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Streptomyces scabies and its habitat Baker, Robert Arnold 1952

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C-,y 1  STREPT0EYCE3 SCABIES AUDITS HABITAT by ROBERT, ARNOLD. BAKER  A THESIS SUBMITTED' IN PARTIAL MJLPILMEOT OF THE- RE^UIREMEBTS: FOR THE DEGREE OF MASTER. OF SCIENCE. IN AGRICULTURE i n the Department of Agronomy  (Soils)  We a c c e p t t h i s t h e s i s as conforming to t h e standard required: from c a n d i d a t e s f o r the degree- of MASTER. OF SCIENCE IN AGRICULTURE  Member® o f the Department o f Agronomy ( S o i l s ) THE UNIVERSITY OF BRITISH COLUMBIA April,  1952  STREPTOMYCES SCABIES AND  ITS HABITAT  (Abstract)  A study i n v o l v i n g v a r i a t i o n i n s t r a i n s o f the scab organism as i s o l a t e d from a s o i l i s reported.  in British  A s s o c i a t e d with t h i s i s a study of  from s c a b - f r e e and  potato  Columbia soils  scab-infested areas.  Exchange c a p a c i t y and r e l a t e d s t u d i e s of a number of s o i l samples i n d i c a t e a t r e n d toward h i g h e r average exchange c a p a c i t y , h i g h e r average exchange c a l c i u m h i g h e r average calcium-potassium from s c a b - i n f e s t e d a r e a s .  r a t i o s i n the  and  samples  There i s a l s o a t r e n d toward  h i g h e r organic matter content and l i g h t e r s o i l  textures  i n the scab-producing  soils.  definite correlations  can be e s t a b l i s h e d under the method  of s o i l  sampling  Thirty-four  I n s p i t e of these trends  adopted. strains  of Streptomyces s c a b i e s i s o l a t e d  from d i s e a s e d White Rose tubers grown on the ranch markedly i n c u l t u r a l c h a r a c t e r i s t i c s and The  no  i n pathogenicity.  e f f e c t of hydrogen i o n c o n c e n t r a t i o n on f o u r of  s t r a i n s shows a p o s i t i v e  vary  c o r r e l a t i o n between pH,  these  amount o f  growth and hydrogen i o n c o n c e n t r a t i o n up t o the optimum pH of 7 t o £ and beyond t h i s range a negative exists.  The  i n h i b i t i n g a c i d pH i s 3.4  f o r two  correlation . strains  and  between 4.0 and 5.5 f o r the other s t r a i n s .  The l i m i t i n g  a l k a l i n e pH appears t o be beyond pH 11.6. Microphotographs of the Streptomyces s c a b i e s show t y p i c a l open s p i r a l s and chains o f c o n i d i a  0.5 t o 1.0 microns i n diameter.  Scab c o n t r o l measures conducted i n pots i n the greenhouse and  using a severely  scab-infested  soil  sample from the ranch  i n d i c a t e no c o n t r o l by mercuric c h l o r i d e a p p l i c a t i o n s . cations  of sulphuric  Appli-  a c i d , sulphur and c a l c i u m hydroxide  i n d i c a t e t h a t a pH o f $.0 or g r e a t e r i s an e f f e c t i v e but not complete c o n t r o l .  An a c i d pH o f 5.0 g i v e s l e s s c o n t r o l than  pH 8.0 and more a c i d i c r e a c t i o n s applications  g i v e even l e s s c o n t r o l .  The  o f these necessary t o e f f e c t c o n t r o l a r e t o o h i g h  t o be of p r a c t i c a l v a l u e . The  f u n g i c i d a l e f f e c t o f compound P-162 as determined under  laboratory field  procedures i s no i n d i c a t i o n o f i t s e f f i c a c y i n the  o r greenhouse.  L a b o r a t o r y technique i n d i c a t e s t h a t most  s t r a i n s are completely i n h i b i t e d a t 100 t o 230 p a r t s  per m i l l i o n  of compound P-162 w h i l e i n the greenhouse t e s t s 40 p a r t s per m i l l i o n proved e f f e c t i v e i n g i v i n g p a r t i a l c o n t r o l . p r a c t i c a l value o f P-162 i n the f i e l d since  i s as y e t t o be determined  i t s commercial value and i t s u s e f u l n e s s as a  measure i n the f i e l d  i s unknown. .  The  control  ACKNOWISDGMENTS:  The w r i t e r wishes, to; express h i s a p p r e c i a t i o n to D r . D.G. L a i r d and D r . C.A. Howies o f t h e D e p t . o f Agronomy ( S o i l s ) , U.B.C-. f o r t h e i r encouragement, h e l p f u l c r i t i c i s m s and t h e use of l a b o r a t o r y  facilities.  S i n c e r e a p p r e c i a t i o n i s expressed t o D r . RJS;. l i t z ; p a t r . i c k and. D r . IT..S-. Wright o f the Dominion S l a n t Pathology L a b o r a t o r y and to Dr.- W»C. Gibson of the Grease C l i n i c Research U n i t f o r t h e use o f photographic equipment.  The. a u t h o r also, wishes t o acknowledge the  h e l p of Mr. L . Gilmore and the. o p e r a t o r s of Richmond Farms, Soda Creek, B.C'., i n the c o l l e c t i o n o f s o i l samples a n d p r o v i d i n g the data r e l a t i v e t o t h e h i a t d r y , c l i m a t e and a g r i c u l t u r a l p r a c t i c e s on t h e farm. F i n a l l y the author wishes, to express h i s a p p r e c i a t i o n to h i s . w i f e who not only a s s i s t e d m a t e r i a l l y but also, put up w i t h h i s . i d i o s y n c r a s i e s d u r i n g t h e course o f t h i s  atudy.  TABLE 03? CONTENTS  INTRODUCTION  I  REVIEW OF LITERATURE;  3  The c a u s a t i v e agent o f common p o t a t o scab  3  V a r i a t i o n w i t h i n s t r a i n s of Streptomyces s c a b i e s .  4  Presence of Streptomyces s c a b i e s i n the  soil.  The e f f e c t o f pathogen on the h o s t . C o n t r o l measures  •j  5 6 7  Dips  7  B r e e d i n g f o r r e s i s t a n c e t o scab  8  I n f l u e n c e of s o i l o r g a n i c matter and microbial populations.  9  E f f e c t of. s o i l m o i s t u r e , a e r a t i o n and temperature. EXPERIMENTAL  10 12  H i s t o r y of the a r e a  12  The s o i l s under study  15  Chemical study of s o i l samples  16  B u f f e r c a p a c i t y of s o i l sample X V I I I  20  B a c t e r i o l o g i c a l counts o f s o i l samples. 23 Streptomyces s t u d i e s I s o l a t i o n of s t r a i n s of Streptomyces scabies^ Proof o f i d e n t i t y of the streptomyces isolates  25 25 27  Greenhouse p a t h o g e n i c i t y t r i a l s R e i s o l a t i o n of the i n o c u l a t e d organisms  29 34  I s o l a t i o n from the tubers.  34  I s o l a t i o n from the q u a r t z sand  34  Morphology o f t h e Streptomyces s c a b i e s isolates  35  S u s c e p t i b i l i t y of s t r a i n s t o hydrogen ion  36  concentration  Methods f o r c o n t r o l o f scab i n c i d e n c e  46,  Influence of s o i l r e a c t i o n  47  E f f e c t of increased aeration  52  E f f e c t of mercuric  54  chloride  I n f l u e n c e o f Compound P ~ l 6 2 E f f e c t o f P-162 on Streptomyces s c a b i e s s t r a i n s under study. Greenhouse t r i a l s w i t h P » l 6 2 SUMMARY AND CONCLUSIONS BIBLIOGRAPHY APPENDIX I «- Micro- photographs o f r e p r e s e n t a t i v e I s o l a t e s o f Streptomyces scabies, s t r a i n s under study. APPENDIX I I - Composition, o f media used i n t h i s study.  55 56 6l 63:  TABLES  Table I  Base exchange a n a l y s e s of s o i l samples  Table I I  T o t a l counts o f f u n g i , b a c t e r i a and. actinomycetes of s o i l . samples 24  Table. I l l  C u l t u r a l i d e n t i f i c a t i o n , of Streptomyces s c a b i e s i s o l a t e s ;  28  Table I T  Streptomyces i s o l a t e s grouped . a c c o r d i n g t o type o f l e s i o n  31  Table. V  I n i t i a l and f i n a l pH. of medium i n which Streptomyces. s c a b i e s s t r a i n s are grown for. 21 days, a t 27°C.  39  The e f f e c t of. s o i l r e a c t i o n i n the c o n t r o l of common potato scab,  $1  The e f f e c t of s o i l r e a c t i o n and a e r a t i o n i n the c o n t r o l of common potato scab  53  E f f e c t of. mercuric c h l o r i d e In the c o n t r o l of common potato scab  55  The f u n g i s t a t i c and f u n g i c i d a l e f f e c t of Compound: P-162 on Streptomyces s c a b i e s i s o lates  59  E f f e c t of Compound P-162 as a c o n t r o l f o r common potato scab  62  T a b l e VI  Table: V I I  Table V I I I  Table IX  Table X  18  FIGURES  Fig* 1  Richmond Farms, Soda Creek, B.C..  Fig. 2  S u l p h u r i c a c i d buffer, curve of sample; No* X V I I I .  21  C a l c i u m hydroxide b u f f e r curve of sample No. XVIII..  22  The e f f e c t o f hydrogen Ion c o n c e n t r a t i o n , on. Streptomyces. s c a b i e s s t r a i n 27*  41  The e f f e c t of hydrogen i o n c o n c e n t r a t i o n on Streptomyces s c a b i e s s t r a i n 33•-  42  The e f f e c t of. hydrogen i o n c o n c e n t r a t i o n on Streptomyces s c a b i e s s t r a i n 39 •  43  The e f f e c t of hydrogen i o n c o n c e n t r a t i o n on Streptomyces s c a b i e s s t r a i n 48*  44  The e f f e c t of hydrogen i o n c o n c e n t r a t i o n on Streptomyces scabies eastern s t r a i n .  45  T y p i c a l samples of tubers w i t h r a t i n g they were g i v e n .  48  Fig. 3 Fig. 4  Fig.. 5  Figi 6  Fig. 7  Fig. 8  Fig. 9  14  1. "Common scab  INTRODUCTION 11  of the potato h a d been r e c o g n i z e d  for  many years, p r i o r t o the t u r n of the present  yet  little  century  or no a t t e n t i o n had: been f o c u s e d upon i t .  i s apparent from a statement by B o l l e y (7) who  This,  reported i n  1893:At present**.the d i s e a s e i s so common an accompaniment of the crop that l i t t l e a t t e n t i o n , seems to be g i v e n the m a t t e r i n the making of s a l e s . Scabbed and f a i r skinned potatoes are bought and s o l d as i n d i f f e r e n t l y as are large: and small eggs* The only p o i n t markedly n o t i c e a b l e i s t h a t , when t h e r e i s a, chance f o r the e x e r c i s e of c h o i c e , the smooth product i s always selected.. Despite: t h i s obvious ing  l a c k of i n t e r e s t , an awaken-  to the s e r i o u s n e s s of the d i s e a s e was  becoming apparent  d u r i n g the f i r s t decade of the present century, but the blem was  pro-  not s q u a r e l y faced, i n the United S t a t e s nor i n Can-  ada, u n t i l about 1918  and 1919  r e s p e c t i v e l y . During  these  y e a r s both c o u n t r i e s e s t a b l i s h e d potato grades which were based on a number of f a c t o r s i n c l u d i n g s i z e , and 1  freedom  2  from blemishes*  T h i s p r o v i d e d the s t i m u l a t i o n n e c e s s a r y t o  focus the a t t e n t i o n o f r e s e a r c h workers on potato scab trol.,, but the problem  i s s t i l l f a r from being  con-  satisfactorily  solved. Potato scab has, u n t i l r e c e n t l y , been o f minor importance  i n B r i t i s h Columbia  but w i t h the? e x t e n s i o n o f ^  commercial  potato p r o d u c t i o n i n t o many areas- o f the I n t e r i o r  i t s c o n t r o l i s becoming a problem  o f major Importance.  Iso-  l a t e d i n s t a n c e s of s e r i o u s scab i n f e c t i o n have been r e p o r t e d and one of t h e s e , from the C a r i b o o , has prompted the study reported a t t h i s  time.  S o i l i s the natural, h a b i t a t f o r the organism p o n s i b l e f o r potato scab, and y e t , some s o i l s produce  resscab  when p l a n t e d to. p o t a t o e s w h i l e o t h e r s do not, even on the one ranch and w i t h i n a l i m i t e d a r e a .  S o i l d i f f e r e n c e s are  therefore being i n v e s t i g a t e d , a s a r e s t r a i n s of the organism and t h e response: o f these t o various, treatments.  3 2.  REVIEW OF LITERATURE.  The c a u s a t i v e agent o f common potato  scab.  Thaxter (103) i n I89O was the f i r s t t o i s o l a t e ; and prove the p a t h o g e n i c i t y of the organism r e s p o n s i b l e f o r common potato  scab.  He named h i s I s o l a t e Oospora  s c a b i e s and gave a s h o r t d e s c r i p t i o n o f i t s , morphology and its effect  on the potato  tuber.  The present nomenclature o f "Streptomyces s c a b i e s " came about i n two d i s t i n c t s t e p s .  F i r s t , Gussow (35) i n  I.914 r e c o g n i z e d the: s i m i l a r i t y between Oospora s c a b i e s o f Thaxter and the Actinomyces bo v i s of H a r z .  Since H a r z  1  g e n e r i c name had precedence Gusaow p l a c e d the scab organism w i t h the Actinomyces.  Waksman and H e n r i c i (108) were r e s -  p o n s i b l e f o r the change of nomenclature from Actinomyces t o Streptomyces.  T h e i r change; was. n e c e s s i t a t e d by the r e a l i z a -  t i o n t h a t Actinomyces b o v i s d i f f e r e d from the other members of t h i s genus both p h y s i o l o g i c a l l y and m o r p h o l o g i c a l l y and s i n c e , as. a l r e a d y mentioned,, Actinomyces b o v i s had precedence the new. g e n e r i c name o f Streptomyces was adopted. organism r e s p o n s i b l e f o r the p r o d u c t i o n of potato  Thus the scab eame  to be known a s Streptomyces s c a b i e s (Thaxter) Waksman and Henrici*  The genus i s d e s c r i b e d as being s t r i c t l y  aerohic  and composed o f t r u e mycelium, t h a t m u l t i p l i e s by chains o f c o n i d i a from a e r i a l hyphae*  4. V a r i a t i o n w i t h i n s t r a i n s , of Streptomyces  scabies*  I t has become obvious that many s t r a i n s o f S t r e p t o myces s c a b i e s e x i s t i n t h e i r n a t u r a l environment, the s o i l * Both Waksman Cl06) and G i l l e s p i e  (29) have p o i n t e d out the  v a r i a b i l i t y of d i f f e r e n t s t r a i n s i n t h e i r tolerance to acidity*  Waksman found that, while some s t r a i n s f a i l e d t o  grow, i n a r t i f i c i a l media o f PH5*6* o t h e r s grew s l o w l y a t PH4*8*  G i l l e s p i e observed the same type o f EH v a r i a t i o n  when using t a r t a r i c a c i d to i n c r e a s e the hydrogen i n conc e n t r a t i o n o f h i s medium. & p o s i t i v e tyrosinase r e a c t i o n i s given as a d i s t i n g u i s h i n g c h a r a c t e r i s t i c of Streptomyces s c a b i e s y e t Waksman (106)= i n 1922 c l a i m e d t h a t not a l l s t r a i n s o f the organism do produce a brown pigment  i n tyrosin.  f a c t has a l s o been observed by D o u g l a s ^ 1  This  latter  1952.  M i l l a r d and B a r r (74J, i n England proved that the v a r i a b i l i t y o f the pathogen makes i t s e l f apparent i n the type o f l e s i o n s produced by i n d i v i d u a l s t r a i n s .  Thus, they  showed t h a t e l e v e n d i f f e r e n t s t r a i n s produced v a r y i n g t y p e s of  scab l e s i o n s and only one of the e l e v e n produced the same  type o f l e s i o n as Thaxter*s o r i g i n a l i s o l a t e .  Physiological  and m o r p h o l o g i c a l v a r i a t i o n s e x i s t e d between a l l these strains*  S c h a a l (90) concludes that new p a r a s i t i c r a c e s o f  Streptomyces s c a b i e s may a r i s e from v a r i a n t s produced  Personal  communication.  either  5. i n the s o i l or on the t u b e r . Leach et a l . (53) v a r i e t y may  observed t h a t whereas a potato  be r e s i s t a n t t o one  s t r a i n o f Streptomyces s c a b i e s ,  another s t r a i n w i l l produce severe scabbing on t h a t same tuber v a r i e t y .  F o r i n s t a n c e , Cayuga p o t a t o e s , a n o r m a l l y  s c a b - r e s i s t a n t v a r i e t y , have been shown to be s e v e r e l y scabbed by two  d i f f e r e n t s t r a i n s of Streptomyces s c a b i e s ( 4 1 ) .  Thomas (104) observed t h a t s i x p h y s i o l o g i c r a c e s of S t r e p t o myces s c a b i e s v a r i e d markedly i n t h e i r p a t h o g e n i c i t y on t e n d i f f e r e n t potato v a r i e t i e s . Bresence o f Streptomyces s c a b i e s i n the s o i l . Pratt. (82)  and Lutman (58). have presented  showing t h a t the scab organism not n e c e s s a r i l y brought eased t u b e r s .  evidence  I s Inherent, i n some s o i l s and  i n through the i n t r o d u c t i o n of d i s -  They p l a n t e d s c a b - f r e e , d i s i n f e c t e d t u b e r s on  v i r g i n s o i l and h a r v e s t e d s e v e r e l y scabbed o b s e r v a t i o n s by Lutman (59)  erops.  Further  i n d i c a t e t h a t scab w i l l r e t u r n  a f t e r f i v e t o s i x y e a r s of c o n t i n u o u s potato c r o p p i n g  on  l a n d p r e v i o u s l y under a varied, nineteen-year r o t a t i o n of c r o p s other than p o t a t o e s .  Millard  (73)  on the other hand  found severe scab i n the f i r s t potato crop grown on l a n d t h a t had been i n permanent pasture f o r the p r e v i o u s f i f t y years. That the actinomycetes  spores and mycelium  may  e x i s t i n a. v i a b l e s t a t e over a p e r i o d of y e a r s i s i n d i c a t e d  by Lutman ( 6 l ) who  r e p o r t e d the presence  of such spores  and  mycelium i n the i n t e r i o r of thoroughly d i s i n t e g r a t e d p o t a t o humus a f t e r a. p e r i o d o f t h r e e to seven years.The e f f e c t o f pathogen on the h o s t . The outward appearances of the scab p u s t u l e s or l e s i o n s a r e w e l l known, but the p o r t of e n t r y of the a c t i n o mycete and  i t s subsequent a c t i o n on the tuber are not  too  clear. Both F e l l o w s (24) and Lutman (56),  are of the o p i n i o n  t h a t i n f e c t i o n of the t u b e r occurs through time of t h e i r c o n v e r s i o n to l e n t i e e l s . tuber development the epidermis  the stomata a t the  At t h i s p o i n t i n  of the new  and  incompletely-  formed corky l a y e r i s r u p t u r e d to expose the parenchyma c a l l s underneath.  F e l l o w s found t h a t i n f e c t i o n o c c u r r e d o n l y a t  the a p i c a l or growing end of the t u b e r .  Histological sections  of these i n f e c t e d t u b e r s showed t h a t the e f f e c t of the a c t i n o mycete f i l a m e n t s extended along the p h e l l o g e n of the c e l l s of the subepidermal  l a y e r , by way  became t h i c k e n e d and  o f the middle l a m e l l a which  darkened*  Lutman has concluded t h a t the a c t u a l scab d i s e a s e d tuber i s due cork cambium.  to the hypertrophy  of.the  of the c e l l s o f the  The c o n d i t i o n i s always accompanied, i n deep  scab, by an abnormal i n e r e a a e i n the c e l l s of t h a t l a y e r ,  due  to the c o n t i n u e d r e g e n e r a t i o n of the cork cambium l a y e r from the outer c e l l s of the s t a r c h parenchyma.  The  h y p e r t r o p h i c d a r e a are g r e a t l y t h i c k e n e d due tion*  c e l l s of the  to t h e i r s u b e r i s a -  I h i l e comparing s u s c e p t i b l e and o f tubers Lutman ('57)  resistant varieties  observed that r e s i s t a n t r u s s e t v a r i e t i e s  were c h a r a c t e r i z e d by c l o s e - t e x t u r e d l e n t i c e l s p a r t l y b u r i e d under the s k i n s u r f a c e and f i l l e d w i t h s m a l l c e l l s t h a t somewhat p r o t e c t e d the tuber from i n f e c t i o n . D a r l i n g (19) f i r m e d Lutman*s o b s e r v a t i o n ,  and  con-  f u r t h e r found t h a t , i n the  case of r e s i s t a n t v a r i e t i e s , the periderm was. s u b e r i z e d l i e r and  extended f u r t h e r i n t o the l e n t i c e l s .  r e s u l t e d a s h o r t e r i n f e c t i o n p e r i o d and  ear-  Thus there  greater protection of  the u n d e r l y i n g meristematic t i s s u e s from t h e i n f e c t i n g a c t i n o mycete. Hot  o n l y does Streptomyces s e a b i e s a f f e c t the  tuber  but i t a l s o causes n e c r o t i c l e s i o n s on the potato stems. T h i s has been demonstrated by Hooker (38), (40) and by Lutman  Hooker and  Kent  (.62).  A l t h o u g h the potato i s the main host f o r the genic Streptomyces s c a b i e s , i n f e c t e d by the organism.  patho-  i t i s not the only p l a n t t h a t i s Hooker (38)  reported that a single  c u l t u r e of Streptomyces s c a b i e s t h a t caused r o o t n e c r o s i s p o t a t o s i m i l a r l y a f f e c t e d s e e d l i n g s of b a r l e y , o a t s , tomato, egg bean.  onion,  p l a n t , squash, r e d beet, c a r r o t , p a r s n i p and  Lefebv.re C54);» too, has  reported  on  Lima  the presence of  Streptomyces s c a b i e s on r a d i s h grown i n A l a s k a . C o n t r o l measures. Dips. The  e a r l i e s t c o n t r o l measure a g a i n s t potato scab  the use o f d i p a % . or a d i s i n f e c t i o n of the seed t u b e r s . H  was  Bolley  8. (7)  i n 1893  recommended the use o f b i c h l o r i d e of mercury a t  a. 311000 d i l u t i o n .  He found mercuric c h l o r i d e more e f f e c t i v e  than e i t h e r Bordeaux mixture or potassium s u l p h i d e . Garman (28)  i n Kentucky s t a t e d that c o r r o s i v e sublimate  e f f e c t i v e a s a control,, while formol was tive.  1898  In  Work by Jones (46),  (6) and Cairns: (10)  Coons, (16)>  relatively  was  ineffec-  B l o d g e t t and Howe  indicated, t h a t formaldehyde  c h l o r i d e were e f f e c t i v e c o n t r o l measures.  and m e r c u r i c  These were s u p e r i o r  to a v a r i e t y of o r g a n i c and i n o r g a n i c compounds t e s t e d a t varying concentrations.  C o n t r a r y to the above, Sanford  (87)  r e p o r t e d a b s o l u t e l y no c o n t r o l from the use of seed tuber disinfectants i n f i e l d t r i a l s  on s e v e r e l y i n f e c t e d  soil*  Breeding f o r r e s i s t a n c e to scab. Lutman (57)  and D a r l i n g (19)  have observed that  r u s s e t p o t a t o v a r i e t i e s appear more r e s i s t a n t to scab t i o n than smooth-skinned p o t a t o e s . vantage  infec-  They a t t r i b u t e d t h i s a d -  to the nature o f the l e n t i c e l s of the r u s s e t v a r i e t y .  D a r l i n g concludes from h i s progeny b r e e d i n g t e s t s t h a t the occurrence of r e s i s t a n t s e e d l i n g s and t h e i r breeding may  behaviour  r e s u l t i n the development of s c a b - r e s i s t a n t v a r i e t i e s of  commercial  value.  Krantz and S i d e (50)  i n 1941  confirmed  D a r l i n g * a o b s e r v a t i o n s and c o n c l u s i o n s . On the other hand M o r r i s and A f a n a s i e v (77)  reported  t h a t , o f twenty-six potato v a r i e t i e s t e s t e d i n Montana, o n l y f i v e produced  over f i f t y p e r c e n t . h e a l t h y t u b e r s .  Of  these  f i v e v a r i e t i e s , two v a r i e t i e s produced over n i n e t y  percent  s c a b - f r e e t u b e r s and none showed 100% r e s i s t a n c e .  In t h i s  c o n n e c t i o n , and as a l r e a d y d i s c u s s e d , i t i s i n t e r e s t i n g to observe t h a t a potato v a r i e t y may be r e s i s t a n t t o one s t r a i n of Streptomyces s c a b i e s and s u s c e p t i b l e t o another. I n f l u e n c e o f s o i l organic matter and m i r c r o b i a l populations. Millard  (73)  showed t h a t scab may be i n h i b i t e d by  l i b e r a l a p p l i c a t i o n s o f green manure t o the s o i l .  By way o f  e x p l a n a t i o n he assumed t h a t scab organisms; l i v e s a p r o p h y t i c a l l y on organic matter so long as i t i s p r e s e n t .  When t h i s  of food i s d e p l e t e d , t h e organism a t t a c k s the p o t a t o sitically.  I n l a t e r work w i t h T a y l o r (75)  f i e d his. ideas and concluded  source para-  however, he modi-  t h a t the b e n e f i c i a l e f f e c t o f  green manuring i s due t o s u p p r e s s i o n of Streptomyces s c a b i e s by the i n c r e a s e d numbers o f b a c t e r i a and other actinomycetes observed t o e x e r c i s e an i n h i b i t o r y i n f l u e n c e on Streptomyces scabies.  The l a c k o f c o n t r o l by s o i l organic m a t t e r as  observed i n some circumstances  was. e x p l a i n e d as being  due t o  a h i g h degree o f a c i d i t y suppressing b a c t e r i a l numbers, and y e t , M i l l a r d i n a p r e v i o u s paper (.73) organism i s absent from peat  r e p o r t e d t h a t t h e scab  s o i l s o f a low PH.  In c o n t r o l l e d l a b o r a t o r y experiments Goss  (32)  found t h a t s e v e r i t y o f scab was; c o r r e l a t e d w i t h amount of inoculum i n the s o i l and the amount of inoculum was a f f e c t e d 1  by degree o f c o m p e t i t i o n  of other s o i l microorganisms.  found t h a t manure f i l t r a t e s , c o n t a i n e d  He  organisms i n h i b i t o r y t o  10  his  s t r a i n o f Streptomyce s s c ab i es: but a pure s t r a i n of  Streptomyces  praecox was. i n e f f e c t i v e *  Other, workers  (4,  89)  nave shown that a d d i t i o n s : o f  soybeans, r y e , and clover: a l l a i d i n r e d u c i n g scab a t reactions, optimum f o r Streptomyces  scabies a c t i v i t y *  soil The  con-  t r o l e f f e c t has been a t t r i b u t e d t o b i o l o g i c a l changes p a r t i s c u l a r l y i n the r h i z o s p h e r e . the  Lochhead  (55)  bas i n d i c a t e d t h a t  percentage i n c i d e n c e as w e l l as. t o t a l numbers o f s a p r o -  p h y t i c actinomycete3 a n t a g o n i s t i c to Streptomyces  scabies are  g r e a t l y i n c r e a s e d i n the rhizosphere, of potatoes grown on a soybean-cover-crop-treated s o i l * In  f i e l d experiments Goss and, A f a n a s i e v (33)  found  l o n g r o t a t i o n s more e f f e c t i v e than short r o t a t i o n s i n r e d u c i n g scab*  In a f o u r year r o t a t i o n w i t h p o t a t o e s i n the l a s t y e a r ,  manure had no e f f e c t when a p p l i e d a t the b e g i n n i n g of the. r o t a tion. ing,  When the manure was a p p l i e d i n the y e a r of potato p l a n t both y i e l d and scab increased., but percentage scab a c t -  u a l l y decreased. E f f e c t of s o i l m o i s t u r e , a e r a t i o n and A l l microbiological l i f e  temperature*  i s a f f e c t e d by c o n d i t i o n s  of m o i s t u r e , a e r a t i o n and temperature, and Streptomyces s c a b i e s i s no exception.*  Jones and McKinney (47)  suggested that p e r -  haps temperature was. a f a c t o r i n producing s c a b - f r e e p o t a t o e s under f i e l d c o n d i t i o n s .  They observed that i n c e r t a i n a r e a s  i n Europe where temperature was. g e n e r a l l y c o o l e r than i n p o t a t o  11 scab, areas, of the U n i t e d S t a t e s , c l e a n potato crops c o u l d be produced c o n t i n u o u s l y on the same p l o t . l e d them to conclude that t h e r e was  Their observations  a g r e a t e r p r e v a l e n c e of  scab i n Wisconsin d u r i n g the warm summers than i n n o r t h e r n Maine where c o o l summers predominated..  Goss (32)  however, i n  c o n t r o l l e d experiments, found t h a t temperatures: r a n g i n g from below 22.°C to 30°C had no e f f e c t on the s e v e r i t y of scab i n u n s t e r i l i z e d s o i l s , yet s t e r i l i z e d s o i l s i n o c u l a t e d w i t h Streptomyces  s c a b i e s showed l e s s scab a t temperatures below  22°C than at h i g h e r temperatures* I f One may  assume t h a t c o o l summers, and g r e a t e r  p r e c i p i t a t i o n go, t o g e t h e r , then the: work of M i l l a r d Sanford (84,  85 > 88) may  (73)  and  b e t t e r explain, the p r e l i m i n a r y  servations; of Jones, and McKinney.  ob-  M i l l a r d and Sanfiord showed  t h a t 'scab i s more p r e v a l e n t i n dry s o i l s than i n wet ones;: f o r example, s o i l s a t 12^  and 18^ moisture gave s e v e r e l y  scabbed, t u b e r s while, s o i l s a t 28^ moisture gave almost clean tubers.  Sanford found no apparent temperature  a t 14°C and 22°C.  effect  The c o n c l u s i o n s drawn are t h a t moisture  c l o g s the pores o f the s o i l , reduces: a e r a t i o n and the pathogen*s a c t i v i t y * work of Dippenaar  100%  inhibits  On the other hand, and based on the  (88)- and Goss (32),  the moisture e f f e c t  be due t o a g r e a t e r a n t a g o n i s t i c p o p u l a t i o n i n the wet  may  soils*  Both Dippenaar and Goss found a h i g h e r percentage o f a c t i n o myces, than b a c t e r i a , i n dry s o i l s while, i n the wet bacteria  predominated*  s o i l s the  12 3. EXPERIMENTAL The Cariboo country, p a r t i c u l a r l y t h a t portionl y i n g between Williams. Lake and Quesnel, holds; promise o f becoming an important  seed potato producing area,.  There i s ,  however, one f a c t o r m i l i t a t i n g a g a i n s t the success o f the venture and t h a t i s the prevalence of common potato I t s presence  scab*  on the s o i l s o f Richmond Farms,, which a r e l o c -  a t e d a d j a c e n t t o the P r i n c e George Highway a few m i l e s n o r t h of Soda. Creek, h a s n e c e s s i t a t e d the abandonment o f White Rose as a v a r i e t y f o r t h i s r a n c h . S o i l from badly i n f e c t e d f i e l d s ; on t h i s ranch was chosen f o r the 3tudy r e p o r t e d a t t h i s  time*  H i s t o r y of t h e Area* The a r e a was, home steaded i n 1859 and u n t i l 1946 was  u t i l i z e d p r i m a r i l y f o r s t o c k g r a a i n g on the s l o p e s while;  the f l a t s were r e t a i n e d permanently f o r a l f a l f a , hay p r o d u c t i o n . In 1946, 16 a c r e s o f White Rose and Netted Gems were p l a n t e d i n f i e l d s 1 2 , 13 and 14 a s shown on map*  Excellent  yields  r e s u l t e d w i t h both v a r i e t i e s but the White Rose potatoes; Jgrown on the s l o p e s were s e v e r e l y scabbed*  N e v e r t h e l e s s the newly  broken a r e a planted: i n 194?» i n c l u d i n g a l l o f or p a r t s o f f i e l d s 4 to< 11. i n c l u s i v e showed no evidence  of s,cab.  The h i s t o r y of the a r e a f o r the. ensuing t h r e e y e a r s may  be best expressed by i n d i c a t i n g the r o t a t i o n used which  Reference Figure- I , Map of Richmond,Farm.  13. i s as f o l l o w s : l s t year  -  oats seeded t o a l f a l f a .  2nd  year  -  alfalfa.  3rd year  -  a l f a l f a , cut f o r hay and the a f t e r m a t h turned under.  4th year  -  potatoes  5th year  -  potatoes or r o t a t i o n r e p e a t e d .  In  June 195°» when s o i l samples; were secured f o r  study, the f i e l d s were under the f o l l o w i n g , c r o p s : Field  4 (east h a l f ) - o a t s  H  4 (west h a l f ) - potatoes  •*  5  - oats  "  6.  ~ oats  •"•  7  - alfalfa.  "  8  - potatoes  9  - alfalfa  F i e l d s 12, 13 and 14- a l f a l f a , , timothy and c l o v e r mixture and no l o n g e r i n c l u d e d i n the r o t a t i o n because o f t h e i r h i g h scab Fertilizers of the potato, p l a n t i n g .  infection.  are a p p l i e d by placement  a t the time  In 1949, 400 pounds per a c r e o f  6-30-15 was a p p l i e d t o a l l f i e l d s .  I n 1950,the N e t t e d Gems  r e c e i v e d 600 t o 700 pounds per a c r e o f 2«l6-6 w h i l e the White Rose: r e c e i v e d fOO, pounds per a c r e o f 4-10-10* Potato tops are burned a s soon as. p o s s i b l e a f t e r removal o f the c r o p * The f i e l d s a r e furrow i r r i g a t e d d u r i n g the growing  season, t h e f i r s t  two or three- times,  irrigation  usually  Fig.. 1. P l a n of Richmond. Farms,, Soda Greek,. B.C. Key: - a) - F o o t of slope "**)' Approx. scab boundary - east side, i s scabby area. c) - D i r e c t i o n of slope dJI -XVII- L o c a t i o n and numbering of s o i l samples e ) l - 14 - Operators numbering of f i e l d s w i t h acreages:.  m  15* o c c u r r i n g i n mid or l a t e J u l y .  The source o f i r r i g a t i o n i s  McLeese Lake s i t u a t e d i n the a d j a c e n t h i l l s  some t h r e e m i l e s  away. While no a c c u r a t e r e c o r d s a r e a v a i l a b l e on the c l i m a t e o f the a r e a , a. few g e n e r a l o b s e r v a t i o n s on p r e c i p i t a t i o n and temperature may be made.  The annual p r e c i p i t a t i o n  averages from 14 t o 16 i n c h e s , the l a r g e p r o p o r t i o n o f which occurs, as r a i n which i s f a i r l y w e l l d i s t r i b u t e d throughout t h e year.  Summer temperatures average. 70 t o 75°^' w i t h few ex- •  tr.emes o f 92.°3?.  S p r i n g f r o s t s c o n t i n u i n g u n t i l the end o f May  or b e g i n n i n g o f June determine- i n l a r g e measure the time- o f planting*  Occasional, n i g h t f r o s t s ; hare been noted d u r i n g  summer months. The s o i l s under s t u d y . Potatoes grown on c e r t a i n areas, o f the r a n c h are more, s u b j e c t t o scab than those grown elsewhere on the farm,, hence i t was. reasoned: that s o i l d i f f e r e n c e s may account f o r the v a r i a t i o n s i n scab p r e v a l e n c e .  With t h i s i n mind s i x samples  of s o i l from non-scabby areas, and e l e v e n samples from scabby areas were c o l l e c t e d f o r l a b o r a t o r y study.. Reference t o P i g . I w i l l d i s c l o s e the approximate l o c a t i o n s from which these seventeen samples were t a k e n . S o i l sample X V I I I was, c o l l e c t e d by the farm o p e r a t o r s from f i e l d s 12: and 14 i n J u l y 1951.  T o t a l sample  weighed  2-500 pounds and on a r r i v a l a t the. greenhouse was t h o r o u g h l y mixed to ensure homogeneity  o f sample, and then spread out t o  16 a i r dry.. Chemical study o f s o i l T o t a l exchange  samples*  c a p a c i t y and exchangeable bases;  were determined by the ammonium a c e t a t e method o f S c h o l l e n b e r g e r and Simon; (92)» w h i l e organic matter was; determined by the wet combustion potassium dichrornate method of Peach et a l . ( 8 1 ) * S o i l . pH*s were determined: on the Beckman Model G- pH meter  foX-  lowing A.O.A.C. procedures: and textures; were done manually and confirmed by Mr. A* Tzogoeff o f the S o i l the  Survey D i v i s i o n of  Dominion E x p e r i m e n t a l Farms S e r v i c e at the U n i v e r s i t y o f  British  Columbia* For  convenience the r e s u l t s of the f o r e g o i n g a n a l y s e s ,  as g i v e n i n Table I , a r e arranged w i t h the s i x s c a b - f r e e I,  samples,"  I I , I I I , V, VI and VII,. f o l l o w e d by the data on s c a b — i n f e s t e d  samples*  The r e s u l t s do not appear to i n d i c a t e any o u t s t a n d i n g  d i f f e r e n c e s between the s c a b - f r e e and s c a b - i n f e s t e d  samples.  However i n a n a l y z i n g these r e s u l t s the method of sampling must be borne i n mind.  Extremes, o f v a r i a t i o n that occur may  have  been smoothed out had a composite sample been taken from each field.  T h i s was not done and hence v a r i a t i o n s t h a t e x i s t w i t h i n  a. s i n g l e f i e l d are made apparent. may  e x p l a i n why  Thus, the method of sampling  one, or even two or t h r e e , samples v a r y markedly,  from the r e s t o f the samples, w i t h i n the s c a b - f r e e or s c a b - I n fested, a r e a s . T e x t u r e s i n d i c a t e t h a t t h e non scabby samples a r e heavy t e x t u r e d , except sample VTI, w h i l e the scabby samples a r e  17. l i g h t t e x t u r e d w i t h the e x c e p t i o n of sample X I I I .  While  evid-  ence i s not forthcoming t h a t t e x t u r e i s a d e c i s i v e f a c t o r In the incidence: o f scab y e t the f a c t that the: c a u s a t i v e  organism  i s an o b l i g a t e aerobe suggests:, a t l e a s t , that the d i f f e r e n c e i n a e r a t i o n between heavy and l i g h t  s o i l s , may  be a  factor.  Support f o r t h i s r e a s o n i n g comes from S a n f o r d (84) who  con-  c l u d e d that excess m o i s t u r e i n the s o i l , a t the time of tuber f o r m a t i o n reduces a e r a t i o n , thus c u r t a i l i n g actinomycete a c t i v i t y , and r e d u c i n g the l i k e l i h o o d of t u b e r i n f e c t i o n * S o i l r e a c t i o n shows no s i g n i f i c a n t differences:, the f i r s t s i x samples o f Table: T, r e p r e s e n t i n g non-scabby have a. pH. range of 6»4 t o 7*2 while- the other twelve range from pH: 5»5  t© 7*2*  soils, samples  S i m i l a r l y , o r g a n i c matter does not  appear t o have e x e r t e d any i n f l u e n c e on scab i n f e c t i o n .  While  the range i s s l i g h t l y h i g h e r i n the s c a b - i n f e s t e d s o i l s , b e i n g from 5*11#  t o 10.84^ as compared t o 4.02^  c l e a n soils.,, s t i l l  to 6.58^  f o r the  t h e r e a r e s i x samples of the former  soils  that show organic matter contents: lower than the two h i g h e s t of the s c a b - f r e e s o i l s . Since no hydrogen was  i n d i c a t e d i n the ammonium a c e -  t a t e s o l u t i o n a f t e r the s o i l s had. been leached,, and  since  sodium was not determined q u a n t i t a t i v e l y , the d i f f e r e n c e between the t o t a l exchange c a p a c i t y and the sum of the determined c a t i o n s , c a l c i u m , magnesium and potassium, is, i n c l u d e d a s h y d r o gen p l u s sodium*  I t w i l l a l s o be noted t h a t samples IX, XV"  and XVII i n d i c a t e d no hydrogen plus; sodium and t o t a l s of c a l c i u m ,  Table I  Base exchange a n a l y s e s of s o i l  Sample No.  Texture  pH  I II III  Clay Clay Clay (silty)  6.8-  V VI VTI IV VIII IX X XI XII XIII XIV XV XVI XVII XVIII  H B  61.6 6.6  samples  % ' T o t a l exchange Ca Mg K H Ratio of O r g a n i c capacity-m.e./ plus CatK M a t t e r 100 gms. ovenHa dry s o i l m.e./lOO gms. oven-dry s o i l .  5*73 4.02 4*75  6.4 6.5  6.58 6.58 5*54  24*83 19*31 22.62  12.42  9.96 12.64  -  51.60 63*80  17*86  28.40  14.56  I9.88  5*06 5*51 4*82 4.34 5*31 3.84 7*61 8*69 6*85  1*84 0.19 Q.83  2.25:1 2*3:1 3.3:1  5*87 6.78 6.45  20.26 28.44 0.54  3:1 2*9:1 2*2:1  0.83 0.18  2:1 211  •  Gravelly Loam  7»"2.  Loam Gravelly Loam Loam Gravelly Loam Sandy Loam  6*3 7*1  7*95 7*25  33*59 32.21  18.38 17.48  -5*75 8.63 6.23 8.32  "6.6 •5*5  6*9.0 6008-  24.41  28.80  18.52 14.08  5*01 4.80  3*41  1.98  7.94  5*4:1 7:1  6.5  7*83.  29.74  18.74  6.90  3*09  1.01  6:1  7*2 S i l t y c l a y 6.3  6.82 5*11  29*39 27.64  22.30 15.50  5.73 6.83  1.30 2.32  0.06 2:*99  . 17:1 6.6 s i  33*30  19.52  7.01 6.89 6.89 5*07 11.00  3*82 7*36 8.49 3*54 9*05  2*95  5:1 2*3:1 2:1 3*5:1 3:1  .'  — •  Loam Loam( s i l t y ) 6.2 S i It-Loam 6.6 L s a m f s i l t y ) 6.3 Loam 6.6 Loamc, 6.6  -  5*67 5*89 5.14  6.06 10.84  24.65  32.40 20.6G.  47.40  16*88  16.66 12*48 26.07  O.36 1.28  19. magnesium and potassium exceeded the t o t a l exchange c a p a c i t y * T h i s d i f f e r e n c e i s probably i n the s o i l  due  t o s o l u b l e salts- b e i n g  independent of the exchange complex.  As  present  i s evid-  ent from the d a t a there is; a. wide range i n t o t a l exchange capacity.  T h i s may  be due  s o i l sample r e p r e s e n t s  i n p a r t a t l e a s t to the f a c t t h a t each t h a t from a s i n g l e l o c a t i o n r a t h e r than  a composite i n order to b r i n g out the v a r i a t i o n e x i s t i n g i n the s o i l f o r each a r e a .  Samples from the s c a b - f r e e a r e a  cate a range i n exchange c a p a c i t y from 19*3 63.8  while  m.e/iOQ gms.  to:  ;  the scab I n f e s t e d samples present  present  indi-  a. much  narrower range and l y i n g w i t h i n t h a t a l r e a d y - n o t e d . -. . I t -..is c o n c l u d e d , therefore,, t h a t exchange- c a p a c i t y of these s o i l s i s not r e l a t e d to i n c i d e n c e o f s c a b .  >  v  I n d i v i d u a l c a t i o n s of the exchange complex i n d i c a t e a similar situation. (93)  A review of the work of Schroeder and A l b r e c h t  i n d i c a t e s t h a t w i t h a c a l c i u m potassium r a t i o of approximately one ecab i n c i d e n c e i s a t i t s l o w e s t .  U s i n g hydrogen s a t u r a t e d  c l a y s and  then a d j u s t i n g c a l c i u m potassium l e v e l s to between  0 and 100  m i l l i e q u i v a l e n t s , Schroeder and A l b r e c h t found t h a t *  i r r e s p e c t i v e o f pH l e v e l , l e s s scab occurred when Ca.K  60.50 m i l l i e q u i v a l e n t s than a t the r a t i o s 0:50,  100:50,  was  60:10  or 60:100. G r i e s et a l . (34)  found a s i m i l a r e f f e c t , but  scab i n c i d e n c e depended upon which c a t i o n was  at  the  controlled i n  20. order t o reduce the r a t i o .  They found t h a t r e d u c i n g the  c a l c i u m potassium r a t i o by i n c r e a s i n g potassium and h o l d i n g calcium constant i n c r e a s e d scab w h i l e i f potassium was h e l d constant; and c a l c i u m decreased to reduce the r a t i o , scab decreased. The c a l c i u m potassium r a t i o s recorded i n Table I a r e a l l g r e a t e r than 1:1. Although h i g h e r r a t i o s tend t o predominate; i n scabby samples, s t i l l there a r e those which show a r a t i o comparable non-scabby s o i l s .  samples  t o the r a t i o s r e c o r d e d f o r the  Hence i t must be concluded that the c a l c i u m  potassium r a t i o has, not e x e r t e d any s i g n i f i c a n t e f f e c t on scab i n c i d e n c e i n these f i e l d s . B u f f e r c a p a c i t y o f s o i l sample X V I I I . S i n c e s o i l sample XVIII was to be used f o r extens i v e greenhouse  s t u d i e s a. knowledge o f i t s b u f f e r i n g c a p a c i t y  was; e s s e n t i a l . The b u f f e r c u r v e s , as presented i n P i g s . 2 and 3, were prepared by shaking 10 gram samples o f the s o i l w i t h a l i quots o f 0.4 H-H2SO4 o r 0.04 N-ea(pH) made up. to a t o t a l v o l 2  ume of 100 mis.  The samples were: shaken on the r e c i p r o c a l  shaker f o r 2 hours and then l e t s t a n d 48 h o u r s .  A t the end o f  t h i s time the pH*s o f the suspensions were determined on the Beckman Model G pH meter, and these r e s u l t s p l o t t e d a g a i n s t weight o f a c i d or base r e q u i r e d t o a t t a i n that, pH.  Thus the  amount of a c i d or base r e q u i r e d f o r a d e s i r e d pH i n any d e s i r e d  g i g . 2.  Sulphuric  a c i d b u f f e r curve of Sample Ho.  XVIII  H  23 weight o f s o i l may be r e a d i l y c a l c u l a t e d . A. c r i t i c a l examination of the b u f f e r c u r v e s shows that w h i l e the s o i l i s s l i g h t l y b u f f e r e d i n the range pH 9.0 to  10.4, the a c i d curve shows no b u f f e r i n g e f f e c t  i s reached.  u n t i l pH 3  Under these c o n d i t i o n s one should expect  t i v e l y c o n s i s t e n t greenhouse  rela-  or f i e l d r e s u l t s provided the  a c i d o r base added i s i n a r e a c t i v e B a c t e r i o l o g i c a l counts o f s o i l  form. samples.  B a c t e r i a l counts were made on a l l samples by the p l a t e - d i l u t i o n technique*  S u i t a b l e d i l u t i o n s were p l a t e d  u s i n g glucose peptone agar a d j u s t e d t o  pH4*5 f o r the f u n g i  counts and sodium albuminate agar a d j u s t e d t o b a c t e r i a l and actinomycetes counts. to  pH6.8 f o r the  An endeavour  was made  separate actinomycetes and b a c t e r i a a f t e r a seven days i n -  c u b a t i o n p e r i o d , but such a s e p a r a t i o n i s sometimes i n borderline cases.  difficult  Where any doubt e x i s t e d the c o l o n y was  p l a c e d w i t h the b a c t e r i a . The r e s u l t s , as expressed i n T a b l e I I , a r e as d i f f i - * c u l t t o a n a l y z e a s were the r e s u l t s f o r exchange c a p a c i t y * A l l counts average h i g h e r i n the scabby s o i l s than i n the nonscabby s o i l s . the  T h i s i s p a r t i c u l a r l y apparent, i n the case o f  f u n g i but not a s n o t i c e a b l e f o r the b a c t e r i a and s t r e p t o -  myces*  However -both h i g h and low counts occur i n both  and ranges a r e s i m i l a r * to  soils  I n s o f a r as the r a t i o , of one s p e c i e s  the other i s concerned, the b a c t e r i a actinomycetes ratio i s  24 Table I I .  T o t a l counts of f u n g i , b a c t e r i a , and actinomycetes per gram of s o i l  Sample No.  No* of fungi  I II III V VI VII IV VIII IX X XI XII XIII XIV XV XVI XVII XVIII  the  only one  that  No* of bacteria  x 10,000  x 10,000  1.3 1*3 1.2 2*9 4-34.6  173 16 o 80 7© 800. 320  1*6 20.0 2.0 2.6 42*6. 31*3 17.0 8.3 13.3 39-0 36*3 17*0  ill 170 200 90 470  x 10,000 40  30 30 26 300, 100 42  60 53 36 130  53  150 210 233  1°  83: 143: 130 250  370 850  i s s i m i l a r throughout.  h i g h e r f u n g i counts i n the  No. of actinomycetes  scab-infested  r a t i o i n v o l v i n g t h i s species  The  somewhat  s o i l s makes  any  lower when computed f o r those  soils. A l t h o u g h no  d e f i n i t e c o r r e l a t i o n e x i s t s between  numbers of f u n g i , b a c t e r i a or actinomycetes and  scabby or  non-scabby samples* t h i s does not p r e c l u d e the  possibility  that organisms have no e f f e c t i n the c o n t r o l of scab i n these f i e l d s .  However, to adequately determine whether or  not a n t a g o n i s t i c  e f f e c t s are: present would r e q u i r e  extensive  s t u d i e s of the p h y s i o l o g y of the numerous groups of organisms, p r e s e n t , and  a. comparison of the b a c t e r i a l e q u i l i b r i u m s  in  25. the: v a r i o u s s o i l samples*  A study based on the n u t r i t i o n a l  requirements o f the various* groups, o f organisms and a comp a r i s o n o f the " B a c t e r i a l . Balance Index"" as f o r m u l a t e d by Loch'head (55)  may be i n d i c a t i v e o f the b i o l o g i c a l  differ-  ences between s c a b - i n f e s t e d and s c a b ^ f r e e s o i l s and e x p l a i n t h e i r p r o x i m i t y t o one another.  Streptomyces- S t u d i e s . I s o l a t i o n o f s t r a i n s o f Streptomyces: s c a b i e s . I n f e c t e d t u b e r s were c o l l e c t e d from the 195© grown on the s o i l s a l r e a d y reported, upon*  crops  These, i s o l a t e d  t u b e r s r e p r e s e n t e d those, w i t h severe deep l e s i o n s , s m a l l s u r f a c e lesions-, or simple r us s e t t i n g of the s k i n . - They were s t o r e d a t 40°F u n t i l r e q u i r e d f o r s t u d y . In p r e p a r a t i o n f o r i s o l a t i o n o f the organism, sur«f a c e of the tuber was. thoroughly cleaned w i t h soap and water* F o l l o w i n g this,, treatment w i t h hydrogen p e r o x i d e as recommended by Shapovalov (94): o r w i t h mercuric c h l o r i d e as. recommended by Ken Knight and Muncie (49) proved i n e f f e c t i v e i n e l i m i n a t i n g contaminants such as. f u n g i :  when c o n c e n t r a t i o n  of d i s i n f e c t a n t had been i n c r e a s e d t o the p o i n t where contami n a n t s ceased t o appear the scab organism had a l s o been destroyed. The detergent " T i d e * was, f i n a l l y adopted f o r removi n g contaminants; from the s u r f a c e o f the t u b e r s .  Scabby  26. p o r t i o n s were; s l i c e d off. the tubers: by means' of a s t e r i l e , s c a l p e l and p l a c e d i n tubes, of s t e r i l e , water*  These were  macerated by means of a, s t e r i l e , g l a s s r o d and the suspension p l a t e d i n the u s u a l manner. were used f o r p l a t i n g ; :  A number of d i f f e r e n t media  these i n c l u d e d n u t r i e n t agar, p o t a t o  dextrose agar, a. t h i n glucose agar* sodium a s p a r a g i n a t e g l y c e r o l agar, a s p a r a g i n glucose a g a r j egg albumen agar and extract agar. to the others*  No one medium however was, markedly  soil  superior  The p l a t e s were incubated a t 27°C and a f t e r  seven days s i x t e e n s t r e p t o m y c e s - l i k e i s o l a t e s : were p i c k e d . L a t e r twelve a d d i t i o n a l c o l o n i e s were p i c k e d from  smeared  plates. Another procedure i n v o l v i n g the use of * T i d e  w  f o l l o w e d by submerging the tubers, f o r three minutes i n a one t o one P e r f e x - s t e r i l e water s o l u t i o n (100) r e s u l t e d i n a n a d d i t i o n a l twenty three i s o l a t i o n s .  Thus f i f t y - o n e  iso-  l a t i o n s i n a l l were made from the v a r i o u s media and h e l d f o r further study. A l l . i s o l a t e s were seeded on sodium a s p a r a g i n a t e g l y c e r o l agar s l o p e s and incubated a t 27°C. Upon p r e l i m i n a r y examination f o l l o w i n g seven days i n c u b a t i o n , t h i r t y f o u r i s o l a t e s , appeared a s t y p i c a l streptomyces, i . e . , . growth  was  of a. tough l e a t h e r y c o n s i s t e n c y , a. white to grey a e r i a l mycelium was apparent, and most i s o l a t e s gave? evidence of a yellow-brown to. brown pigment. Por purposes of comparison a. s t r a i n of the organism,  2?. Streptomyces s c a b i e s , was of  o b t a i n e d from J.K.  Richardson,  the Dominion Plant; Pathology Laboratory,, S t . C a t h a r i n e s ,  Ontario'.  T h i s organism had, been i s o l a t e d from a potato  scab l e s i o n and had been proven to have s t r o n g p a r a s i t i c capabilities. P r o o f of identjly of the streptomyces The  d e s c r i p t i o n o f Streptomyces s c a b i e s as; p r e -  sented by Bergey (8) of  isolates.  were observed  isolates.  served as a. b a s i s f o r i d e n t i f i c a t i o n  C u l t u r a l , c h a r a c t e r i s t i c s of the 35  isolates  on n u t r i e n t agar, g l u c o s e a s p a r a g i n agar  t y r o s i n agar, and  i n mannitol yeast extract asparagin  medium and litmus, m i l k .  and fluid  The i s o l a t e s were a l s o t e s t e d f o r  the h y d r o l y s i s of s t a r c h and the r e d u c t i o n of n i t r a t e s to nitrites.  The data a r e presented i n Table III and are r e -  p o t t e d as ^ p o s i t i v e " , , negative r e s u l t s ; being l e f t b l a n k . A " p o s i t i v e * r e p o r t r e l a t i v e to each medium i n d i c a t e s t h a t the i s o l a t e conforms t o the growth c h a r a c t e r i s t i c s ; which may  be  d e s c r i b e d as f o l l o w s : Litmus m i l k -  T y r o s i n agar S t a r c h agar -  brown r i n g w i t h g r e e n i s h t i n g e ; coagulated;, p e p t o n i z e d w i t h a l k a line reaction. - tyrosinase reaction positive grey-white a e r i a l mycelium.  with  t h i n , t r a n s p a r e n t spreading growth. Starch, i s hydrolyzed.  N i t r i t e s produced  from  nitrates.  Brown s o l u b l e pigment formed. The two main t e s t s f o r the; s e p a r a t i o n of Streptomyces  28. Table I I I .  Cultural  i d e n t i f i c a t i o n of actinomycetes  &. a o  • O  ^  fl  p , >>jd H p  a)  -p  to H oa M  o  OJ H -rtv_,  ctf 4^ Pi o +> 3 -H  fjCfl  -  ;  4  I 9  10;  11. 12 13 ^ 16 17 22. 27 30 31 32 33 34 35 37 38 39 41  45 47 48 49 .50 51 E.I. Notes:-  !tJ £}  > > 01  M  P r o d u c t i o n of pigment on; 8  C bOH O G'H  bp cfl  +3  a  <ri -H Q M  O to 3 c 3 *d .£ g 0 0 + 3  W  ^  -H  m  o o  H  EH  C  -ri  0) M win  • o u o cs u d  »  CO  CU saj 08  +»  a  <u  £j  H  o 43  >H  bp o ri «H +s aj h -P  •<-{ u ' u vi era u 8 u +>bD [2.  CO  +»  cs  J *ft« i o f  pcj  1 2  3:  O +>  *H  P M  '  <D  isolates.  pes. pos  pos. pos pos  pos pos  pos. pos. pos.  pos  pos pos pos pos pos pos.  pos  pos  pos. pos pos pos pos  pos pos pos pos pos  pos  pos. pos POS pOS; pes  pos. pos pos pos  pos  pos.  pos.  pos  pos pb3 pos pos pos  pos pos POS: pos pos. pos pos pos pOS: pos pos. pos:. POS:. pos pos; pos pos pos pos gos pos; pos POS: pos pos  pos  pos; pos pos: POS: pos pos pos  pos. pos pos pos  pos pos pos pos pos pos  pos pos pos pos  pos  pos pos  pos  pos  : POS  pos  pos pos  pos pos pos  pos pos  pes pos pos pos pos pos pos  POS: pos pos pos  pos pos pos pos pos pos pos  pos  pos:  pos  pos  pos  pos  pos  pOS pos POS pos. pos pos POS:  w  pos pos pos pos pos pos; pos. pos pos  pos  pos pos  pos,  pos pes pos. pos  pes. POS.  pos pos; pos  pos  pos; pos  (1) See context f o r i n t e r p r e t a t i o n of d a t a . (2) E . I . i s the i s o l a t e o b t a i n e d from P l a n t P a t h o l o g y L a b o r a t o r y , S t . Catharines,, O n t a r i o . n  M  29. s c a b i e s from other s p e c i e s a r e a p o s i t i v e t y r o s i n a s e r e a c t i o n and the p r o d u c t i o n of a brown r i n g on m i l k .  Bergey s t a t e s  t h a t a p o s i t i v e t y r o s i n a s e r e a c t i o n i s the primary  separatpry  feature. A review o f Table I I I r e v e a l s t h a t a l l i s o l a t e s : under study were t y r o s i n p o s i t i v e and one h a l f produced: the t y p i c a l brown r i n g i n m i l k and reduced n i t r a t e but not n e c e s s a r i l y the same ones.  A l l but e i g h t h y d r o l y z e d s t a r c h .  While o n l y t h r e e I s o l a t e s showed " p o s i t i v e " i n every r e s p e c t , it  i s concluded from the c u l t u r a l data.submitted  t h a t the  35 i s o l a t e s a r e t y p i c a l Streptomyces s c a b i e s or v a r i a n t s o f the same.  A f a n a s i e v ( l ) , Douglas of Ontario A g r i c u l t u r a l  C o l l e g e and the Dominion P l a n t Pathology L a b o r a t o r y a t S t . C a t h a r i n e s have shown t h a t s t r a i n s of the scab- organism are not c o n s i s t e n t i n a l l c u l t u r a l  characteristics.  Greenhouse p a t h o g e n i c i t y t r i a l s . White Rose seed p i e c e s a f t e r submerging f o r 15 minutes i n  1::1000  mercuric chloride, s o l u t i o n were p l a n t e d i n  quartz sand i n 8-inch pots p r e v i o u s l y treated! w i t h 1:500 t i o n of mercuric; c h l o r i d e .  solu-  While the q u a r t z sand, was not  s t e r i l i z e d i t was t e s t e d f o r the presence  of actinomycetes  w i t h negative results,. Por i n o c u l a t i o n purposes, the t h i r t y - f i v e  isolates  were grown i n 3,0 m i s . o f m a n n i t o l yeast e x t r a c t a s p a r a g i n  30. f l u i d medium.. B e f o r e u s i n g , the c u l t u r e f l a s k s were shaken to break up the m y c e l i a l mat  as much as; p o s s i b l e .  The. whole,  medium plus, growth,- was: then added t o the s u r f a c e of a. pot  and  a l i g h t w a t e r i n g was: g i v e n t o f a c i l i t a t e washing the growth i n t o the r e g i o n of tuber f o r m a t i o n . p l a n t s 28,  Inoculum was  added to the  45 and 65 days a f t e r planting.. While a. s i n g l e pot was  used f o r each i s o l a t e under  study t h i r t e e n check pots were d i s t r i b u t e d throughout  the  greenhouse, as a p r e c a u t i o n a r y measure i n case of need.. Nutrient, s o l u t i o n s c o n t a i n i n g magnesium s u l p h a t e , potassium c h l o r i d e , ammonium n i t r a t e , monocalcic  phosphate  and  f e r r o u s sulphate were added, to a l l pots, once every two weeks-. Extreme c a u t i o n was  e x e r c i s e d to guard a g a i n s t organisms being  c a r r i e d from p o t t o another* efrery other day s u f f i c i e n t  Water was. added  approximately  to m a i n t a i n the t u r g i d i t y of the  plants* At the time of watering the greenhouse f l o o r s were thoroughly dampened to keep dust a t a. minimum* of i n s e c t pests:, and p a r t i c u l a r l y white f l i e s ,  F o r the control, the greenhouse  s e c t i o n was. t r e a t e d twice d u r i n g the growing season w i t h Para,thion* Fourteen weeks a f t e r p l a n t i n g the t u b e r s were h a r v e s t e d and the presence  or absence o f scab l e s i o n s recorded*  At the same  time a. sample o f the quartz sand surrounding the r o o t s and of tuber f o r m a t i o n was  taken i n s t e r i l e p e t r i p l a t e s .  zone  Owing t o  31  the s m a l l s i z e of the t u b e r s i t was. sometimes d i f f i c u l t d i s t i n g u i s h t y p i c a l scab l e s i o n a . e x i s t e d i t was  to  Where this, d i f f i c u l t y  assumed that the t u b e r s were f r e e o f severe  scabbing and they were d e s c r i b e d as h a v i n g " a t y p i c a l s m a l l The number of t u b e r s per p l a n t ranged from 6 to  spots".  w i t h an average  of 12  23  per pot*  Examination of the t u b e r s r e v e a l e d t h a t t h e r e was  a s i d e range  tested.  They may  i n p a t h o g e n i c i t y of the v a r i o u s i s o l a t e s be c l a s s i f i e d i n t o 3 categories; as f o l l o w s ,  1) those producing r u s s e t t i n g and a t y p i c a l s m a l l ( l cm. 2)  extremely  or l e s s i n diameter) l e s i o n s . -  those producing r u s s e t t i n g and t y p i c a l scab lesions; of a diameter exceeding 1 mm. mm.  3  but not exceeding  i n diameter,.  3) , those i s o l a t e s producing t y p i c a l l e s i o n s of 2  mm.  or g r e a t e r diameter and producing a deep c o r k y type of l e s i o n of no determinate shape. A. grouping of the Organisms i n accordance the type of l e s i o n s produced i s presented i n Table  •  Table XV.  Streptomyces I s o l a t e s grouped to type of l e s i o n  Category  1 2 3  with  IV:  according  Isolate I , 2, 5, 8 , 11,  12, 3., 4, 6, 7, 10i, 15, 33, 35, 38, 41, 47, 9, 17, 27, 34, 37,  Eastern s t r a i n .  13, 30, 51* 16, 22, 31, 32, 49, 5039,. 4 5 , 48,  32 I n r e s p e c t to the check p o t s , those  grown i n the  immediate v i c i n i t y o f the i n o c u l a t e d pots showed, o c c a s i o n a l evidence  o f r u s s e t t i n g and a few t u b e r s showed the, a t y p i c a l  small spots.  However the check pots: set out a t a. d i s t a n c e  from th4 i n o c u l a t e d pots gave c l e a n tubers i n a l l cases. These r e s u l t s , provided f u r t h e r evidence s t r a i n s o f actinomycetes were present were any d i s e a s e - p r o d u c i n g  t h a t no; pathogenic  i n the q u a r t z sand, nor  organisms present  i n the t a p water  used f o r w a t e r i n g . These p a t h o g e n i c i t y studies, p r o v i d e f u r t h e r e v i d ence t h a t the 35 i s o l a t e s r e p r e s e n t s t r a i n s o f Streptomyces s c a b i e s , however t h e r e i s a, wide range i n p a t h o g e n i c i t y , as observed i n T a b l e IV. Nine o f the 35 s t r a i n s demonstrated d i s t i n c t l y weak p a t h o g e n i c i t y w h i l e nine were h i g h l y pathogenic.  E v e n w i t h i n each of the f o r e g o i n g groups there i s a  l a c k o f u n i f o r m i t y i n r e s p e c t t o c u l t u r a l c h a r a c t e r i s t i c s as i s evident, from f u r t h e r r e f e r e n c e t o T a b l e I I I . tion,however, i s q u i t e i n l i n e w i t h the evidence  This v a r i a appearing  i n the l i t e r a t u r e . Afanasiev  ( l % f o r instance i n  the comparative p h y s i o l o g y pathogenic,  1937*  when s t u d y i n g  o f 2$ i s o l a t e s , 7 of which were  found t h a t a l l the pathogenic  s t r a i n s and three o f  the IS saprophytes produced melanin i n the presence o f t y r o s i n plus, an a d d i t i o n a l n i t r o g e n  source.  T a y l o r and Decker (102)  i n 1947  s t u d i e d the c u l t u r a l  33. c h a r a c t e r i s t i c s of 143 s t r a i n s of actinomycetes;. t h a t a b i l i t y t o produce t y p i c a l scab l e s i o n s  They found  on t u b e r s c o r -  r e l a t e d p e r f e c t l y w i t h the p r o d u c t i o n o f a dark brown r i n g o f s u r f a c e growth i n s e p a r a t e d m i l k w i t h o r without The  Dominion P l a n t  indicator.  Pathology L a b o r a t o r y a t S t .  C a t h a r i n e s showed t h a t 38 out of 39 s t r a i n s p r o d u c i n g a brown r i n g on m i l k were pathogenic, while only one of 30 non-brown r i n g producers was m i l d l y that t y r o s i n a s e  parasitic.  reaction positive  I t was f u r t h e r  indicated  s t r a i n s , are brown r i n g  posi-  t i v e and that n e g a t i v e s t r a i n s a r e a l s o brown r i n g n e g a t i v e . Douglas o f the O n t a r i o A g r i c u l t u r a l C o l l e g e , however, has i n d i cated that pathogenic s t r a i n s a r e not n e c e s s a r i l y r i n g p o s i t i v e and t y r o s i n a s e  both brown  r e a c t i o n p o s i t i v e but may be nega-  t i v e t o one t e s t and. p o s i t i v e to the o t h e r .  Saprophytic  strains  on the other hand a r e negative f o r both tests; i n the l a r g e m a j o r i t y of c a s e s . A l l the i s o l a t e s i n this, study gave a p o s i t i v e s i n a s e r e a c t i o n and a l l but one of the s t r o n g l y gave a brown r i n g p o s i t i v e t e s t i n m i l k . ium  p a t h o g e n i c i t y , designated a s 2  the m i l k .  tt  Eight  tt  tyro-  parasitic strains  Those i s o l a t e s of medr  gave v a r i a b l e  results i n  of those i s o l a t e s ' were p o s i t i v e brown r i n g and  nine were n e g a t i v e .  Three i s o l a t e s r e c o r d e d as m i l d l y p a r a s i t i c  showed p o s i t i v e t e s t s on both m i l k and t y r o s i n .  Thus both the  s l i g h t v a r i a b i l i t y and the u n i f o r m i t y of these two. t e s t s and t h e i r c o r r e l a t i o n t o p a t h o g e n i c i t y i s borne o u t .  34. R e i s o l a t i o n o f the i n o c u l a t e d  organisms.  I s o l a t i o n from the t u b e r s . A r e p r e s e n t a t i v e tuber was  s e l e c t e d from each group  of p o t a t o e s from each pot f o r r e i s o l a t i o n o f the pathogen w i t h which that p a r t i c u l a r t h i s i s o l a t i o n was the  pot was  inoculated.  The technique f o r  s i m i l a r to that p r e v i o u s l y d e s c r i b e d , and  t h i n g l u c o s e agar was  used f o r the p l a t i n g .  Where t y p i c a l  l e s i o n s o c c u r r e d an i s o l a t e s i m i l a r t o the i n o c u l a n t was lated.  iso-  S i m i l a r i t y was based, on c h a r a c t e r o f growth on n u t r i e n t  agar, i n l i t m u s m i l k and on t y r o s i n a g a r . have been c a r r i e d t o t h e i r f u l f i l m e n t  Thus iCochs p o s t u l a t e s  by,  a) i s o l a t i o n o f pathogen from h o s t , b) i n f e c t i n g host, w i t h i s o l a t e , and  1  c) r e i s o l a t i o n o f same pathogen from the host infected  i n (>);.  Repeated attempts to i s o l a t e streptomyces from r u s s e t t e d a r e a s or from the a t y p i c a l s m a l l s p o t s were unsuccessful.  However, as Goss (32) observed, r u s s e t t i n g is. a s u p e r -  f i c i a l form of scab from which i t i s d i f f i c u l t to i s o l a t e actinomycetes. I s o l a t i o n from the q u a r t z sand. R e i s o l a t i o n of the streptomyces i s o l a t e s from the quartz sand was r e a d i l y accomplished a t a. d i l u t i o n o f 1:100,000. The t h i n g l u c o s e agar was  used, as the i s o l a t i o n medium.  Cultures  of the c o l o n i e s p i c k e d from these p l a t e s were t e s t e d f o r growth  35* c h a r a c t e r i s t i c s , en n u t r i e n t agar, i n l i t m u s m i l k , and  on  t y r o s i n agar and compared to both the I s o l a t e s from the t u b e r s and the o r i g i n a l inoculum. o f complete  correlation.  In only two cases* was  there a l a c k  The inoculum of i s o l a t e s 5 and 10 as  i s o l a t e d from the q u a r t z sand gave a t y p i c a l r e s u l t s i n l i t m u s m i l k and on t y r o s i n agar although they d i d produce ment In n u t r i e n t  brown p i g -  agar.  Morphology of the Streptomyces  scabies i s o l a t e s .  Although morphology of organisms, i s not an end i n itself, still  i t i s an a i d i n the- c l a s s i f i c a t i o n and c h a r a c t e r -  i z a t i o n o f many forms of m i c r o b i o l o g i c a l  life.  With t h i s i n mind, s l i d e s were prepared a f t e r the technique of S k i n n e r et a l . (95)  but w i t h some m o d i f i c a t i o n s .  Drawn out g l a s s t u b i n g of c a p i l l a r y s i z e and h e l d w i t h p a r a f f i n wax  on the s l i d e was  cover g l a s s . was  used as a support upon which to r e s t the  A drop of m a n n i t o l y e a s t e x t r a c t a s p a r a g i n agar  r u n under the cover g l a s s , a l l o w e d t o s o l i d i f y and then a  drop of growth suspension added.  The prepared s l i d e s were then  p l a c e d on a p i e c e of «Z -shaped s o l i d g l a s s rod i n a B  petriplate.  S u f f i c i e n t s t e r i l e water was  sterile  added to the p l a t e t o  m a i n t a i n a moist atmosphere but not flood, the e n t i r e bottom o f the p l a t e . weeks.  The  s l i d e s were incubated a t 27 °G f o r a t l e a s t s i x  The nature of the medium was  such as to p r o l o n g the  v e g e t a t i v e p e r i o d of growth without producing f r u i t i n g b o d i e s , hence the l o n g i n c u b a t i o n p e r i o d . As the s l i d e s d r i e d somewhat,  36. c o n d i t i o n s became l e s s conducive to v e g e t a t i v e growth and  spores  began to appear i n e v e r i n c r e a s i n g numbers. "Spores' here may 1  be d e f i n e d as. those p e c u l i a r i t i e s  of growth which are evident a t the ends of the a e r i a l hyphae. These may  take a number o f forms aa ao a b l y demonatrated f o r  numerous streptomyces by B r e c h a l e r  (21).  G e n e r a l l y the  sporea  of Streptomyces s c a b i e a are l o n g or s h o r t c h a l n a of round c o c c i l i k e forms a t the ends of the a e r i a l hyphae. s p i r a l forms a r e e v i d e n t but as the spore  Occasionally  they are not formed as  extenaively  chaina.  R e c o r d i n g the r e s u l t s by means o f microphotographic techniques  proved t a be an e x c e l l e n t procedure p a r t i c u l a r l y  where the c o n i d i a - I i k e forms appeared. d i s t i n c t diaadvantage i n t h a t , due d i f f i c u l t and s p i r a l forma. are presented  However t h e r e was  t o depth of f o c u a ,  it  Some o f these p i c t u r e s w i t h s h o r t d e s c r i p t i o n s i n Appendix I . concentration.  Four of the c u l t u r e a i a o l a t e d i n t h i a work, and e a s t e r n s t r a i n were chosen f o r more extenaive  i a o l a t e a , 27,  was  sometimea impoaaible t o get good p i c t u r e a o f  S u s c e p t i b i l i t y o f atraina. t o hydrogen i o n  i 8 o l a t e was  one  atudy.  The  chosen f o r comparison purposes while the other 33,  p a t h o g e n i c i t y and  39 and  the eaatern four  48 were a e l e c t e d on the b a a l a of t h e i r  t h e i r c h a r a c t e r i a t i c reaemblance t o  myces s c a b i e s on v a r i o u s c u l t u r e media.  Strepto-  It i a believed that  37  the l a t t e r f o u r i s o l a t e s are r e p r e s e n t a t i v e of the  strains  causing scab i n the a r e a under study. T h i r t y ml., p o r t i o n s of m a n n i t o l y e a s t e x t r a c t a s p a r a g i n f l u i d medium was sterilized.  dispensed i n t o 12!?-ml erlenmeyer f l a s k s  A f t e r s t e r i l i z a t i o n t h e pH of the  and  individual  f l a s k s was a d j u s t e d w i t h s t e r i l e a l i q u o t s of e i t h e r Q;.04HH S © 4 or 0.02 2  B-Ca(OH)2•  The: f i v e I s o l a t e s under study were grown f o r seven days on m a n n i t o l yeaat e x t r a c t a s p a r a g i n agar s l o p e s and then 5 mis., of d i s t i l l e d water was added to them. was  The  s u r f a c e of the growth  l i g h t l y scraped w i t h a flamed l o o p , the tube a g i t a t e d , and  the suspension added to t h e e f l u i d medium.  D i l u t i o n p l a t e s of  s e v e r a l of these suspensions i n d i c a t e d that s l i g h t l y over f i v e b i l l i o n spores were added per f l a s k and t h a t the inoculum  was.  r e a s o n a b l y constant f o r a l l f l a s k s .  con-  A l l flasks including  t r o l s of no inoculum were incubated a t 27°C f o r 21 days.. At of  the end of 21 days the growth was f i l t e r e d  o f f by means  s i n t e r e d g l a s s f i l t e r s ; and d r i e d to constant weight  atlI.0°C.  The pH of the medium and the percent l i g h t t r a n s m i t t a n c y as determined w i t h a Ho. 425-B f i l t e r i n the F i s h e r e l e c t r o p h o t o meter, were both r e c o r d e d a t t h i s time.  For graphical presenta-  t i o n the photometer r e a d i n g was, s u b t r a c t e d from 100 and  plotted  as " I n t e n s i t y of Pigmentation" r a t h e r than %. l i g h t t r a n s m i t t e d . " n  jghls had the e f f e c t o f i n v e r t i n g the curve and i t was  felt  that  38* by so doing a. b e t t e r r e p r e s e n t a t i o n  of pigment p r o d u c t i o n  r e l a t e d to weight of growth would be The  i n i t i a l and  i n Table V*  given*  f i n a l pH of the v a r i o u s media are  data tend to c o n f i r m Waksman's (105)  The  as  presented observa-  t i o n s that most s t r a i n s of Streptomyces scabies, tend to  adjust  r e a c t i o n of t h e i r environment i n the d i r e c t i o n of optimum f o r t h e i r growth*  Thus, a d i s t i n c t l y a c i d medium becomes l e s s a c i d i c  and a. d i s t i n c t l y a l k a l i n e medium becomes l e s s a l k a l i n e * Since no a n a l y s e s  were done on the medium the  precise  nature of the changes r e s p o n s i b l e f o r the a l t e r a t i o n s i n pH not  known*  However Waksman (I07)  s t a t e s t h a t s i n c e the  are  actino-  mycetes; p r e f e r proteins, to carbohydrates as. a source of energy, ammonia, i s r a p i d l y produced*  With p r o t e i n as the  only  carbon  source ammonia might accummulate to the p o i n t where the medium would become too a l k a l i n e f o r growth*  Even when a s u i t a b l e  carbohydrate energy source i s added and a c i d i s produced, p r o b a b l y a l a c t i c , the tendency i s always toward a maximum a l k a l i n i t y of. pH 8*6 to 8*8*  Presumably any a c i d produced that w i l l  to. b u f f e r a g a i n s t ammonium i s decomposed to 0:02  a  n  d  H  2  G  3 0  tend that  i t s buffering capacity i s l o s t * Although the f o r e g o i n g may  e x p l a i n a change of pH  a c i d i c t o a l k a l i n e i n the present  from  i n s t a n c e , i t does not  explain:  a r e a c t i o n change from extremely a l k a l i n e to l e s s a l k a l i n e , B o t h the phenomena may b o x y l l a t i o n . and  be e x p l a i n e d  on the b a s i s of decar-  deamination of the p r o t e i n i n the media*  Since  39 Table Y.  I n i t i a l and f i n a l pH o f medium i n which. S t r e p t o myces s c a b i e s s t r a i n s a r e grown f o r 21 days a t  27°C  ~  Initial pH  F i n a l pH of medium o f strain indicated  27 2.00 2.50  3.OO 3.40  4.00 5.5O  7.IO  7*70 8.65 9.00 9*85 ' 11.60  33  2.00 2.5a 3.00  2.05 2.60 3.05 3.50 4.20 6.20 7.60 8.00 , 8.10. 8.30 8.50 8.70  3.40  £.00 7.00 6.90 7.70: 8.10 8.30 8.30 8.20  39  4-8  2.00 2.60. 3.10, 3.50  2.00 2.50 3*05 3*45 4.10 7.10 8.05 8.10 8.00. 8.30  6.50, 7.60 7.00 7.90 8.10 8.30 7.90.  E.I,  2.00 2.50 3..10 3.50 7.20 7.60 7.50 7.30 8.30 8.6O. 8.60 8.70;  8.40.  8.20:  ^ Contaminated w i t h f u n g i . d e c a r b o x y l a t i o n accurs i n an a c i d medium the r e s u l t is, a loss; of CO2 from the medium and a g r e a t e r c o n c e n t r a t i o n o f -HEL^groups to  increase a l k a l i n i t y .  Deamination on the other hand w i l l r e -  p l a c e d e c a r b o x y l l a t i o n when the environment i s a l k a l i n e . a l o s s o f NH3 r e s u l t s , -GOOH groups become more and the. pH. becomes l e s s a l k a l i n e .  concentrated  While t h i s s i t u a t i o n h o l d s as  a g e n e r a l r u l e i n b a c t e r i a l metabolism, s t i l l prove the e x c e p t i o n .  Thus  actinomycetes. may  I t c o n t r a d i c t s - Waksman s statements that 1  deamination occurs a t a pH o f 6 . 8 , and t h a t ammoniacal n i t r o g e n w i l l be present  i n the medium a t this, pH.  Further, i t infers,  that the change i n r e a c t i o n i s due, not o n l y t o the  accumulation  of a b a s i c compound but a l s o t o the l o s s o f an a c i d i c component of that, compound.  S i m i l a r l y the change o f pH on the a l k a l i n e  40:. s i d e i s due b o t h to a l o s s of an a l k a l i n e component and accumulation  of an a c i d i c  From Figs*. 4 ,  an  compound. 6 and 7»  5»  graphic r e l a t i o n s h i p s between pH,  a n  8,  d  c  a  be  n  seen the  growth and pigment  production.  G e n e r a l l y , t h e r e i s a p o s i t i v e ; c o r r e l a t i o n , between pH, weight of growth and  i n t e n s i t y of pigment to a. maximum and  c o r r e l a t i o n occurs.. myces. 33,  then a  negative  T h i s i s p a r t i c u l a r l y apparent f o r S t r e p t o -  4 8 , and the e a s t e r n c u l t u r e .  Streptomyces 27  39  and  however show a secondary peak i n growth a f t e r a d e c r e a s e .  The  i n t e n s i t y of pigmentation  these  l a t t e r two  strains.  does hot show the same t r e n d f o r  I t i s p o s s i b l e t h a t these  two  s t r a i n s are 48  more r e s i s t a n t to the e f f e c t o f pH than are s t r a i n s 33, the e a s t e r n i s o l a t e . growth a t any  T h i s i s borne out by the g r e a t e r  s p e c i f i c pH f o r s t r a i n s 27 and 39.  The  and  total f a c t that  pigment i n t e n s i t y d i d not i n c r e a s e to a second peak f o r 27  and  39 appears t o i n d i c a t e t h a t there; i s a c l o s e r r e l a t i o n s h i p between pigment and pH than between growth and The  optimum pH f o r s t r a i n s 39,,  t u r e i s between pH 7 and 8 .  pigment.  48 and  the e a s t e r n  T h i s a l s o h o l d s f o r s t r a i n 27  culi f the  S t r a i n 33 however shows a  second growth i n c r e a s e is. n e g l e c t e d . s l i g h t l y h i g h e r optimum between pH 8.6  and 9 .  The  first  four  organisms c o n f i r m Waksman s o b s e r v a t i o n (.105) t h a t the optimum 1  pH  i s 7*8 to. 8 . In the same work Waksman s t a t e s t h a t the l i m i t i n g h y d r o -  gen i o n c o n c e n t r a t i o n s are a t pH 5  a n a  -  9>  e a s t e r n i s o l a t e show r e l a t i v e l y e x t e n s i v e case of s t r a i n s 33,  However: both 27 and growth at pH 4 .  39 and 48 however, the l i m i t i n g pH  In  the the  i s . between  41.  F i g . 4. The e f f e c t o f Hydrogen ion c o n c e n t r a t i o n on growth and pigmentation. Crosses (x) i n d i cate growth and c i r c l e s (o) r e present i n t e n s i t y of pigmentation.  42 .  g * 5* The e f f e c t of Hydrogen i o n c o n c e n t r a t i o n on growth and pigmentation. Crosses (x) i n d i cate growth and c i r c l e s (o) r e present i n t e n s i t y of pigmentation. F l  Fig» 6> The e f f e c t o f Hydrogen i o n c o n c e n t r a t i o n on growth and pigmentation. Grosses (x) i n d i cate growth and c i r c l e s (o) r e present i n t e n s i t y of pigmentation.  44.  F i g * 7» The e f f e c t of Hydrogen i o n c o n c e n t r a t i o n on growth and pigmentation. Crosses (x) i n d i c a t e growth and c i r c l e s (o) r e present i n t e n s i t y of pigmentation.  4£.  a» The e f f e c t of Hydrogen i o n c o n c e n t r a t i o n on growth and pigmentation. Crosses (x) i n d i cate growth and c i r c l e s (o) r e present i n t e n s i t y of pigmentation.  46. 4 and 5-5  and so q u i t e p o s s i b l y these t h r e e organisms, would  have been i n h i b i t e d a t about, a. pH o f 5'. A l t h o u g h i n h i b i t i o n i s i n d i c a t e d on the a l k a l i n e s i d e complete i n h i b i t i o n has not been a t t a i n e d  even at pH 11*6.  P h y s i o l o g i c a l d i f f e r e n c e s between the f i v e are borne out by the v a r y i n g  amounts, o f growth and the v a r y i n g  pigment i n t e n s i t i e s a t s p e c i f i c pH*s. a l s o evident  strains  These differences? a r e  i n the f a c t t h a t the i n h i b i t o r y a c i d pH i s not.  the same f o r a l l s t r a i n s . Methods f o r C o n t r o l The has  s o i l used f o r the f o l l o w i n g greenhouse  been d i s c u s s e d The  of Scab I n c i d e n c e . studies  i n a p r e v i o u s s e c t i o n of t h i s paper.  White Rose v a r i e t y o f potato, was used f o r a l l  gfeenhouse t e s t s .  The tubers, f o r p l a n t i n g were s u p p l i e d by  Dr- N.S. Wright of the Dominion P l a n t Pathology L a b o r a t o r y , U n i v e r s i t y o f B r i t i s h Columbia, and so f a r as c o u l d be a s c e r t a i n e d , were; f r e e of scab, f l e a , beetle,, or other common potato diseases.  As a further, p r e c a u t i o n  a l l t u b e r s were submerged  f o r 1$ minutes i n a Ls 100.0 s o l u t i o n of mercuric c h l o r i d e . k n i f e used f o r c u t t i n g the seed p i e c e s  waa dipped, i n t o 1:1000  mercuric c h l o r i d e s o l u t i o n p r i o r t o each i n d i v i d u a l c u t . p i e c e s were p l a n t e d  The  Seed  immediately a f t e r c u t t i n g .  I n d i v i d u a l t u b e r s o f the crop were r a t e d f o r scab  47. u s i n g the most s e r i o u s l y scabbed  t u b e r s , which occurred i n the  checks, f o r comparison and g i v i n g them a r a t i n g of B 3 , r : » f r e e tubers were r a t e d as o° n  w h i l e r a t i n g s of " l  and  w  Scabtt  2  accorded t u b e r s showing a scab i n c i d e n c e between the two  were  M  ex-  tremes.  P i g . 9 shows the extent of scab at each i n d i v i d u a l  rating.  Only those spots showing b l a c k on the photograph are  a c t u a l scab l e s i o n s .  As. an i n d i c a t i o n of the s e v e r i t y of scab  under each treatment,  every tuber h a r v e s t e d from t h a t set of  p o t s was. a s s i g n e d a r a t i n g . ment were then averaged mal f r a c t i o n .  A l l tuber r a t i n g s f o r t h a t t r e a t -  and r e c o r d e d as a whole number and  A l s o r e c o r d e d was  from a p a r t i c u l a r treatment l e s s of s e v e r i t y .  the percentage  tubers harvested  t h a t showed any scab at a l l i r r e g a r d -  T h i s f i g u r e , expressed as a percent was  s i d e r e d t o be the prevalence of scab under t h a t I n f l u e n c e of s o i l  was  106):  con-  treatment.  reaction.  With the i n i t i a l work of G i l l e s p i e Waksman (105,  deci-  i n 1919  and 1922,  (29)  i n 1918  an a s p e c t of scab  presented t h a t has. continued to the present t i m e .  and  control The  above workers found t h a t i n c u l t u r e media Streptomyces s c a b i e s (termed Actinomyces chromogenus by G i l l e s p i e ) was a pH of 5.0 scab may  Supporting evidence t o the e f f e c t that  be c o n t r o l l e d a t a pH of $.2. or lower  M a r t i n (66, (14, 15).  or lower.  i n h i b i t e d at  67), Cook and Houghland, (13)  i s presented  and Cook and Nugent  The f i e l d o b s e r v a t i o n s of G i l l e s p i e and Hurst  of B l o d g e t t and Howe (6)  by  based on surveys of d i f f e r e n t  h e l p to c o n f i r m the f e a s i b i l i t y of c o n t r o l l i n g scab  (30).  areas  through  and  48.  TUBER RATING FOR  Fig* 9  SCAB  T y p i c a l samples of tubers g i v e n r a t i n g as i n d i c a t e d  49. lowering of .pK.  On the c o n t r a r y the f i n d i n g s o f Raedar  (20), Taubenhaus (98)  Dippenaar  and S c h a a l (91)  (83)',  i n d i c a t e that  an a p p l i c a t i o n of sulphur f a i l e d to. prevent scab..  I t should  be borne i n mind, however, t h a t i n these cases the d e s i r e d of  5»2  et  a l . (78):  of  5.2  or lower was not always reached. and L a r s o n et a l . (51)  E d d i n s (22),  pH  Muncie  found that a l t h o u g h a pH  c o n t r o l l e d scab, y i e l d was a d v e r s e l y a f f e c t e d . t h i s study t h r e e s e r i e s of 12-inch pots each  For c o n t a i n i n g 10 treatment.  pounds o f s o i l were s e t up i n t r i p l i c a t e f o r each  One  s e r i e s i n v o l v e d additions, of HgSO^at r a t e s t o  provide a. range i n pH from 2.5  to 5 i n c l u s i v e a t 0.5  pH  intervals.  The H2SO4 was a p p l i e d at a c o n c e n t r a t i o n of 6 normal and a t r a t e s c a l c u l a t e d from the. a c i d b u f f e r curve of f i g u r e 2.  A  second  s e r i e s covered the same pH range w i t h sulphur as, the amendment. The t h i r d s e r i e s involved: the a d d i t i o n of C a ( O H ) amounts to provide a pH range o.f 8 to 10  2  i n varying  i n c l u s i v e , applications:  being c a l c u l a t e d from the base b u f f e r curve of f i g u r e 3 . check c o n s i s t e d of the u n t r e a t e d s o i l of pK For  The  6.6.  d e t a i l s , aa to p r e c i s e amount of amendment added  i n each case and the r e l a t i o n of this, to the u l t i m a t e pH of the soil,  see Table V I . At  h a r v e s t i n g , 90 to 100  days a f t e r p l a n t i n g , the t u b e r s  were r a t e d f o r s c a b b i n e s s , and s o i l samples were taken from the r e g i o n of tuber development f o r pH d e t e r m i n a t i o n s .  r  Y i e l d was  low  5o.  and size, was s m a l l , no more than g i v e t u b e r s being taken from any one pot and the average diameter b e i n g 3/4 i n c h . The r e s u l t s p r e s e n t e d i n Table VI i n d i c a t e that the d e s i r e d pH has been g i v e n by t h e H2SQ4 and sulphur a d d i t i o n s as c a l c u l a t e d from the a c i d b u f f e r curve o f F i g . 2.  T h i s may be  expected i n the case of treatment of s o i l w i t h 6H H2SO4 which has hydrogen bases.  i o n s immediately a v a i l a b l e t o r e p l a c e exchangeable  Sulphur however i s an i n s o l u b l e element  that r e q u i r e s •  o x i d a t i o n to H2SO4 before i t s a c i d i c e f f e c t becomes; apparent. That t h i s r e a c t i o n must have o c c u r r e d i s evident from the d a t a , so one may conclude t h a t s u l f o f y i n g organisms a r e abundant and active i n this  soil.  The Ca(0H)2 a d d i t i o n s have not shown the same d e s i r a b l e r e s u l t s , . T h i s I s not unusual s i n c e the C a ( 0 H )  2  would be r a p i d l y  converted to the even more i n s o l u b l e GaCO^ on being added t o the soil.  Calcium i n the l a t t e r form i s going t o a c t s l o w l y and  over an e x t e n s i v e period, o f time before the d e s i r e d pH w i l l be apparent. The extent o f scab c o n t r o l i a obvious from the r e s u l t s . Some; c o n t r o l has been e x e r c i s e d by almost a l l amendments, a t  1 l e a s t i n s o f a r a s s e v e r i t y of scab i s concerned.  The same cannot  be s a i d f o r scab prevalence s i n c e many cases occur where scab i s l e s s severe but a l l t u b e r s have been i n f e c t e d .  This situation  i s p a r t i c u l a r l y apparent i n the case o f the H2SO4 and sulphur additions.  With these two amendments t o o , b e t t e r c o n t r o l i s  51 T a b l e VT.  Desired. PH  The e f f e c t of s o i l r e a c t i o n i n the c o n t r o l of common potato scab.  2.5 3-0 3*5 4.0; 5*0.  H S0  2.5 3*0; 3*5 4.0 5*0 6.8  Sulphur  8.0 8*5 9*0 10.0 See  2  4  Check Ca(OH)  Tuber rating*  Application pH •» a t l b s / a c . , .harvest  Amendment used  51,938 36,856 28,366 21,574 . 11.586  2.8 3*1 4*06  16,958 12,090 9,150 7,180 3,590;  2*9 3.55 3*05 4.20 5*05 6.8  3.00(100^) 2.10(100^) 1.90(100^) 0.83 ( 8 « 0.60 (60^)  7.36 7*73 7*82 8.11  1.70 (80%) 0.50 (50^) 0.83 (66^1  0.75(100^} 1.75(100^) 1.20 (80%) 1.00(100^)  5*40  4.96  aw  2,880 5,200 8.490 19,190  2  no germinat i o n  2.60(100^)  -0.14 (.14§£)  context f o r e x p l a n a t i o n o f tuber r a t i n g s .  i n d i c a t e d a t pH 5 than a t lower pH*a. The  Ca(0H)  2  applications  show a s t r a i g h t l i n e  rela-  t i o n s h i p between amount o f a p p l i c a t i o n , o r pH, and both severity; and  prevalence o f scab.  T h i s treatment a l s o i n d i c a t e s  better  r e s u l t s than the two a c i d treatments.. A second greenhouse experiment waa s e t up i n a s i m i l a r manner t o the f i r s t and i n c l u d e d  the t h r e e lowest a p p l i c a -  t i o n s o f a c i d , the f o u r lowest a p p l i c a t i o n s three h i g h e s t  o f sulphur, and the  a p p l i c a t i o n a o f c a l c i u m . The r e a u l t s of this, e x p e r i  ment, g i v e n i n Table V I I , i n d i c a t e the same t r e n d s as a r e appar-  52. ent  i n the f i r s t experiment a l t h o u g h a c t u a l f i g u r e s  vary  may  slightly.  E f f e c t of i n c r e a s e d a e r a t i o n . In  o r d e r t o observe the e f f e c t of i n c r e a s e d a e r a t i o n  and p e r m e a b i l i t y of the s o i l ,  sawdust and peat a d d i t i o n s  were made t o p o t s a s set up i n the second experiment. s e r i e s o f p o t s r e c e i v e d two  One  i n c h e s of cedar sawdust of no  d e f i n i t e s i z e and t h o r o u g h l y mixed w i t h the s o i l .  A  second  s e r i e s of pots r e c e i v e d p e a t , a p p l i e d and mixed i n the same f a s h i o n as the sawdust. O b s e r v a t i o n of t h e p l a n t s throughout  the  experiment  i n d i c a t e d no d i f f e r e n c e s i n t o p growth between s o i l a l o n e , s o i l p l u s sawdust and s o i l  plus peat.  The same h o l d s t r u e  i n the case o f scab c o n t r o l and pH changes,  as i n d i c a t e d i n  T a b l e V I I . While a few i s o l a t e d cases a r e apparent where s l i g h t d i f f e r e n c e s do occur, the d a t a are The r e s u l t s of these experiments  comparable. on the e f f e c t of  r e a c t i o n have confirmed the r e s u l t s of Menzies  (76)  who  e x c e l l e n t scab c o n t r o l a t a. pH of 8 or g r e a t e r . And  found  they  have, a t l e a s t p a r t i a l l y , confirmed the work of those r e s e a r c h e r s who  lowered pH. i n order t o c o n t r o l scab.  The d i f f e r e n c e , of  Course, i s i n the f a c t t h a t scab appeared t o become more severe a t pH*s lower than  5*0*  This factor  particularly,  c o n t r a d i c t s the f i n d i n g s of Oswald and Wright b e t t e r scab c o n t r o l a t pH 4.2  than a t pH  5»2.  (80)  who  found  53 Table. T I L E f f e c t o f s o i l r e a c t i o n and a e r a t i o n i n the c o n t r o l of common potato, scab*  o  H  H  H  b  to  •r-(  6  to  (A  H  CM  H  ft <1>  H  •H  4*1  21,574  4.3  4.3  4.6  11,586  4.9  5.2  4.8  12,090  3.4  3*0  3.1  3*5  9,150  3*5  3*3  3*5  4.0  7,180  3*8  3*8  4.0  5.0  3,590  4*7  4*7  4.7  6.8  6*7  6.3  7*5  7*7  7*5  5.0  Sulphur  6.8  Check  8.5  Ga(OH)  2  5200  9.0  8490  8.2  810  8.0  10.0  19190  7*9  8.3  8.1  See context f o r e x p l a n a t i o n of tuber  c3  o  ,b CO  4.2 -  o  H (3  3.7  3*0  K  s; w  28.366  H2S04  4.0 1  -p CQ to 3 EJ ^  H  ca  3*5  Tuber r a t i n g 3t  pH a t harvest  D e s i r e d Amendment Applica-? pH used tioh lbs/ac.  1.42  1*37 100%  1.10 100^  -p td td 3  as •H  in Pi  0)  H  b  coi  1.52 70% 1.25 80^ 1.20 100$  i.5.4 1.40  73% 0.98 92^  2.1 100^ 1.17 IQQ%: 83^. 1*7 l-t100^ 100^ 0.82 0*9 82^: 7A%  2.2 100^: 0.80 61% 1.0 83^ 0.87 63^-  100^  £*8  2.7 100^  2.6 100%  1.7  1*57  0.85 64^ 0.10 10%'  0.45 43* 0.15 i5£  1.54 89^ 0.80 70% 0.25 12^;  2.3 10 2.0  82^  rating  54  E f f e c t o f mercuric  chloride.  As: i s the case i n the adjustment of pH f o r scab c o n t r o l , v a r i a b l e r e s u l t s have been r e p o r t e d  concerning  the a p p l i c a t i o n o f mercury compounds f o r c o n t r o l of M a r t i n (69)  i n 1931  a p p l i c a t i o n s i n one (70)  he r e p o r t s  reported  c o n t r o l of scab by  p a r t o f Hew  increased  J e r s e y and  scab, due  scab.  mercurial  four years l a t e r  to m e r c u r i a l  applica-  tions, i n a d i f f e r e n t p a r t of the same s t a t e . (17)  Under Long: I s l a n d c o n d i t i o n s , Cunningham and  Cunningham and Wessels (18)  r e p o r t good c o n t r o l a p p l y -  i n g y e l l o w oxide of mercury or m e r c u r i c c h l o r i d e a t r a t e of 4 pounds per a c r e , w h i l e T a y l o r Blodgett  i n western Hew  York.  are apparent throughout the l i t e r a t u r e . workers achieves, a c o n t r o l i n one seabbiness. w i t h the  Qn ment was  and  Taylor  and  (.101) observed more severe scab through m e r c u r i c  chloride additions  increased  (99)  the  the b a s i s  Similar results While one  a r e a another group f i n d  same amendments i n another  of t h i s c o n t r o v e r s i a l data, an  set out t o t e s t t h e ' e f f i c a c y of m e r c u r i c  a s a scab c o n t r o l measure on the Applications  group of  Chloride  s o i l used i n this, study.  were made at the r a t e s of 5,  pounds per a c r e w i t h the  experi-  10,  15  and  20  s a l t b e i n g added to the pots i n s o l u -  t i o n to ensure a, thorough d i s t r i b u t i o n .  55  From the results:, T a b l e V I I I , i t i s obvious t h a t no c o n t r o l has occuned.  Table V I I I .  E f f e c t of mercuric c h l o r i d e i n the c o n t r o l of common potato scab.  R a t e of application  • Tuber r a t i n g — • Severity of Prevalence o f scab; scab  5 10 15 20  1.78 2.55 2.50 2.70  See. context  f o r explanation  Ken Knight (48)  100%  100^10.0^ 90^ of tuber r a t i n g ; .  showed t h a t , whereas; mercuric  c h l o r i d e would c o n t r o l s t r a i n s of Streptomyces s c a b i e s from one p a r t o f the country, i t i n c r e a s e d seabbiness. i n the case of s t r a i n s from some other r e g i o n .  He e x p l a i n s t h a t i n cases  where the s t r a i n o f Streptomyces. s c a b i e s v i g o r o u s l y  resists  the e f f e c t of HgCl2, s u s c e p t i b l e organisms i n the s o i l are reduced i n numbers t h e r e b y p e r m i t t i n g the. i n f e c t i n g organism to m u l t i p l y t o a marked degree. Influence  of Compound  B-162.  With the development o f innumerable organic  fungi-  c i d e s i t was n a t u r a l that some a t t e n t i o n should, be d i r e c t e d toward potato scab c o n t r o l by these compounds. et a l . (72)  Michaelson  t e s t e d the e f f e c t of 2-4>dichlorophenoxyacetic  56. a c i d on s i x p h y s i o l o g i c s t r a i n s o f Actinomyces scabies, a t v a r i o u s hydrogen i o n concentrations..  They found t h a t the  organisms: could: be i n h i b i t e d i n c u l t u r e by the a c i d , e s t e r and  s a l t forms of  per m i l l i o n .  2-4:-©  a t concentrations, as low as,  Garber- e t al.. (27)  found t h a t  56  parts  pentachloro-  phenoxyacet.ic a c i d was. f u n g i s t a t i c f o r one s t r a i n of S t r e p t o myces, s c a b i e s a t 32 t o 500 p a r t s per m i l l i o n and f u n g i c i d a l at  1000 and 2000  at  0 to 16 p a r t s per m i l l i o n , growth was l i m i t e d a t 32 t o  parts, per m i l l i o n . .  No e f f e c t was i n d i c a t e d  64 p a r t s per m i l l i o n and i n h i b i t e d a t 125 The  parts per m i l l i o n .  f i e l d a p p l i c a t i o n o f p e n t a c h l o r o p h e n o y a c e t i c a c i d has  i n d i c a t e d i n h i b i t i o n or growth p r e v e n t i o n  of Streptomyces  scabies, a t a p p l i c a t i o n s o f I and 10 pounds: per a c r e . scab-free  tubers and shallower  scab p u s t u l e s  More  i n d i c a t e d , some  control. The  J u l i u s Hyman Co. o f Denver Colorado (.44)  have  r e c e n t l y developed, a. c h l o r i n a t e d hydrocarbon which they des i g n a t e as Compound  P-162..  Company l i t e r a t u r e d e a l i n g w i t h  t h i s compound i n d i c a t e s t h a t Streptomyces scabies, i s I n h i b i t e d by c o n c e n t r a t i o n s P-162  as low as 0.4 to 0.6 p a r t s per m i l l i o n of  i n c u l t u r e medium,, while, f i e l d a p p l i c a t i o n s of 40 pounds  per a c r e o f t h e compound show e x c e l l e n t c o n t r o l o f common scab i n C o l o r a d o . E f f e c t of P-162 on Streptomyces s t r a i n s under, s t u d y . In order  scabies  to determine the f u n g i s t a t i c and f u n g i -  c i d a l effectiveness of  P-162',  a s e r i e s of d i l u t i o n p l a t e s  57. were; prepared, r a n g i n g from 0 to 2000. ppm. e x t r a c t a s p a r a g i n agar was  M a n n i t o l yeast  used", as the. growth medium and. was  quant i t a t i v e l y d i s p e n s e d i n tubes b e f o r e s t e r i l i z a t i o n . Because of the h i g h l y v o l a t i l e nature of P-162  i t c o u l d not  be s t e r i l i z e d , and. had. to, be added, by p i p e t t e i n approximate q u a n t i t i e s to each I n d i v i d u a l p l a t e a t the time of p o u r i n g . Even t h i s technique must have r e s u l t e d i n the l o s s of a degree of e f f e c t i v e n e s s of the P-162  f o r i t s odor was  n o t i c e a b l e when added t o the f l u i d agar-.  After  solidifica-  t i o n the plates; were s t r e a k e d with the streptomyces Check p l a t e s were c a r r i e d  quite  isolates.  throughout..  S i n c e compound P - l 6 2 i s almost i n s o l u ,ble i n water the i n i t i a l concentration, i s made up with acetone. of P-162. i n 100  mis of acetone g i v e s a. c o n c e n t r a t i o n of  10,000 parts, per m i l l i o n of t o t a l compound. P-162  One gram  i s only 90.8^  However s i n c e  pure the necessary adjustment was made  to g i v e the r e q u i r e d parts- per m i l l i o n . A l l p l a t e s were incubated a t 27°C f o r 14 days and then observed f o r amount o f growth*  On a l l p l a t e s where  growth d i d not. occur a smear, was. taken and sown onto mannitol. yeast e x t r a c t a s p a r a g i n agar, slants, t o determine whether the i n h i b i t i o n had been f u n g i s t a t i c or f u n g i c i d a l . were then observed f o r growth after- 21  The  slants  days I n c u b a t i o n at 27°C.  The r e s u l t s as. presented i n Table I X are s e l f explanatory..  The m a j o r i t y of organisms have been i n h i b i t e d a t  t o 227  p a r t s per m i l l i o n .  9O..8  Only nine organisms, have withstood  a greater  than 227  p a r t s per m i l l i o n c o n c e n t r a t i o n ,  have withstood 1000  parts, per m i l l i o n , , and  been i n h i b i t e d at c o n c e n t r a t i o n s million*  Streptomyces 47  pound w h i l e 35  was  was  only  l e s s than 9O..8  none  five have -  parts, per  most susceptible, to the com-  the most r e s i s t a n t .  These r e s u l t s are s i m i l a r to those of Garber e t a l . (27)  who  t e s t e d the f u n g i s t a t i c and f u n g i c i d a l p r o -  p e r t i e s of pentachlor.ophenoxyac.etic a c i d . found, no v i s i b l e e f f e c t a t 0 to 16 l i m i t e d growth at 3 at. 125 at  2  64  and  p a r t s per m i l l i o n .  32! to 500  Garber. et a l .  p a r t s per  million,  parts, per m i l l i o n and The  inhibition  a c i d proved t o be. f u n g i s t a t i c  p a r t s per m i l l i o n and  f u n g i c i d a l at 1000  and  2000 p a r t s per m i l l i o n . . Garber*s. tests- were c a r r i e d out on f o u r d i f f e r e n t species, of organisms i n c l u d i n g one Streptomyces  of  scabies.  The; J u l i u s Hyman CO. t h a t 0.4  3train  to 0.6  i n t h e i r Release. No.  p a r t s per m i l l i o n , was  inhibitory for  p a r t i c u l a r Streptomyces s c a b i e s c u l t u r e they t e s t e d . technique u s i n g a. f l u i d medium and medium completely a i r t i g h t  4  claim the Their  keeping the tubes, of sown  i s s u p e r i o r to adding the  P-162  to- f l u i d agar i n p l a t e s s i n c e g r e a t e r c o n t r o l , i s e x e r c i s e d over the a c t u a l c o n c e n t r a t i o n mentioned the c o n c e n t r a t i o n decreased t o some extent the w r i t e r .  i n each d i l u t i o n .  of a c t i v e  i n pouring  As  previously  P-162. must have been  the agar p l a t e s used by  However i t is: f e l t that t h i s loss: would not  s u f f i c i e n t to account f o r the tremendous d i s c r e p a n c y the J u l i u s Hyman r e s u l t s and those recorded  i n Table  be  between IX.  \  Table IX. The f u n g i s t a t i c and f u n g i c i d a l e f f e c t o f P - 1 6 2 . „ ' D i l u t i o n - p a r t s per m i l l i o n . Org. -• •• -  No. 0 1 +++ 2 11 3 tt 4  5 6 7 8 9 10 11 12 13 15 16 17 22 27 30 31 32 33 34  35 37 38 39  ii it it  m  tt it it  ifc  0.4^4 0.908 2.27 4.54 9.O8 13.62 22.7 45.4 68.1 90.8 227 454 681 +++ Ifc II It tt It tt  Ifc It' It tl? Ifc  4+4 •t II It It  444 it tt tt 11  TTT It n it it  +4+  m  tt it  115  II; It tt Ifc  it 11? tt  It:  It  Ifc ti-  Its  lt  It It  II* It  m  444 It It It tt  444 it, 11 tt tt?.  4++  »  it lb It  It It  It ttlt  tt 11? it.  It tte It  tt tfe  tfe it  tt tt  It  it  It  tl»  tr-  It tt It  tt It It  lb  m  Iti  +44 it it •It*  +4 it  +  ++ It: It  tfe  4  ci at  +4  H.  4  St at  4  11  tt  at at ci  ci ci ci ci ci ci ci  4  ci ci at  »  Ifc It?  ifc  ite  It  It  It?  tfe  It.  it  it  It  It  It,  it  It  tt  tt Wr-  it li-  lt< Its  It lb  It It  It It  it Its  It It  ite  lt  Ite  tfe  tt  It  It  It  It  It  It  It  It  It  tfe  It  lb it  ifc  It  It It  It: It-  It It  H;  tt'  Hi  44 It  4+ It  Ifc  It  44+  +4  ++  +  444  at at  at St  ci ci  tt  m  »  it= it 11,  It  it  it  tt  It  It  11  Its  It!  tt?  it?  It  tt  It  tti  tt  tt  it  It  It  Ifc  Ifc  tt  «s  It  It  . It" tt  tt:  tt  It  It  tt; Ifc  lis It  tt It  It Ifc  44+4+ tt?  4  ci  +++  444  4 444  444  it  ci it  It*  at  +  tfe  44 tt  444 tt  st St St St  ++4 It  at  +4 tt  908  —  at  CI  ci  - -  ci at at St  ci at at ci  4  ci ci ci st ci  ci  4  ci at  ci  CJl  T a b l e I X . - Continued.  The f u n g i s t a t i c and f u n g i c i d a l e f f e c t o f P-162 D i l u t i o n - . p a r t s per m i l l i o n .  Org.'  Ha. 0 0.54 0.908 2.27 4.54 9.08 13.62 22.7 45.4 68.1 90.8 227 454 681 908 41 t + 4  45 47 48  49  50 51  E.I.  Noter-  +V4 Ite  It*  lb  »  It:  ft  tt-  tt:  lift  Ife  it  It  <¥4  44  44* -4-  +•*  44 44* 44444 44  +4 +44 4 +44 44  ci  tilt  it  Hi  it:  It;  11  Ms  tt>  u  It:  II?  It:  llt  v  44444 4+  at  St  ci 444 44 4/  ci St St St St  ci  ci ci ci ci  l ) The f o u r d i l u t i o n s g r e a t e r than 1000 p.p.m. and up t o a r e not shown because o b v i o u s l y they a r e f u n g i c i d a l s 2);  •at*" - f u n g i s t a t i c  3)  °ci  4)  4,  M  - fungicidal  ........ least, growth ......more growth 4+4, ......most growth and comparable, t o checks.  2000  p.p.m.  61, S i n c e approximately 100 p a r t s per. m i l l i o n i s the i n h i b i t o r y c o n c e n t r a t i o n f o r the organisms r e p o r t e d upon a t t h i s time, the l o s s would hare t o amount t o over 99$ o f a c t i v e compound to  d u p l i c a t e the 0.4 to. 0 . 6 p a r t s per m i l l i o n  inhibitory  c o n c e n t r a t i o n c l a i m e d by t h e J u l i u s Hyman Go* The f a c t that t h i s , i s an a r b i t r a r y procedure o n l y i s admitted by the J u l i u s Hyman Co. when they s t a t e that i t r e q u i r e s , 4 0 pounds p e r a c r e t o c o n t r o l scab i n the f i e l d . I f this, d i f f e r e n c e between l a b o r a t o r y r e s u l t s and f i e l d r e s u l t s i s due to l o s s o f a c t i v e compound by v o l a t i l i z a t i o n , then we can assume that t h e r e i s a l o s s amounting t o 97% to 9&%.  Reviewing  the data as p r e s e n t e d i n Table IX, I n the  l i g h t o f a. 9&% l o s s due to v o l a t i l i z a t i o n , an i n h i b i t o r y c o n c e n t r a t i o n o f 100 parts, per m i l l i o n would, a c t u a l l y amount to  I . 3 6 p a r t s per. m i l l i o n .  This concentration i s i n closer  agreement w i t h the, company's r e s u l t s , than the d a t a submitted at  t h i s time. Greenhouse t r i a l s w i t h P«»l62. A greenhouse experiment was l a i d  out i n v o l v i n g :  a p p l i c a t i o n s of 20, 40, and 80 pounds p e r a c r e t o pots cont a i n i n g 10; pounds, o f s o i l .  The compound was: a p p l i e d i n emul-  s i o n form as. recommended by the company. That compound P-162 may have p o s s i b i l i t i e s as a scab c o n t r o l measure on Richmond Farms i s apparent from t h e  62 r e s u l t s shown i n Table  Table. X.  X.  E f f e c t of. compound. P-162 as a. c o n t r o l f o r common potato scab,. Tuber r a t i n g *  4  Application lbs/ac.  20. 4.0 80  pH of s o i l at harvest  6.7I  6.70  Prevalence of scab  Intensity of scab  2.20 1.12 0.45  100% Q7% 45%  See context f o r e x p l a n a t i o n of, tuber r a t i n g . .  Thus an a p p l i c a t i o n of P-162  at 80 pounds per  a c r e g i v e s the same c o n t r o l as pH 4 to 5 or" pH 7.5  to 8 ,  and a t a much lower, a p p l i c a t i o n of amendment than i s necessary i n the case of the adjustment  o f pH..  It i s possible  t h a t a. s l i g h t l y h i g h e r r a t e o f a p p l i c a t i o n of P-162. would have g i v e n complete c o n t r o l of common potato scab i n t h i s soil.  63.  4.-»  SUMMARY AND CONCLUSIONS.  S o i l s ; on one p a r t of a ranch i n the Cariboo demons t r a t e d p o t a t o scab of h i g h i n t e n s i t y while those on another p a r t of t h e same r a n c h f a i l e d t o demonstrate  the presence of  scab even when a scab s e n s i t i v e v a r i e t y o f potato was: grown. With the method o f f i e l d sampling, adopted,  laboratory studies  of these s o i l s ; r e v e a l e d no c o n s i s t e n t d i f f e r e n c e s i n r e s p e c t to:1.) Base exchange i n v o l v i n g t o t a l exchange capacity,, degree of base s a t u r a t i o n , percent or. p r o p o r t i o n of the. v a r i o u s c a t i o n s and c a l c i u m potassium  ratio,  2) Hydrogen i o n concentration,. 3) Organic matter 4)  content.  S o i l s i n s c a b - f r e e areas, were predominately  clays  w h i l e w i t h few exceptions, the s o i l s w i t h a h i g h evidence of scab were loams or of l i g h t e r , texture.. Thus t e x t u r e or a e r a t i o n may be a. f a c t o r determining the i n c i d e n c e o f scab. 5).  B a c t e r i a l counts o f s c a b - i n f e s t e d and s c a b - f r e e s o i l s showed a h i g h e r average o f bacteria,, actinomycetes and p a r t i c u l a r l y f u n g i i n the scab i n f e s t e d samples. s i g n i f i c a n c e o f t h i s has. n®t been  6)  The  determined..  T h i r t y f o u r s t r a i n s o f Streptomyces  s c a b i e s were  i s o l a t e d from White Rose, t u b e r s grown on the r a n c h under  .64.  study.  These i s o l a t e s , were compared w i t h a s t r a i n  iso-  l a t e d by the Dominion P l a n t Pathology l a b o r a t o r y a t St C a t h a r i n e s , Ontario.. C u l t u r a l c h a r a c t e r i s t i c s of the t h i r t y f i v e  strains  conformed r e a s o n a b l y w e l l t o d e s c r i p t i o n s o u t l i n e d i n Bergey's Manual of D e t e r m i n a t i v e B a c t e r i o l o g y .  Four  of  the s t r a i n s answered e x a c t l y t o Bergey's d e s c r i p t i o n s i n t h e tests, c a r r i e d out.., The p r o d u c t i o n o f pigment i n t y r o s i n medium and the p r o d u c t i o n of a brownmng i n m i l k areaccepted, as r e l i a b l e d i a g n o s t i c t e s t s f o r s e p a r a t i o n of. pathogenic and  saprophytic s t r a i n s .  A l l s t r a i n s , produced  a, brown pigment i n t y r o s i n agar w h i l e o n l y n i n e t e e n p r o duced a. brown ring; i n l i t m u s "milk.. When added, to quartz, sand i n which White Rose p o t a t o p l a n t s were: growing, nine s t r a i n s ; produced m i l d scab^ seventeen produced moderately produced  severe scab and  severe acab l e s i o n s , on the tuber Except  i n two  crop.  cases the organism was  from both the q u a r t z sand and the. new  nine  reisolated  t u b e r s , thus 33; of  the i s o l a t e s conformed t o Koch's p o s t u l a t e s . V a r i a t i o n i n response t i o n was  to hydrogen i o n c o n c e n t r a -  investigated using f i v e s t r a i n s only.  The  results  indicated::a) Optimum pH range v a r i e d w i t h s t r a i n between pH 7 and b) The s t r a i n s without e x c e p t i o n demonstrated a b i l i t y to a d j u s t pH. of medium t o a more s u i t a b l e  level.  c) A d e f i n i t e c o r r e l a t i o n e x i s t e d between pK of medium,  8.  65. amount, of growth and pigment produced* d) C r i t i c a l pH f o r 3 s t r a i n s , was above pH 4 w h i l e the other two. d i d not succumb u n t i l about a pH o f 3.4. Morphological  s t u d i e s d i s c l o s e d the r e p r o d u c t i v e  bodies, as s p i r a l s and chains, of c.onidia. which are t y p i c a l of Streptomyces The  scabies.  t h i r t y f i v e s t r a i n s , o f Streptomyces  scabies  v a r i e d In t h e i r r e s i s t a n c e to the e f f e c t o f compound P-l62.  One s t r a i n was; i n h i b i t e d a t 2.27 p a r t s , per  million  of P-162 while another was. r e s i s t a n t up to. 908 p a r t s per m i l l i o n o f the compound..  The m a j o r i t y  of. the i s o l a t e s  were: completely i n h i b i t e d a t c o n c e n t r a t i o n s ranging  of P-162  f r o m 90.8 t o 227 p a r t s per m i l l i o n .  Scab c o n t r o l , measures,, u s i n g a s e v e r e l y s i c a b — i n f e s t e d s o i l from t h e r a n c h and White Rose seed p o t a t o e s , out  carried  i n the greenhouse gave t h e f o l l o w i n g r e s u l t s :  a.) mercuric c h l o r i d e a p p l i e d at 5, 1QV 15 h d 20 l b s / a c a  was. i n e f f e c t i v e . . b) S u l p h u r i c  a c i d a p p l i e d at. f i v e l e v e l s , r a n g i n g  from  11,500 to 51»000 l b s / a c . and t o give a pH range from 5.0 to 2.5 showed best or pH  c o n t r o l a t 11,500 l b s / a c  5.  c) Sulphur a p p l i e d a t f i v e l e v e l s r a n g i n g  from 3,600 t o  17,000 l b s / a c and t o give a. pH range from 5 t o 2..5 showed best- c o n t r o l at, pH 5* d) Calcium hydroxide a p p l i e d a t f o u r l e v e l s ranging  2880 t o 19,190. l b s / a c and t o give a pH range from  from  66. 8 t o 10 gave an a c t u a l pH range from 7*4 t o 8.1 and  showed best c o n t r o l a t 19,  190 l b s / a c or pH  8.1.  e}: Sawdust and peat a p p l i e d t o i n c r e a s e a e r a t i o n had no e f f e c t on s i z e o f t u b e r s , y i e l d , or c o n t r o l o f scab. f ) Compound P>l62 a p p l i e d a t 20, 40 and 80 l b s / a c showed best c o n t r o l a t 80 l b s / a c . g) I t may be concluded t h a t of a l l the amendments s t u d i e d , c a l c i u m hydroxide a t 19, the best c o n t r o l . P-162  190 l b s / a c gave  T h i s was f o l l o w e d  i n t u r n by  a t 80 l b s / a c , sulphur a t 3,.6'0Q lb3/ac,  sul-  p h u r i c a c i d a t 11,500 l b s / a c and w i t h mercuric c h l o r i d e g i v i n g no c o n t r o l .  1  67  BIBLIOGRAPHY  A f a n a s i e v , M * M * C o m p a r a t i v e p h y s i o l o g y of Actinomyces i n r e l a t i o n to. potato scab, Neb. Agr» E x p . St a . R e s . B u l l * 92, 2.  Artachwager,. E . , Studies; on the potato tuber>  3*  Assoc n  4.  A t k i n s o n , R.G* and R o u a t t , J.W.* The e f f e c t o f the i n c o r p o r a t i o n ' o f c e r t a i n cover crops on the m i c r o f l o r a o f potato scab i n f e s t e d s o i l , A b s t r a c t i n Proceedings of Phytopathology S o c i e t y , 16":  Agr. Res* 27*809-836,  r  Jour* o f  o f O f f i c i a l A g r i c u l t u r a l Ghemists, O f f i c i a l and t e n t a t i v e methods o f a n a l y s i s j o f the Assoc*n of O f f i c i a l A g r i c . 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L.A., V a r i a t i o n s and p h y s i o l o g i c s p e c i a l i z a t i o n s i n the common scab fungus (Actinomyces s c a b i e s ) , Jour, Afer* R e s . 69:169-186, 1944T"  91*  S c h a a l , L.A., Seed and s o i l treatment f o r c o n t r o l o f potato) s c a b , Amer. P o t . J o u r . 23:163^17^1946.  92.  S e h o l l e n b e r g e r ^ C. J . and Simon, R.H., D e t e r m i n a t i o n o f exchange c a p a c i t y a n d exchangeable-bases; i n soil-ammonium a c e t a t e method, S o i l S c i . 5 9 :  93*  S c h r o e d e r , R*A* and Alb*echt> ¥.A., P l a n t n u t r i t i o n and the h y d r o g e n i o n I I Potato s c a b , S o i l S c i .  94*.  Shapovalov, M.,, E f f e c t o f temperature oh g e r m i n a t i o n and growth o f t h e common potato scab organism, Jour, o f A g r . Res. 4 : 1 2 9 - 1 3 5 . 1 9 1 5 .  95*  S k i n n e r , C.E., Emmons, C;.W* and T s u c h i g a , H*M*, H e n r i c i ' s Molds1,1 Yeasts- and Actinomyces , New York*, John Wiley and Sons, 1947*  96*  S t a t u t e s of Canada, 1918, Ch* 29,. sec* 337A. Stuart,,. ¥., The Potato.. New York,, J.B.  lipplncott,  75  98*  Taubenhaus, J . J . , S t u d i e s on-potato scab c o n t r o l , Phytopathology 24*836,- 1934.  99*  T a y l o r , C.F*, F i e l d experiments oh p o t a t o scab cont r o l i n western New York, Amer. P o t . J o u r . II:40-4J>, 1934 c i t e d i n D a i n e s , R.H*,. S o i l amendments f o r d i s e a s e c o n t r o l , S o i l S c i * 61:55-66. 1946.  100.  T a y l o r , G.F., A method f o r the i s o l a t i o n o f a c t i n o mycetes from scab l e s i o n s on potato t u b e r s and beet r o o t s , Phytopathology 26:387-388, 1936. '  101.  T a y l o r , C*F. and B l o d g e t t , E.M., F u r t h e r f i e l d e x p e r i ment s on potato scab c o n t r o l i n western New York. Amer. P o t . J o u r * 138145-150. 1936 c i t e d i n Cunningham, H*S. and l e s s e l s , P»H.» G b h t r o i l i n g common scab o f the p o t a t o on Long J s l a n d by the a d d i t i o n o f mercury compounds and the r e l a t i o n o f s o i l r e a c t i o n to the treatment. N.Y. S t a t e A g r . Exp* S t a . B u l l . 6 b 5 s l - 2 0 , 1939*  102.  T a y l o r , C.F. and Decker, A c o r r e l a t i o n between pathogenicity a n d c u l t u r a l c h a r a c t e r i s t i c s i n t h e genus Actinomyces* Phytopathology 37: 49-58, 1947*.  103.  Thaxter, R*, The potato scab; Conn. A g r . E x p . S t a . R p t . PP* 3^4, b l - 9 5 , 153-161, I 8 9 1 .  104.  Thomas, W.D., Growth and V a r i a t i o n o f s i x p h y s i o l o g i c r a c e s o f Actinomyces s c a b i e s on d i f f e r e n t c u l t u r e mediae Phytopathology 37*319*331, 1947.  105*  Waksman, S*A», C u l t u r a l s t u d i e s o f s p e c i e s Actinomyces, S o i l S c i . 8:71-207, 1919* "•  '  106*  Waksman, S*A*, The infIiience o f s o i l r e a c t i o n upon the g r o w t h o f Actinomyces c a u s i n g potato scab, S o i l S c i . 14:61-79, 1922.  107.  Waksman, S.A*, The Actinomycetes, Mass*, Chronica. B b t a n i c a , Co*, 1950*  108•  Waksman, S.A. and H e n r i c i , A.T., The nomenclature and c l a s s i f i c a t i o n o f t h e Actinomycetes, J o u r . B a c t . 64:337-341, 1943.  109*  W e i n d l i n g , R . „ M i c r o b i a l antagonism-and S o i l S c i . 61:23-30, 1946.  disease c o n t r o l ,  APPENDIX I MICROPHOTOGRAPHS OP REPRESENTATIVE ISOLATES M a g n i f i c a t i o n i s X440.  APPENDIX I I C o n s t i t u t i o n o f the media used i n t h i s study Sodium Albuminate Agar Agar Glucose D l p o t a s s i u m phosphate Magnesium sulphate F e r r i c sulphate Egg albumen (powdered) Water, d i s t i l l e d R e a c t i o n i s about  12.-5 gm 10.0 " 0*5 0.2 » B  trace  0.25' 1000  gm ml  7.2"  S o i l e x t r a c t Agar Agar Glucose D l p o t a s s i u m phosphateS o i l extract (stock) Tap water R e a c t i o n should be. pH 6.8  12.5 gm: 1.0 0.5 100 ml 90.0 ml w  n  Stock s o l u t i o n of s o i l e x t r a c t . T h i s i s prepared by h e a t i n g 1000 gm. o f garden s o i l w i t h 1000 ml of t a p water i n the autoclave, f o r 30 minutes. A s m a l l amount of. CaCO^ i s added and t h e whole f i l t e r e d through a double paper, f i l t e r . . The t u r b i d f i l t r a t e should be poured back onto the f i l t e r u n t i l i t comes through c l e a r . x  Asparagin-Glucose- AgarAgar Glucose Asparagin D l p o t a s s i u m phosphate D i s t i l l e d water  15.O 10.0 0.5 0.5" 1000  gm " " w  ml  Peptone Glucose A c i d Agar Agar Monopotassium phosphate Magnesium sulphate Peptone Glucose Water.  25.0 1.0 0.5 5.0 10.0 1000  Reaction. pH 3«8 to 4.0 Sodium A s p a r a g i n a t e - G l y c e r o l Agar.  gm w  w  * *• ml  C o n s t i t u t i o n of the media used i n t h i s  study  Sodium. A s p a r a g i n a t e G l y c e r o l Agar Agar Glycerol D i p o t a s s i u m phosphate Sodium asparaginate: WaterR e a c t i o n approximately Potato; Dextrose  15.0 gm 10.0 1.0 * 1.0 ,fc  7»  pH  lOOp, ml  Agar  Peeled; potatoes Glucose Agar Tap"water .7 1000 ml R e a c t i o n i a pH 6.8 The potatoes; are cut i n t o s m a l l cubes to which 350 ml of water i s added, and. the whole steamed f o r t h r e e q u a r t e r s of. an h o u r . The e x t r a c t i s s t r a i n e d through fine: m u s l i n without, squeezing the p u l p . The other n u t r i e n t s are; d i s s o l v e d i n 350 ml o f water which Is then added to the potato e x t r a c t , and. the whole, steamed f o r three, q u a r t e r s of an hour.. The mixture- i s then made up to b u l k , s t a n d a r d i z e d and f i l t e r e d , a f t e r which the agar i s added.. M a n n i t o l Yeast. E x t r a c t A s p a r a g i n Agar 15.O  Agar Mannitol Asparagin. Yeast E x t r a c t D i p o t a s s i u m phosphate Magnesium sulphate F e r r o u s sulphate D i s t i l l e d , water R e a c t i o n i s pH 6.8 to 7  gm  10.0 * 0.5 * 0.5" 0.5 * O.2.5 gm m  trace  2000 ml  T y r o s i n agarAgar Glucose Tyrosin Yeast E x t r a c t ( o r KNO3) D i p o t a s s i u m phosphate D i s t i l l e d water R e a c t i o n a d j u s t e d to pH  15.O  gm  10.0 2.0. • 2.0 * 0.5 * 2000; m2 W:  6.8  C o n s t i t u t i o n of the media, used i n t h i s  study  H i t rate; Sucrose- Agar. Agar. Sodium: n i t r a t e : D l p o t a s s i u m phosphate Magnesium sulphate Potassium: c h l o r i d e F e r r o u s sulphate Sucrose D i s t i l l e d water. R e a c t i o n approximately  15»° gm 2.0 " 1.0 * 0.5 * 0.5 trace 3 0 . 0 gin 1000 ml m  7  pH  S t a r c h Agar Soluble, s t a r c h D i p o t a s s i u m phosphate Magnesium sulphate Galeium c h l o r i d e Sodium n i t r a t e Asparagin F e r r o u s sulphate Washed agar. D i s t i l l e d water R e a c t i o n a d j u s t e d to pH  2 . 0 gm 0..5 * 0.2: 0.05 gm 0.05 0.05 " trace 2 0 . 0 gm 1000 ml tt;  n  V  6.8  T h i n Glucose Agar Agar; Glucose Monopotassium phosphate Sodium n i t r a t e Potassium c h l o r i d e Magnesium sulphate D i s t i l l e d water R e a c t i o n a d j u s t e d to pH  ,  6.8  15.0 1.0 0.1 0.1 0.1 0.1 1000  gm ,,: Ul fti m  * ml  

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