rflp soybean

5
Proc. Natl. Acad. Sci. U S A Vol. 92 , p p . 4656-4660, M a y 1995 Genetics Interactions between quantitative trait loci i n soybean i n which trait variation a t one locus i s conditional upon a specific allele a t another (epistasis/maximum likelihood/recombinant inbreds) KARL G . LARKtS, KEVIN CHASEt, FRED ADLERt§, LEVI M . MANSURt+, AND JAMES H . ORFII Departments of tBiology a n d §Mathematics, University of Utah, Salt Lake City, UT 84112; 1Facultad d e Agronomia, Universidad Catolica d e Valparaiso, Quillota, Chile; a n d IIDepartment of Agronomy a n d Plant Genetics, University of Minnesota, S t . Paul, MN 55108 Communicated b y Mario R . Capecchi, University o f Utah, Salt Lake City, U T , January 2 6 , 1995 (received f o r review October 1 4 , 1994) ABSTRACT A large recombinant inbred population o f soybean h a s been characterized f or 2 2 0 restriction fragment- length polymorphism (RFLP) markers. Values f o r agronomic traits also have been measured. Quantitative trait loci f or height, yield, a n d maturity were located by their linkage t o RFLP markers. Q T L controlling large amounts of trait varia- tion were analyzed f o r th e dependence o f trait variation o n particular alleles at a second locus b y comparing cumulative distributions o f t h e trait f o r each genotype (four genotypes p e r pair of loci). Interesting pairs o f loci were analyzed statisti- cally with maximum likelihood a n d Monte Carlo comparison of additive a n d epistatic models. F o r each locus affecting height, variation w a s conditional upon t h e presence of a particular allele a t a second unlinked locus that itself e x - plained little o r no trait variation. T h e results show that interactions between Q T L a re frequent a nd control large effects. Interactions distinguished between different Q T L i n a single linkage group a n d between Q T L that affect different traits closely linked t o o n e RFLP marker-i.e., distinguished between pleiotropy a n d closely linked genes. T h e implications for the evolution o f inbreeding plants a nd f o r t h e construction o f agronomic breeding strategies a r e discussed. Polygenic quantitative traits result from interactions between multiple genes a n d t h e environment (1). Detailed genetic analysis o f these traits h a s become possible with t h e availability o f a large number o f molecular markers t o which quantitative trait loci (QTL) c a n b e linked (2). I n addition, estimation o f trait values c a n b e greatly improved b y t h e u s e o f recombinant inbred (RI) populations i n which individual lines represent stable inbred (therefore homozygous) segregant progeny from a single genetic cross (3 , 4 ) . With us e o f such a population, trait values c a n b e measured repeatedly in different environments, a n d genetic variation c a n b e separated from environmental effects. Because i t i s easy t o store a n d maintain seed, large R I populations o f plants c a n b e prepared a n d maintained. This makes possible t h e isolation a n d identification o f rare geno- types involving combinations o f parental alleles that produce phenotypes with values o f quantitative traits more extreme than those o f th e parents (5). I n this paper, w e analyze a R I population o f soybean derived from a cross between t w o cultivars, Minsoy a nd Noir 1 , that shows transgressive variation among th e segregant progeny ( 6 , 7)-i.e., variation that e x - tends beyond th e range o f th e parents. W e have searched for epistatic effects between QTL that produce large amounts of trait variation. A s examples, w e have considered Q TL that explain large amounts o f trait variation, b u t for which t h e effect is conditional upon a n allele a t another T h e publication costs o f this article were defrayed i n part b y page charge payment. This article must therefore b e hereby marked "advertisement" i n accordance with 1 8 U.S.C. §1734 solely t o indicate this fact. Locus 2 Noir Noir Mi n 0 _ _ M i n FIG. 1 . Epistasis between Q T L regulates trait variation. I n this example (see Fig. 2 ) t h e trait i s height. Variation controlled by alleles at locus 1 i s conditional upon t h e presence o f a Noir 1 allele a t locus 2 . unlinked locus (which, b y itself, is n ot associated with trait variation). This type o f interaction i s shown schematically i n Fig. 1 . I n this example, a difference i n height produced b y different alleles a t locus 1 i s conditional upon t h e presence of a Noir 1 allele a t locus 2 . Only t h e R I lines with th e Noir 1 allele a t locus 2 will show differences i n height produced b y t h e first locus. To identify such pairs o f loci, w e chose a s t h e first locus Q T L that had been found t o explain significant variation i n a quantitative trait. We then scanned through unlinked second loci, dividing t h e population R I lines into four genotypic classes b y pairing each o f t h e alleles a t t h e first locus witheach o f th e alleles a t t h e second locus. These pairwise comparisons have identified second loci with substantial epistatic effects o n plant height a n d o n other traits such a s seed yield. MATERIALS AND METHODS Th e soybean R I population used here a n t h e measurement o f t h e traits have been described i n detail (7). Briefly, 2 2 4 different segregants were used that had been derived from crossing t h e soybean cultivars Minsoy (P I 27890) a nd Noir 1 ( P I 290136). Traits were measured during tw o seasons i n tw o locations, three replications each (1 2 replications total), during t h e F 9 t o F1 2 generation o f inbreeding. Heritabilities (H2) were calculated t o b e 0.93 f o r height (cm), 0.84 f o r maturity (days from planting), a nd 0.77 f o r yield [kg/hectare (ha)]. Abbreviations: RFLP, restriction fragment-length polymorphism; QTL, quantitative trait locus o r loci; R I , recombinant inbred; lod, logarithm o f odds. 4 T o whom reprint requests should b e addressed. 4656

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8/6/2019 RFLP Soybean

http://slidepdf.com/reader/full/rflp-soybean 1/5

P r o c .N a t l .A c a d .S c i .USAVo l .9 2 ,p p .4 6 5 6 - 4 6 6 0 ,M a y1 9 9 5G e n e t i c s

I n t e r a c t i o n sbe tween q u a n t i t a t i v et r a i t l o c i i n s o y b e a ni n whicht r a i t v a r i a t i o n a t one l o c u s i s c o n d i t i o n a lu p o na s p e c i f i ca l l e l ea t a n o t h e r

( e p i s t a s i s / m a x i m u ml i k e l i h o o d / r e c o m b i n a n ti n b r e d s )

KARLG . L ARK t S ,K E V I NCHA S E t ,FREDAD L E R t § ,L EV IM. MAN S U R t + ,AND J A M E SH . OR F I ID e p a r t m e n t so ft B i o l o g ya n d §M a t h e m a t i c s ,U n i v e r s i t yo f U t a h ,S a l tL a k eC i t y ,UT 8 4 1 1 2 ;1 F a c u l t a dd e A g r o n o m i a ,U n i v e r s i d a dC a t o l i c ad e Va l p a r a i s o ,Qu i l l o t a ,C h i l e ;a n d I I D e p a r t m e n to f A g r o n o m ya n dP l a n tG e n e t i c s ,Un i v e r s i t yo f M i n n e s o t a ,S t .P a u l ,MN 5 5 1 0 8

C o m m u n i c a t e db yM a r i oR .Ca p e c c h i ,U n i v e r s i t yo fU t a h ,S a l tL a k eC i t y ,U T ,J a n u a r y2 6 ,1 9 9 5( r e c e i v e df o rr e v i e wO c t o b e r1 4 ,1 9 9 4 )

ABSTRACT A l a r g er e c o m b i n a n ti n b r e d p o p u l a t i o no f

s o y b e a nh a s b e e nc h a r a c t e r i z e df o r2 2 0 r e s t r i c t i o nf r a g m e n t -l e n g t hp o l y m o r p h i s m( R F L P )m a r ke r s . Va l ue sf o ra g r o n o m i ct r a i t sa l s oh a v eb e e n m e a s u r e d .Q u a n t i t a t i v et r a i tl o c i( Q T L )f o rh e i g h t ,y i e l d ,a n dm a t u r i t yw e r el o c a t e db yt h e i rl i n k a g et oRFLP m a r k e r s .QT Lc o n t r o l l i n gl a r g ea m o u n t so f t r a i tv a r i a -t i o nw e r e a n a l y z e df o rt h e d e p e n d e n c eo f t r a i tv a r i a t i o n o n

p a r t i c u l a ra l l e l e sa t a s e c o n dl o c u sb yc o m p a r i n gc u m u l a t i v ed i s t r i b u t i o n so f t he t r a i tf o re a c hg e n o t y p e( f o u rg e n o t y p e sp e rp a i ro f l o c i ) .I n t er es t i ng p a i r so f l o c iw e r ea n a l y z e ds t a t i s t i -c a l l yw i t hmax imum l i k e l i h o o da n dM o n t eC a r l oc o m p a r i s o no f a d d i t i v ea n d e p i s t a t i cm o d e l s .F o r e a c h l o c u s a f f e c t i n gh e i g h t ,v a r i a t i o n w a s c o n d i t i o n a lu p o nt h e p r e s e n c eo f ap a r t i c u l a ra l l e l ea t a s e c o n d u n l i n ke dl o c u s t h a t i t s e l fe x -p l a i n e dl i t t l eo r n o t r a i tv a r i a t i o n .T h e r e s u l t ss h o w t h a ti n t e r a c t i o n sb e t w e e nQT La r e f r e q u e n ta n d c o n t r o l l a r g ee f f e c t s .I n t e r a c t i o n sd i s t i n g u i s h e db e t w e e nd i f f e r e n tQ TLi nas i n g l el i n k a g eg r o u pa n d b e t w e e nQT Lt h a ta f f e c td i f f e r e n tt r a i t sc l o s e l yl i n k e d t o o n eRFLPm a r k e r - i . e . ,d i s t i n g u i s h e db e t w e e np l e i o t r o p ya n dc l o s e l yl i n k e dg e n e s .T h e i m p l i c a t i o n sf o rt h e e v o l ut i o no f i n b r e e d i n gp l a n t sa n df o rt h e c o n s t r u c t i o no f

a g r o n o m i cb r e e d i n gs t r a t e g i e sa r e d i s c u s s e d .

P o l y g e n i cq u a n t i t a t i v et r a i t sr e s u l tf r o mi n t e r a c t i o n sb e t w e e nm u l t i p l eg e n e sa n d t h e e n v i r o n m e n t( 1 ) .D e t a i l e dg e n e t i ca n a l y s i so f t h e s et r a i t sh a s b e c o m ep o s s i b l ew i t h t he a v a i l a b i l i t yo fa l a r g en u m b e ro f m o l e c u l a rm a r k e r st o w h i c hq u a n t i t a t i v et r a i tl o c i( Q T L )c a n b e l i n k e d( 2 ) .I n a d d i t i o n ,e s t i m a t i o no ft r a i tv a l u e sc a n b e g r e a t l yi m p r o v e db yt h eu s e o fr e c o m b i n a n ti n b r e d ( R I )p o p u l a t i o n si n w h i c hi n d i v i d u a ll i n e sr e p r e s e n ts t a b l ei n b r e d( t h e r e f o r eh o m o z y g o u s )s e g r e g a n tp r o g e n yf r o ma s i n g l eg e n e t i cc r o s s ( 3 ,4 ) .W i t hu s e o f s u c ha p o p u l a t i o n ,t r a i tv a l u e sc a n b e m e a s u r e dr e p e a t e d l yi nd i f f e r e n te n v i r o n m e n t s ,a n d g e n e t i cv a r i a t i o nc a n b e s e p a r a t e df r o m e n v i r o n m e n t a le f f e c t s .

B e c a u s ei t i s e a s yt o s t o r ea n d m a i n t a i ns e e d ,l a r g eRIp o p u l a t i o n so f p l a n t sc a n b e p r e p a r e da n d m a i n t a i n e d .Th i sm a k e sp o s s i b l et h ei s o l a t i o na n d i d e n t i f i c a t i o no f r a r e g e n o -t y p e si n v o l v i n gc o m b i n a t i o n so f p a r e n t a la l l e l e st h a tp r o d u c ep h e n o t y p e sw i t h v a l u e so f q u a n t i t a t i v et r a i t smore e x t r e m et h a n t h o s e o f t h ep a r e n t s( 5 ) .I n t h i sp a p e r ,we a n a l y z ea RIp o p u l a t i o no f s o y b e a nd e r i v e d f r o m a c r o s s b e t w e e nt w oc u l t i v a r s ,M i n s o ya n dN o i r1 ,t h a ts h o w st r a n s g r e s s i v ev a r i a t i o na m o n gt h es e g r e g a n tp r o g e n y( 6 ,7 ) - i . e . ,v a r i a t i o n t h a te x -t e n d sb e y o n dt h er a n g eo f t h ep a r e n t s .We h a v e s e a r c h e df o re p i s t a t i ce f f e c t sb e t w e e nQTL t h a t

p r o d u c el a r g ea m o u n t so f t r a i tv a r i a t i o n .As e x am p l e s ,we h a v ec o n s i d e r e dQTL t h a te x p l a i nl a r g ea m o u n t so f t r a i tv a r i a t i o n ,b u t f o rw h i c ht h ee f f e c ti sc o n d i t i o n a lu p o na n a l l e l ea t a n o t h e r

T h e p u b l i c a t i o nc o s t so ft h i s a r t i c l ew e r ed e f r a y e di np a r tb yp a g e c ha rg ep a y m e n t .Th i s a r t i c l em u s tt h e r e f o r eb e h e r e b ym a r k e d" a d v e r t i s e m e n t "i na c c o r d a n c ew i t h 1 8 U . S . C .§ 1 7 3 4s o l e l yt o i n d i c a t et h i sf a c t .

Locus 2No i r

N o i r

M i n

0

_ _

M i n

F I G .1 . E p i s t a s i sb e t w e e nQTL r e g u l a t e st r a i tv a r i a t i o n .I n t h i se x a m p l e( s e eF i g .2 )t h et r a i ti sh e i g h t .Va r i a t i o nc o n t r o l l e db ya l l e l e sa t l o c u s1 i sc o n d i t i o n a lu p o nt h ep r e s e n c eo f a N o i r 1 a l l e l ea t l o c u s2 .

u n l i n k e dl o c u s( w h i c h ,b yi t s e l f ,i s n o t a s s o c i a t e dw i t h t r a i tv a r i a t i o n ) .Th i s t y p eo f i n t e r a c t i o ni s s h o w ns c h e m a t i c a l li nF i g .1 . I n t h i se x a m p l e ,a d i f f e r e n c ei n h e i g h tp r o d u c e db yd i f f e r e n ta l l e l e sa t l o c u s1 i sc o n d i t i o n a lu p o nt h ep r e s e n c eo fa N o i r1 a l l e l ea t l o c u s2 .O n l yt h eRI l i n e sw i t ht h eN o i r1 a l l e l ea t l o c u s2 w i l ls h o wd i f f e r e n c e si nh e i g h tp r o d u c e db yt h ef i r s tl o c u s .To i d e n t i f ys u c hp a i r so f l o c i ,we c h o s ea st h ef i r s tl o c u sQTL t h a th a d b e e nf o u n dt o e x p l a i ns i g n i f i c a n tv a r i a t i o ni n aq u a n t i t a t i v et r a i t .We t h e n s c a n n e dt h r o u g hu n l i n k e ds e c o n dl o c i ,d i v i d i n gt h ep o p u l a t i o no f RI l i n e si n t of o u r g e n o t y p i cc l a s s e sb yp a i r i n ge a c ho f t h ea l l e l e sa t t h ef i r s tl o c u sw i t h e a c ho f t h ea l l e l e sa t t h es e c o n dl o c u s .T h e s ep a i r w i s ec om p a r i s o nh a v ei d e n t i f i e ds e c o n dl o c iw i t hs u b s t a n t i a le p i s t a t i ce f f e c t so n

p l a n th e i g h ta n d o n o t h e r t r a i t ss u c h a s s e e dy i e l d .MATER IALSAND METHODS

T h es o y b e a nRI p o p u l a t i o nu s e dh e r e a n dt h em e a s u r e m e n to ft h e t r a i t sh a v e b e e n d e s c r i b e di n d e t a i l( 7 ) .B r i e f l y ,2 2 4d i f f e r e n ts e g r e g a n t sw e r e u s e d t h a th a d b e e nd e r i v e d f r o mc r o s s i n gt he s o y b e a nc u l t i v a r sM i n s o y( P I2 7 8 9 0 )a n d N o i r 1( P I2 9 0 1 3 6 ) .T r a i t sw e r em e a s u r e dd u r i n gt w o s e a s o n si n t w ol o c a t i o n s ,t h r e er e p l i c a t i o n se a c h( 1 2r e p l i c a t i o n st o t a l ) ,d u r i n gt h eF 9 t o F 1 2 g e n e r a t i o no f i n b r e e d i n g .H e r i t a b i l i t i e s( H 2 )w e r e c a l c u l a t e dt o b e 0 . 9 3f o rh e i g h t( c m ) ,0 . 8 4f o rma t u r i t y( d a y sf r o mp l a n t i n g ) ,a n d 0 . 7 7f o ry i e l d[ k g / h e c t a r e( h a ) ] .

A b b r e v i a t i o n s :R F L P,

r e s t r i c t i o nf r a gm e n t - l e n g t hp o l y m o r p h i sQTL ,q u a n t i t a t i v et r a i tl o c u so r l o c i ;R I ,r e c o m b i n a n ti n b r e d ;l o d ,

l o g a r i t hmo f o d d s .4 Towh om r e p r i n tr e q u e s t ss h o u l db e a d d r e s s e d .

4 6 5 6

8/6/2019 RFLP Soybean

http://slidepdf.com/reader/full/rflp-soybean 2/5

P r o c .N a t l .A c a d .S c i .USA 9 2 ( 1 9 9 5 ) 4 6 5 7

M e a s u r e m e n t so f s e g r e g a t i n gr e s t r i c t i o nf r a gm e n t - l e n g t hp o l y m o r p h i s m( R F L P )m a r k e r s h a v e b e e n d e s c r i b e d( 8 ) .T h e s e were l i n k e db yu s i n gMAPMAKER ( 9 ) .A p r e l i m i n a r yg e n e t i cmap b a s e don F 2 s e g r e g a n t sf r o mt h i sc r o s s ha s b e e np u b l i s h e d( 8 ) ,a n d a more c om p l e t em a p ,d e r i v e df r o mt h eRIp o p u l a t i o n ,w i l lb e p u b l i s h e de l s e w h e r e .B e c a u s ea common

g e n e t i cmap r e c o n c i l i n gm a r k e r sf r o md i f f e r e n tc r o s s e s w i t hc h r o m o s o m ec y t o l o g y( i ns o y b e a n ,n = 2 0 )i sn o t y e ta v a i l a b l ei ns o y b e a n ,t h el i n k a g eg r o u p si nF i g .4 h a v en o t b e e na s s i g n e dt o p a r t i c u l a rc h r o m o s o m e s .QTL d a t a i nTa b l e 1 w e r e d e t e r m i n e db yu s i n ga n a l y s i so f

v a r i a n c e( 1 ,1 0 ) .P a i r w i s ec om p a r i s o n so fQTL ( s e ei nTa b l e2 ;s e e a l s oR e s u l t s )w e r e made b yu s i n ga c o m p u t e rp r o g r a md e v i s e db yK . C . ,t o b e p u b l i s h e de l s e w h e r ei n d et a i l .T h ep r o g r a md i s p l a y st h ec u m u l a t i v ed i s t r i b u t i o n so f t r a i tv a l u e sf o rt h etwo a l l e l e sa t e a c h l o c u s( a si nF i g .2 T o po r Bo t t om ) ,a s w e l la s t h e f o u r d i s t r i b u t i o n sc o r r e s p o n d i n gt o t h ef o u rp o s s i b l eg e n o t y p e si n v o l v i n gt h ep a i r so f l o c i( e . g . ,F i g .2M i d d l e ) .C om p a r i s o no ft h ed i s t r i b u t i o n sr e v e a l sc a n d i d a t e sf o ri n t e r a c t i v ee f f e c t s .W i t ht h i sp r o g r a m ,i t was p o s s i b l et o m a k ev i s u a la n d q u a n t i t a t i v ec om p a r i s o n so f a n yg i v e nQTL t o c a .

2 0 0 o t h e r l o c iw i t h i n a c o u p l eo f h o u r s .We u s e d l i k e l i h o o dr a t i o s

( 1 1 )t o

s t a t i s t i c a l l yc o m p a r ea n

e p i s t a t i ca n d a n a d d i t i v em o d e l .L e t AB i n d i c a t ea g e n o t y p ew i t hN o i r 1 a t l o c u s1 a n dM i n s o ya t L o c u s2 ,e t c . ,a n d d e n o t et h e e s t i m a t e dmean b yJ L A B ,t h es a m p l emean b yAA B ,a n d t h es a m p l es i z eb yn A B .T h ee p i s t a t i cm o d e la s s um e s n o c o n s t r a i n t so n t h emeans a n d c om p u t e st h el o g a r i t h mo f o d d s( l o d )s c o r e

a s s o c i a t e dw i t h t h emax imum l i k e l i h o o de s t i m a t o r o f e a c hm e a n . T h e a d d i t i v em o d e la s s um e s - L A A+ I L B B= LAB + - L BAa n d c o m p u t e st h e l o ds c o r e a s s o c i a t e dw i t h t h emaximuml i k e l i h o o de s t i ma t or o ft h emeans s u b j e c tt o t h i sc o n s t r a i n t .T h e l o gl i k e l i h o o df u n c t i o n[ l o g ( L ) ] ,u p t o a n a d d i t i v ec o n -

s t a n t ,i n e a c h c a s e i s ( u n d e rt h ea s s u m p t i o nt h a tt h ed i s t r i b u -t i o n sa r e n o r m a la n d t h a tt h ev a r i a n c ei sg i v e nb yt h eu n c o r -r e c t e ds a m p l ev a r i a n c e s=C A B ,e t c . )a s f o l l o w s :

l o g ( L )=

- n A A ( - L A AAAA ) / 2 ' AA ,- n A B ( I A B- L A B ) 2 / 2 TA B ,- n BA ( I B A- I A B A ) 2 / 2 B A ,- n BB ( LBB- A L B B ) 2 / 2 ^ B B .

U n d e rt h ee p i s t a t i cm o d e l ,t h emax imuml i k e l i h o o de s t i m a t o r so f t h e means a r e t h e s a m p l em e a n s . U n d e rt h e a d d i t i v ec o n s t r a i n t ,t h emaximum l i k e l i h o o de s t i m a t o r sa r e a s f o l l o w s :

F ' A A= LA A- S CAA / C ,-A B = I f A B+ 8 C A B / C ,

IBA = A B A+ q C BA / C ,/ L B B= 1BB-- C B B / C ,w h e r eCA A = 0 ' A A / n AA ,e t c . ,c = CA A + CA B + CBA + CBB ,a n d8 = ( A A A+ AB B )- ( A A B+ I B A ) .r e p r e s e n t st h e" d e v i a t i o nf r o ma d d i t i v i t y . "

1 0 0

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( I ) MI N MI N

20 _- ' d - - F 1 ( - - )NO I R M I N

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g e n o t y p e sa t t h ep a i ro f RFLP l o c i ,2 1 4 H 1 0a n dA 3 9 7 .T h e g e n o t y pa r e n o t e di n t h ef i g u r e .Mean v a l u e so fh e i g h tf o rM i n s o y( M I N )( I )a n dN o i r 1 ( T) a l s oa r e i n d i c a t e d .S i m i l a rd i s t r i b u t i o n sw e r e o b t a i n e dw h e nt h el o c u sBLT29 o r A 1 0 9 awas s u b s t i t u t e df o rA 3 9 7 .T h e s el o c ia r e c l o s e l yl i n k e dt o A 3 9 7 .

T h e n u m b e r sr e p o r t e da s " l o d s c o r e s a g a i n s tt h ea d d i t i vm o d e l "s u b t r a c tt h e l o ds c o r e o ft h ea d d i t i v em o d e lf r o mt h a to f t h ee p i s t a t i cmo d e l .A s m a l ld i f f e r e n c ei n d i c a t e s t h a tt hed a t a c a n b e e f f e c t i v e l ye x p l a i n e db yt h ea d d i t i v em o d e l ,wh i l ea l a r g ed i f f e r e n c ei n d i c a t e s t h a tt h ed a t a a r e i n c o n s i s t e n tw i t ht h ea d d i t i v e c o n s t r a i n t .B e c a u s esome g e n o t y p e sa n d t r a i t sd on o t s a t i s f yt h en o rm a l i t ya n d v a r i a n c ea s s um p t i o n s ,we c o n -

d u c t e dM o n t eC a r l os i m u l a t i o n sb ys p l i t t i n gt h ed i s t r i b u t i o

r e p r e s e n t i n gt he e f f e c to ft h ef i r s tl o c u si n t of o u r

" g e n o t y pt o f i n dt h ep r o b a b i l i t yP ( l o d )o f e x c e e d i n gt he m e a s u r e dd i f -f e r e n c ei nl o d s co r e s b yc h a n c e .As a c h e c k ,we a l s oc a l c u l a t et he p r o b a b i l i t yP ( , )o fe x c e e d i n gt he m e a s u r e dd e v i a t i o nf r o m

Ta b l e 1 . QTL a f f e c t i n gh e i g h tQTL P>F R 2 Acm QTL P>F R 2 Acm

QG 1 7 3 t b * < 1 0 - 4 0 . 2 8 2 1 Q A 2 9 5 0 . 1 3 0 . 0 2 4 . 3Q A 3 6 3 b * < 1 0 - 4 0 . 1 3 1 6 Q B LT 5 3 1 0 . 7 9 < 0 . 0 1 0 . 7Q A 3 9 7 < 1 0 - 4 0 . 1 3 1 4 Q 2 1 4 H 1 0 0 . 7 2 < 0 . 0 1 1 . 9Q L 5 0 t 3 * < 1 0 - 4 0 . 1 1 1 3 QBLT4 0 . 4 4 0 . 0 1 3 . 1Q R 7 9 < 1 0 - 4 0 . 0 8 1 1 Q A 3 4 3 0 . 0 3 0 . 0 3 5 . 0Q A 6 0 2 x 1 0 - 4 0 . 0 8 1 1 Q L 5 0 d r l 3 0 . 2 6 0 . 0 1 0 . 6QBLT7 0 . 0 0 1 6 0 . 0 6 0 9 Q G 1 7 3 t a 0 . 3 9 < 0 . 0 1 1 . 0

QTL a r e l i n k e dt o t h eRFLP l o c if o rw h i c ht h e ya r e n a m e d .Acmwa s c a l c u l a t e da s t h ed i f f e r e n c ei nmean h e i g h t sb e t w e e np o p u l a t i o n sw i t hMi n s o y - d e r i v e da n dN o i r1 - d e r i v e da l l e l e sf o re a c hl o c u s .Va l u e so f P > F a n dR 2w e r e o b t a i n e df r o ma n a l y s i so fv a r i a n c e( 1 0 ) .* L i n k e dl o c i( s e eF i g .4 ) .

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g e n o t y p e sa t t h eRFLP l o c iG 1 7 3 T ba n dA 2 9 5 .H e i g h t so ft h ep a r e n t s ,M i n s o y( ) a n dN o i r 1 ( T) ,a r e i n d i c a t e d .

a d d i t i v i t y ,8 .To c o r r e c t f o rt h ef a c tt h a twe s e a r c h e dt h r o u g h3 2 l i n k a g eg r o u p so r 2 2 0 l o c i ,we t r a n s f o r m e dt h ep r o b a b i l i t yP t h a ta s i n g l et r i a le x c e e d e dt h eo b s e r v e dv a l u ei n t o1 - ( 1-

p ) 3 2o r 1 - ( 1 - p ) 2 2 0t o e s t i m a t es t a t i s t i c a ls i g n i f i c a n c e .

RESULTSI n t e r a c t i o n sA f fe c t i ng H e i g h t .Ta b l e1 l i s t sm a j o rQTL t h a t

d e t e r m i n eh e i g h t .On t h el e f ta r e l i s t e ds e v e n l o c il i n k e dt oQTL t h a tt o g e t h e ra c c o u n tf o rmos t o f t h ev a r i a t i o ni n t h e

s e g r e g a n t so b t a i n e df r o mt h i sc r o s s . On t he r i g h ta r e s e v e n l o c ia s s o c i a t e dw i t hQTL t h a ta l o n eh a v e no s i g n i f i c a n te f f e c to nh e i g h t .H o w e v e r ,a s d e s c r i b e db e l o w,e a c h o f t h e s eQTLr e g u l a t e st h ev a r i a t i o ne x p l a i n e db yt h ec o r r e s p o n d i n gl o c u sont h el e f t .Tw o e x am p l e sa r e p r e s e n t e di n d e t a i l .F i g .2 p r e s e n t s

c u m u l a t i v ed i s t r i b u t i o n ss h o w i n gt h ed e p e n d e n c eo f h e i g h to nt h ei n t e r a c t i o no f s p e c i f i cQTL a l l e l e sa t l o c il i n k e dt o RFLP

m a r k e r sA 3 9 7a n d2 1 4 H 1 0 .( H e n c e f o r t h ,we s h a l lr e f e rt o QTLb yt h enames o ft h eRFLP l o c it o w h i c ht h e ya r e l i n k e d - i . e .Q 2 1 4 H 1 0i s l i n k e dt o 2 1 4H 1 0 . )When a n a l y z e da s a s i n g l el o c u s ,Q A 3 9 7c l e a r l yc o n t r o l sv a r i a t i o ni nh e i g h t( Ta b l e1 a n dF i g .2To p ) .T h eN o i r1 a l l e l ei sa s s o c i a t e dw i t hs h o r tp l a n t s ,a n dt h eM i n s o y ,w i t h t a l lp l a n t s .I n c o n t r a s t ,t h e r ei s n o d e m o n -s t r a b l e e f f e c to f Q21 4H1 0 ,b e c a u s et h e d i s t r i b u t i o n so f h e i g h tf o rp o p u l a t i o n sw i t h t h eN o i r 1 a n d t h eM i n s o ya l l e l e sa t2 1 4 H 1 0n e a r l yc o i n c i d e( F i g .2B o t t om ) .H o w e v e r ,F i g .2 M i d d l es h o w st h a tt h ee f f e c to f Q A 3 9 7i sc o n d i t i o n a lu p o nQ 2 1 4 H 1 0 .P l a n t sw i t h t h eM i n s o ya l l e l ea t 2 1 4 H 1 0s h o wno s i g n i f i c av a r i a t i o ni nh e i g h ta s s o c i a t e dw i t hA 3 9 7 ,wh i l ep l a n t sw i t h t h eN o i r 1 a l l e l ea t 2 1 4 H1 0 s ho wa l a r g ev a r i a t i o n( a l s os ee Ta b l e2 ) .T h e r e f o r e ,v a r i a t i o ni nh e i g h td u e t o Q A 3 9 7i sc o n d i t i o n a

u p o nt h ep r e s e n c eo f a N o i r 1 a l l e l ea t Q 2 1 4H 1 0 .F i g .3 p r e s e n t sa n e x a m p l eo f a QTL i n w h i c ho n l yonee x t r e m eo f v a r i a t i o n( s h o r tp l a n t s )i s c o n d i t i o n e db yi n t e r a c -t i o nw i t h a n o t h e rl o c u s .C o n s i d e r e di n i s o l a t i o n ,Q A 2 9 5ha sl i t t l ee f f e c ton h e i g h ta n dw o u l db e d i s c a r d e di n a s c r e e n f o rQTL ( F i g .3 B o t t o ma n d Ta b l e 1 ) .I n c o n t r a s t ,Q G 1 7 3 T bc o n t r o l sa l a r g ef r a c t i o no f t h ev a r i a t i o ni n t h ep o p u l a t i o( Ta b l e1 a n dF i g .3To p ) .T h e c u m u l a t i v ed i s t r i b u t i o n si nF i g .3M i d d l es h o wt h a tt h eN o i r1 a l l e l eo f Q A 2 9 5i n t e r a c t sw i t ht h eM i n s o ya l l e l eo f Q G 1 7 3 T bt o p r o d u c ev e r ys h o r tp l a n t s ,b u t i tha s n o e f f e c ton t h eN o i r 1 a l l e l eo f Q G 1 7 3 T b( a n dt h e r e f o r eQ A 2 9 5ha s n o e f f e c ton t a l lp l a n t s ) .I n t h i si n t e r a c t i o n ,t h ea l l e l es p e c i f i c i t yi sg r e a t e rt h a n t h a ts h o w ni nF i g .2 b e c a u s eo n l yt h eM i n s o ya l l e l eo f Q G 1 7 3 T bi s a f f e c t e d .

Ta b l e2 s u mm a r i z e sd i f f e r e n ti n t e r a c t i o n st h a ta f f e c th e i g h t .T h emean h e i g h t sf o rt he g e n o t y p e sa r e l i s t e dt o g e t h e rw i t ht h el o go f t h el i k e l i h o o do f e x p l a i n i n gt h eo b s e r v a t i o n sw i t h a n

a d d i t i v emo d e l .I n e a c hc a s e t h e a d d i t i v em o d e li sr e j e c t e db ya s u b s t a n t i a ll o d s c o r e , a n d t h ed i f f e r e n c eb e t w e e nmeans f o ra l l e l e sa t t h ef i r s tl o c u sd e p e n d su p o nt h ea l l e l ea t t h es e c o n dl o c u s .F o re x am p l e ,i nt h ec a s e o fQL5 0 t 3a n dQBLT 4 ,AM( t h ed i f f e r e n c ew h e nBLT4 i sM i n s o y )i s o n l y1 c m , b u t A N( t h ed i f f e r e n c ew h e nBLT4 i s N o i r 1 ) i s 2 3 c m . I f t h ea l l e l e si n t e r a c t e da d d i t i v e l y ,t h e s etwo v a l u e sw o u l dc o i n c i d e .How-e v e r ,i n a l lb u t o n e c a s e , t he d i f f e r e n c e8 = A M- A N( t h ed e v i a t i o nf r o ma d d i t i v i t y )e x c e e d st h ev a l u e o fA i n Ta b l e 1( t h ee f f e c to f t h ef i r s tl o c u sa l o n e ) .

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L o c u s2 i sM i n s o y L o c u s2 i sN o i r 1P a i r so f l o c i

L o c u s1 L o c u s1 L o c u s1 L o c u s1L o c u s1 L o c u s2 M I N NO IR 1 AM M IN NOIR 1 A N S l o d P ( l o d )X 1 0 3 1 - ( 1 ) nG 1 7 3 t b A 2 9 5 6 8 8 4 1 6 5 4 8 6 3 2 1 6 6 . 8 0 . 8 0 . 1 1 0 . 0 2 * *A 3 6 3 b B LT 5 3 1 7 1 7 7 6 6 1 8 5 2 3 1 7 5 . 3 2 . 1 0 . 3 1- > 0 . 0 6 *A 3 9 7 2 1 4 H 1 0 7 5 7 1 4 8 6 6 2 2 4 2 0 8 . 1 0 . 1 0 . 0 2- 0 . 0 0 4 * * *L 5 0 t 3 BLT4 7 2 7 3 1 6 3 8 6 2 3 2 2 8 . 6 0 . 1 0 . 0 1- 0 . 0 0 2 * * *R 7 9 A 3 4 3 6 2 8 4 2 2 7 6 7 9 3 1 9 5 . 7 1 . 4 0 . 2 0 0 . 0 3 * *A60 L 5 0 d r l 3 6 5 8 3 1 8 7 2 7 5 3 1 5 4 . 9 1 . 9 0 . 3 4 0 . 0 5 8 *B LT 7 G 1 7 3 t a 6 3 8 1 1 8 7 4 7 4 0 1 8 5 . 4 0 . 9 0 . 2 9 - >0 . 0 5 *P a i r so f QTL a r e d e s i g n a t e db yt h eRFLP L o c i( 1a n d2 )t ow h i c ht h e ya r el i n k e d .T h e l o ds c o r e s( n a p e r i a nl o g a r i t h m s )a g a i n s tt h ea d d i t i v em o d e l

a r e p r e s e n t e d .T h ep r o b a b i l i t yo f o b t a i n i n gt h a tl o dv a l u e[ P ( I o d ) ]b yr a n d o mc h a n c ew a se s t i m a t e db ys i m u l a t i o n( s e eM a t e r i a l sa n dMe t h o d s ) .Th i sp r o b a b i l i t yw a sa d j u s t e di nt h ef a r - r i g h tc o l u m nf o rt h en u m b e ro f l o c io r l i n k a g eg r o u p ss e a r c h e d( l o c i-> l i n k a g e g r o u p s ) .A M ,D i f f e r e n c eb e t w e e np l a n t h e i g h tm e a n sw h e nl o c u s2 i sM i n s o y ;A N ,d i f f e r e n c ewhen l o c u s2 i sNo i r1 ;8 ,d e v i a t i o nf r o ma d d i t i v i t y( t h ea b s o l u t ev a l ue o ft h ed i f f e r e n c eb e t w e e nA Ma n dAN ) ;* * * ,v e r ys i g n i f i c a n t ;** ,s i g n i f i c a n t ;* ,ma r g i n a ls i g n i f i c a n c e .

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F I G .4 . I n t e r a c t i o n sb e t w e e np a i r so fu n l i n k e dl o c i .L o c i t h a tb yt h e m s e l v e ss h o wt r a i tv a r i a t i o n( o )a r e c o n n e c t e db ya r r ow s f r o ml o c it h a tr e g u l a t et h e m( O ) .T r a i t sa r e h e i g h t( - > ) ,y i e l d( - - - - - ) ,a n dma t u r i t y( = ) .L i n k a g eg r o u p s a r e n o t s p e c i f i e d( s e eM a t e r i a l sa n dMe t h o d s ) .

T h u s ,l a r g ed e v i a t i o n sf r o ma d d i t i v i t y( 8 )w e r e o b s e r v e df o ra l ls e v e n p a i r so f l o c ii nTa b l e2 .As d e s c r i b e di nM a t e r i a l sa n dM e t h o d s ,we u s e d M o n t eC a r l o s i m u l a t i o nt o e s t i m a t et hep r o b a b i l i t i e so f o b t a i n i n gt h e " l o d " v a l u e ss h o w na n d t o

e s t i m a t et he d e v i a t i o n sf r o ma d d i t i v i t y( 8 )s h o w n .T h e s ev a l u e sP ( l o d )a n dP ( s )w e r e v e r ys i m i l a r( a lm o s ti d e n t i c a l )i na l lb u t o n ec a s e [ B LT 7 ,i nw h i c hP ( 6 )was 1 / 1 0o f P ( o d ) ] .T h e s o m e w h a tmore c o n s e r v a t i v ev a l u e so fP ( 1 o d )a r e p r e s e n t e di nTa b l e2 .F o rf o u r o f t h ep a i r s( * * *a n d* * ) ,t h ed e v i a t i o nf r o ma d d i t i v i t yi ss t a t i s t i c a l l ys i g n i f i c a n t .T h ed e v i a t i o no ft h er e m a i n i n gt h r e ei sm a r g i n a l .Te s t s o ft h e s ei na new p o p u l a t i o ns h o u l dc o n f i r mo rr e f u t e t h e i rs i g n i f i c a n c e .T h e r e l a t i o n s h i p sb e t w e e nf i v eo ft h e s es e v e n m a j o rh e i g h tl o c ia n d t h eQTL t h a tr e g u l a t et h e i ra c t i o na r e s h o w ni n F i g .4 . ( F o rs i m p l i c i t y ,t h ei n t e r a c t i o n si n v o l v i n gt h el e s si m p o r t a n tl o c i ,Q A 6 0a n dQBLT 7 ,h a v eb e e no m i t t e d ) .T h r e eo f t h eQT L - Q L 5 0 t 3 ,Q G 1 7 3 t b ,a n dQ A 3 6 3 b - a r ei n

o n e l i n k a g eg r o u p . E a c h o f t h e s ei n t e r a c t sw i t h a d i f f e r e n tQTL l i n k e dt o BLT4 ,A 2 9 5 ,o r B LT 5 3 1 ,r e s p e c t i v e l y .T h ei n t e r a c t i o n sa r e q u i t es p e c i f i c( d a t an o t s h ow n ) .T h u s ,QL 5 0 t 3

i s c o n d i t i o n a lo n QBLT4 b u t i s n o t a f f e c t e db yQ A 2 9 5o rQBLT 5 3 1 ,Q G 1 7 3 T bi s c o n d i t i o n a lon Q A 2 9 5b u t i s n o ta f f e c t e db yQ B LT 4o r QBLT 5 3 1 ,e t c .B e c a u s et h e s et h r e el i n k e dQTLi n t e r a c tw i t hd i f f e r e n tl o c i ,t h e yr e p r e s e n t s e pa n d d i s t i n c tQTL c o n t r o l l i n gh e i g h t .D i f f e r e n t i a t i n gT r a i t s L i n k e dt o a S i n g l eRFLP. I n t e r a c t i o

a l s oc a n d i s t i n g u i s hb e t w e e ne f f e c t son d i f f e r e n tt r a i t so f w h a tm i g h th a v e b e e nr e g a r d e da s a s i n g l eQTL on t he b a s i so f i t sl i n k a g et o a s i n g l eRFLP. I n F i g .4 ,t h el i n k e dRFLP l o c iA 3 9 7a n dBLT29 a r e l i n k e dt o o n e ( o rp o s s i b l ymo r e )QTLf o rh e i g h( P > F , < 0 . 0 0 0 1 ) .T h e s e l o c ia l s oa r e l i n k e dt o QTL f o rma t u r i t y( P> F ,< 0 . 0 0 0 1 )a n dy i e l d( P> F ,= 0 . 0 0 1 ) .A s i m p le x p l a n a t i o nw o u l db e t o a s s u m e t h a tp l a n t st h a tmatu r e l a t ew i l lb e t a l la n d b e a r more s e e d .T h a t i s ,t h a ta s i n g l eg e n e tc h a n g eha s p l e i o t r o p i ce f f e c t s .How e v e r ,i n t e r a c t i o n s o c c u r b e t w e e nQBLT29 a n d

Q B LT 5 3 1t h a ta f f e c ty i e l db u t n o t ma t u r i t yo r h e i g h t( F i g .4a n d Ta b l e 3 ) .Th i s e f f e c ti s l a r g e( 8= 3 9 3k g / h e c t a r e )a n ds t a t i s t i c a l l ys i g n i f i c a n t( P ( l o d )= 5 . 3X 1 0 - 4 ) .T h e a b s e n c e o fa ne f f e c to f Q B LT 5 3 1o n ma t u r i t yo r h e i g h ti n d i c a t e st h a tas e p a r a t eg e n emay e x i s tw h i c ho n l yr e g u l a t e sy i e l d .D i f f e r e ng e n e t i ci n t e r a c t i o n sc a n t h u ss e r v e t o d i s t i n g u i s hb e t w e e nd i f f e r e n t ,c l o s e l yl i n k e d ,QTL .

DISCUSS ION

T h e i n t e r a c t i o n sd e s c r i b e di nF i g s .2 , 3 ,a n d4 a n d i nTa b l e s1 ,2 , a n d 3 w e r e c h o s e nb e c a u s et h e yi n v o l v e do n e l o c u st h a tc o n t r o l l e ds i g n i f i c a n tt r a i tv a r i a t i o n( e . g . ,t h ed a t a i n t h el e f tc o l u m n so f Ta b l e1 )a n d a s e c o n dl o c u s t h a tb yi t s e l fh a d no

d e m o n s t r a b l ee f f e c to n t h et r a i t( e . g . ,t h el o c ii nt h er i g h th a n dc o l u m n so fTa b l e 1 ) .T h u s ,t h ei n t e r a c t i v ee f f e c t st h a tw e r e

o b s e r v e dc o u l dn o t b e d u e t o i n d e p e n d e n ta n da d d i t i v ee f f e c ta c o n c l u s i o nb o r no u t b yt h emaximum l i k e l i h o o dr e j e c t i oo fa n a d d i t i v emo d e l .An u n e x p e c t e dr e s u l tw a s t h a ta l a r g en u m b e ro f i n t e r a c t i o n swere f o u n d a n d t h a te a c h o f t h e s ec o n t r o l l e da l a r g eamoun t o f v a r i a t i o n( Ta b l e2 ) .C l e a r l ys u c h

e p i s t a t i ce f f e c t sa r e

q u i t es i g n i f i c a n t .F i g .4 s u m m a r i z e smos t o f t h ei n t e r a c t i o n st h a twe h a v ed e s c r i b e d( A 6 0w i t h L 5 0 d r l 3a n d BLT7 w i t h G 1 7 3 T aa r eo m i t t e d ) .T h ed a t a on h e i g h ts h o ws i g n i f i c a n t ,l a r g ee f f e c t sd u et o i n t e r a c t i o n si n v o l v i n gd i f f e r e n tp a i r so f l o c i ,w h i c ha c c o u n tf o rmos t o ft h ev a r i a t i o ni nh e i g h ts e g r e g a t i n gi n t h i sc r o s s .I n t e r a c t i o n sb e t w e e nQTL i m p l i c a t et h e a c t i o no f s e v e r a

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t h a ta s i n g l eQTL l i n k e dt o BLT29 e x e r t sm u l t i p l ee f f e c t so nm a t u r i t y ,h e i g h t ,a n dy i e l d .I t i so fc o u r s ea l w a y sp o s s i b l et h a ta s i n g l el o c u si n t e r a c t sw i t h a n u m b e ro f d i f f e r e n tQTL t op r o d u c et h e s ee f f e c t s .H o w e v e r ,i t i s d i f f i c u l tt o i m a g i n eas i n g l eg e n ep r o d u c tw i t h t h e s ec a p a b i l i t i e s . )E v o l u t i o n a r yI m p l i c a t i o n s .A l l o f t h ei n t e r a c t i o n st h a twe

h a v er e p o r t e do c c u rb e t w e e nl o c io n d i f f e r e n tl i n k a g eg r o u p s .S o y b e a ni s a n o b l i g a t ei n b r e e d i n gp l a n t .I n s uc h a no r g a n i s m ,p a i r so fa l l e l e ss e l e c t e da t i n t e r a c t i n gl o c ib e l o n g i n gt od i f f e r -e n t l i n k a g eg r o u p sc a n b e m a i n t a i n e d .I no u t c r o s s i n gp l a n t s ,w ee x p e c ti n t e r a c t i n gl o c ie i t h e rt o e x e r tl e s so f a n e f f e c to r t ob e l i n k e d ,t h el i n k a g ed i s t a n c er e f l e c t i n gt h ed e g r e et ow h i c hs e l e c t i o nf a v o r si n t e r a c t i o n sb e t w e e nd i f f e r e n ta l l e l e s .We h a v e s e e n t h a tc o m b i n a t i o n so f p a i r so f l o c ic a n e x e r t

l a r g ee f f e c t so n q u a n t i t a t i v ep h e n o t y p e s .I t i s t e m p t i n gt os p e c u l a t ea b o u t t h er o l eo f s u c h i n t e r a c t i o n si n i n b r e e d i n gp l a n t s .I f i n t e r a c t i o n sa l s ow e r ec o n d i t i o n e db ye n v i r o n m e n t a ls i g n a l s ,s u c h l o c iw o u l dp r o v i d et h ep l a n tw i t h a l a r g ea m o u n to f f l e x i b i l i t yi nr e s p o n s et oe n v i r o n m e n t a lc h a n g e .Th i s t y p eo ff l e x i b i l i t yc o u l d s u b s t i t u t ef o r t h ef l e x i b i l i t yc o n f e r r e do no u t c r o s s i n gp l a n t sb yh e t e r o s i s .F u t u r es t u d i e so f t h er e s p o n s eo fs p e c i f i cg e n o t y p e st o e n v i r o n m e n t a ls t r e s ss h o u l de s t a b l i s hw h e t h e ri n t e r a c t i n gl o c ip l a ys u c h a r o l e .I m p l i c a t i o n sf o rP l a n tB r e e d i n g .A l t h o u g ht h e r e s u l t sd e -

s c r i b e dh e r e w e r eo b t a i n e d w i t hs o y b e a n ,i t s e e m sl i k e l yt h a to the r i n b re dc r o p s ,s u c h a s r i ceo r w h e a t ,ma ys h o ws i m i l a re p i s t a t i ce f f e c t s .B r i m ( 1 2 )n o t e d t h a td i f f e r e n tb r e e d i n gs t r a t e g i e sa r er e q u i r e dw h e nd e a l i n gw i t h e p i s t a t i cQTL .O u rr e s u l t se m p h a s i z et h i s ,e s p e c i a l l yf o rs t r a t e g i e su s i n gm a r k e r -d i r e c t e ds e l e c t i o n .C l e a r l yt h ep h e n o t y p e so f o f f s p r i n gw i l lb es t r o n g l yi n f l u e n c e db yt h eg e n e t i cb a c k g r o u n di n t ow h i c ha n yt r a i ti sb e i n gm o v e d .F o r e x am p l e ,a n a t t e m p tt o t r a n s f e rt h eQTL f o rh e i g h t ,l i n k e dt o A 3 9 7( F i g .2 ) ,c o u l d r e s u l ti n n oc h a n g ei n p h e n o t y p ew i t ho u t s i mu l t an e o ust r a n s f e ro f t h ea p p r o p r i a t ea l l e l eo f t h e u n l i n k e dQTL a s s o c i a t e dw i t h2 1 4 H 1 0 .

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w e i g h t ,y i e l d ,l o d g i n g ,e t c . )w i l lb e p u b l i s h e dl a t e r .H o w e v e rp r e l im i n a r ya n a l y s e si n d i c a t et h a tt h en u m b e ra n d e x t e n to ft h e s ei n t e r a c t i o n sa r e s i m i l a rt o t h o s e s e e nw i t hp l a n th e i g h t .T h e s es u b s t a n t i a lc o n t r i b u t i o n st ot r a i tv a l u e ss u g g e s tt h a tw i t hs e l e c t i o no f a p p r o p r i a t eRI g e n o t y p e s ,f u r t h e rg e n e t i cc r o s s e sc a n i n c r e a s eo r d e c r e a s et r a i tv a l u e st oe x t r e m e smuch g r e a t e rt h a n t h o s ef o u n d i n t h i sp o p u l a t i o n .B r e e d e r si n t e r e s t e di nd i s s e c t i n gc o m p l e xp h e n o t y p e ss u c ha sy i e l d ,s e e dp r o t e i n ,e t c . ,

ma yn e e dt oe s t a b l i s ha n da n a l y z ea n u m b e ro f RI p o p u l a t i o nb o t h t od e t e r m i n ee p i s t a s i sa n dt op r o v i d eu s e f u lg e n o t y p e st os e r v ea sb r e e d i n gs t o c k .O u rr e s u l t sf o ry i e l d( Ta b l e3 )s u g g e s tt h a tt h e e s t ab l i s hme n t o f s u c hp o p u l a t i o n sc o u l d b e v e r yv a l u a b l e .

Th i sw o r kw a ss u p p o r t e db yg r a n t sf r o mt h eN a t i o n a lI n s t i t u t e so fH e a l t h( G M4 2 3 3 7 ) ,f r o m t h eA m e r i c a nS o y b e a nA s s o c i a t i o n ,a n df r o mt h eM i n n e s o t aS o y b e a nR e s e a r c ha n d P r o m o t i o nC o u n c i l .

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Ta n k s l e y,S .D . ( 1 9 9 3 )A n n u .R e v .G e n e t .2 7 ,2 0 5 - 2 3 3 .Du d l e y ,J .W . ( 1 9 9 3 )C r o pS c i .3 3 ,6 6 0 - 6 6 8 .B u r r ,B . ,B u r r ,F. A . ,T h o m p s o n ,K. H . ,A l b e r t s o n ,M .C . &S t u b e r ,C .W. ( 1 9 8 8 )G e n e t i c s11 8 ,5 1 9 - 5 2 6 .C a r r i l l o ,J .M . , R ou s s e t ,M . ,Qu a l s e t ,C .0 . & K a s a r d a ,D . D .

( 1 9 9 0 )T h e o r .Ap p l .G e n e t .7 9 ,3 2 1 - 3 3 0 .M a n s u r ,L .M . , L a rk ,K. G . & O r f ,J . ( 1 9 9 3 )T h e o r .Ap p l .G e n e t .8 6 ,9 1 4 - 9 1 8 .M a n s u r ,L .M . ,L a r k ,K. G . ,K r o s s ,H . & O l i v e i r a ,A . ( 1 9 9 3 )T h e o r .Ap p l .G e n e t .8 6 ,9 0 7 - 9 1 3 .M a n s u r ,M . & O r f ,J . ( 1 9 9 4 )C r o pS c i . ,i np r e s s .L a r k ,K . ,We i s s e m a n n ,J .M . ,M a t h e w s ,B .F . ,P a l m e r ,R . ,C h a s e ,K. & M a c a l m a ,T . ( 1 9 9 3 )T h e o r .Ap p l .G e n e t .8 6 ,9 0 1 - 9 0 6 .L i n c o l n ,S .E . & L a n d e r ,S .L . ( 1 9 9 3 )MA PM A K E R / E X3 . 0a n dMA PM A K E R / Q T L1 . 1( W h i t e h e a dI n s t .o f M e d .R e s . Te c h . Re p . ,C am b r i d g e ,MA ) .SAS I n s t i t u t e( 1 9 8 8 )SAS P r o c e d u r e sG u i d eR e l e a s e6 . 0 3( S A SI n s t .I n c . ,G a r y ,NC ) .B i c k e l ,P .J . & D o k s o n ,K . A . ( 1 9 7 7 )Ma t h e m a t i c a lS t a t i s t i c s( H o l d e nD a y ,O a k l a n d ,CA ) .B r i m ,C .A . ( 1 9 7 3 )i n S o y b e a n s :I m p r o v e m e n t ,P r o d u c t i o na n d

Us e s ,e d .C a l d w e l l ,B .E . ( A m .S o c .Ag r o n . ,M a d i s o n ,W I ) .

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