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The genetics of disease interaction in the lodgepole pine : western gall rust host : parasite system Schulting, Maureen Joan 1988

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THE GENETICS OF DISEASE INTERACTION IN THE LODGEPOLE PINE : WESTERN GALL RUST HOST : PARASITE SYSTEM by MAUREEN JOAN SCHULTING B . S c , U n i v e r s i t y of V i c t o r i a , 1983. A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of F o r e s t r y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d s THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1988 © Maureen Joan S c h u l t i n g In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6(3/81) i i A b s t r a c t One hundred and e i g h t y , t h r e e y e a r o l d l o d g e p o l e p i n e ( P i n u s  c o n t o r t a v a r . l a t i f o l i a Dougl.) s e e d l i n g s , r e p r e s e n t i n g e i g h t e e n h a l f s i b l i n g f a m i l i e s were each i n o c u l a t e d w i t h f i v e d i f f e r e n t s p o r e s o u r c e s of w e s t e r n g a l l r u s t ( E n d o c r o n a r t iuro h a r k n e s s i i ( J . P . Moore) H i r a t s u k a ) i n June 1985 t o i n v e s t i g a t e the g e n e t i c s of d i s e a s e i n t e r a c t i o n i n t h i s h o s t : p a r a s i t e s y s t e m . P o s s i b l e e a r l y symptoms of i n f e c t i o n were r e c o r d e d f o u r t e e n days a f t e r i n o c u l a t i o n . T a b u l a t i o n s of the number of g a l l s per s h o o t and sh o o t l e n g t h were made i n September 1985 and June 1986. F i f t y - t w o p e r c e n t (567 out of 1088) of the i n o c u l a t e d s h o o t s became i n f e c t e d . The mean number of g a l l s per i n f e c t e d s h o o t was 3.33. S t a t i s t i c a l a n a l y s e s i n d i c a t e d t h a t o n l y h o r i z o n t a l ( q u a n t i t a t i v e ) r e s i s t a n c e was p r e s e n t i n the l o d g e p o l e p i n e -w e s t e r n g a l l r u s t p a t h o s y s t e m . The l o d g e p o l e p i n e h a l f s i b l i n g f a m i l i e s and s e e d l i n g s v a r i e d g r e a t l y i n t h e i r h o r i z o n t a l r e s i s t a n c e . The v a r i a t i o n i n l e v e l s of r e s i s t a n c e found i n l o d g e p o l e p i n e w i l l a l l o w f o r a s u c c e s s f u l w e s t e r n g a l l r u s t r e s i s t a n c e b r e e d i n g program. The number of g a l l s per t r e e f o r the female p a r e n t t r e e s d i d not s i g n i f i c a n t l y c o r r e l a t e w i t h the p e r c e n t a g e of s h o o t s i n f e c t e d on t h e h a l f - s i b l i n g progeny. Hence, t r e e b r e e d e r s w i l l have t o t e s t the r e s i s t a n c e of progeny. Red s t a i n i n g was found more f r e q u e n t l y on s h o o t s t h a t became i n f e c t e d s u g g e s t i n g t h a t r e d s t a i n i n g i s a p o s s i b l e e a r l y symptom of i n f e c t i o n by w e s t e r n g a l l r u s t . i i i A cknowledgements F u n d i n g f o r t h i s r e s e a r c h was t h r o u g h an NSERC award t o Dr. B a r t van der Kamp, G r a n t #6703. I would l i k e t o thank Dr. van d e r Kamp f o r h i s g u i d a n c e and John S c h u l t i n g f o r h i s p a t i e n c e . i v T a b l e of C o n t e n t s 1.0 I n t r o d u c t i o n 1 2.0 Western G a l l Rust 3 2.1 D i s t r i b u t i o n and h o s t s p e c i e s 3 2.2 L i f e c y c l e 4 2 . 3 Damage 5 2.3.1 T r e e M o r t a l i t y 5 2.3.2 Stem d e f o r m i t y and r e d u c t i o n i n i n c r e m e n t . . 6 3.0 R e s i s t a n c e 6 3.1 V e r t i c a l r e s i s t a n c e 8 3.2 H o r i z o n t a l r e s i s t a n c e 12 3.3 I n d i g e n o u s h o s t : p a r a s i t e s y s t ems 13 3.4 H o s t : p a r a s i t e i n t e r a c t i o n s i n p i n e : r u s t s y s t ems..15 4.0 H y p o t h e s i s 18 5.0 Methods 19 5.1 S e e d l i n g s and s p o r e s o u r c e s used 20 5.2 Shoot i n o c u l a t i o n 23 5.3 Data c o l l e c t i o n 25 5.4 A n a l y s i s . . . . 26 T a b l e o f C o n t e n t s ( c o n ' t ) 6.0 R e s u l t s and d i s c u s s i o n 28 6.1 G e r m i n a t i o n r a t e s and i n o c u l a t i o n r e s u l t s . . . . . . . . 28 6.2 T e s t s f o r v e r t i c a l r e s i s t a n c e 30 6.3 T e s t s f o r h o r i z o n t a l r e s i s t a n c e 39 6.4 C o m p a r i s o n t o p a r e n t t r e e s 45 6.5 Comparison t o f i e l d d a t a 45 6.6 Red s t a i n i n g 47 7.0 B r e e d i n g s t r a t e g y 50 8.0 Summary 51 9.0 L i t e r a t u r e c i t e d 52 Append i c e s 56 1. Append i x A 56 2. Appendix B 57 3. A p p e n d i x C 58 4. Appendix D 59 5. Appendix E 60 6. Appendix F 61 7. Appendix G 62 8. Appendix H 63 9 . Appendix I 6 4 v i L i s t of T a b l e s 1. Terms used to d e s c r i b e the two t y p e s of r e s i s t a n c e 9 2. Mechanisms of r e s i s t a n c e i n p i n e s t o p i n e stem r u s t s , c a u s e d by C r o n a r t i u m s pp. and h a r k n e s s i i 17 3. The p e r c e n t a g e of s p o r e s g e r m i n a t e d and the number of s p o r e s c o u n t e d f o r each s p o r e s o u r c e 29 4. The number of s h o o t s and t r e e s i n o c u l a t e d , mean s h o o t l e n g t h , p e r c e n t a g e of s h o o t s i n f e c t e d and mean g a l l s per i n f e c t e d s h o o t f o r each f a m i l y 31 5. The number of s h o o t s i n o c u l a t e d , mean s h o o t l e n g t h , p e r c e n t a g e of s h o o t s i n f e c t e d and mean g a l l s per i n f e c t e d s h o o t f o r each s p o r e s o u r c e 32 6. R e s u l t s of the S c h e f f e and B o n f e r r o n i m u l t i p l e range t e s t s on the sum o f g a l l s per t r e e f o r the f a m i l i e s 41 7. R e s u l t s of the S c h e f f e and B o n f e r r o n i m u l t i p l e range t e s t s on the s p o r e s o u r c e s 43 8. The p e r c e n t a g e of s h o o t s d e m o n s t r a t i n g r e d s t a i n f o r each f ami l y 48 9. The p e r c e n t a g e of s h o o t s d e m o n s t r a t i n g r e d s t a i n f o r ea c h s p o r e s o u r c e 4 5 , v i i L i s t of F i g u r e s 1. The l o c a t i o n of the Buckhorn Lake e x p e r i m e n t a l s i t e 21 2. The d i s t r i b u t i o n o f g a l l s per t r e e f o r the f i e l d t r e e s a t Buckhorn Lake 22 3. F r e q u e n c y h i s t o g r a m of t h e number o f i n f e c t i o n s per l o d g e p o l e p i n e s h o o t 27 4. The c a l c u l a t e d e x p e c t e d d i s t r i b u t i o n of the number of i n f e c t i o n s per s h o o t 35 5. F r e q u e n c y h i s t o g r a m o f t h e o b s e r v e d and e x p e c t e d p r o p o r t i o n of s h o o t s I n f e c t e d 38 6. The p e r c e n t a g e o f s h o o t s i n f e c t e d v e r s u s t h e number o f i n f e c t i o n s per i n f e c t e d s h o o t f o r each s e e d l i n g 44 7. F r e q u e n c y h i s t o g r a m o f the g a l l s per t r e e f o r the p r o g e n y t r e e s 46 v i i i L i s t of Appendices A. Dates of i n o c u l a t i o n of the spore s o u r c e s . B. The number of shoots i n o c u l a t e d by each spore source f o r each f a m i l y . C. G e r m i n a t i o n r a t e s of the spore sources throughout the i n o c u l a t i o n p r o c e s s . D. A sample c a l c u l a t i o n of the b i n o m i a l d i s t r i b u t i o n of g a l l s per shoot. E. The f o r t r a n program used to c a l c u l a t e the expected d i s t r i b u t i o n of g a l l s per shoot based on a b i n o m i a l d i s t r i b u t i o n . F. A sample c a l c u l a t i o n of the p r o b a b i l i t y of 0, 1 or 2 s h o o t s i n f e c t e d . G. The f o r t r a n program used to c a l c u l a t e the p r o b a b i l i t y of 0, 1 or 2 shoots i n f e c t e d . H. R e s u l t s from the a n a l y s i s of v a r i a n c e : Sum of g a l l s per t r e e = f a m i l y + c o v a r i a t e of the sum of the l e n g t h s of the s h o o t s . I. R e s u l t s from the a n a l y s e s of v a r i a n c e t e s t s u s i n g red s t a i n . 1 1.0 I n t r o d u c t i o n As more money and e f f o r t i s put i n t o i n t e n s i v e f o r e s t management t o i n c r e a s e the v a l u e of our t r e e c r o p s , the need t o p r o t e c t t h e s e t r e e s from f o r e s t p e s t s i n c r e a s e s . Many f o r e s t p e s t p roblems a r e a m p l i f i e d by s i l v i c u l t u r e p r o c e d u r e s s u c h as f e r t i l i z a t i o n , t h i n n i n g and s i t e p r e p a r a t i o n . An example o f t h i s i s the i n c r e a s e of a t t a c k by f u s i f o r m r u s t ( C r o n a r t i u m f u s i forme Hedge, and Hunt ex. Cumm.) on f e r t i l i z e d s l a s h p i n e ( P i n u s  e l l i o t t i i E n g e l . ) and l o b l o l l y p i n e (P_^ t a e d a L.) p l a n t a t i o n s i n the s o u t h e a s t e r n U n i t e d S t a t e s ( Z o b e l 1982). T r e e improvement programs have been e s t a b l i s h e d t h r o u g h o u t N o r t h A m e r i c a . The g o a l of t h e s e programs i s t o produce t r e e s w i t h more o f t h e e c o n o m i c a l l y d e s i r a b l e t r a i t s and fewer of t h o s e t r a i t s t h a t a r e u n d e s i r a b l e . I t seems a l o g i c a l p r o g r e s s i o n of t h e s e programs t o i n c l u d e p e s t r e s i s t a n c e . Z o b e l (1982) r e p o r t s t h a t s i n c e b o t h e c o n o m i c a l l y d e s i r a b l e t r a i t s and p e s t r e s i s t a n c e a r e c o n t r o l l e d by m u l t i p l e genes, b o t h g o a l s can be a c h i e v e d . Such a combined b r e e d i n g program has been i n p l a c e i n the s o u t h e a s t e r n U n i t e d S t a t e s s i n c e 1950. The f i r s t s t e p i n d e v e l o p i n g a b r e e d i n g program f o r p e s t r e s i s t a n c e i s t o s t u d y the g e n e t i c s of d i s e a s e i n t e r a c t i o n i n t h e h o s t - p a r a s i t e p a t h o s y s t e m of i n t e r e s t . The b r e e d i n g program w i l l d i f f e r i f the r e s i s t a n c e i s g o v e r n e d by one t p s e v e r a l major genes or by a complex of minor genes. Hence, t h i s t h e s i s i n v e s t i g a t e d the g e n e t i c s of d i s e a s e i n t e r a c t i o n i n the l o d g e p o l e p i n e ( P i n u s c o n t o r t a v a r . l a t i f o l i a D ougl.) - w e s t e r n g a l l r u s t ( E n d o c r o n a r t i u m h a r k n e s s 1 i ( J . P . Moore) H i r a t s u k a ) h o s t -p a r a s i t e s y s t e m i n c e n t r a l B r i t i s h C o l u m b i a . L o d g e p o l e p i n e i s an i m p o r t a n t p l a n t a t i o n s p e c i e s i n the B r i t i s h C o l u m b i a i n t e r i o r . A p p r o x i m a t e l y 35 m i l l i o n l o d g e p o l e p i n e s e e d l i n g s a r e p l a n t e d a n n u a l l y i n the p r o v i n c e . Western g a l l r u s t c a u s e s s i g n i f i c a n t damage i n Canada ( Z i l l e r 1974, P o w e l l and H i r a t s u k a 1973) and i s c o n s i d e r e d t o be one of t h e most i m p o r t a n t r u s t s of h a r d p i n e s i n w e s t e r n Canada ( H i r a t s u k a and P o w e l l 1976). Some p l a n t a t i o n s o f l o d g e p o l e p i n e have undergone e x t e n s i v e w e s t e r n g a l l r u s t a t t a c k . I n c i d e n c e l e v e l s of 50% (stem i n f e c t i o n s ) have been r e c o r d e d i n c e n t r a l B r i t i s h C o l u m b i a (van der Kamp 1981). Western g a l l r u s t has been e s t i m a t e d t o cause a f i v e per c e n t volume l o s s a t r o t a t i o n i n open s t a n d s i n B r i t i s h C o lumbia (van der Kamp 1981). L o s s e s a r e h i g h e s t n o r t h of the 51st p a r a l l e l . Volume l o s s o c c u r s due t o stem d e f o r m i t y , t r e e m o r t a l i t y r e s u l t i n g from stem i n f e c t i o n s and p o s s i b l e r e d u c t i o n i n i n c r e m e n t ( Z i l l e r 1974). In the B r i t i s h C o l u m b i a i n t e r i o r , l o d g e p o l e p i n e i s commonly found a s a p i o n e e r s p e c i e s on burned s i t e s , u s u a l l y i n dense, even aged s t a n d s . These n a t u r a l s t a n d s can have 30 tho u s a n d or more stems per h e c t a r e and t h u s r e q u i r e t h i n n i n g . Western g a l l r u s t has been c o n s i d e r e d t o be a n a t u r a l t h i n n i n g a g e n t . However, t h i s pathogen c a u s e s d e a t h o n l y a f t e r many y e a r s . D i s e a s e d t r e e s 3 r e m a i n i n t h e s t a n d c o m p e t i n g f o r l i g h t and n u t r i e n t s . These a r e not d e s i r a b l e c h a r a c t e r i s t i c s f o r a t h i n n i n g a g e n t . In p l a n t a t i o n s t h e r e a r e fewer stems per h e c t a r e ( a p p r o x i m a t e l y 1200-1500). T h i s p l a n t i n g d e n s i t y a l l o w s f o r a c e r t a i n p e r c e n t a g e of m o r t a l i t y due t o b i o t i c or a b i o t i c f a c t o r s . However, i f w e s t e r n g a l l r u s t or o t h e r f a c t o r s d e c r e a s e the s u r v i v a l beyond the a l l o w a b l e p e r c e n t a g e , the s t a n d w i l l be u n d e r s t o c k e d . Thus due t o t h e lower d e n s i t y i n p l a n t a t i o n s , a t t a c k by w e s t e r n g a l l r u s t i s more l i k e l y t o c a u s e s t o c k i n g d e f i c i e n c i e s . As the p r o p o r t i o n of l o d g e p o l e p i n e p l a n t a t i o n s i n c r e a s e s , the need f o r knowledge of the l o d g e p o l e p i n e - w e s t e r n g a l l r u s t p a t h o s y s t e m i n c r e a s e s . 2.0 Western G a l l Rust 2.1 D i s t r i b u t i o n and h o s t s p e c i e s To d a t e har kness i i has o n l y been found i n N o r t h A m e r i c a . I t ' s range e x t e n d s from A l a s k a ( H i r a t s u k a and Maruyama 1968) t o the N o r t h w e s t T e r r i t o r i e s ( Z i l l e r 1974), s o u t h t h r o u g h Canada i n c l u d i n g much of t h e e a s t e r n p r o v i n c e s ( H i r a t s u k a and Maruyama 1968), west t o the P a c i f i c Ocean and s o u t h t o n o r t h e r n Mexico ( P e t e r s o n 1960). I t i s p a r a s i t i c on most n a t i v e and e x o t i c 'hard' p i n e s , w i t h l o d g e p o l e p i n e and Jack p i n e ( b a n k s i a n a Lamb.) b e i n g the main n a t u r a l h o s t s i n Canada. Other h o s t s a r e P^ mugo T u r r a , P_^  mur i c a t a D.Don, P_^  n i g r a A r n o l d , P_^  p i n a s t e r A i t , P.  ponder osa Laws., 9^ r a d i a t a D. Don and P_;_ s y l v e s t r i s L. ( Z i l l e r 4 1974 ) . 2 . 2 L i f e c y c l e Western g a l l r u s t i s an a u t o e c i o u s r u s t w i t h an e n d o c y c l i c l i f e c y c l e . U n l i k e most r u s t s i t does not c y c l e between two h o s t s p e c i e s but i s found o n l y on t h e p i n e h o s t . Western g a l l r u s t may r e p r e s e n t a much r e d u c e d l i f e c y c l e of C r o n a r t i u m f u s i f o r m e (Oak -p i n e r u s t ) . The d e l e t i o n of the oak or t e l i a l h o s t of t h e l i f e c y c l e has l e f t t he p i n e s t a g e ( a e c i a l h o s t ) . Hence, t h e l i f e c y c l e of w e s t e r n g a l l r u s t i s v e r y s i m p l e . In s p r i n g , when the new s h o o t s o f the p i n e a r e e l o n g a t i n g , t h e bark on t h e E.  h a r k n e s s i i g a l l s b r e a k s open r e l e a s i n g newly d e v e l o p e d a e c i o s p o r e s . These s p o r e s a r e w i n d - d i s p e r s e d . S u c c e s s f u l s p o r e s l a n d on the e l o n q a t i n g new s h o o t o f a h o s t p i n e t r e e , g e r m i n a t e and p e n e t r a t e I n t o the s h o o t . The growth of t h e mycelium up and down the s h o o t i s i n h i b i t e d by some mechanism w i t h i n t h e s h o o t . T h i s r e s t r i c t i o n i n l a t e r a l growth and t h e s t i m u l a t i o n of t h e i n f e c t e d c a m b i a i i n i t i a l r e s u l t i n the t y p i c a l g l o b o s e woody g a l l s of t h i s p athogen. In s p r i n g , t h e y e a r a f t e r i n f e c t i o n , a d i s t i n c t s w e l l i n g i s a p p a r e n t on t h e b r a n c h or stem a t the p o i n t of i n f e c t i o n . Two t o t h r e e y e a r s a f t e r i n f e c t i o n , the g a l l matures and s p o r u l a t e s i n the s p r i n g a n n u a l l y . The m y c e l i u m of Ej_ h a r k n e s s i i i s monokaryot i c . H i r a t s u k a ( 1 9 6 9 ) , o b s e r v e d t h a t karyogamy and m e i o s i s o c c u r a t s p o r e g e r m i n a t i o n . The s p o r e s p r o d u c e d w i t h i n the g a l l a r e t h e r e f o r e 5 a e c i d i o i d t e i i o s p o r e s . These a r e s p o r e s which have the a p p e a r a n c e of a e c i o s p o r e s but g e r m i n a t e and f u n c t i o n somewhat l i k e t e i i o s p o r e s ( H i r a t s u k a e t a l 1966). The o c c u r r e n c e of p y c n i o s p o r e s i s v e r y r a r e i n Western Canada, hence, the r u s t i s p r e s u m a b l y h o m o t h a l l i c . 2.3 Damage Some w e s t e r n g a l l r u s t g a l l s have been known t o l i v e and s p o r u l a t e f o r up t o 100 y e a r s . Most g a l l s have a much s h o r t e r l i f e span ( P e t e r s o n 1960, B y l e r e t a l ^ 1972). However, t h e g a l l t i s s u e l i v e s on and c o n t i n u e s t o grow. Damage due t o E• h a r k n e s s i i t a k e s two forms; t r e e m o r t a l i t y and stem d e f o r m i t y . R e d u c t i o n i n i n c r e m e n t p r e s u m a b l y o c c u r s due t o the l o s s of p h o t o s y n t h e t i c a r e a r e s u l t i n g from b r a n c h m o r t a l i t y , but t h i s has not been d e m o n s t r a t e d ( G r o s s 1983). 2.3.1 T r e e m o r t a l i t y T r e e m o r t a l i t y due t o E_^ h a r k n e s s i i i s t h e r e s u l t of wind breakage a t the g a l l or s e c o n d a r y a g e n t s k i l l i n g i n f e c t e d b a r k . Rodents chew a t the g a i i s d e c r e a s i n g t h e s t r e n g t h of t h e stem. T h i s and a t t a c k f r o m i n s e c t s p r o v i d e avenues of i n f e c t i o n f o r s e c o n d a r y p a r a s i t e s . S e c o n d a r y f u n g i which can a t t a c k g a l l e d t i s s u e o f t e n p r e v e n t s p o r u l a t i o n and can o f t e n i n v a d e the stem or b r a n c h d i s t a l to the g a l l c a u s i n g m o r t a l i t y ( B y l e r e_t a_l 1972 ). 6 2.3.2 Stem d e f o r m i t y Stem d e f o r m i t y r e s u l t s from the p r e s e n c e of t h e g a l l and i s i n c r e a s e d by sub s e q u e n t r o d e n t and i n s e c t a t t a c k . 3.0 R e s i s t a n c e A g r e a t d e a l of v a r i a t i o n i n h o s t s p e c i f i c i t y e x i s t s between d i f f e r e n t groups of p l a n t p a r a s i t e s . P a r a s i t e s p e c i f i c i t y r a nges from t h o s e which a r e n o n - s p e c i f i c and can l i v e on b o t h l i v i n g and dead t i s s u e s ( f a c u l t a t i v e ) t o t h o s e which a r e r e s t r i c t e d to l i v i n g t i s s u e ( o b l i g a t e ) of a s p e c i f i c h o s t v a r i e t y . Among f o r e s t p a thogens the r o o t d i s e a s e s have the w i d e s t h o s t range and a r e o f t e n f a c u l t a t i v e . P h e l l i n u s w e i r i i (Murr.) G i l b e r t s o n and A r m i l l a r i a o b s c u r a ( P e r s . ) H e r i n k a r e good examples of pathogen s p e c i e s w i t h a wide h o s t r a n g e . P h e l l i n u s we i r i i i s found on most c o n i f e r o u s s p e c i e s , w h i l e A^ o b s c u r a c an be found on b o t h c o n i f e r s and hardwoods. Other f o r e s t p a thogens have a much narrower s p e c i e s r a n g e . Dwarf m i s t l e t o e s ( A r c e u t h o b i u m spp.) u s u a l l y have a 2-3 h o s t t r e e s p e c i e s r a n g e . T r e e r u s t s , however, c a n be v e r y h o s t s p e c i f i c . Some r u s t s p e c i e s a r e so s p e c i a l i z e d t h a t t h e y have s p e c i f i c r a c e s b e i n g a b l e t o i n f e c t o n l y one v a r i e t y of t h e h o s t s p e c i e s (Raddi and R e g a z z i 1982, K a i s and Snow 1972 ) . The q e n e t i c s of h o s t - p a r a s i t e s y s t e m s has been w i d e l y d i s c u s s e d and i n v e s t i g a t e d (Vander P l a n k 1968, R o b i n s o n 1980, 7 N e l s o n 1978 and 1982, P e r s o n e t al_ 1982, E l l i n g b o e 1981). In 1905, B i f f e n r e p o r t e d on the i n h e r i t a n c e of r e s i s t a n c e i n the c r o s s i n g of two wheat c u l t i v a r s . A l t h o u g h o t h e r s had o b s e r v e d d i f f e r e n c e s i n r e s i s t a n c e i n c r o p s , B i f f e n o b s e r v e d s e g r e g a t i o n i n t h e s e c o n d f i l i a l g e n e r a t i o n . B a r r u s (1914), was t h e f i r s t t o d e m o n s t r a t e t h a t pathogen i s o l a t e s v a r i e d i n t h e i r a b i l i t y t o p roduce d i s e a s e on a s e r i e s o f c u l t i v a r s . Stakman and L e v i n e (1922) f i r s t e s t a b l i s h e d t h e c o n c e p t of a p h y s i o l o g i c a l r a c e . The u n d e r s t a n d i n g of a p h y s i o l o g i c a l r a c e e x p l a i n e d why a c u l t i v a r was r e s i s t a n t i n one a r e a and s u s c e p t i b l e i n a n o t h e r . I t a l s o e x p l a i n e d why a r e s i s t a n t c u l t i v a r became s u s c e p t i b l e o v e r t i m e . F l o r (1942 and 1955), i n t r o d u c e d a n o t h e r major c o n c e p t i n h o s t -p a r a s i t e r e l a t i o n s w i t h h i s work on f l a x (Linum u s i t i s s i m u m L.) and f l a x r u s t (Melampsora 1 i n i ( P e r s . ) L e v . ) . He s t u d i e d the i n h e r i t a n c e of h o s t r e s i s t a n c e and s u s c e p t i b i l i t y and pathogen v i r u l e n c e and a v i r u l e n c e . With t h i s he d e m o n s t r a t e d the g e n e - f o r -gene t h e o r y of r u s t r e s i s t a n c e . F o r e ach r e s i s t a n c e gene i n the h o s t , t h e r e was a c o r r e s p o n d i n g gene f o r v i r u l e n c e i n t h e p a t h o g e n . He found t h a t p u s t u l e t y p e , an i m p o r t a n t f a c t o r f o r b o t h h o s t r e s i s t a n c e and p a r a s i t e p a t h o g e n i c i t y was c o n d i t i o n e d by p a i r s of genes p r e s e n t i n the h o s t and p a r a s i t e . In t h e f l a x -f l a x r u s t p a t h o s y s t e m t w e n t y - f i v e s u c h p a i r s of genes have been i d e n t i f i e d . Vander P l a n k (1963) c a t e g o r i z e d r e s i s t a n c e i n t o two t y p e s : v e r t i c a l and h o r i z o n t a l . V e r t i c a l r e s i s t a n c e was due t o one t o s e v e r a l genes f o r r e s i s t a n c e and v i r u l e n c e w h i l e h o r i z o n t a l 8 r e s i s t a n c e was due t o many genes a c t i n g i n an a d d i t i v e manner. V a r i o u s terms have s i n c e been used t o d e s c r i b e t h e s e two t y p e s o f r e s i s t a n c e ( T a b l e 1 ) . The p a t h o g e n i c i t y o f a p a r a s i t e c a n a l s o be c l a s s i f i e d i n t o two t y p e s . A g r e s s i v e n e s s i s the c o u n t e r p a r t of h o r i z o n t a l r e s i s t a n c e . A pathogen's a g r e s s i v e n e s s a r i s e s f r o m a number of genes f o r p a t h o g e n i c i t y a c t i n g i n an a d d i t i v e manner and i s measured by t h e d e g r e e o f i n f e c t i o n o f s u s c e p t i b l e h o s t s and t h e r a t e of s p o r e p r o d u c t i o n . The v i r u l e n c e of a p a t h o g e n i s d e t e r m i n e d by one t o many major genes f o r p a t h o g e n i c i t y and i s d e s c r i b e d by the s e t of h o s t v a r i e t i e s which a r e s u s c e p t i b l e t o a p a r t i c u l a r p a thogen i s o l a t e or r a c e . In a h o r i z o n t a l r e s i s t a n c e s y s t e m , t h e r e l a t i v e a g r e s s i v e n e s s o f a g i v e n p a t h o g e n r a c e d o e s n ' t change when exposed t o a s e r i e s of h o s t s t r a i n s . L i k e w i s e , the r e l a t i v e r e s i s t a n c e of a h o s t s t r a i n d o e s n ' t change when ex p o s e d t o a s e r i e s of pathogen r a c e s . However, i n a v e r t i c a l s y s t e m , the v i r u l e n c e of a pathogen r a c e depends on the h o s t s t r a i n i n v o l v e d . F o r the h o s t s t r a i n , r e s i s t a n c e i s dependant on which pathogen r a c e i s a t t a c k i n g i t . 3.1 V e r t i c a l r e s i s t a n c e V e r t i c a l r e s i s t a n c e o c c u r s i n h o s t - p a r a s i t e s y s t e m s i n which h o s t p a t h o g e n i n t e r a c t i o n s o c c u r i n two d i s t i n c t c l a s s e s . These c l a s s e s r e p r e s e n t a l e s s e r e x t e n t of d i s e a s e and a g r e a t e r e x t e n t of d i s e a s e . F o r example the h o s t c o u l d be i n f e c t e d 20% or the time or 80%; 0% or 100%. The groups a r e d i s c r e e t , t h e r e i s no T a b l e 1. Terms used t o d e s c r i b e the two t y p e s of r e s i s t a n c e . H o r i z o n t a l V e r t i c a l Q u a n t i t a t i v e Q u a l i t a t i v e U n i f o r m D i f f e r e n t i a l Race n o n - s p e c i f i c Race s p e c i f i c S t a b l e N o n - s t a b l e P o l y g e n i c O l i g o g e n i c Minor gene Major gene 10 o v e r l a p . The i d e n t i f i c a t i o n of pa t h o g e n r a c e s i s based on the d i f f e r e n t i a l r e a c t i o n s of the h o s t v a r i e t i e s . F o r example, i f pathogen A and B have s i m i l a r s u s c e p t i b l e h o s t v a r i e t i e s t h e n A and B a r e e q u a l i n terms of v i r u l e n c e . V e r t i c a l r e s i s t a n c e and v i r u l e n c e a r e due t o i n d i v i d u a l genes o p e r a t i n g on a g e n e - f o r -gene b a s i s between the h o s t and pathogen ( P a r l e v l i e t and Zadoks 1976). T h i s t y p e of r e s i s t a n c e was f i r s t d e s c r i b e d by F i o r (1955) i n h i s g e n e - f o r - g e n e t h e o r y o f r e s i s t a n c e where he s t a t e d t h a t f o r e a c h h o s t gene f o r r e s i s t a n c e t h e r e was a c o r r e s p o n d i n g gene f o r v i r u l e n c e . A v i r u l e n c e gene c o u i d overcome a h o s t gene f o r r e s i s t a n c e o n l y i f i t c o r r e s p o n d e d t o (matched) t h i s r e s i s t a n c e gene. A pathogen r a c e would be a v i r u l e n t on h o s t s p o s s e s s i n g unmatched r e s i s t a n c e genes. The h o s t can be r e s i s t a n t t o most r a c e s of the pathogen due t o the p r e s e n c e of a gene f o r r e s i s t a n c e . However, t h e r e may be one or more pathogen r a c e s t h a t can overcome t h i s r e s i s t a n c e gene because t h e y c a r r y a m a t c h i n g v i r u l e n c e gene. The p r e s e n c e of many o f t h e s e genes f o r r e s i s t a n c e i n t h e pathogen (a s u p e r -v i r u l e n t pathogen) i s uncommon. T h i s may be due t o the f a c t t h a t t h e s e genes f o r r e s i s t a n c e and v i r u l e n c e may be d e l e t e r i o u s or be l i n k e d t o a n o t h e r d e l e t e r i o u s gene. The b u i l d - u p o f r e s i s t a n c e and v i r u l e n c e genes would t h e r e f o r e be d e t r i m e n t a l t o the o r g a n i s m . Thus super r e s i s t a n t or v i r u l e n t o r g a n i s m s would be l e s s f i t (Vander P l a n k 1968, Manion 1981). A n e g a t i v e feedback a p p e a r s t o o c c u r which p r e v e n t s the s i t u a t i o n where a h o s t v a r i e t y would be f u l l y r e s i s t a n t t o a l l p athogen r a c e s . L i k e w i s e , 11 a p a t h o g e n r a c e v i r u l e n t t o a l l h o s t v a r i e t i e s would not s u r v i v e . V e r t i c a l r e s i s t a n c e i s o f t e n viewed as a s p o r e d i l u t i n g type of r e s i s t a n c e . In a n a t u r a l p a t h o s y s t e m w i t h t h i s t y p e of r e s i s t a n c e t h e r e a r e s e v e r a l r a c e s of t h e pathogen and s e v e r a l s t r a i n s o f t h e h o s t . Each t r e e has one or more genes f o r r e s i s t a n c e . Any one of t h e s e genes r e s u l t s i n a r e s i s t a n t h o s t e x c e p t t o t h e c o r r e s p o n d i n g v i r u l e n c e genes. Hence, i n d i v i d u a l t r e e s a r e r e s i s t a n t t o most pathogen r a c e s . T h i s r e d u c e s the chance o f a p a r t i c u l a r r a c e of pathogen r e a c h i n g i t s s u s c e p t i b l e h o s t . As t h e r e a r e s e v e r a l d i f f e r e n t p a thogen r a c e s and h o s t s t r a i n s , t h i s s y s t e m i s o f t e n r e f e r r e d t o as a m u l t i l i n e (Vander P l a n k 1968). The c o m p o s i t i o n of p a t h o g e n r a c e s and h o s t s t r a i n s i n a m u l t i l i n e w i t h i n an a r e a i s not s t a t i c . R a t h e r t h e r a c e s and s t r a i n s a r e i n a dynamic e q u i l i b r i u m r e g u l a t e d over tme by n e g a t i v e feedback (Manion 1981). Those h o s t s t r a i n s t h a t have no m a t c h i n g pathogen r a c e or whose m a t c h i n g pathogen r a c e i s p r e s e n t i n t h e p o p u l a t i o n a t a v e r y low f r e q u e n c y do w e l l and t h e i r f r e q u e n c y i n c r e a s e s . T h i s p r o d u c e s g r e a t s e l e c t i o n p r e s s u r e f o r a p a t h o g e n which can overcome the r e s i s t a n c e . S i m i l a r l y , i f a m a t c h i n g pathogen r a c e i s p r e s e n t i n the p o p u l a t i o n a t h i g h f r e q u e n c y , a h o s t s t r a i n does not do w e l l and i t s f r e q u e n c y i n the p o p u l a t i o n d e c r e a s e s . When the number of s u s c e p t i b l e h o s t s d e c l i n e s , s t r o n g s e l e c t i o n p r e s s u r e i s e x e r t e d f o r a p a t h o g e n i c gene ( r a c e ) which can i n f e c t the o t h e r h o s t s t r a i n s . New pathogen r a c e s a r i s e by s e x u a l r e a r r a n g e m e n t of v i r u l e n c e genes, 12 p a r a s e x u a l i t y or r n u t a c i o n . When t h i s o c c u r s , the new pathogen r a c e f l o u r i s h e s on the h o s t s t r a i n whose r e s i s t a n c e genes have been overcome. T h i s p a r t i c u l a r h o s t s t r a i n becomes l e s s s u c c e s s f u l and w i l l d e c l i n e i n f r e q u e n c y i n the p o p u l a t i o n . Any h o s t s t r a i n s which a r e l e s s s u s c e p t i b l e w i l l i n c r e a s e i n number u n t i l a r a c e e v o l v e s i n t h e p athogen p o p u l a t i o n which can a t t a c k them. T h i s n e g a t i v e f e e d b a c k r e g u l a t e d s y s t e m p r o v i d e s i n t e r n a l s t a b i l i t y f o r the p o p u l a t i o n s of b o t h h o s t and p a t h o g e n . A l t h o u g h t h e f r e q u e n c i e s of the v a r i o u s s t r a i n s and r a c e s a r e c o n s t a n t l y c h a n g i n g , the p r o p o r t i o n of i n f e c t e d t r e e s r e m a i n s f a i r l y c o n s t a n t . Depending on the p a t h o s y s t e m , t h a t p r o p o r t i o n may or may not be a c c e p t a b l e f o r economic c r o p p r o d u c t i o n . 3.2 H o r i z o n t a l r e s i s t a n c e H o r i z o n t a l r e s i s t a n c e i s a q u a n t i t a t i v e t r a i t . A q u a n t i t a t i v e + c r a i t i s one which v a r i e s over a c o n t i n u u m . T h e r e a r e no d i s c r e e t c l a s s e s , r a t h e r t h e r e e x i s t s a range o v e r which th e t r a i t i s e x p r e s s e d . Many genes p a r t i c i p a t e i n t h e e x p r e s s i o n of a q u a n t i t a t i v e t r a i t , as a s i n g l e gene c o u l d not be r e s p o n s i b l e f o r the v a r i a b i l i t y t h a t i s f o u n d . In a q u a n t i t a t i v e system, r e s i s t a n c e i n the h o s t i s due t o the e x p r e s s i o n of a complex of genes a c t i n g a d d i t i v e l y . S i m i l a r l y , p a thogen a g g r e s s i v e n e s s i s due t o a complex of genes. The s u c c e s s o f i n f e c t i o n must be r a t e d or measured s i n c e a c o n t i n u u m of s u s c e p t i b i l i t y from low to h i g h e x i s t s (hence the term q u a n t i t a t i v e ) . The h o s t v a r i e t i e s can g e n e r a i y be ranked i n o r d e r of d i s e a s e r e s i s t a n c e or 13 s u s c e p t i b i l i t y and the pathogen r a c e s i n terms of a g g r e s s i v e n e s s . The r a n k i n g of a pathogen r a c e r e m a i n s c o n s t a n t when t e s t e d a g a i n s t a s e r i e s of ho s t v a r i e t i e s . 3.3 I n d i g e n o u s h o s t - p a r a s i t e systems I t i s human n a t u r e t o s e p a r a t e t h i n g s i n t o c l a s s e s , hence the e v o l u t i o n of the two c l a s s e s of r e s i s t a n c e ; v e r t i c a l and h o r i z o n t a l . However, s e v e r a l a u t h o r s argue t h a t t h e s e a r e perhaps the extremes on a c o n t i n u u m of t y p e s of r e s i s t a n c e and t h a t t h e m a j o r i t y of n a t u r a l p a t h o s y s t e m s c o n t a i n a c o m b i n a t i o n o f t h e s e r e s i s t a n c e t y p e s ( S c o t t e_t a l 1978, Browning e t a l ^ 1982, P a r l e v l i e t and Zadoks 1976, Vander P l a n k 1984). S t u d i e s o f h o s t -p a r a s i t e systems i n u n d i s t u r b e d n a t u r a l e c o s y s t e m s have shown t h a t i n d i g e n o u s pathogens a r e s e l d o m d e s t r u c t i v e ( S e g a l et^ al^ 1982). T h i s i s due to a p r o l o n g e d c o - e v o l u t i o n of the h o s t and p a r a s i t e , which over time have been m o n i t e r e d by n e g a t i v e feedback of the h o s t and p a r a s i t e t o each o t h e r . The g e n e t i c d i v e r s i t y needed i n a n a t u r a l e c o s y s t e m f o r the p o p u l a t i o n t o s u r v i v e a g a i n s t a wide range of b i o t i c and a b i o t i c f a c t o r s has r e s u l t e d i n many m o r p h o l o g i c a l and p h y s i o l o g i c a l e x p r e s s i o n s i n both h o s t and pathogen and hence a b a l a n c e i n the s y s t e m between them. Browning e_t a_± (1982) have a s l i g h t l y d i f f e r e n t i n t e r p r e t a t i o n of the s u a b i l i t y of i n d i g e n o u s p o p u l a t i o n s . They b e l i e v e t h a t the many phenotypes of the h o s t p o p u l a t i o n p r e s e n t a t any time p r o v i d e i t w i t h g e n e r a l r e s i s t a n c e or t o l e r a n c e t o the pathogen 14 which s i m i i a r i l y has a g e n e r a l a g g r e s s i v e n e s s t o t h e h o s t . T h i s can be viewed as a h o r i z o n t a l s y s t e m where the g e n e r a l r e s i s t a n c e p r e s e n t t h r o u g h o u t the h o s t p o p u l a t i o n i s a c o n t i n u u m from r e l a t i v e l y s u s c e p t i b l e t o r e l a t i v e l y r e s i s t a n t . Browning e t aX (1982), f e e l t h a t over t i m e , o l i g o g e n i c , s p e c i f i c r e s i s t a n c e or v i r u i e n c e genes have been s u p e r i m p o s e d on s u c h . a s y s t e m . Hence, the end r e s u l t i n an i n d i g e n o u s s y s t e m i s a c o m b i n a t i o n of v e r t i c a l and h o r i z o n t a l s y s t e m s . These s y s t e m s , a l o n g w i t h n a t u r a l a n t a g o n i s t s and n o n - h o s t immunity b u f f e r t h e n a t u r a l h o s t - p a r a s i t e s y s t e m a g a i n s t d r a s t i c changes ( e p i d e m i c s ) . The b e l i e f t h a t both k i n d s of r e s i s t a n c e a r e p r e s e n t i n n a t u r a l p o p u l a t i o n s i s a l s o h e l d by Zadoks ( 1 9 7 2 ) . Zadoks b e l i e v e s t h a t minor genes ( h o r i z o n t a l system) and major genes ( v e r t i c a l system) can b o t h be found i n n a t u r a l h o s t - p a r a s i t e p o p u l a t i o n s . Vander P l a n k (1984), s t a t e s t h a t h o r i z o n t a l and v e r t i c a l r e s i s t a n c e a r e n o t m u t u a l l y e x c l u s i v e . B o t h forms of r e s i s t a n c e can and must c o - e x i s t when the pathogen comes as a m i x t u r e of r a c e s . He d e m o n s t r a t e d t h i s i n the p o t a t o : P h y t o p h t h o r a i n f e s t a n s p a t h o s y s t e m . Two p o t a t o c u l t i v a r s , Kennebec and M a r i t t a b o t h have a r e s i s t a n c e gene making them t o t a l l y r e s i s t a n t t o some r a c e s of P_. i n f e s t a n s . To o t h e r r a c e s of P. i n f e s t a n s , however, t h e s e two v a r i e t i e s v a r y i n r e s i s t a n c e . M a r i t t a i s l e s s s u s c e p t i b l e t h a n Kennebec i n a l l i n s t a n c e s . Hence, a l t h o u g h a v e r t i c a l r e s i s t a n c e s y s t e m i s p r e s e n t t h a t d e t e r m i n e s which r a c e s of P_^  i n f e s t a n s w i l l be s u c c e s s f u l , f o r t h o s e r a c e s which a r e s u c c e s s f u l , t h e r e i s a h o r i z o n t a l s y s t e m 15 p r e s e n t which d e t e r m i n e s how s u c c e s s f u l t h e s e a t t a c k s a r e (Vander P l a n k 1964). 3.4 H o s t - P a r a s i t e i n t e r a c t i o n s i n p i n e - r u s t systems Many s t u d i e s have been c o n d u c t e d on p i n e - p i n e r u s t p a t h o s y s t e m s i n N o r t h A m e r i c a . Most of t h i s r e s e a r c h has f o c u s s e d on C r o n a r t ium f u s i forme ( f u s i f o r m r u s t ) and C. r i b i c o l a J.C. F i s c h e r ( w h i t e p i n e b l i s t e r r u s t ) . F u s i f o r m r u s t and w h i t e p i n e b l i s t e r r u s t have r e s u l t e d i n much t i m b e r l o s s a c r o s s N o r t h A m e r i c a . However, f u s i f o r m r u s t i s i n d i g e n o u s t o N o r t h A m e r i c a and as s u c h would be e x p e c t e d t o d e m o n s t r a t e a b a l a n c e d h o s t -p a r a s i t e s y s t e m . The d e v elopment of p l a n t a t i o n s t h r o u g h o u t the s o u t h e a s t e r n U n i t e d S t a t e s has l e d t o t h e d i s p e r s i o n o f p r o v e n a n c e s o f f u s i f o r m r u s t h o s t s . Hence, a p r o v e n a n c e of s l a s h p i n e i n t r o d u c e d i n t o a new a r e a w i l l be a t t a c k e d by f u s i f o r m r u s t w i t h which i t d i d not c o - e v o l v e . The movement of p i n e i n l a n d from the sandy c o a s t a l p l a i n s t o the hardwood (oak) f o r e s t s , has l i k e l y moved the h o s t i n t o a c l i m a t e and e n v i r o n m e n t ( i n c r e a s e d p r e s e n c e of a l t e r n a t e h o s t ) more s u i t a b l e f o r r u s t i n f e c t i o n . T h i s has r e s u l t e d i n a breakdown of the b a l a n c e of t h e h o s t -p a r a s i t e s y s t e m and an i n c r e a s e i n the amount of d i s e a s e p r e s e n t . The s i t u a t i o n w i t h w h i t e p i n e b l i s t e r r u s t i s d i f f e r e n t . The i n t r o d u c t i o n o f w h i t e p i n e b l i s t e r r u s t i n t o N o r t h A m e r i c a i n the e a r l y t w e n t i e t h c e n t u r y was d e v a s t a t i n g . Wnite p i n e had no n a t u r a l C r o n a r t i u m p athogen and as s u c h had no c o a d a p t i v e s e l e c t i o n p r e s s u r e s t o d e v e l o p r e s i s t a n c e . N o r t h A m e r i c a n n a t i v e 16 w h i t e p i n e s had some r e s i s t a n c e t o w h i t e p i n e b l i s t e r r u s t d e m o n s t r a t e d by the f a c t t h a t not a l l w h i t e p i n e s became i n f e c t e d . The r e s i s t a n c e was p r e s e n t a t a low f r e q u e n c y i n the p o p u l a t i o n as the r e s i s t a n t t r e e s r e p r e s e n t e d a s m a l l p r o p o r t i o n of the w h i t e p i n e p o p u l a t i o n . The r e s i s t a n c e was a l s o randomly d i s t r i b u t e d t n r o u g h o u t the p o p u l a t i o n (Hunt et_ al_ 1985). Hoff and MacDonald (1972) d e m o n s t r a t e d t h a t an A s i a n h o s t o f the endemic w h i t e p i n e b l i s t e r r u s t ; armand p i n e ( P ^ armand i i F r a n c h ) had much more v a r i a b i l i t y i n i t s r e s i s t a n c e t o w h i t e p i n e b l i s t e r r u s t t h a n N o r t h American h o s t s . A summary of r e s i s t a n c e mechanisms and g e n e t i c s of t h e s e mechanisms f o r N o r t h American p i n e s and t h e i r r u s t s i s found i n T a b l e 2. The p r e s e n c e of v e r t i c a l r e s i s t a n c e has been d e m o n s t r a t e d i n some p i n e - p i n e r u s t p a t h o s y s t e m s . D i f f e r e n t i a l i n t e r a c t i o n s have been shown w i t h C_;_ auercuum on P^ b a n k s i a n a and P^ v i r g i n i a n a M i l l . , w i t h r u s t fungus i s o l a t e s f r o m each t r e e s p e c i e s ( K a i s and Snow 1972, Powers 1972). Each t r e e s p e c i e s was r e s i s t a n t t o o t h e r s p e c i e s i n o c u l u m . On an i n t r a s p e c i f i c l e v e l , Snow e t a l (1975), found d i f f e r e n t i a l r e a c t i o n s between s l a s h p i n e p r o g e n i e s and C.  fu s i forme r u s t i s o l a t e s from f i v e s t a t e s . D i f f e r e n t i a l r e a c t i o n s can be d e m o n s t r a t e d w i t h an a n a l y s i s o f v a r i a n c e . S i g n i f i c a n c e of the i n t e r a c t i o n e f f e c t s i s i n d i c a t i v e of a d i f f e r e n t i a l r e a c t i o n ( v e r t i c a l r e s i s t a n c e ) (Vander Plank 1963). Snow e t a l (1975), found a s i g n i f i c a n t i n o c u l u m s o u r c e by f a m i l y i n t e r a c t i o n among C . f u s i f o r m e r u s t i s o l a t e s c o l l e c t e d on Mechanism Host-pathogen Hypothesized A u t h o r i t y i n h e r i t a n c e Foliage H y p e r s e n s i t i v i t y Premature needle shed E x c l u s i o n of d i f f e r e n t i a l races Reduced r e c e p t i v i t y to i n f e c t i o n I n h i b i t i o n of fungal i n f e c t i o n s t r u c t u r e s ( v e s i c l e s ) Birk I n c o m p a t i b i l i t y ( v a r i a b l e expression) H y p e r s e n s i t i v i t y (as a special;, case of i n c o m p a t i b i l i t y ) Slow fungal growth Site undetermined Seduced i n f e c t i o n r a t e (slow r u s t i n g ) Ontogenetic r e s i s t a n c e D i f f e r e n t i a l i n t e r a c t i o n s (host genotype-pathogen limbertitna - r i b i c o l i armandii - r i b i c o l i < aonticoli - r i b i c o l i •aonticoli - r i b i c o l i .aonticoli - ribicolt strobus - ribicola .aonticoli • ribicol» lambertiana - r i b i c o l i strobus - r i b i c o l i iranndii - r i b i c o l i e l l i o t t i i ' fusifonoe tiedi • fusiforme sylvestris - harknessii ponderosi - harknessii pinea • flaccidum * aonticoli - r i b i c o l i lambertiana - r i b i c o l i e l l i o t t i i ' fusifonoe tiedi - fusifonoe ,wonticoli - r i b i c o l i limbertiim - r i b i c o l i e l l i o t t i i - fusifonoe strobus ~ r i b i c o l i , ^aonticoli • r i b i c o l i 1 aabertiam - r i b i c o l i tiedi - fusiforme 'race') e l l i o t t i i - fusifonoe pinet - fltccidua pimster - fltccidum nign - fltccidua dominant r e c e s s i v e p o l y g e n i c r e c e s s i v e dominant o l i g o g e n i c o l i g o g e n i c p o l y g e n i c p o l y g e n i c o l i g o g e n i c o l i g o g e n i c o l i g o g e n i c o l i g o g e n i c o l i g o g e n i c K i n l o c h 4 L i t t l e f i e l d , Hoff 4 McDonald, 1975 Hoff 4 McDonald, 'lcDonald & Hoff, Hoff 4 McDonald, Patton, 1967 1977 1971 1975; McDonald, 1980 1978 Bingham e t a l . , 1960 K i n l o c h 4 L i t t l e f i e l d , 1977 Struckmeyer 4 Riker, 1951 Hoff 4 McDonald, 1972 M i l l e r e t a l . , 1976; J e w e l l 4 Sp e i r s , Lundquiat, 1979 1976 .Hutchinson, 1935; True, 1938 .Quick, 1966 Mittempergher 4 Raddi, 1977 McDonald 4 Hoff, 1971; Hoff 4 McDonald, 1971 K i n l o c h 4 L i t t l e f i e l d , 1977 M i l l e r e t a l . , 1976; t h i s paper Lundquist, 1979; t h i s paper Bingham e t a l . , 1971 K i n l o c h 4 B y l e r , 1981 Cri g g s 4 Dinus, 1977 Patton, 1961, 1967 Bingham, 1966 K i n l o c h 4 B y l e r , 1931 Powers e t a l . , 1977; t h i s paper Snow et a l . , 1975; t h i s paper Mittempergher 4 Raddi, 1977; t h i s paper Mittempergher 4 Raddi, 1977; t h i s paper Mittempergher 4 Raddi, 1977; t h i s paper Table 2 . Mechanisms of r e s i s t a n c e i n pines t o pine stem r u s t s , caused by Cronartium spp. and Endocronartlum, h a r k n e s s i i . . ^ K i n l o c h 1982. 18 e a s t - w e s t t r a n s e c t s ( F l o r i d a t o Texas) and n o r t h - s o u t h t r a n s e c t s ( M i s s i s s i p p i t o G e o r g i a and F l o r i d a t o G e o r g i a ) . However, t h e s e s t u d i e s were c o n d u c t e d on l a r g e g e o g r a p h i c a r e a s . The r e s u l t s may have been d i f f e r e n t i f i n d i v i d u a l c o - e p i c e n t e r s were s t u d i e d . A c o - e p i c e n t e r i s d e f i n e d as the g e o g r a p h i c a r e a w i t h i n which the h o s t and p a r a s i t e have c o - e v o l v e d . T h i s a r e a i s d e l i n e a t e d by t h e s p r e a d of s p o r e s w i t h i n an a r e a . There i s a c e r t a i n amount of i m m i g r a t i o n and e m m i g r a t i o n of s p o r e s , but the b u l k of the s p o r e s r e s u l t from p o p u l a t i o n i n f e c t i o n s and a r e not i m m i g r a n t s . The main s t a b i l i t y of an i n d i g e n o u s h o s t - p a r a s i t e s y s t e m i s due t o c o - e v o i u t i o n of the h o s t and pathogen w i t h i n each s p e c i f i c c o - e p i c e n t e r . The i n t r o d u c t i o n of new i n o c u l a t i o n s o u r c e s by i m m i g r a t i o n or m u t a t i o n i s r e s p o n d e d t o by the l a r g e g e n e t i c v a r i a b i l i t y p r e s e n t i n t h e h o s t p o p u l a t i o n . A r e s i s t a n c e gene p r e s e n t a t low f r e q u e n c i e s i n the p o p u l a t i o n may i n c r e a s e i n f r e q u e n c y i f the h o s t s w i t h t h i s gene a r e more r e s i s t a n t and hence b e t t e r c o m p e t i t o r s t h a n the h o s t s w i t h o u t t h i s gene. T h i s t h e s i s i n v o l v e s a s t u d y i n t o a c o - e p i c e n t e r of l o d g e p o l e p i n e and w e s t e r n g a l l r u s t i n c e n t r a l B r i t i s h C o l u m b i a . 4 . 0 H y p o t h e s i s T h i s s t u d y was d e s i g n e d t o t e s t the h y p o t h e s i s t h a t t h e l o d q e p o i e p i n e - w e s t e r n q a l i r u s t p a t h o s y s t e m i s a m u l t i l i n e such t h a t w i t h i n each s t a n d or c o - e p i c e n t e r s e v e r a l r u s t r a c e s and h o s t v a r i e t i e s , each d e f i n e d by a d i s t i n c t s e t of v i r u l e n c e and r e s i s t a n c e genes, a r e p r e s e n t . A m u l t i l i n e a l l o w s f o r 19 h o r i z o n t a l r e s i s t a n c e t o be p r e s e n t but not d o m i n a t i n g . The a l t e r n a t i v e h y p o t h e s i s i s t h a t the p a t h o s y s t e m e x h i b i t s o n l y h o r i z o n t a l r e s i s t a n c e . The h y p o t h e s i s f o l l o w s the views of Browninq et_ a l _ ( 1982 ), S e q a i e t a 1 ( 1982 ), P a r l e v l i e t and Zadoks (1976) and Vander P l a n k (1984) and t h e i r t h e o r i e s of i n d i g e n o u s h o s t and p a r a s i t e p o p u l a t i o n s . 5.0 Methods To t e s t the h y D O t h e s i s , h a l f s i b l i n g p rogeny ( t h r e e y e a r o l d s e e d l i n g s ) f r o m female p a r e n t t r e e s known t o v a r y i n s u s c e p t i b i l i t y t o w e s t e r n g a l l r u s t i n the f i e l d were i n o c u l a t e d w i t h w e s t e r n g a l l r u s t s p o r e s . Lack of a s i g n i f i c a n t i n t e r a c t i o n between t h e s p o r e s o u r c e and s e e d l i n g s (and p o s s i b l y f a m i l i e s ) c o u p l e d w i t h l a r g e , s i g n i f i c a n t main e f f e c t s would c a u s e non a c c e p t a n c e of t h e h y p o t h e s i s . The i n t e r a c t i o n may of c o u r s e be masked by e x p e r i m e n t a l e r r o r . Hence, n o n - a c c e p t a n c e o c c u r s i f main e f f e c t s a r e s i g n i f i c a n t , which d e m o n s t r a t e s t h a t i f i n t e r a c t i o n s were p r e s e n t a t a b i o l o g i c a l l y s i g n i f i c a n t l e v e l , t h e y would have been d e t e c t e d . At l e a s t two d i f f e r e n t r a c e s of s p o r e s ( d i f f e r i n g i n v i r u l e n c e ) were r e q u i r e d . A s p o r e s o u r c e was d e f i n e d as s p o r e s c o l l e c t e d from a s i n g l e g a l l . As each g a l l i s b e l i e v e d t o a r i s e from i n f e c t i o n by a s i n g l e s p o r e , a l l s p o r e s p r o d u c e d by a g a l l a r e g e n e t i c a l l y u n i f o r m . F i v e s p o r e s o u r c e s s e l e c t e d i n the f i e l d ( c o l l e c t e d from f o u r d i f f e r e n t t r e e s ) were used i n an a t t e m p t t o 20 e n s u r e a h i g h p r o b a b i l i t y o f a t l e a s t two d i f f e r e n t s p o r e s t r a i n s b e i n g r e p r e s e n t e d . Assuming t h a t no p a t h o g e n r a c e c o m p r i s e d more than f i f t y p e r c e n t of the p o p u l a t i o n , the p r o b a b i l i t y of i n c l u d i n g a t l e a s t two d i f f e r e n t s p o r e r a c e s was: 1 - 2(0.5**5) = 0.9375 Any c o m b i n a t i o n of r a c e s , none more f r e q u e n t t h a n f i f t y p e r c e n t of t h e p o p u l a t i o n would r e s u l t i n a h i g h e r p r o b a b i l i t y of two d i f f e r e n t r a c e s b e i n g s e l e c t e d . F o r example i f t h e r e were t h r e e r a c e s p r e s e n t i n the p r o p o r t i o n s o f 45%, 45% and 10%, the p r o b a b i l i t y o f p i c k i n g two d i f f e r e n t r a c e s would be: P = 1 - (0.45**5 + 0.45**5 + 0.1**5) = 0.96308 Two or t h r e e s h o o t s o f e a c h t r e e were i n o c u l a t e d w i t h each s p o r e s o u r c e . The number of s h o o t s i n o c u l a t e d per t r e e was dependent on t h e number of s u i t a b l e s h o o t s p r e s e n t . 5.1 S e e d l i n g s and s p o r e s o u r c e s used Two l o t s o f o p e n - p o l l i n a t e d l o d g e p o l e p i n e s e e d were c o l l e c t e d s o u t h e a s t o f P r i n c e George, B.C. i n 1982. The f i r s t s e t of n i n e h a l f - s i b l i n g f a m i l i e s (PG I) was c o l l e c t e d from th e Buckhorn Lake 13 X 13 e x p e r i m e n t a l t r i a l r e p l i c a t e 2 p l a n t a t i o n ( F i g u r e 1 ) . The s econd s e t (PG I I ) , a l s o composed o f n i n e h a l f - s i b l i n g f a m i l i e s was from n a t u r a l r e g e n e r a t i o n s u r r o u n d i n g t h a t p l a n t a t i o n . Each f a m i l y c o n t a i n e d between 3 and 14 s e e d l i n g s f o r a t o t a l o f 175 s e e d l i n g s i n the e x p e r i m e n t . The number of g a l l s p r e s e n t on each mother t r e e was r e c o r d e d when the s e e d s were c o l l e c t e d . The d i s t r i b u t i o n of g a l l s per t r e e f o r b o t h PG I and PG II i s shown i n F i g u r e 2. There were more g a l l s p e r t r e e i n the n a t u r a l s (PG 21 F i g u r e 1. The l o c a t i o n of the Buckhorn Lake e x p e r i m e n t a l s i t e s c a l e : 1,250,000. F i g u r e 2 The d i s t r i b u t i o n of g a l l s per t r e e f o r the f i e l d t r e e s at Buckhorn Lake. 32 \ \ 7 \ \ \ \ \ \ \ / \ \ N \ \ \ F \ \ \ \ \ \ 10 14 18 22 26 30 34 38 42 46 50 54 58 62 66 70 Number of qolls. PG I PG II I I ) as t h e y were o l d e r . The seeds c o l l e c t e d from t h e s e t r e e s were sown i n 1983 a t t h e U n i v e r s i t y of B r i t i s h C o l u m b i a . F i v e s p o r e s o u r c e s were c o l l e c t e d as mature g a l l s from the Buckhorn Lake s i t e i n l a t e May, 1985. The g a l l s were removed from the t r e e and t r a n s p o r t e d by a i r t o Van c o u v e r , B.C.. The s p o r e s were t h e n removed and s t o r e d a t 0 d e g r e e C e l c i u s u n t i l use. S i n c e t h e s p o r e s o u r c e s were b e i n g g a t h e r e d i n P r i n c e George i n l a t e May, i t was n e c e s s a r y t o d e l a y t h e s h o o t e l o n g a t i o n of the s e e d l i n g s i n Vancouver, B.C. (800 km s o u t h ) t o c o i n c i d e w i t h t h e n a t u r a l t i m e of e l o n g a t i o n of l o d g e p o l e p i n e s h o o t s a t the Buckhorn Lake s i t e . T h i s was to c o - o r d i n a t e the a p p l i c a t i o n of the s p o r e s a t t h e same time ( i n s e e d l i n g d e v e l o p m e n t ) as t h e y would have been d i s s e m i n a t e d n a t u r a l l y a t the Buckhorn Lake s i t e . To d e l a y t h e e i o n q a t i o n of new s h o o t s t h e s e e d l i n g s were br o u g h t t o the U n i v e r s i t y of B r i t i s h Columbia R e s e a r c h F o r e s t i n Maple R i d g e , B.C. and p l a c e d on snow a t 300 m e l e v a t i o n on A p r i l 1, 1985. These s e e d l i n g s were br o u g h t back t o the U.B.C. Campus on May 22, 1985. 5.2 Shoot i n o c u l a t i o n I n i t i a l l y a l l the s h o o t s on each s e e d l i n g i n d i v i d u a l l y were c o v e r e d w i t h p l a s t i c baqs and s e a l e d s h u t w i t h masking tape t o p r e v e n t c o n t a m i n a t i o n between s p o r e s o u r c e s . One s p o r e s o u r c e a t a time was used to i n o c u l a t e a i l s e e d l i n q s u n e d a t e s of 24 i n o c u l a t i o n a r e q i v e n i n Appendix A ) . For each s h o o t the p l a s t i c bag was removed and s p o r e s were a p p i i e a w i t h a s m a l l b r u s h t o a c h i e v e a u n i f o r m a p p l i c a t i o n of s p o r e s . The amount of s p o r e s a p p l i e d was e s t i m a t e d t o be p r o p o r t i o n a t e t o t h e l e n g t h of t h e s h o o t . A f t e r i n o c u l a t i o n , the s h o o t s were m i s t e d w i t h d i s t i l l e d water from a p l a n t s p r a y e r t o j u s t b e f o r e the p o i n t of r u n - o f f . The bags were the n r e p l a c e d and t i e d a t the base w i t h a c o l o r e d w i r e i n d i c a t i n g which s p o r e s o u r c e the s h o o t was i n o c u l a t e d w i t h . The number of s h o o t s i n o c u l a t e d by each s p o r e s o u r c e f o r each f a m i l y i s l i s t e d i n Appendix B. F o r each t r e e , a t l e a s t one s h o o t was bagged but not i n o c u l a t e d . These s h o o t s s e r v e d as c o n t r o l s h o o t s t o e n s u r e t h a t the p l a s t i c bags p r o v i d e d an adequate b a r r i e r t o c o n t a m i n a t i o n from o t h e r s p o r e s o u r c e s used i n the e x p e r i m e n t and from i n c o l u a t i o n i n the f i e l d b e f o r e and a f t e r the l a b i n o c u l a t i o n p r o c e d u r e . F o r each s p o r e s o u r c e , g e r m i n a t i o n t e s t s were c o m p l e t e d . T h i s i n v o l v e d the s p r e a d i n g of s p o r e s onto water agar i n p e t r i p l a t e s and l e a v i n g them a t room t e m p e r a t u r e t o g e r m i n a t e . Samples of each s p o r e s o u r c e f o r g e r m i n a t i o n t e s t s were t a k e n a t the o n s e t of t h e i n o c u l a t i o n p r o c e s s and e v e r y 45 minute s t o one hour t h r o u g h o u t t h e p r o c e s s . S i x t e e n h o u r s a f t e r s a m p l i n g , the p e t r i p l a t e s were examined m i c r o s c o p i c a l l y . Ten f i e l d s on each p l a t e ( a v e r a g i n g f o u r t e e n s p o r e s ) were t a l l i e d t o d e t e r m i n e the p e r c e n t g e r m i n a t i o n . The p l a s t i c bags were l e f t on t h e s h o o t s u n t i l 48 ho u r s a f t e r the l a s t i n o c u l a t i o n . T h i s was t o e n s u r e i d e a l c o n d i t i o n s and 25 s u f f i c i e n t time f o r s p o r e g e r m i n a t i o n and p e n e t r a t i o n . The bags were t h e n removed, l e a v i n g the c o l o r e d w i r e s a t t h e base of the sho o t f o r i d e n t i f i c a t i o n of the s p o r e s o u r c e u s e d . The s e e d l i n g s were moved o u t s i d e and the p o t s p l a n t e d i n a p e a t moss, sand and sawdust s o i l mix. T h i s was t o enhance s e e d l i n g growth t h r o u g h t h e p r o v i s i o n of g r e a t e r a v a i l a b l e a r e a f o r r o o t g rowth. Once the p o t s were p l a n t e d , the s e e d l i n g s were f e r t i l i z e d w i t h 20-20-20 NPK ( N i t r o g e n , P h o s p h o r u s and P o t a s s i u m ) f e r t i l i z e r w i t h m i c r o e l e m e n t s and a g a i n e v e r y f o u r to s i x weeks d u r i n g the summer. 5.3 Data C o l l e c t i o n Two weeks a f t e r i n o c u l a t i o n , t h e s h o o t s were examined f o r t h e p r e s e n c e of any p o t e n t i a l e a r l y symptoms. Such symptoms might i n d i c a t e s u c c e s s f u l i n o c u l a t i o n s or a h o s t r e s i s t a n c e r e a c t i o n . A i l u n u s u a l d i s c o l o r a t i o n s of the stems or o t h e r p o s s i b l e r e a c t i o n s were r e c o r d e d and p h o t o g r a p h e d . Some m o r t a l i t y was note d a t t h i s time caused by F u s a r i um s p . which a t t a c k e d the s h o o t s w h i l e t h e y were c o v e r e d w i t n the p l a s t i c bags a f t e r i n o c u l a t i o n . D u r i n g t h e summer many of the i n o c u l a t e d s h o o t s d i e d or became i n f e s t e d w i t h T r i s e t a c u s campnodus K e i f e r (a p i n e m i t e ) . The m i t e s had s p r e a d t o the s e e d l i n q s from a d j a c e n t l o d g e p o l e p i n e t r e e s i n t h e UBC s o u t h campus f i e l d . In most c a s e s t h e m i t e s 26 c a u s e d s e v e r e c h l o r o s i s a n d t w i s t i n q o f t h e n e e d l e s d ue t o t h e i r t e e d i n q i n t n e n e e d l e f a s i c i e . In e a r l y f a l l , a n o t h e r s e t of o b s e r v a t i o n s were made. In some c a s e s m o r t a l i t y of the s h o o t s had o c c u r r e d . D u r i n g t h e s e o b s e r v a t i o n s the l e n g t h of each s h o o t , the number of g a l l s p r e s e n t on each s h o o t and the p r e s e n c e or a b s e n c e o f campnodus were r e c o r d e d . In A p r i l , 1986 the s e e d l i n g s were f e r t i l i z e d w i t h 20-20-20 NPK w i t h m i c r o e l e m e n t s . In June, 1986 t h e s e e d l i n g s were re - e x a m i n e d and the number of g a l l s was r e t a b u l a t e d . None of the c o n t r o l s h o o t s ( u n i n o c u l a t e d s h o o t s ) became i n f e c t e d , hence t h e p l a s t i c bags were deemed t o be an a d e q u a t e b a r r i e r to c o n t a m i n a t i o n by o t h e r s p o r e s o u r c e s . The d a t a c o l l e c t e d a t t h i s time was the number o f q a l l s per s h o o t . 5 . 4 A n a l y s i s I n i t i a l l y , i t was p r o p o s e d t h a t the d a t a ( g a l l s per s h o o t ) would be a n a l y s e d u s i n g a n e s t e d u n b a l a n c e d a n a l y s i s of v a r i a n c e . However, upon o b s e r v a t i o n of the f r e q u e n c y d i s t r i b u t i o n of the d a t a ( F i g u r e 3), i t was d e t e r m i n e d t h a t the p o p u l a t i o n of g a l l s per s h o o t was c l e a r l y not n o r m a l l y d i s t r i b u t e d . R a t h e r , i t a p p e a r e d t o be b i m o d a l . Hence, an a n a l y s i s of v a r i a n c e on the whole d a t a s e t as p e r f o r m e d by Vander P l a n k (1963) would be i n v a l i d as the b a s i c r e q u i r e m e n t of n o r m a l i t y f o r the a n a l y s i s of v a r i a n c e was not met. Any t r a n s f o r m a t i o n of the d a t a t o a c h i e v e n o r m a l i t y would s t i l l r e s u l t i n a l a r g e number of z e r o s . I n s t e a d , a number o f o t h e r s t a t i s t i c a l t e s t s were used t o s e a r c h f o r Figure 3. Frequency histogram of the number of infect ions per lodgepole pine shoot. N u m b e r of g a l l s . 28 d i f f e r e n c e s i n v i r u l e n c e among the s p o r e s o u r c e s and i n r e s i s t a n c e among f a m i l i e s and t r e e s . 6.0 R e s u l t s and D i s c u s s i o n 6.1 G e r m i n a t i o n r a t e s and i n o c u l a t i o n r e s u l t s The g e r m i n a t i o n r a t e s o f the f i v e s p o r e s o u r c e s used i n the e x p e r i m e n t were h i g h , r a n g i n g from 89% t o 93% ( T a b l e 3 ) . The g e r m i n a t i o n r a t e s r e m a ined h i g h t h r o u g h o u t the e x p e r i m e n t (Appendix C ) . Those s h o o t s found t o be i n f e c t e d w i t h T ^ campnodus had s i g n i f i c a n t l y fewer g a l l s (a mean of 0.451) t h a n the h e a l t h y s h o o t s (a mean of 1.67, P=0.00). There e x i s t e d much v a r i a t i o n i n the c o n d i t i o n of mite i n f e c t e d s h o o t s a t the time of t a b u l a t i o n i n June 1986. These s h o o t s were g e n e r a l l y i n poor c o n d i t i o n and many had d i e d . T h e r e f o r e , i t was d e c i d e d t o remove t h i s s e t of s h o o t s from the a n a l y s i s . They c o u l d not be a n a l y s e d s e p a r a t e l y due t o the v a r i a t i o n i n m i t e i n f e s t a t i o n . Removal of t h e s e s h o o t s r e d u c e d t h e d a t a s e t t o 1134 s h o o t s . Shoots l e s s t h an f o u r c e n t i m e t e r s l o n g were i n f r e q u e n t l y i n f e c t e d ( 6 . 5 % became i n f e c t e d ) . In most c a s e s t h e s e were s h o o t s which had been broken o f f d u r i n q t r a n s p o r t a t i o n a f t e r i n o c u l a t i o n . Hence, a l l s h o o t s i e s s t h a n f o u r c e n t i m e t e r s were removed from the d a t a s e t , as i t was f e l t t h a t t h e s e s h o o t s had a v e r y low p r o b a b i l i t y of i n f e c t i o n and t h u s would b i a s the d a t a s e t . T h i s r e d u c e d the d a t a s e t from i i 3 4 t o 1088 s n o o t s . 29 T a b l e 3. The p e r c e n t a g e of s p o r e s g e r m i n a t e d and the number of s p o r e s c o u n t e d f o r each s p o r e s o u r c e . Spore s o u r c e P e r c e n t Number of T r e e of g e r m i n a t e d s p o r e s c o u n t e d o r i g i n * 1 89 1309 P G II-H 2 88 1185 P G I I - E 3 90 548 P G I I - B 4 91 653 P G I I - E 5 91 970 P G I I - i * T r e e s H, E and B a r e from the n a t u r a l r e g e n e r a t i o n ( P G I I ) s u r r o u n d i n g the Buckhorn Lake e x p e r i m e n t a l s i t e . T r e e i i s from an unmarked n a t u r a l r e g e n e r a t i o n t r e e i n the v i c i n i t y . 30 F i v e hundred and s i x c y - s e v e n (52%) of the 1086 s h o o t s i n o c u l a t e d became i n f e c t e d . The mean number of g a l l s per s h o o t was 1.74. F o r t h o s e s h o o t s which became i n f e c t e d , the mean number of g a l l s per s h o o t was 3.33 ( r a n g e : 1 t o 1 3 ) . T a b l e 4 l i s t s t h e mean s h o o t l e n g t h , p e r c e n t of s h o o t s i n f e c t e d , g a l l s per i n f e c t e d s h o o t and the sample s i z e f o r t h e e i g h t e e n h a l f s i b l i n g f a m i l i e s . The p e r c e n t o f s h o o t s i n f e c t e d by f a m i l y v a r i e d from 24% ( f a m i l y PG I I - J ) t o 77% ( f a m i l y PG I I - E ) . T a b l e 5 l i s t s t h e s e v a r i a b l e s f o r the f i v e s p o r e s o u c e s u s e d . The p e r c e n t of s h o o t s i n f e c t e d v a r i e d from 43% f o r s p o r e s o u r c e 3 t o 57% f o r s p o r e s o u r c e 1. The mean g a l l s per i n f e c t e d s h o o t f o r a s i n g l e s p o r e s o u r c e ranged from 2.8 t o 4.1. 6.2 T e s t s f o r v e r t i c a l r e s i s t a n c e A f t e r a s e r i e s of c o n t r o l l e d i n o c u l a t i o n s s u c h as has been com p l e t e d i n t h i s e x p e r i m e n t , an a n a l y s i s of v a r i a n c e i s u s u a l l y p e r f o r m e d on the d a t a (Vander P l a n k 1963). T h i s i s t o d e t e r m i n e whether the v a r i a t i o n i n the y i e l d v a r i a b l e i s due t o main e f f e c t s ( h o r i z o n t a l r e s i s t a n c e ) , i n t e r a c t i o n e f f e c t s ( v e r t i c a l r e s i s t a n c e ) or both (Vander P l a n k 1963). For t h i s d a t a s e t ( g a l l s per s h o o t ) however, t h e b a s i c r e q u i r e m e n t s of a normal d i s t r i b u t i o n of d a t a f o r an a n a l y s i s of v a r i a n c e c o u l d not be met due t o the l a r g e number of z e r o g a l l s per s h o o t . A f r e q u e n c y d i s t r i b u t i o n of the g a l l s per s h o o t ( t h e y i e l d v a r i a b l e i f an a n a l y s i s of v a r i a n c e were run) i s g i v e n i n F i g u r e 31 T a b l e 4. Numbers o f s h o o t s and t r e e s i n o c u l a t e d , mean s h o o t l e n g t h , p e r c e n t of s h o o t s i n f e c t e d and mean g a l l s per i n f e c t e d s h o o t f o r each f a m i l y . F a m i l y Number Number of s h o o t s o f t r e e s i n o c . *1 i n o c . Mean % s h o o t s s h o o t i n f e c t e d l e n g t h (cm) Mean g a l l s per i n f e c t s h o o t *2 Number g a l l s fern, pare . *3 PG 1-1 PG 1-2 PG 1-3 PG 1-6 PG PG PG PG PG 1-7 1-8 I-10 1-11 1-12 93 59 64 91 101 70 69 72 54 12 9 14 13 13 8 9 10 7 11. 13 , 11. 10 . 11. 11. 11. 9 . 8 12 . 0 2 1 9 4 1 7 4 35 73 38 53 63 50 64 68 30 0 27 25 0 10 13 0 6 9 PG 11-A PG I I - B PG I I - C PG II-D PG I I - E PG I I - G PG I I - H PG I I - I PG I I - J 78 21 50 33 57 16 52 53 55 12 6 10 5 10 3 13 10 11 12 . 0 12 . 5 11 10 11.0 7 . 2 9 11, 10 51 52 60 67 77 56 3 8 42 24 0 16 4 0 77 1 42 0 10 Average 60 . 4 9 . 7 11.0 52 . 3 3.22 13 . 3 *1 i n o c . = i n o c u l a t e d *2 i n f e c t . = i n f e c t e d * 3 fern. p a r e . - female p a r e n t 32 T a b l e 5. Number o f s h o o t s i n o c u l a t e d , mean s h o o t l e n g t h , p e r c e n t s h o o t s i n f e c t e d and mean g a l l s per i n f e c t e d s h o o t f o r e ach s p o r e s o u r c e . Spore Number of Mean P e r c e n t Mean g a l l s s o u r c e s h o o t s s h o o t s h o o t s per i n f e c t e d i n o c u l a t e d l e n g t h i n f e c t e d s h o o t 1 276 10.4 56.9 4.1 2 224 10.8 50.4 2.8 3 208 11.6 43.3 3.3 4 159 12.7 52.2 3.3 5 221 10.9 56.1 2.9 Average 217.6 11.26 51.78 3.27 33 3. The d i s t r i b u t i o n a p p e a r e d t o be b i m o d a l . T h i s d i s t r i b u t i o n c o u l d r e p r e s e n t two d i f f e r e n t c a s e s . The a p p a r e n t b i m o d a l d i s t r i b u t i o n c o u l d be the r e s u l t of s a m p l i n g a t r u l y b i m o d a l p o p u l a t i o n w i t h each t r e e and s p o r e s o u r c e b e i n g b i m o d a l i n i t s d i s t r i b u t i o n of g a l l s per s h o o t . T h i s c a s e c o u l d r e p r e s e n t a v e r t i c a l s y s t e m . The mode a : z e r o would r e p r e s e n t t r e e s w i t h a major unmatched r e s i s t a n c e gene f o r one or more o f the s p o r e s o u r c e s a p p l i e d . The i n f e c t e d s h o o t s would r e p r e s e n t the p r o p o r t i o n o f the sample p o p u l a t i o n i n which no unmatched r e s i s t a n c e gene was p r e s e n t f o r the s p o r e s o u r c e a p p l i e d to the s h o o t . I t i s a l s o p o s s i b l e t h a t the o b s e r v e d d i s t r i b u t i o n ( F i g u r e 3) a r o s e f r o m a non-random s e l e c t i o n of h a l f - s i b l i n g f a m i l i e s or t r e e s . Thus i f the e x p e r i m e n t a l m a t e r i a l c o n s i s t e d of e i t h e r p a r t l y v e r y r e s i s t a n t or p a r t l y v e r y s u s c e p t i b l e f a m i l i e s or t r e e s , a d i s t r i b u t i o n of g a l l s per s h o o t s i m i l a r t o t h a t shown i n F i g u r e 3 might r e s u l t . The z e r o mode would a r i s e from i n o c u l a t i o n of s e e d l i n g s r e s i s t a n t t o a l l f i v e s p o r e s o u r c e s w h i l e the s e c o n d mode would r e p r e s e n t s u s c e p t i b l e s e e d l i n g s . Thus the o b s e r v e d d i s t r i b u t i o n of q a i i s per s h o o t does n o t n e c e s s a r i l y i m p l y v e r t i c a l r e s i s t a n c e . Tne s e c o n d i n t e r p r e t a t i o n of the d i s t r i b u t i o n o f g a l l s per sh o o t was e x p l o r e d i n more d e t a i l . F i r s t , an a n a l y s i s of v a r i a n c e of the p r o p o r t i o n of s h o o t s i n f e c t e d ( p e r h a l f s i b l i n g f a m i l y ) showed no s i q n i t i c a n t d i f f e r e n c e between s p o r e s o u r c e s (P=0.349). 34 However, tne D r o o o r t i o n on s h o o t s i n f e c t e d b y f a m i l y were s i g n i f i c a n t l y d i f f e r e n t ( p = 0 . 0 0 0 ) . T h i s i n d i c a t e d v a r i a t i o n i n the r e s i s t a n c e o f the f a m i l i e s but not whether t h i s was h o r i z o n t a l or v e r t i c a l r e s i s t a n c e . An e x p e c t e d d i s t r i b u t i o n of g a l l s per s h o o t was c a l c u l a t e d . Each s e e d l i n g had a p a r t i c u l a r number o f s h o o t s and g a l l s . I t was assumed t h e r e was no d i f f e r e n c e i n v i r u l e n c e between s p o r e s o u r c e s due t o the l a c k of s i g n i f i c a n t d i f f e r e n c e i n the p r o b a b i l i t y o f a s p o r e s o u r c e i n f e c t i n g a t r e e . The p r o b a b i l i t y t h a t a p a r t i c u l a r s h o o t on t h a t s e e d l i n g would have z e r o , one, two or up t o 'n' g a l l s ('n' b e i n g the t o t a l number of g a l l s o b s e r v e d on t h a t s e e d l i n g ) was t h e n c a l c u l a t e d . A sample c a l c u l a t i o n i s p r e s e n t e d i n Appendix D. By m u l t i p l y i n g each of t h e s e p r o b a b i l i t i e s by t h e number of s h o o t s i n o c u l a t e d on the s e e d l i n g and then summing the r e s u l t s o v e r a i l t h e s e e d l i n g s , an e x p e c t e d d i s t r i b u t i o n o f g a l l s per s h o o t was d e r i v e d . The F o r t r a n program used t o make the n e c e s s a r y c a l c u l a t i o n s a p p e a r s i n Appendix E. A f r e q u e n c y h i s t o g r a m o f the c a l c u l a t e d e x p e c t e d d i s t r i b u t i o n of g a l l s per s h o o t and the o b s e r v e d d i s t r i b u t i o n i s found i n F i g u r e 4. U s i n g the c a l c u l a t e d e x p e c t e d d i s t r i b u t i o n a C h i - s q u a r e goodness of f i t t e s t was p e r f o r m e d . T h i s i n d i c a t e d t h a t the o b s e r v e d d i s t r i b u t i o n v a r i e d s i g n i f i c a n t l y from the b i n o m i a l (X-2 = 142, Df = 9 and P^ G . G u l ) . Hence, the b i m o d a i d i s t r i b u t i o n of g a i i s per s h o o t was not due s o l e l y t o the s e l e c t i o n o f r e s i s t a n t f a m i l i e s o r t r e e s but c o u l d have been due t o v e r t i c a l r e s i s t a n c e . Figure 4. The c a l c u l a t e d expected d i s t r i b u t i o n of the number of i n f e c t i o n s per shoot. 4 5 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 N u m b e r of ga l l s . CO 36 The s i g n i f i c a n t d i f f e r e n c e between the o b s e r v e d and e x p e c t e d ( b i n o m i a l ) d i s t r i b u t i o n o f g a l l s per s h o o t d e m o n s t r a t e d t h a t t h e d i s t r i b u t i o n o f g a l l s per s h o o t was not random based on the mean number of g a l l s per s h o o t f o r each t r e e . That i s , f o r a p a r t i c u l a r s e e d l i n g more g a l l s t h a n a v e r a g e were found on some s h o o t s and l e s s g a l l s t h an a v e r a g e on o t h e r s . T h i s c o u l d have been due t o v e r t i c a l r e s i s t a n c e . However, t h i s t e s t d i d not c o n c l u s i v e l y d e m o n s t r a t e v e r t i c a l r e s i s t a n c e as no i n t e r a c t i o n between t r e e and s p o r e s o u r c e was shown. To a t t e m p t t o d e m o n s t r a t e t r e e by s p o r e s o u r c e i n t e r a c t i o n an a n a l y s i s o f v a r i a n c e u s i n g the p r o p o r t i o n of s h o o t s i n f e c t e d as the y i e l d v a r i a b l e would be c o m p l e t e d . The t r e e ( w i t h i n f a m i l y ) by s p o r e s o u r c e i n t e r a c t i o n c o u l d t h e n be t e s t e d and s i g n i f i c a n t v e r t i c a l r e s i s t a n c e would be shown. However i n t h i s c a s e , t h i s t e s t c o u l d -not be c o m p l e t e d due t o the l a c k of r e p l i c a t i o n ( o n l y one d a t a p o i n t per c e l l ) . T h i s was the c r i t i c a l t e s t t h a t would d i s t i n g u i s h between a s t r i c t l y h o r i z o n t a l and a m u l t i l i n e s y s t e m . However, the t e s t o f i n t e r a c t i o n was p e r f o r m e d i n a n o t h e r way. I n t e r a c t i o n was t e s t e d f o r u s i n g a c o m p a r i s o n o f the p r o p o r t i o n of s h o o t s i n f e c t e d (when two s h o o t s were i n o c u l a t e d i n a t r e e by s p o r e s o u r c e c o m b i n a t i o n ) w i t h a b i n o m i a l e x p e c t e d d i s t r i b u t i o n of p r o p o r t i o n of s h o o t s i n f e c t e d . In 356 of the 815 p o s s i b l e t r e e by s p o r e s o u r c e c o m b i n a t i o n s , two s h o o t s were i n o c u l a t e d and s u r v i v e d u n t i l the l a s t d a t a c o l l e c t i o n i n June 1986. F o r each o f t h e s e , the p o s s i b l e outcomes 37 were t h r e e , namely; b o t h s h o o t s i n f e c t e d , b o t h u n i n f e c t e d , or one i n f e c t e d and one u n i n f e c t e d . I f t h e l o d g e p o l e p i n e - w e s t e r n g a l l r u s t s y s t e m w e r e s r r i c r i y h o r i z o n t a l , the f i v e s p o r e s o u r c e s would a l l a c t s i m i l a r l y w i t h r e s p e c t t o the p r o p o r t i o n of s h o o t s i n f e c t e d on each t r e e . T h i s i s s u g g e s t e d by the l a c k of s i q n i f i c a n t d i f f e r e n c e s i n p r o p o r t i o n of s h o o t s i n f e c t e d between s p o r e s o u r c e s on each t r e e (P=0.349). The p r o b a b i l i t y t h a t a s i n g l e t r e e by s p o r e s o u r c e p a i r of s h o o t s had z e r o , one or two s h o o t s i n f e c t e d c o u l d be e s t i m a t e d from the p r o p o r t i o n of s h o o t s i n f e c t e d on t h a t t r e e as a whole. I f 50% of the s h o o t s on a t r e e a r e i n f e c t e d , t h e n f o r each s p o r e s o u r c e by t r e e c o m b i n a t i o n i n a h o r i z o n t a l system, 50% of the s h o o t s would be i n f e c t e d by each s p o r e s o u r c e . A sample c a l c u l a t i o n of the p r o b a b i l i t y of z e r o , one or two s h o o t s i n f e c t e d a p p e a r s i n Appendix F. The f o r t r a n program used t o c a l c u l a t e t h i s i s g i v e n i n A ppendix G. By summing t h e s e t h r e e p r o b a b i l i t i e s over a l l 356 p a i r s of s h o o t s , an e x p e c t e d d i s t r i b u t i o n was d e r i v e d and compared w i t h the o b s e r v e d d i s t r i b u t i o n ( F i q u r e 5 ) . A C h i - s q u a r e goodness o f f i t t e s t showed t h a t the o b s e r v e d d i s t r i b u t i o n d i d not s i g n i f i c a n t l y d i f f e r from t h e e x p e c t e d (P>0.50). The f a c t t h a t t h e d i s t r i b u t i o n of p a i r s of s h o o t s " f i t s " the b i n o m i a l , and t h u s no d i f f e r e n t i a l i n t e r a c t i o n was shown (e a c h s p o r e s o u r c e on a t r e e had the same p r o b a b i l i t y of h a v i n g z e r o , one or two s h o o t s i n f e c t e d ) , d e m o n s t r a t e d t h a t t h e r e were no d i f f e r e n c e s i n the v i r u l e n c e of t h e s p o r e s o u r c e s . The s p o r e s o u r c e used to i n o c u l a t e a p a r t i c u l a r s h o o t d i d not a f f e c t whether or not t h a t s h o o t would be i n f e c t e d . The g e n e t i c m a K e - u p of che t r e e d e t e r m i n e d i f che s n o o t would be i n f e c t e d . On Figure 5. Frequency histogram of the observed and expected proportion of shoots infected. 39 an i n d i v i d u a l t r e e , each s p o r e s o u r c e p r o d u c e d s i m i l a r r e s u l t s . These r e s u l t s d i d not show d i f f e r e n t i a l i n t e r a c t i o n between s p o r e s o u r c e and t r e e and hence s u q g e s t e d t h a t o n l y h o r i z o n t a l r e s i s t a n c e was p r e s e n t i n t h i s p a t h o s y s t e m . The d i s t r i b u t i o n of g a l l s per s h o o t was found t o be bimodal and c o u l d not be p r e d i c t e d w i t h a b i n o m i a l e q u a t i o n based on the f r e q u e n c y of g a l l s per s h o o t f o r each t r e e . T h i s s u g g e s t e d v e r t i c a l r e s i s t a n c e , but t o c o n c l u d e v e r t i c a l r e s i s t a n c e an i n t e r a c t i o n between t r e e and s p o r e s o u r c e would have t o be d e m o n s t r a t e d . T h i s was a t t e m p t e d u s i n g t h e p r o p o r t i o n o f s h o o t s i n f e c t e d f o r each s p o r e s o u r c e by t r e e c o m b i n a t i o n . V e r t i c a l r e s i s t a n c e was not found t o be p r e s e n t as t h e p r o p o r t i o n of s h o o t s i n f e c t e d c o u l d be p r e d i c t e d u s i n g the mean f o r the sp o r e s o u r c e and t r e e s . 6.3 T e s t s f o r H o r i z o n t a l R e s i s t a n c e A two f a c t o r a n a l y s i s of v a r i a n c e u s i n g the sum of g a l l s per t r e e as the y i e l d v a r i a b l e and s p o r e s o u r c e and f a m i l y as the f a c t o r s c o u l d not be c o m p l e t e d as t h i s c o n f i g u r a t i o n r e s u l t e d i n 43% o f the c e i l s h a v i n a a v a l u e of z e r o . I n s t e a d , one way a n a l y s e s or v a r i a n c e u s i n q the s p o r e s o u r c e and f a m i l y s e p a r a t e l y as f a c t o r s were c o m p l e t e d . An a n a l y s i s of v a r i a n c e u s i n q the sum o f g a i i s per t r e e as the y i e l d v a r i a b l e and the sum of s h o o t l e n g t h s as a c o v a r i a t e was c o m p l e t e d . The sum of q a l i s was used as i t i n c o r p o r a t e d b o t h the 40 p e r c e n t a q e of s n o o t s m r e c t e d and t h e number of g a l l s Der i n f e c t e d s h o o t . The sum of the l e n g t h of the s h o o t s was used as the c o v a r i a t e as t h i s a f f e c t e d the number of g a l l s due t o d i f f e r e n c e s i n the amount of s u r f a c e a r e a . The f a c t o r t e s t e d was f a m i l y and t h e sum o f g a l l s per t r e e was t r a n s f o r m e d t o t h e 0.58187 power t o a c h i e v e homogeneity of v a r i a n c e . F a m i l i e s were found t o be s i g n i f i c a n t l y d i f f e r e n t i n t h e amount of g a l l s per t r e e (P=0.03). The c o v a r i a t e , sum of t h e l e n g t h of the s h o o t s was a l s o found t o be s i g n i f i c a n t (Appendix H). R a n k i n g s of t h e h a l f -s i b l i n g f a m i l i e s by t h e sum of g a l l s per t r e e w i t h S c h e f f e ' s and B o n f e r r o n i ' s m u l t i p l e range t e s t s a r e p r e s e n t e d i n T a b l e 6. One homogenous subgroup c o n t a i n i n g a l l f a m i l i e s was f o u n d . The s i g n i f i c a n t d i f f e r e n c e i n t h e number of g a l l s per t r e e found i n the a n a l y s i s of v a r i a n c e w i t h f a m i l y as t h e f a c t o r was i n d i c a t i v e of h o r i z o n t a l r e s i s t a n c e . No i n t e r a c t i o n between t r e e and s p o r e s o u r c e ( v e r t i c a l r e s i s t a n c e ) was d e m o n s t r a t e d i n e a r l i e r t e s t s . The d i f f e r e n c e i n number o f g a l l s per t r e e was t h e r e f o r e due t o d i f f e r e n c e s i n h o r i z o n t a l r e s i s t a n c e . S i n c e the f i v e s p o r e s o u r c e s were grouped t o g e t h e r , t h e r e a c t i o n of i n d i v i d u a l t r e e s t o s i n g l e s p o r e s o u r c e s c o u l d n ot be examined. T h i s f a c t o r was examined e a r l i e r w i t h t h e p r o p o r t i o n of s h o o t s i n f e c t e d by s p o r e s o u r c e and t r e e c o m b i n a t i o n and no e v i d e n c e f o r v e r t i c a l r e s i s t a n c e was f o u n d . A s i m i l a r a n a l y s i s of v a r i a n c e was c o m p l e t e d w i t h s p o r e s o u r c e as the f a c t o r . The sum of g a l l s was t h e y i e l d v a r i a b l e and the 41 T a b l e 6. R e s u l t s o f the S c h e f f e and B o n f e r r o n i m u l t i p l e r a n g e t e s t s on the sum o f g a l l s per t r e e f o r the f a m i l i e s . F a m i l y Mean g a l l s Subgroup * per t r e e PG I I - J 1.57 a PG 1-12 2.42 a PG 1-3 1.93 a PG I I - H 2.57 a PG 1-1 6.46 a PG I I - B 3.11 a PG 1-8 8.65 a PG I I - I 7.12 a PG 1-6 8.95 a PG I I - A 9.73 a PG I I - C 10.28 a PG I I - G 7.34 a PG 1-10 12.21 a PG II-D 12.60 a PG 1-7 14.72 a PG I I - E 12.97 a PG 1-2 16.86 a PG 1-11 18.51 a * homogenous s u b g r o u p s have the same l e t t e r . sum of the l e n g t h of the s h o o t s was used as the c o v a r i a t e . The sum of g a l l s was t r a n s f o r m e d t o t h e 0.50819 power t o a c h i e v e homogeneity o f v a r i a n c e . F a m i l i e s were used as r e p l i c a t e s . The s p o r e s o u r c e s were found t o be s i g n i f i c a n t l y d i f f e r e n t (P=0.009). S c h e f f e and B o n f e r r o n i m u l t i p l e range t e s t s were c o m p l e t e d and two homogenous subgroups were found ( T a b l e 7 ) . S pore s o u r c e s were found t o be s i g n i f i c a n t l y d i f f e r e n t (P=0.009). T h i s s i g n i f i c a n t d i f f e r e n c e i n s p o r e s o u r c e s can o n l y be e x p l a i n e d as h o r i z o n t a l r e s i s t a n c e . I n t e r a c t i o n between s p o r e s o u r c e and t r e e was not found d u r i n g t e s t s f o r v e r t i c a l r e s i s t a n c e , l e a v i n g h o r i z o n t a l r e s i s t a n c e as the o n l y p o s s i b l e s o u r c e f o r t h e s e d i f f e r e n c e s . C o r r e l a t i o n m a t r i c e s o f the p e r c e n t s h o o t s i n f e c t e d and g a l l s per i n f e c t e d s h o o t were c o m p l e t e d a t the f a m i l y by s p o r e s o u r c e l e v e l . G a l l s per i n f e c t e d s h o o t and p e r c e n t s h o o t s i n f e c t e d , when c a l c u l a t e d on a s o o r e s o u r c e by f a m i l y b a s i s , were not s i g n i f i c a n t l y c o r r e l a t e d (r = 0.184, r a t 0.05 =0.208, n=69, F i g u r e 6 ) . A s i g n i f i c a n t c o r r e l a t i o n between the f r e q u e n c y of i n f e c t i o n ( p e r c e n t s h o o t s i n f e c t e d ) and the s e v e r i t y o f i n f e c t i o n (number of g a l l s per i n f e c t e d s h o o t ) would be e x p e c t e d i n a s t r i c t l y h o r i z o n t a l s y s t e m . In a h o r i z o n t a l s y s t e m , f a m i l i e s w i t h low i n f e c t i o n l e v e l s would a l s o have low numbers o f g a l l s per s h o o t . However, i n t h i s s t u d y h a l f - s i b l i n g f a m i l i e s were used. The f a m i l i e s were thus l i k e l y to be h e t e r o g e n o u s i n the amount of r e s i s t a n c e p r e s e n t . T h i s h e t e r o g e n y would make s i g n i f i c a n t c o r r e l a t i o n u n l i k e l y . r a b l e 7 . R e s u l t s of the S c h e f f e and B o n f e r r o n i m u l t i p l e range t e s t s on the sum of g a l l s per t r e e f o r t h e s p o r e s o u r c e s . Spore s o u r c e S u b g r o u p * 3 a 2 a 5 a b 4 a b 1 b homogenous s u b g r o u p s have t h e same l e t t e r . Figure 6. The percentage of shoots in fec ted versus the number of i n f e c t i o n s per infected shoot for each s e e d l i n g . 1 00 90 H 80 70 -60 -50 -40 -30 -20 -10 -0 -4 4, 0 • Q Q 2 2 3 2 LTLTJ2D L~P LTD— • • • • • Q n m • • • • • • • • • • • • 3 • • • • cn • • • • 2 • • 2 • • 2 • • • • • • • • • • • • • m • • • • • ° • • • • • • • CP • • 3 • • • • • "T~ 6 Q 2 Number of galls per Infected shoot. 45 6.4 C o m p a r i s o n t o p a r e n t t r e e s The c o r r e l a t i o n between t h e number o f g a l l s o c c u r r i n g on the female p a r e n t t r e e s i n the f i e l d and t h e p e r c e n t a g e of s h o o t s i n f e c t e d on the p r o g e n y was not s i g n i f i c a n t (r=0.296; r a t 0.05 = 0.4683; n=18). The c o r r e l a t i o n between t h e number of g a l l s per i n f e c t e d s h o o t i n t h e h a l f - s i b l i n g f a m i l i e s and t h e number of g a l l s o c c u r r i n g on the female p a r e n t t r e e s was a l s o n ot s i g n i f i c a n t (r=-0.182; r a t 0.05 = 0.4683, n=18). The l a c k of s i g n i f i c a n t c o r r e l a t i o n s may have been due t o t h e s m a l l number of s e e e d l i n g s per f a m i l y or the f a c t t h a t t h e number of g a l l s on t h e female p a r e n t was the r e s u l t of many y e a r s of i n f e c t i o n d u r i n g which r e - i n o c u l a t i o n from g a l l s p r e s e n t on the t r e e s c o u l d have o c c u r r e d . A l s o , the unknown male p a r e n t may have i n t r o d u c e d r e s i s t a n c e f a c t o r s n ot found i n t h e fe m a l e p a r e n t . As w e l l , r e s i s t a n c e i n the female p a r e n t may not be s t r o n g l y h e r i t a b l e . 6.5 C o m p a r i s o n t o f i e l d d a t a F i g u r e 2 i s the f r e q u e n c y h i s t o g r a m o f g a l l s per t r e e f o r the f i e l d t r e e s f r o m t h e Buckhorn p l a n t a t i o n s and s u r r o u n d i n g n a t u r a l s . The g a l l s per t r e e f o r the p r o g e n y t r e e s used i n t h i s s t u d y a r e shown i n F i g u r e 7. The l e v e l s of i n f e c t i o n were much g r e a t e r f o r t h e f i e l d t r e e s (20.3% have more t h a n 44 g a l l s per t r e e ) . T h i s i s l i k e l y due to y e a r s of r e - i n f e c t i o n i n the f i e l d . B a s i c a l l y , the d i s t r i b u t i o n of g a l l s per t r e e on the progeny was F i g u r e 7. F r e q u e n c y h i s t o g r a m of the g a l l s per t r e e f o r the progeny t r e e s . Number of gal ls. 47 s i m i l a r t o t h a t of p l a n t a t i o n s and n a t u r a l s t a n d s . T h e r e f o r e , t h e r e was no e v i d e n c e t h a t the i n o c u l a t i o n t e c h n i q u e used produced u n u s u a l r e s u l t s . 6.6 Red s t a i n i n g Red s t a i n i n g on t h e e p i d e r m i s of the e l o n g a t i n g s h o o t was found co be p r e s e n t on 13.14% of the s h o o t s two weeks a f t e r i n o c u l a t i o n . The p r o p o r t i o n of s h o o t s i n each f a m i l y which e x h i b i t e d r e d s t a i n i n g i s shown i n T a b l e 8. T a b l e 9 l i s t s the p e r c e n t a g e o f s h o o t s which e x h i b i t e d r e d s t a i n i n g f o r each s p o r e s o u r c e . The f a m i l i e s d i f f e r e d s i g n i f i c a n t l y i n p r o p o r t i o n of s h o o t s w i t h r e d s t a i n (P=0.00) (Appendix I ) . F a m i l y PGII-G had the h i g h e s t p r o p o r t i o n of s h o o t s w i t h r e d s t a i n (31.3%) w h i l e f a m i l y PGI-8 had t h e l o w e s t ( 1 . 4 % ) . The s p o r e s o u r c e s a l s o d i f f e r e d s i q n i f i c a n t l y i n the p e r c e n t a g e of s h o o t s w i t h r e d s t a i n (P=0.0G) (Appendix I ) . Spore s o u r c e 1 had t h e h i g h e s t p e r c e n t a g e of r e d s t a i n e d s h o o t s (20.65%) and s p o r e s o u r c e 4 had the l o w e s t ( 6 . 9 2 % ) . A n a l y s i s of v a r i a n c e found t h a t r e d s t a i n i n g was s i g n i f i c a n t l y more f r e q u e n t i n t h o s e s h o o t s which d e v e l o p e d g a l l s t h a n i n t h o s e s h o o t s which d i d not d e v e l o p g a l l s (P=0.0409) (Appendix I ) . The r e s u l t s i n d i c a t e d t h a t r e d s t a i n e d s h o o t s more o f t e n r e s u l t e d i n i n f e c t i o n t h an non s t a i n e d s h o o t s . Red s t a i n may t h e r e f o r e be an e a r l y i n d i c a t i o n of i n f e c t i o n by g a l l r u s t . However, more work needs t o be c o m p l e t e d on t h i s as some s h o o t s had r e d s t a i n i n g but d i d not d e v e l o p g a l l s and o t h e r s h o o t s 48 T a b l e 8. The p e r c e n t a g e o£ s h o o t s d e m o n s t r a t i n g r e d s t a i n f o r e a c h f a m i l y . F a m i l y N P e r c e n t a g e o f P e r c e n t a g e of s h o o t s w i t h s h o o t s r e d s t a i n i n f e c t e d PG 1-1 93 8.60 35 PG 1-2 59 8.47 73 PG 1-3 64 9.38 38 PG 1-6 91 4.40 53 PG 1 -7 101 17.80 63 PG 1-8 70 1.43 50 PG 1-10 69 4.35 64 PG 1-11 72 15.30 68 PG 1-12 54 14.80 30 PG I I - A 78 16.70 51 PG I I - B 21 9.52 52 PG I I - C 50 4.00 60 PG 1I-D 33 15. 2 0 - • .- 67 PG I I - E 57 47.40 77 PG II-G. 16 31.30 56 PG II-H 52 19.20 38 PG I I - I 53 7.55 42 PG I I - J 55 20.00 44 T a b l e 9. The p e r c e n t a g e of s h o o t s w i t h r e d s t a i n f o r each s p o r e s o u r c e . Spore s o u r c e P e r c e n t a g e of s h o o t s w i t h r e d s t a i n 1 20.65 2 16 .07 3 11. 06 4 6 .92 5 7 .24 50 w i t n o u t r e d s t a i n i n q d i d Decome i n f e c t e d . 7.0 B r e e d i n q s r r a t e q y The r e s u l t s of t h i s s t u d y s u g g e s t e d t h a t i n t h e c o - e p i c e n t e r s t u d i e d , the l o d g e p o l e p i n e - w e s t e r n g a l l r u s t p a t h o s y s t e m i s e s s e n t i a l l y h o r i z o n t a l . The p r e s e n c e of h o r i z o n t a l r e s i s t a n c e i n the w e s t e r n g a l l r u s t - l o d g e p o l e p i n e p a t h o s y s t e m a l l o w s f o r t r e e s t o be b r e d f o r r e s i s t a n c e t o w e s t e r n g a l l r u s t w i t h no f e a r t h a t t h e r e w i l l be a d i s a s t r o u s l o s s of r e s i s t a n c e i n the f i e l d due t o changes i n t h e p a r a s i t e . Those t r e e s e x h i b i t i n g r e s i s t a n c e i n the f i e l d and w i t h good g e n e r a l c o m b i n i n g a b i l i t y f o r r e s i s t a n c e can be s e l e c t e d f o r use i n a b r e e d i n g program. The poor p a r e n t - o f f s p r i n g c o r r e l a t i o n of number of g a l l s per t r e e ( F i g u r e 6) and the l a c k of s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n between the p e r c e n t a g e of s h o o t s i n f e c t e d and the mean number of g a l l s per i n f e c t e d s h o o t i n d i c a t e d t h a t t h e u s e f u l n e s s (the g e n e r a l c o m b i n i n g a b i l i t y ) of a" p a r e n t can o n l y be d e t e r m i n e d by t e s t i n g i t s h a l f or f u l l s i b l i n g p r o g e n y . F i e l d t r e e s d i s p l a y i n g d e s i r a b l e t r a i t s i n terms of t i m b e r v a l u e and r e s i s t a n c e t o w e s t e r n g a l l r u s t s h o u l d be s e l e c t e d . Cones of t h e s e t r e e s s h o u l d be c o l l e c t e d ( e i t h e r from open - p o l l i n a t e d or c o n t r o l l e d p o l l i n a t i o n s ) and the s e e d s grown. The p r o g e n y s h o u l d be t e s t e d f o r r e s i s t a n c e t o w e s t e r n g a l l r u s t by the use of c o n t r o l l e d i n o c u l a t i o n s . S e e d l i n g s r e s i s t a n t t o w e s t e r n g a l l r u s t or p a r e n t s o f r e s i s t a n t f a m i l i e s s h o u l d t h e n be i n c o r p o r a t e d i n t o c u r r e n t 51 l o d g e p o l e p i n e b r e e d i n g programs. 8.0 Summary F i f t y - t w o p e r c e n t of the l o d g e p o l e p i n e s h o o t s i n o c u l a t e d became i n f e c t e d w i t h w e s t e r n g a l l r u s t . The d i s t r i b u t i o n of the q a i i s p e r s h o o t a p p e a r e d t o be b i m o d a l . T h i s s u g g e s t e d t h a t a v e r t i c a l s y s t e m o f r e s i s t a n c e was p r e s e n t i n the w e s t e r n g a l l r u s t - l o d g e p o l e p i n e p a t h o s y s t e m . However, f u r t h e r s t u d y of t h e p r o p o r t i o n of s h o o t s per t r e e i n f e c t e d by s p o r e s o u r c e found no i n t e r a c t i o n between the s p o r e s o u r c e s and t r e e s . Hence, no e v i d e n c e f o r v e r t i c a l r e s i s t a n c e was f o u n d . T h i s i s i n agreement w i t h t h e work o f O l d e t a l (1986). O l d e t a l (1986) found l a r g e d i f f e r e n c e s i n s u s c e p t i b i l i t y between f i v e n a t i v e p o p u l a t i o n s o f P. r a d i a t a a t a s i n g l e e x p e r i m e n t a l s i t e . These d i f f e r e n c e s were found t o be due t o h o r i z o n t a l r e s i s t a n c e o n l y . No e v i d e n c e f o r v e r t i c a l r e s i s t a n c e was found i n t h a t p a t h o s y s t e m . A poor c o r r e l a t i o n was found between female p a r e n t t r e e s and t h e i r h a l f s i b l i n g p r o g e n y . T h i s i n d i c a t e d t h a t f u t u r e r e s i s t a n c e b r e e d i n g s h o u l d n o t depend on t h e r e s i s t a n c e of t h e female p a r e n t o n l y . However, the poor c o r r e l a t i o n may be due t o the s m a l l number of s e e d l i n g s per f a m i l y . L i t e r a t u r e C i t e d B a r r u s , M.F., 1914. V a r i a t i o n of v a r i e t i e s of beans i n t h e i r s u s c e p t i b i l i t y t o a n t h r a c n o s e . P h y t o p a t h . 1:190-195. i n E l l i n g b o e 1981. B i f f e n , R.H., 1905. Mendel's laws of i n h e r i t a n c e and wheat b r e e d i n g . J . A g r i c . S c i . 1:4-48. i n E l l i n g b o e 1981. Browning, J.A., M.D. Simons and E. T o r r e s . 1982. Managing h o s t genes: E p i d e m i o l o g i c and g e n e t i c c o n c e p t s , i n P r o c . 3rd I n t . Workshop o f H o s t - p a r a s i t e I n t e r a c t i o n s i n F o r e s t r y . Wageningnen, The N e t h e r l a n d s , 14-21 S e p t . 1980. Chap. 11: 192-212. B y l e r , J.W., F.W. Cobb J r . and J.R. Parmeter J r . 1972. E f f e c t s o f s e c o n d a r y f u n g i on the e p i d e m i o l o g y of w e s t e r n g a l l r u s t . Can. J . Bot. 50:1061-1066. E l l i n g b o e , A.H. 1981. Changing c o n c e p t s i n h o s t - p a t h o g e n g e n e t i c s . Ann. Rev. P h y t o p a t h . 1981, V o l . 19:125-143. F l e m i n g , R.A. and C O . P e r s o n . 1982. Consequences of p o l y g e n i c d e t e r m i n a t i o n o f r e s i s t a n c e and a g g r e s s i v e n e s s i n n o n - s p e c i f i c h o s t : p a r a s i t e r e l a t i o n s h i p s . Can. J . P l a n t P a t h . 4(2):89-96. F l o r , H.H. 1942. I n h e r i t a n c e of p a t h o g e n i c i t y i n Melamp3ora  l l n l . P h y t o p a t h . V o l . 3 2 , No.8 F l o r , H.H. 1955. H o s t - p a r a s i t e i n t e r a c t i o n i n f l a x r u s t . I t s g e n e t i c s and o t h e r i m p l i c a t i o n s . P h y t o p a t h . 45:680-685. G r o s s , H.L. 1983. N e g l i g i b l e c u l l and growth l o s s of j a c k p i n e a s s o c i a t e d w i t h g l o b o s e g a l l r u s t . F o r . Chron. 159(6) :308-311. " H i r a t s u k a , Y. 1969. E n d o c r o n a r t l u m , a new genus f o r a u t o e c i o u s p i n e stem r u s t s . Can. J . B o t . 47:1493-1495. H i r a t s u k a , Y. and P. Maruyama. 1968. I d e n t i f i c a t i o n of P e r i d e r m i u m h a r k n e s s 1 i i n e a s t e r n Canada on the b a s i s of n u c l e a r c o n d i t i o n o f a e c i o s p o r e germ t u b e s . P l a n t D i s . Rep. 52:650-651. H i r a t s u k a , Y., W. Morf and J.M. P o w e l l . 1966. C y t o l o g y of the a e c i o s p o r e s and a e c i o s p o r e germ tubes of Per idermium h a r k n e s s i 1 and P_^  s t a l a c t l f orme of the C r o n a r t i u m c o l e o s p o r o l d e s complex. Can. J . Bot. 44:1639-1643. H i r a t s u k a , Y. and J.M. P o w e l l . 1976. P i n e stem r u s t s o£ Canada. E n v i r o . Can., Can. F o r . Se r v . , N o r t h . F o r . Res. Cent., Edmonton, A l t a . F o r . Tech. Rep. 4. Hoff R.J. and G.I. MacDonald. 1972. Stem r u s t s of c o n i f e r s and the b a l a n c e of n a t u r e , pp. 525-535 i n : Bingham, R.T., R.J. H o f f and G.I. MacDonald e d s . B i o l o g y of Rust R e s i s t a n c e i n F o r e s t T r e e s : P r o c e e d i n g s of a NATO - IUFRO Advanced Study I n s t i t u t e . Aug. 17-24, 1969. USDA M i s c . P u b l . 1224. 681 pp. Hunt, R.S., E. von R u d l o f f , M.S. Lapp and J . F . M a n v i l l e . 1985. White p i n e b l i s t e r r u s t i n B r i t i s h Columbia I I I . E f f e c t s on the gene p o o l of western white p i n e . F o r . Chron. Dec. 1985:484-487. H u t c h i n s o n . W.G. 1935. R e s i s t a n c e of P i n u s s y l v e s t r i s t o a g a l l - f o r m i n g P e r i d e r m i u m . P h y t o p a t h . 25:24-49. K a i s , A.E. and G.A. Snow. 1972. Host r e s p o n s e o f p i n e t o v a r i o u s i s o l a t e s of C r o n a r t i u m quercuum and C r o n a r t i u m f u s i f o r m e pp. 495-504 i n Bingham, R.T., R.J. H o f f , and G.I. MacDonald eds. B i o l o g y of Rust R e s i s t a n c e i n F o r e s t T r e e s : P r o c e e d i n g s of a NATO-IUFRO Advanced Study I n s t i t u t e . Aug. 17-24, 1969. USDA M i s c . P u b l . 1224. 681 pp. K i n l o c h , B.B. and M. Comstock. 1981. Race of C r o n a r t i u m r i b i c o l a v i r u l e n t t o major gene r e s i s t a n c e i n sugar p i n e . P l a n t D i s . Rep. 65:604-605. Manion, P.D. 1981. Tr e e d i s e a s e c o n c e p t s . P r e n t i c e - H a l l I n c . New J e r s e y , U.S.A. Ne l s o n , R.R. 1978. G e n e t i c s of h o r i z o n t a l r e s i s t a n c e t o p l a n t d i s e a s e s . Ann. Rev. P h y t o p a t h . 18:189-210. N e l s o n , R.R. 1982. On genes f o r d i s e a s e r e s i s t a n c e i n p l a n t s . 'n wagen. pp:84-93 i n P r o c . 3rd I n t . Workshop on tne G e n e t i c s of H o s t - P a r a s i t e I n t e r a c t i o n s i n F o r e s t r y . Wageningnen, The N e t h e r l a n d s , 14-25 Sept. 1980 . P a r l e v l i e t , J . E . and J.C. Zadoks. 1977. The i n t e g r a t e d c o n c e p t of d i s e a s e r e s i s t a n c e ; a new view i n c l u d i n g h o r i z o n t a l and v e r t i c a l r e s i s t a n c e i n p l a n t s . E u p h y t i c a 26:5-21. P e r s o n , C , R. F l e m i n g and L. Cargeeg. 1982. Non s p e c i f i c i n t e r a c t i o n based on p o l y g e n e s pp:318-325 i n P r o c . 3rd I n t . Workshop on t h e G e n e t i c s of H o s t - P a r a s i t e I n t e r a c t i o n s i n F o r e s t r y . Wageningnen, The N e t h e r l a n d s , 14-25 S e p t . 1980. P e t e r s o n , R.S. i 9 6 0 . Western g a l l r u s t on hard p i n e s . USDA F o r . S e r v . , F o r . P e s t L e a f l . 50. Powers, H.R. J r . 1972. T e s t i n g f o r p a t h o g e n i c v a r i a b i l i t y w i t h i n C r o n a r t i u m f u s i f o r m e and C r o n a r t i u m quercuum pp:505-512 i n Bingham, R.T., R.J. H o f f , and G.I. MacDonald e d s . B i o l o g y of Rust R e s i s t a n c e i n F o r e s t T r e e s : P r o c e e d i n g s of a NATO-IUFRO Advanced Study I n s t i t u t e . Aug. 17-24, 1969. USDA M i s c . P u b l . 1224. 681 pp. Qui c k , C R . 1966. E x p e r i m e n t a l i n o c u l a t i o n of po n d e r o s a p i n e w i t h w e s t e r n g a l l r u s t . P l a n t D i s . Rep. 50:550-552. Ra d d i , P. and A. R a g a z z i . 1982. I t a l i a n s t u d i e s on r e i s i t a n c e t o p i n e b l i s t e r r u s t ( C r o n a r t i u m f l a c c i u m ) pp:435-440 i n P r o c . 3rd I n t . Workshop on t h e G e n e t i c s of H o s t - P a r a s i t e I n t e r a c t i o n s i n F o r e s t r y . Wageningnen, The N e t h e r l a n d s , 14-25 S e p t . 1980. Robinson, R.A. 1980. New c o n c e p t s i n b r e e d i n g f o r d i s e a s e r e s i s t a n c e . Ann. Rev. P h y t o p a t h . 18:189-210. S c o t t , P., R.Johnson, M. Wolfe, H. Lowe and F. B e n n e t t . 1978. Host s p e c i f i c i t y i n c e r e a l p a r a s i t e s i n r e l a t i o n t o t h e i r c o n t r o l . A p p l i e d B i o l o b y 5:349-393. S e g a l , A., J . M a n i s t e r s k i , J.A. Browning, G. F i s h b e c h and I. Wahl. 1982. B a l a n c e i n i n d i g e n o u s p l a n t p o p u l a t i o n s pp: 361-370 i n P r o c . 3rd I n t . Workshop on t h e G e n e t i c s of H o s t - P a r a s i t e I n t e r a c t i o n s i n F o r e s t r y . Wageningnen, The N e t h e r l a n d s , 14-25 Se p t . 1980. Snow, G.A., R.J. Dinus and A. G. K a i s , 1975. V a r i a t i o n i n p a t h o g e n i c i t y of d i v e r s e s o u r c e s of C r o n a r t i u m  f u s 1 forme on s e l e c t e d s l a s h p i n e f a m i l i e s . P h y t o p a t h . 65:170-175. Stakman, E.C. and M.N. L e v i n e , 1922. The d e t e r m i n a t i o n of b i o l o g i c a l forms of P u c c l n i a g r a m l n i s on Tr i t l c u m  s pp. Minn. A g r i c . Exp. S t n . B u l l . 8. 10 pp. i n E l T i n g b o e 1981. True, R . P . 1938. G a l l development on P l n u s s y i v e s t r i s a t t a c k e d by t h e woodgate P e r i d e r m i u m and morphology of the p a r r a s i t e . P h y t o p a t h . 28:24-49. van der Kamp, B . J . 1981. The i n c i d e n c e and impact of western g a l l r u s t and a t r o p e l l l s candor i n managed s t a n d s of l o d g e p o l e p i n e of i n t e r i o r B.C. B.C. Min. of F o r . , Res. Branch, V i c t o r i a , B.C. Vander P l a n k , J . 1963. P l a n t d i s e a s e s , e p i d e m i c s and c o n t r o l . Academic P r e s s , New York. 349 pp. Vander P l a n k , J . 1968. D i s e a s e r e s i s t a n c e i n p l a n t s . Academic P r e s s , New York. Vander P l a n k , J . 1984. D i s e a s e r e s i s t a n c e i n p l a n t s . Academic P r e s s I n c . T o r o n t o , Canada. 194 pp. Zadoks, J.C. 1972. R e f l e c t i o n s on d i s e a s e r e s i s t a n c e i n a n n u a l c r o p s pp:45-64 i n Bingham, R.T., R.J. H o f f , and G.I. MacDonald e d s . B i o l o g y of Rust R e s i s t a n c e i n F o r e s t T r e e s : P r o c e e d i n g s of a NATO-IUFRO Advanced S t u d y I n s t i t u t e . Aug. 17-24, 1969. USDA M i s c . P u b l . 1224. 681 pp. 56 Appendix A. The d a t e s of i n o c u l a t i o n f o r t h e s p o r e s o u r c e s . Spore s o u r c e Date of i n o c u l a t i o n 1 June 2, 1985 2 June 3, 1985 3 June 4 and 5, 1985 4 June 5, 1985 5 June 4, 1985 Appendix B. The number of s h o o t s i n o c u l a t e d w i t h each s p o r e s o u r c e f o r each f a m i l y . Spore s o u r c e F a m i l y 1 2 3 4 5 PG 1-1 PG 1-2 PG 1-3 PG 1-6 PG 1-7 PG 1-8 PG 1-10 PG 1-11 PG 1-12 21 16 18 25 25 14 18 18 12 19 16 16 19 21 11 12 13 10 19 9 8 16 16 15 15 14 11 14 7 11 15 17 14 8 11 9 20 11 11 16 22 16 16 16 12 PG I I - A PG I I - B PG I I - C PG II-D PG I I - E PG I I - G PG II-H PG 11-I PG I I - J 21 8 13 8 12 2 15 13 17 15 4 10 8 18 5 8 10 9 17 3 10 7 11 2 12 10 13 7 4 7 3 6 2 8 9 7 18 3 10 7 10 5 9 11 9 58 Appendix C . G e r m i n a t i o n r a t e s o£ the s p o r e s o u r c e s t h r o u g h o u t the i n o c u l a t i o n p r o c e s s . Spore s o u r c e 1 2 3 4 5 Time *1 % *2 Time % Time % Time % Time % 0 + 00 90 0 + 00 82 0 + 00 94 0 + 00 91 0+00 90 1 + 05 84 1 + 00 87 0 + 50 92 0 + 55 93 1 + 10 90 2 + 00 95 1 + 50 93 1 + 50 88 1 + 55 86 1 + 55 88 3 + 05 86 2 + 55 92 2 + 55 94 2 + 55 94 2 + 55 89 3 + 35 94 5 + 40 89 0 + 00 79 3 + 55 88 3 + 45 93 4 + 40 91 6 + 40 84 1 + 10 90 4 + 45 97 8 + 15 93 7 + 20 87 2+10 96 5 + 20 91 9+10 89 9+40 83 *1 Time: h o u r s + mi n u t e s from s t a r t o f i n o c u l a t i o n (0+00 = s t a r t ) . *2 %: P e r c e n t of s p o r e s t h a t g e r m i n a t e d . 59 Appendix D. A sample c a l c u l a t i o n of the b i n o m i a l d i s t r i b u t i o n of g a l l s per s h o o t . We have: x g a l l s on y sh o o t s . The p r o b a b i l i t y t h a t a p a r t i c u l a r c a n d l e w i l l have 0, 1, 2...x g a l l s i s as f o l l o w s : Number of g a l l s E q u a t i o n to a r r i v e a t p r o b a b i l i t y 0 ( y - l / y ) ** x 1 (x ( y - l / y ) ** x-1) (1 /y) 2 ( ( x ( x - l ) ) / 2 ! ) ( ( y - l / y ) * * x-2) ( l / y ) * * 2 3 ( ( x ( x - l ) ( x - 2 ) ) / 3 « ) ( ( y - l / y ) * * x - 3 ) ( l / y )**3 4 ( ( x ( x - l ) ( x - 2 ) ( x - 3 ) / 4 ! ) ( ( y - 1 ) / y ) * * x - 4 ) ( l - y )**4 e t c . 60 Appendix E. The f o r t r a n program used t o c a l c u l a t e t h e e x p e c t e d d i s t r i b u t i o n of g a l l s per s h o o t based on a b i n o m i a l d i s t r i b u t i o n X i s the number of g a l l s . Y i s the number of c a n d l e s . THE PROGRAM 'BINOMIAL' CALCULATES A FREQUENCY DISTRIBUTION OF GALLS PER SHOOT. ASSUMING THAT ON EACH SEEOLING THE NUMBER OF GALLS OBSERVED ARE RANDOMLY DISTRIBUTED OVER ALL THE INOCULATED SHOOTS -THE HORIZONTAL SYSTEM ASSUMPTION-. INTEGER X.Y REAL*8 A(45)/45*O.ODO/.P(45).0(45),R(45) 1 READ (5.5.EN0=1OO) X.Y 5 FORMAT ( 16X.I7.1X.17) IF (X.GT.O.5) GO TO IO A( 1 )=A(1 ) + Y GO TO 1 10 IF (X.GT.1.5) GO TO 15 A(1 )=A(1)+(Y-1.O) A(2)=A(2)+1.O GO TO 1 15 IF(Y.GT.I.S) GO TO 20 A(X+1)=A(X+1)+1.0 GO TO 1 20 K=X+1 DO 50 1=1. K. 1 P(I ) = 1.ODO Q(I) = 1.ODO R(I)=1.ODO 50 CONTINUE DO 70 1=1. X P ( I + 1 ) = P ( I ) * ( X - ( I - 1 ) ) / ( I * 1 . 0 ) Q(X-I+1)=0(X-I+2)*((Y-1)/(Y*1.0)) R(1+1)=R(I)*(1/(Y*1.O)) 70 CONTINUE DO 80 1=1. K A ( I ) = A ( I ) + P ( I ) - Q ( I ) * R ( I ) * Y 80 CONTINUE GO TO 1 100 DO 110 1=1. 45 J=I-1 WRITE (6.120) J . A ( I ) 120 FORMAT (I8.F12.5) 110 CONTINUE STOP END 61 Appendix F. A sample c a l c u l a t i o n of the e x p e c t e d d i s t r i b u t i o n of p r o p o r t i o n of s h o o t s i n f e c t e d f o r a b i n o m i a l d i s t r i b u t i o n . I f the p r o p o r t i o n o f i n f e c t e d s h o o t s f o r a p a r t i c u l a r s e e d l i n g i s 0.677, t h e n : The p r o b a b i l i t y o f b o t h s h o o t s b e i n g i n f e c t e d i s : P = ( l - 0 . 6 6 7 ) * * 2 = 0.11 The p r o b a b i l i t y o f one s h o o t b e i n g i n f e c t e d i s : P = (0.677 ) ( 0 . 333) (2) = 0.444 The p r o b a b i l i t y of no s h o o t s b e i n g i n f e c t e d i s : P = (0.677)**2 = 0.445 62 Appendix G. The F o r t r a n program used t o c a l c u l a t e t h e e x p e c t e d d i s t r i b u t i o n of p r o p o r t i o n of s h o o t s i n f e c t e d i n a b i n o m i a l d i s t r i b u t i o n . 1 INTEGER F,T,S,G,BH(20,15,5)/1500*0/ 2 REAL C,D,E,A(20,15,3)/900*0 .0/ 3 OO.O 4 D=0 . 0 5 E = 0 . 0 6 4 READ(5,5,END=100)F,T,S,G 7 5 FORMAT(3(I2,1X),10X,I2 8 A(F,T,1)=A(F,T,1)+1.0 9 IF(C.EG.O) GO TO 8 10 A(F,T,2)=A(F,T,2)+1.0 11 8 B(F,T,S)=B(F,T,S)=1 12 GO TO 4 13 100 DO 55 F=l,20 14 DO 45 T=l,15 15 X=A(F,T,1) 16 IF(X.LT.0.5)X=1.0 17 A ( F , T , 3 ) = A ( F , T , 2 ) /X 18 40 CONTINUE 19 50 CONTINUE 20 DO 50 F=l,20 21 DO 40 T=l,15 22 DO 30 S=l,5 23 IF (B:F,T,S).NE.2) GO TO 30 24 C=C-(A(F,T,3)**2.0) 25 D=D-(A(F,T,3)*(1.0-A(F,T, 3*2.0) 26 B=B-(T-D-A(F,T,3))**2.0 27 30 CONTINUE 28 40 CONTINUE 29 50 CONTINUE 30 WRITE (8.80)C,D,E 31 80 FORMAT(3(F7.2)) 32 STOP 33 END Appendix H. R e s u l t s from the a n a l y s i s o f v a r i a n c e : Sum o f g a l l s per t r e e = f a m i l y + c o v a r i a t e : the sum of t h e l e n g t h s of the s h o o t s f o r each t r e e . S o urce of Sum of Df Mean F - r a t i o P r o b a b i l i t y V a r i a t i o n S q u a r e s Square F a m i l y 202.6 17 11.9 2.4 0.0028 C o v a r i a t e : Sum of s h o o t l e n g t h s 54.9 1 54.9 10.9 0.0012 R e s i d u a l 787.9 157 5.0 64 Appendix I. R e s u l t s from the a n a l y s e s of v a r i a n c e t e s t s u s i n g r e d s t a i n . I. Model: Y i e l d v a r i a b l e = p e r c e n t a g e o f s h o o t s w i t h r e d s t a i n F a c t o r = F a m i l y S o u r c e of V a r i a t i o n Between W i t h i n T o t a l Sum of Squares Df 79 200 17 573 000 674 652 000 691 Mean Square 4658 851 F - r a t i o 5 . 4 8 P r o b a b i l i t y 0 . 0 0 0 I I . Model: Y i e l d v a r i a b l e = P e r c e n t a g e of s h o o t s w i t h r e d s t a i n F a c t o r = Spore s o u r c e Source of V a r i a t i o n Between W i t h i n T o t a l Sum o f Squares 20 600 632 000 652 000 Df 4 687 691 Mean Square 5 1 5 1 . 7 919 .8 F - r a t i o P r o b a b i l i t y 5 . 6 0 0 . 0002 65 Model I I I . Y i e l d v a r i a b l e = P e r c e n t a g e o f s h o o t s w i t h r e d s t a i n . F a c t o r = I n f e c t i o n s t a t u s . S o u r c e of Sum of Df Mean F - r a t i o P r o b a b i l i t y V a r i a t i o n S q u a r e s Square Between 3 940 1 3942 4.19 0.041 W i t h i n 649 000 690 940 T o t a l 652 000 691 

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