o o s e smut o f w h e a t .  1947.  problem f o r the breeder. Percival,  J. 1921. London.  The w h e a t p l a n t : a momograph, 205 P»  Person,  C.  Genetic aspects  Person,  C. and W.J. C h e r e w i c k . in Ustilago. Can. J .  1967.  45:1193-1203.  Poehlman, J . M , 1949. resistance  1943-48.  T l j d s c h r . PI.  of parasitism.  1964. Genet.  Z.  of  A  53:25-43. Duckworth, L t d .  Can. J .  Bot.  Infection multiplicity & C y t o l . 6:12-18.  Agronomic c h a r a c t e r i s t i c s and d i s e a s e of winter barleys tested i n Missouri, R e s . B u l l . U n i v . M o . N o . 442.  Poehlman, J . M . and C , K . C l o n i n g e r . 1955. Resistance to three barley smut d i s e a s e s i n M i s s o u r i e a r l y b e a r d l e s s s t r a i n s , Agron,  J . 47:243-246.  P o p p , W.  ,  1951. I n f e c t i o n i n seeds and s e e d l i n g s o f wheat and b a r l e y i n r e l a t i o n t o development of l o o s e smut. P h y t o p a t h o l o g y 41:261-275. 1959.  A new a p p r o a c h t o t h e embryo t e s t  l o o s e smut o f wheat i n a d u l t p l a n t s .  49:75-77. Reed,  G.M.  for  predicting  Fnytopathology  1924. V a r i e t a l s u s c e p t i b i l i t y o f wheat t o l a e v i s Kuhn. P h y t o p a t h o l o g y 14:437-450.  Tilletia  109  Reed, G.M.  1929. New physiologic races of the oat smuts. Torrey Bot. Club 56:449-470,  Bull.  , 1933, Influence of the growth of the host on smut development. Proc. Amer. P h i l . Soc. 79s303-326. Reed, G.M. and J.A, F a r i s , 1924. Influence of environal factors on the i n f e c t i o n of sorghum and oats by smuts. I I , Experiments with covered smuts of oats and general considerations. Amer. J , Bot, 11:579-599* Reed, G.M. and T,R. Stanton, 193^. Inheritance of resistance to loose and covered smuts i n Markton oats, J , Agr, Res. 56:159-175. Reichert, I . 1930. The s u s c e p t i b i l i t y of American wheat v a r i e t i e s r e s i s t a n t to T i l l e t i a t r i t i c i . Phytopathology  20:973-980.  Robinson, R.A,  1973. Horizontal resistance.  52:483-501.  Rev. PI. Pathol.  Rodenhiser, H.A, and C.S. Holton, 1942, V a r i a b i l i t y i n reaction i n wheat d i f f e r e n t i a l v a r i e t i e s t o physiologic races of T i l l e t i a l a e v i s and T, t r i t i c i . Phytopathology 32:158-165.  Ross, J.G., W.. Semeniuk, D.K,. Taylor and B.C. Jenkins, 1948. Factors a f f e c t i n g the degree of i n f e c t i o n of barley by loose smut (Ustilago nuda (Jens.)Rostr,). S c i . Agr. 28:481-492. 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E f f e c t i v e methods of inocul a t i n g barley seed with covered smut. Phytopathology  32:1015-1021.  Taylor, J.W. and M.G. Zehner. 193L E f f e c t of depth of seeding on the occurrence of covered and loose smuts of winter barley. J . Amer. Soc. Agron. 23:132-141. Tervet, I.W. 1940. Problems i n the determination of physiologic races of Ustilago avenae and U. l e v i s . Phytopathology  30*900-913. _. 19*1-1.  The r e l a t i v e s u s c e p t i b i l i t y of d i f f e r e n t l o t s  of oat v a r i e t i e s to smut.  Phytopathology  31:672-673,  1944. The r e l a t i o n of seed q u a l i t y to the development of smut i n oats. Phytopathology 34:106-115.  Thomas, P.L. 1965. Virulence i n Ustilago hordei.(Pers.) Lagerh, M.Sc. Thesis, University of Alberta, Edmonton, Canada,  31  P.  Thomas, P.L. and C. Person. 1965. Genetic c o n t r o l of l o w virulence i n Ustilago. Can. J . Genet. & Cytol.  7*583-5^8.  112 Tingey,  D . C . a n d B. T o l m a n . 1934. Inheritance t o l o o s e smut o f w h e a t . J . Ag. Res.  of  resistance  48:631-655.  T i s d a l e , W.H. and V . F . Tapke. 1924. I n f e c t i o n of b a r l e y by U s t i l a g o nuda t h r o u g h s e e d - i n o c u l a t i o n . J . A g , R e s ,  29:263-284,  Vanderwalle.  R.  tritici Vogel, Waud,  Wells,  1942.  Note s u r l a b i o l o g i e d U s t i l a g o nuda 1  Schaf.  Bull. Inst.  Agron.Gembloux  11:103-113.  H, J . 1 9 5 6 . A c o n v e n i e n t g r o w t h medium f o r N e u r o s p o r a crassa. M i c r o b , G e n e t . B u l l , N o . 13. J.L.  and R.J. M e t z g e r . 1970. I n h e r i t a n c e o f a new ( B t 8 ) f o r r e s i s t a n c e t o common b u n t i n w h e a t . Crop S c i . 10:703-704,  factor  S.A, 1958, Inheritance of reaction to U s t i l a g o hordei (Pers.) Lagerh. i n cultivated barley. Can, J .  P I . S c i . 33:45-60.  Welsh,  J.N. 1 9 3 2 . The e f f e c t plant vigor i n oats.  Western,  Williams,  o f smut on r u s t d e v e l o p m e n t Sci. Ag. 13:154-164,  and  J.H. 1 9 3 6 . The b i o l o g y o f o a t s m u t s . TV, The i n v a s i o n o f some s u s c e p t i b l e a n d r e s i s t a n t o a t v a r i e t i e s , i n c l u d i n g Warkton, by s e l e c t e d b i o l o g i c a l species of s m u t , U s t i l a g o a v e n a e ( P e r s . ) J e n s , a n d U". k o l l e r l Wille. A n n . A p p l . B i o l . 23:245-263. W. a n d U , N . V e r m a . 1 9 5 4 , I n v e s t i g a t i o n s on r e s i s t a n c e t o d i s e a s e among s p e c i e s o f t h e g e n u s A v e n a , I, Resistance to p h y s i o l o g i c r a c e s o f U s t i l a g o avenae and U. k o l l e r i . Ann. A p p l . B i o l . 4TT405-416. ;  Woodward,  R.W. a n d D . C . T i n g e y . 1941, w i t h c o v e r e d smut o f b a r l e y ,  33:632-642.  Woolman,  Zade, A .  I n o c u l a t i o n experiments J , Amer, Soc. A g r o n ,  H.M. 1 9 3 0 , I n f e c t i o n phenomena a n d h o s t r e a c t i o n s caused by T . t r i t i c i i n s u s c e p t i b l e and n o n s u s c e p t i b l e v a r i e t i e s of wheat. P h y t o p a t h o l o g y 20:637-653, 1931• Der l a t e n t e p i l z e b e f a l l und s e i n e f o l g e e r s c h e i n u n g e n m i t b e z u g a u f s o r t e n i m m u n i t M t und beizwirkung. F o r t s c h r , D e r L a n d w . 6:338-391.  APPENDIX  113  A  S t a t i s t i c a l  comparison  Two  binomial  a  confidence  using  population  1.96*,  the  means  of  ratios  can  interval  be  0,95  for  ratios  s t a t i s t i c a l l y  about  1964),  (Li,  z, v a l u e  binomial  The  the  compared  difference  shorthand  of  form,  their  using  alpha, l i s :  where 1 D  = The d i f f e r e n c e between the o b s e r v e d ratios w h i c h l a r e to be compared (an e s t i m a t e of their population difference), p-j_= T h e p r o p o r t i o n o f s a m p l e o n e observations of a given outcome, Pg= The p r o p o r t i o n o f sample two observations of a given outcome, ni=  The  number  of  sample  one  observations,  n£=  The  number  of  sample  two  observations,  In the  applying  sample  confidence  contains  (in  difference exists,  the  i f is  one  the  difference  greater  than  direction),  between interval  the  two  about  between  the  there  calculated is  r a t i o s . D,  of  a If  no  course,  zero•  According minimum  test,  p r o p o r t i o n s , D, interval  s i g n i f i c a n t difference  this  sample  s t a t i s t i c s  p^  to  Steel  sizes and  pg  and  must to  be  Torrie  (i960),  observed  accurately  in  certain  order  estimate  the  for  the  114  c o r r e s p o n d i n g p o p u l a t i o n parameters as f o r a normal distribution.  T h i s i s shown i n t a b l e A . l .  TABLE A . l BINOMIAL SAMPLE SIZES FOR NORMAL APPROXIMATION TO APPLY P  _  .  Number o b s e r v e d i n smaller class  .  (ml  ;  ~~~ ' Sample s i z e (n)  0.5  15  30  0.4  20  50  0.3  24  80  0.2  40  200  0.1  60  600  0.05  70  1400  115  APPENDIX B  o>  II  -«  o  <^> "ci  W -<? o  o  •-. o V s: <=i E 2.  3  i -o  =j s  "d •<? <j II «?  ^ •>>  o S "ci ci  3  -  Si  "CJ  «=^ 3 cJ s; ci  o  S E  -a  <j  E -d  Si  £ ^>  3  -z. ( \J  /  / X  O  *  /  ")—^  — > s ^y/  -J  •2 ^ ,  /  /  or /  ^  -S!  0  •o *e~cs ^  c^J  #  3  o  PUBLICATIONS G r o t h , J.V., V.E. Comstock and N.A. Anderson. 1968. R e s i s t a n c e of p a i r s of y e l l o w and brown-seeded i s o g e n i c l i n e s of f l a x to Rhi z o c t on i a s e e d l i n g b l i g h t . Phytop a t h o l o g y 58:1052 ( A b s t . ) . G r o t h , J.V. and N.A. Anderson. 1969. Heterokaryon i n c o m p a t i b i l i t y i n R h i z o c t o n i a s o l a n i . . P h y t o p a t h o l o g y 59:1028 ( A b s t . ) . G r o t h , J.V., V.E. Comstock.and N.A. Anderson. 1970. E f f e c t of seed c o l o r on t o l e r - ance of f l a x to s e e d l i n g b l i g h t caused by R h i z o c t o n i a s o l a n i . Phytopathology 60:379-380. Anderson, N.A., H.M. S t r e t t o n , J.V. Groth and N.T. F l e n t j e . 1972. G e n e t i c s of h e t e r o k a r y o s i s i n Thanatephorus cuc urne r i s. P h y t o p a t h o l o g y 62 : 105 7-1065. G r o t h , J.V. 1973. The e f f e c t of unequal mating-type r e p r e s e n t a t i o n on i n f e c t i o n of b a r l e y by U s t i l a g o h o r d e i . P r o c e e d i n g s of the Second I n t e r n a t i o n a l Congress of P l a n t P a t h o l o g y #708 ( A b s t . ) . Person, C O . and J.V. G r o t h . 19 73. Stab i l i z i n g s e l e c t i o n i n p o l y g e n i c para s i t i c systems. I n v i t e d paper p r e sented a t the Second I n t e r n a t i o n a l Congress of P l a n t P a t h o l o g y . G r o t h , J.V., and C O . person. 197A. The e x p r e s s i o n of r e s i s t a n c e i n b a r l e y to Ustilago hordei. 66th Annual Meeting of the American Phytop a t h o l o g i c a l S o c i e t y , Vancouver ( A b s t . ) .  AWARDS . 1963 1965 1967.  Chapman F o u n d a t i o n F o r e s t r y arship . Member X i Sigma P i Honorary Fraternity . Chaney Award to O u t s t a n d i n g Senior.  ScholForestry Forestry  

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