AN INHERITANCE STUDY OF CORN MATURITY By CHAMP M. JONES A THESIS Subm itted to the S ch ool of G raduate S tu d ies of M ich igan State C o lle g e of A g r ic u ltu r e and A pplied S c ie n c e in p a r tia l fu lfillm e n t of the r e q u ir e m e n ts fo r the d e g r e e of DOCTOR OF PHILOSOPHY D ep artm en t o f F a r m 1952 C rop s AN INHERITANCE STUDY OF CORN MATURITY By Champ M9- J o n e s AN ABSTRACT Sub m itted to the S ch o o l of G raduate S tu d ie s of M ich igan State C o lle g e o f A g r ic u ltu r e and A pplied S c ie n c e in p a r tia l fu lfillm e n t of the r e q u ir e m e n ts fo r the d e g r e e of DOCTOR OF PHILOSOPHY D ep a rtm en t of F a r m Y ear 1952 C rop s CHAMP M. JO NES ABSTRACT The in h e r ita n c e of m a tu r ity and e a r w e ig h t w e r e i n v e s t i ­ gated w ith s ix d iffe r e n t c r o s s e s c o rn . of e a r ly X la te in b red lin e s of D om in an ce r e la tio n s h ip s , gene n u m b e r s, n atu re of gen e a c tio n , and h e r ita b ility w e r e stu d ied . S ilk in g d ate, m o is t u r e c o n ­ ten t of e a r s h a r v e s te d at a u n iform p erio d fr o m tim e of p lan tin g, and e a r m o is tu r e con ten t fifty d a ys a fte r silk in g , w e r e u sed a s m e a s u r e s of m a tu r ity . D ata on e a r w eig h t w e r e ob tain ed a t two h a r v e s t p e r io d s . In e a c h c r o s s , e ith e r c o m p le te phenotypic d o m in an ce or s lig h t h e t e r o s is fo r e a r l in e s s w a s in d ic a te d in a ll m a tu r ity s tu d ie s . Som e d e g r e e of h e t e r o s is fo r e a r lin e s s w a s p rob ab ly in v o lv e d in e a c h c r o s s ; h o w e v e r , the m a jo r p o rtio n of the o b s e r v e d e a r li n e s s a p p ea red to be due to d om in an ce of g e n e s fo r e a r lin e s s . C om p lete g e n ic d om in an ce fo r e a r ly s ilk in g , p a r tia l to c o m ­ p le te g e n ic d om in an ce for lo w e r e a r m o is tu r e at a u n iform h a r v e s t p e r io d fr o m p lan tin g , and v a r ia tio n s fr o m none to c o m p le te g en ic d om in an ce fo r lo w e r e a r m o is tu r e fifty d ays a fte r s ilk in g w e r e i n ­ d ica te d fo r the c r o s s e s . The data s u g g e s t that the c la s s if ic a t io n of in b red lin e s e n t ir e ly on the b a s is of s ilk in g date m a y not fu r n ish the d e s ir e d in fo r m a tio n on m a tu r a tio n . 2 CH AM P M . JO NES ABSTRACT E p is t a s is fo r e a r lin e s s ap p eared to be ex h ib ited by the dom inant g e n e s con trib u ted by the e a r ly in b red R53 and p o s s ib ly by A 158. In b red s containing dom inant e p is ta tic g e n e s fo r e a r l i ­ n e s s should p ro vid e m o r e u n ifo rm ity of m a tu r ity in a double c r o s s of the type (E j X L^) (E^ X L>^) than e a r ly in b r e d s with dom inant but n o n e p ista tic g e n e s fo r e a r lin e s s . E p is t a s is of dom inant g e n e s m a y aid in exp lain in g r e p o r ts that c r o s s e s o f the type (E . A the X L. ) X (E to type ^ £ X L ) w e r e no m o r e v a r ia b le than that of X E 2 ) X (1^ £ X L 2 ). In the m a tu r ity s tu d ie s , it could not be con clu d ed w hether gen e a c tio n w a s fo llo w in g e ith e r the a r ith m e tic o r the g e o m e tr ic sch em es. In a ll c a s e s w h ere ca lc u la te d m e a n s d iffe r e d fr o m the a ctu a l m e a n s , the g e o m e tr ic m e a n s w e re c lo s e r to a g r e e m e n t w ith the ob tain ed . M inim um gen e n u m b ers ranged f r o m 5 to 19 fo r silk in g data, 2 to 11 fo r m o is tu r e con ten t of e a r s h a r v e ste d at a un iform p e rio d fr o m planting, and fro m 1 to 54 fo r m o is tu r e con ten t of e a r s h a r v e s te d fifty d ays a fte r silk in g . M axim um h e r ita b ility v a lu e s ranged fro m p er cen t fo r silk in g d ate, 36 p er cen t to 58 11p er cen t to 48 p er c en t fo r m o is tu r e 3 CHAMP M. JO NES ABSTRACT co n ten t of e a r s h a r v e s te d at a u n ifo rm p er io d fr o m p lan tin g, and 22 p er cen t to 83 p er c e n t fo r m o is tu r e fifty d a y s a fte r s ilk in g . content of e a r s h a r v e ste d H e r it a b ilit ie s of e a r m o is tu r e content a v e r a g e d h ig h e r than h e r ita b ility of silk in g d ate. C o n sid e r a b le h e t e r o s is w a s ex h ib ited fo r h e a v ie r e a r w eig h t in a ll c r o s s e s . Of the e a r ly in b r e d s , R53 w as e x c e p tio n a l in it s co n tr ib u tio n o f fa v o r a b le g e n e s fo r h e a v ie r e a r w eig h t. G en e s a f ­ fe c tin g e a r w e ig h t fo llo w e d the a r ith m e tic s c h e m e . M axim u m h e r ita b ility v a lu e s c a lc u la te d fo r e a r w eig h t in ­ d ic a te d that v e r y l it t le , if any, p r o g r e s s could be e x p ec ted from s e le c t io n fo r h e a v y e a r s w ith in the se g r e g a tin g p r o g e n ie s of any of the c r o s s e s at the u n iform h a r v e s t p e r io d . p rogress could be e x p e c ted fr o m tion o f the c r o s s e s W23) in the c a s e H o w ev er, good s e le c t io n w ithin the genera­ (M S206 X O h40B), (R53 X W23) and (A158 X of a h a r v e s t fifty d ays a fte r silk in g . It w a s p r o p o se d that an F j com b in ation of e a r ly lin e s c o n ­ taining dom inant e p is t a s t ic g e n e s w ith la te lin e s p o s s e s s in g e x c e p ­ tio n a l com b in in g a b ility fo r y ie ld m a y be m ade a s fo llo w s: ( ( E j X L j ) E j ) X « E 2 X L 2 ) E 2 ). ACKNOW LEDGM ENTS The w r ite r w is h e s to e x p r e s s h is s in c e r e thanks to D r. E . C. R o ssm a n fo r h elp fu l s u g g e s tio n s during the c o u r s e of th is in v e stig a tio n and in the p r e p a r a tio n of the m a n u sc r ip t. He a ls o i s in d eb ted to h is w ife, A lm a B r o o k s, for m uch a s s is t a n c e throughout the p r o b le m . The w r ite r d e e p ly a p p r e c ia te s the fin a n c ia l su p p ort of the M ichigan C e r tifie d H ybrid S eed Corn P r o d u c e r s A s s o c ia tio n w hich m ade it p o s s ib le fo r h im to c o m p le te th is in v e s tig a tio n . TABLE OF CONTENTS Page INTRODUCTION REVIEW O F . . LITERATURE 5 MATERIALS AND METHODS EXPERIMENTAL Days from R E S U L T S ON Planting Dominance Nature Gene 1 14 CORNM ATURITY 22 to Silking 22 relationships of g e n e number ' 22 action and 37 heritability 40 M o i s t u r e C o n t e n t of E a r s H a r v e s t e d a t a U n i f o r m P e r i o d f r o m D a t e ot P l a n t i n g • Dommaiu e Nature Gene relationships of g e n e number 43 ac t i o n and 44 . . 5h heritability . bO M o i s t u r e C o n t e n t of E a r s H a r v e s t e d F i f t y D a y s f r o m t h e D a t e o f S i l k i n g ................................... Dominance Nature Gene relationships of g e n e number b3 b4 ac t i o n and heritability 79 . . . . . . . . 82 iv Page EXPERIMENTAL Weight Period RESULTS ....................... 85 of E a r s H a r v e s t e d a t a U n i f o r m f r o m D a t e of P l a n t i n g ......................................................... 85 Dominance Nature Gene ON relationships of g e n e number Nature Gene WEIGHT . . . . . . . . action and Fifty number a c t i o n ....................... and 96 Days relationships of g e n e 86 93 h e r i t a b i l i t y ................... W e i g h t of E a r s H a r v e s t e d f r o m t he D a t e of S i l k i n g D iminance EAR h e r i t a b i l i t y ................................................. 98 98 105 108 I > 1 S C S S I O N ..................................................................................................................... Ill S U M h A R Y ......................................................................................................................... 120 LITERATURE 124 CITED ........................................................................................... IN T R O D U C T IO N C orn h y b r id s adapted to M ich ig a n and oth er n o r th er n a r e a s m us yit fa be r e la t iv e ly e a r ly in m a tu r ity in a d d ition to p o s s e s s in g h ig h ling a b ility and o th e r d e s ir a b le a g r o n o m ic c h a r a c t e r s . >rable c o n d itio n s th e r e a p p e a r s to be a g e n e r a l p o s itiv e U nder cor* r> nation b etw een the la t e n e s s o f c o r n v a r ie t ie s and y ie ld in g a b ility (11, 27, 33). S tr in g fie ld e t a l. (33), fro m a stu d y of the r e la tio n b etw een silk in g date and g r a in y ie ld s in fo u r te en c o u n tie s of n o r th ­ ern Ohio, show ed that a f u ll- s e a s o n co r n hybrid that s ilk s th r e e days la te r than an e a r li e r hybrid w ill y ie ld on the a v e r a g e 6 b u sh e ls m ore per a c r e . R e s u lts fr o m hyb rid c o r n t r ia ls in M ich igan show c o n c lu s iv e ly that so m e e a r ly -m a tu r in g h y b rid s a r e cap ab le of y ie ld in g a s m u ch o r m o r e c o r n p er a c r e than h y b rid s m uch la te r in m a tu r ity . L a te -m a tu r in g h y b rid s m a y not h av e s u ffic ie n t tim e to re a ch fu ll m a tu r ity b e fo r e k illin g f r o s t . R ather and M a rsto n (27) r e ­ p o rted the l o s s in y ie ld that m a y take p la c e due to the c e s s a t io n in d e v e lo p m e n t b e fo r e m a tu r ity . A y ie ld l o s s o f 12 b u s h e ls p e r a c r e o c c u r r e d w hen a la te hyb rid w a s h a r v e s te d at 50 p er cent e a r m o is tu r e co m p a red to h a r v e s t a t 40 p e r cen t m o is t u r e . An a v e r a g e l o s s of 0.75 b u sh e ls p e r a c r e p rem a tu re h a r v e s t. r e su lte d fro m e a c h day of T h ere a r e oth er im p o rta n t ad v a n ta g es in fa v o r of e a r ly -m a tu r in g h y b rid s. L o w er m o is tu r e content of e a r ly h y ­ b rid s at h a r v e s t p e r m its s a fe r sto r a g e and, in turn, p r o v id e s b e t­ te r quality fe e d and l e s s l o s s fr o m s p o ila g e . E a r ly h y b rid s m a y be h a r v e ste d e a r lie r in the fa ll, when w ea th er co n d itio n s a r e m o r e favorab le and the l o s s e s due to sta lk b reak age and dropped e a r s m ay be lo w e r . In d e term in in g the r e la tiv e m a tu r ity of co rn h y b r id s, s e v ­ e r a l d iffe r en t m e a s u r e s have b een em p loyed . Som e a r e b a sed on e x te r n a l a p p e a r a n c e s, su ch a s date of s ilk in g , date of t a s s e lin g , denting or g la z in g of k e r n e ls , or brow ning of the plant. a r e based on in te r n a l m e a s u r e m e n ts , O th ers such a s. the m o is tu r e c o n ­ tent of the e a r or the tr a n slo c a tio n of dry m a tte r to the g r a in . The point at w hich the m a x im u m am ount of dry m a tte r i s a c ­ cum ulated in the gra in a p p e a rs to be the b e s t m e a s u r e o f c o m ­ p lete m a tu rity ; h o w ev er, it i s m o r e d iffic u lt to d e te r m in e . S tu d ies on the in h e r ita n c e o f quan titative c h a r a c te r s p r e ­ se n t s e v e r a l d iffic u ltie s a s a r e s u lt of the m any g e n e s in v o lv ed , the s m a ll e ffe c t of ea ch g en e, and the in flu en ce of en v iron m en t on the d iffe r e n t g en o ty p e s. T h ere a r e p r o b le m s of c la s s if ic a t io n 3 and m e a s u r e m e n t, and it m a y be d iffic u lt to se p a r a te the v a r ia ­ b ility due to e n v ir o n m e n t fr o m that w h ich i s fe r en ce s. due to g e n e tic d if­ Som e q u a n tita tiv e c h a r a c te r s in c o r n - - s u c h a s e a r length, e a r w idth, e a r d ia m e te r , plant h eig h t, and y ie ld - - h a v e c e iv e d c o n s id e r a b ly m o r e study than o t h e r s . T here i s re­ r e la t iv e ly little in fo r m a tio n on in h e r ita n c e of c o r n m a tu r ity , and . th e r e fo r e , m o r e in fo r m a tio n w ould be h elp fu l to the p lan t b r e e d e r who i s r e s p o n s ib le fo r a lte r in g it. A know ledge of the n atu re of a c tio n and the n u m b er of g e n e s c o n tr o llin g the e x p r e s s io n of q u a n tita tiv e c h a r a c te r s i s value to the plant b r e e d e r . T h ey in d ic a te to so m e of e x te n t the p o s s ib ilit ie s fo r im p r o v e m e n t and aid in the planning o f future b reed in g p r o g r a m s . of co rn y ie ld , m eth od In m aking d o u b le - c r o s s hyb rid p r e d ic tio n s "B" of J en k in s (13) i s b a sed upon the a s ­ sum ption of a r ith m e tic gen e a c tio n . A s the n u m ber of g e n e s d e ­ te rm in in g a plant c h a r a c te r b e c o m e s g r e a t e r , th e r e i s l e s s chance of obtaining the d e s ir e d g e n e s in a s in g le plant, and s e le c tio n m u st be p r a c tic e d fr o m la r g e r p o p u la tio n s. In form a tion on the h e r ita b ility of a c h a r a c te r i s im p o rta n t to the plant b r e e d e r b e c a u se i t in d ic a te s the p o s s ib ility and e x ­ ten t to w hich im p r o v e m e n t i s p o s s ib le through s e le c t io n . W right 4 (39) d efin ed th r e e ty p e s of h e r e d ita r y o r g e n e tic v a r ia n c e : (1) a d d itiv e g e n e tic v a r ia n c e , (2) v a r ia n c e due to d om in an ce d e v ia tio n fr o m the a d d itiv e s c h e m e , and (3) v a r ia n c e due to d e v ia tio n s fr o m the ad d itiv e sc h e m e gen es. r e s u ltin g fr o m the in te r a c tio n of n o n a lle lic The a d d itiv e p o rtio n of the g e n e tic v a r ia n c e r e f le c t s the d e g r e e to w h ich the p ro g en y a r e lik e ly to r e s e m b le the p a r e n ts . H e r ita b ility d e n o te s the a d d itiv e g e n e tic v a r ia n c e in p e r c e n t of the to ta l v a r ia n c e . The p u r p o se s of the p r e s e n t study w e r e to obtain in fo r m a ­ tion on dom in an ce r e la tio n s h ip s , natu re of g en e a c tio n , gen e n u m ­ b er, and h e r ita b ility fr o m s ix d iffe r e n t c r o s s e s o f e a r ly X la te in b red lin e s of co rn by a stu d y of silk in g d ate, m o is tu r e and e a r w eig h t. A study w a s m a d e o f e a r m o is tu r e co n ten t and w eig h t fo r two d iffe r e n t s y s t e m s o f h a r v e s tin g . t content, REVIEW OF LITERA TUR E The lite r a tu r e a v a ila b le on d om in a n ce r e la tio n s fo r c o rn m a tu r ity i s not in c lo s e a g r e e m e n t. In a stu d y of m any q u a n ti­ ta tiv e c h a r a c te r s in corn , E m e r s o n and E a s t (7) c r o s s e d two v a r ie t ie s of c o r n d ifie r in g in m a tu r y (T om Thumb pop X M is s o u r i Dent) and found that the p la n ts w e r e d is tin c tly in te r m e d ia te in tim e of a n th e s is and in tim e of rip en in g of the e a r s . The h a r d ­ n e s s of the g ra in and brow ning of the husk w e r e u se d a s m e a s ­ u r e s of e a r m a tu r ity . The F in te r v a l b etw een the p a r e n ts . g e n e r a tio n m o r e than f ille d the E ck h a r t and B ryan (6) in d ic a te d that, in c r o s s e s b etw een e a r ly and la te in b red lin e s of co rn , e a r lin e s s w a s u su a lly dom inant. In fou r c r o s s e s o f m a iz e in b r e d s, L in d stro m (16) found that the F m e a n w a s s ig n ific a n tly la te r than the F^ m e a n and ex p la in e d the r e s u lt s on the h y p o th e sis o f d o m ­ in a n ce in g e n e s fo r fe w e r d a ys to flo w e r in g . F r e e m a n (8) u se d r e c ip r o c a l t r a n s lo c a tio n s lin k ed w ith r e c e s s i v e e n d o sp er m g e n e s in a ttem p tin g to lo c a te g e n e s a ffe c tin g s ilk in g date and found no e v id e n ce that w ould in d ic a te d om in an ce of e a r lin e s s e x c e p t in one cro ss. Yang (40) c r o s s e d two in b red lin e s o f c o rn that w e r e a p ­ p r o x im a te ly eq u al in m a tu r ity and obtained an F^ g e n e r a tio n that b w as m u ch e a r lie r in s ilk in g date than the p a r e n ts . It w a s c o n ­ cluded that h e t e r o s is w a s in v o lv ed and that d o m in an ce of a l l e l o ­ m o rp h s w a s in d ic a te d . In studyin g the t im e - r e la t io n s h ip s in t a s s e l d e v e lo p m e n t of in b red and h yb rid co r n , L>eng (15) d iv id ed the p erio d fr o m p la n t­ ing to an the s i s into two p e r io d s : (1) the p e r io d during w h ich the v e g e ta tiv e s tr u c t u r e s a r e being in itia te d up to the e lo n g a tio n of the grow ing poin t and (2) the p e rio d fr o m to a n th e s is . elo n g a tio n of the t a s s e l B y co m p a rin g the d e v e lo p m e n ta l tim e p a tte r n s of th ree F j h y b rid s and th e ir p a r e n ta l in b r e d s , a g e n e r a l a c c e l e r a ­ tion of d ev e lo p m e n t a s a r e s u lt of h e t e r o s is w a s n oted . The m e a n length of the p e r io d b etw een planting and t a s s e l in itia tio n w a s 4 .0 d a ys l e s s in the h y b r id s than in th e ir in b red p a r e n ts , w h ile the m e a n n um ber of d a y s fr o m t a s s e l in itia tio n to a n th e s is w a s 3.1 days l e s s in the h y b r id s. D om in an ce r e la tio n s h ip s on m & turity in o th e r c r o p s have b een r e p o r ted by s e v e r a l w o r k e r s . In c r o s s e s b etw een e a r ly and la te v a r ie t ie s of so y b e a n s, W illia m s (38). w orking w ith an in t e r ­ s p e c ie s c r o s s of so y b e a n s, r e p o rted that the F^ w a s b etw een the p a r e n ts and that c o n sid e r a b le t r a n s g r e s s iv e tu rity o c c u r r e d in the F ^ . s e g r e g a tio n fo r m a ­ W e is s e t a l. (37) re p o rted that m a tu r ity date in the w a s c o n s is t e n t ly in te r m e d ia te b e tw e e n that of the p a r e n ts in s e v e n te e n d iffe r e n t so y b ea n c r o s s e s . A ls o w o r k ­ ing w ith so y b e a n s, W eber (35) r e p o r te d that th e r e w a s a la c k of dom in an ce of g e n e s d e te r m in in g m a tu r ity and that t r a n s g r e s s iv e s e g r e g a tio n o c c u r r e d in the and F^ g e n e r a tio n s fa r beyond e ith e r p a ren t. R a sm u ss o n (26) stu d ied the in h e r ita n c e o f q u an tita tiv e c h a r ­ a c t e r s in p e a s . He con clu d ed that th e r e w e r e p ro b a b ly two m a in g e n e tic f a c t o r s a ffe c tin g m a tu r ity and that both sh ow ed p a r tia l d om in an ce fo r la t e n e s s . The tw o f a c t o r s a p p eared to be r e s p o n ­ s ib le for about h a lf of the g e n e tic v a r ia tio n w ith in the F^ p op u la­ tion; the o th er h a lf w a s due to m o d ifie r s and en v iro n m e n t. P o w e r s (22) p r e s e n te d data fo r to m a to e s show ing that the p erio d fo r s m a lle r n u m b er o f d a y s fr o m se e d in g to f i r s t c o m ­ p lete change in c o lo r o f any fr u it w a s c o m p le te ly dom inant in a c r o s s of D anm ark X J o h a n n isfeu er in one y e a r and that h e t e r o s is . »» w a s ex h ib ited in the sa m e c r o s s the fo llo w in g y e a r . T h is e v i ­ d en ce w a s u se d in su p p ort o f the h y p o th e sis that h e t e r o s is and dom in an ce a r e dependent upon the sa m e p h y s io lo g ic a l g e n e tic p rocesses. P o w e r s e_t a l. (24) stu d ied th r e e d iffe r e n t s t a g e s b e ­ tw een the tim e of se e d in g and f i r s t rip e fr u it in a tom ato c r o s s . 8 In e v e r y p e r io d e a r l i n e s s e x h ib ited c o m p le te o r a lm o s t c o m p le te phenotypic and g e n ic d o m in a n ce. B u rton (2) found that d o m in a n ce w a s in d ic a ted fo r e a r lin e s s of h eading in s i x d iffe r e n t c r o s s e s of p e a r l m ille t . T h ere a r e two ty p e s of g e n e a c tio n fo r q u a n tita tiv e char* a c t e r s that can be d istin g u ish e d by s t a t is t ic a l a n a ly s is o f the data in in h e r ita n c e stu d ie s: F i r s t , th e r e m a y be no in te r a c tio n s b e ­ tw een the g e n e s a ffe c tin g the q u a n tita tiv e c h a r a c te r , in w hich c a s e the e f f e c t s of the g e n e s a r e a r it h m e t ic a lly c u m u la tiv e . T h is i s b e s t illu s t r a t e d by the w ork of M a n g e lsd o r f and F r a p s (19). who found that in c o r n the V itam in A u n it s - p e r - g r a m p r o x im a te ly 2 .2 5 fo r e a c h ad d itio n a l Y g e n e . in c r e a s e d a p ­ S eco n d ly , the n atu re of the in te r a c tio n of the g e n e s a ffe c tin g a q u a n titative c h a r a c te r m a y be su ch that the e f f e c t s of the g e n e s a r e g e o m e tr ic a lly cu m u la tiv e (m u ltip lic a tiv e ). E a ch g en e su p p o se d ly m u ltip lie s the phenotype by a fix e d am ount. C h a r le s and Sm ith (4) and P o w e r s and L yon (25)^^presented fo r m u la s fo r the e s tim a tio n of a r ith m e tic and g e o m e tr ic m e a n s . The author i s not a w a re o f any r e p o r ts of stu d ie s of gen e a c tio n fo r c o r n m a tu r ity . In a so y b ea n c r o s a , W eber (35) r e ­ p orted that the n atu re of the gen e a c tio n fo r m a tu r ity ap p eared 9 to b e a d d i t i v e . P ow ers an d L y o n (25 ) in in h e r ita n c e duration of d e v e lo p m e n ta l s t a g e s in tom a to c r o s s e s , stu d ie s o n th e r e p o r te d about the sa m e v a lu e s fo r the a r ith m e tic and g e o m e tr ic m e a n s . B urton (2) r e p o r ted that the c a lc u la te d a r ith m e tic m e a n s fo r m a tu r ity in p e a r l m ille t w e r e c l o s e r to a g r e e m e n t to the obtained F £ m eans in s ix c r o s s e s than w e r e the g e o m e tr ic m e a n s . F r e e m a n (8) m ad e u se of r e c ip r o c a l tr a n s lo c a tio n s , lin k ed w ith r e c e s s i v e e n d o sp e r m g e n e s w x, su, and p r, to fa c ilit a te the id e n tific a tio n of p la n ts c a r r y in g the tr a n s lo c a te d c h r o m o s o m e s and to lo c a te g e n e s a ffe c tin g silk in g date in in b red lin e s of c o r n . w as found that g e n e s fo r la te silk in g in in b red F lo r id a N o. p e a red to be lo c a te d in c h r o m o so m e c h r o m o so m e 8 . 1 ap­ 3, in c h r o m o so m e 5, and in In in b red F lo r id a N o. 2, g e n e s w e r e lo c a te d the sa m e a s in F lo r id a N o. in c h r o m o so m e It 1 and 2. 1 and, in ad d ition , w e r e prob ab ly lo c a te d It w a s con clu d ed that in b red F lo r id a N o. 2 had fiv e g e n e s fo r la t e n e s s , and F lo r id a N o. 1, on ly th r e e g e n e s in th o se p o r tio n s of the c h r o m o s o m e s ex a m in ed . Yang (40), in a stu d y on the natu re of g e n e s c o n tr o llin g hybrid v ig o r a s it a f f e c t s silk in g tim e in co rn , con clu d ed that the g e n e s in v o lv e d fo r hybrid v ig o r in r e s p e c t to silk in g tim e a p ­ p e a r e d to be s m a ll in num ber w ith e f f e c t s of co m p a ra b le m agn itu d e 10 and in d ep en d en tly in h e r ite d . H is c o n c lu s io n w a s b a se d on o b s e r ­ v atio n of the fr e q u e n c y d is tr ib u tio n of the F and r e c ip r o c a l b a ck - c r o s s g e n e r a tio n s fo llo w in g a c r o s s of two in b red lin e s o f c o r n that w e r e s im ila r in m a tu r ity . In an in t e r s p e c if ic so y b e a n c r o s s , W eber (35) c a lc u la te d that on ly one m a jo r g en e w a s d iffe r e n tia tin g m a tu r ity . G oodw in (10) r e p o r te d that the m in im u m n u m b er of gen e su b stitu tio n s w hich d e te r m in e s t a g e s o f m a tu r ity in g o ld en rod w a s n in e. B urton (2) re p o rted that date o f h ead in g fo r s ix c r o s s e s of p e a r l m il le t w as c o n tr o lle d by a m in im u m of two to s e v e n g e n e s . P o w e r s e t a l. (24) in a n a ly z in g data on q u an titative c h a r ­ a c t e r s to a s c e r t a in the n um ber of g en e p a ir s d iffe r e n tia tin g the p a r e n ts in tom ato c r o s s e s , u se d w hat he te r m e d the p a rtitio n in g m eth od of a n a ly s is . T h ree g e n e s w e r e found to be d iffe r e n tia tin g the p e r io d fr o m tim e o f se e d in g to f i r s t bloom ; th r e e , fr o m f i r s t b loom to f i r s t fr u it s e t; and tw o g e n e s , fr o m f ir s t fr u it s e t to f i r s t fr u it r ip e . In fo rm a tio n a s to the p r o g r e s s to be e x p e c te d fr o m a p p ly ­ ing s e le c t io n p r e s s u r e to a s e g r e g a tin g pop u lation i s in d e sig n in g a b reed in g p r o g r a m . e s s e n t ia l In the study of q u an titative c h a r a c te r s , to ta l v a r ia b ility m u s t be se p a r a te d in to g e n e tic and 11 en v iro n m en ta l v a r ia b ility in o r d e r to obtain an e s t im a t e of the h e r ita b ility of a c h a r a c te r . W right (39) outlined p r o c e d u r e s fo r e stim a tin g g e n e tic v a r ia n c e s and d is c u s s e d th e ir a p p lic a tio n s. L ush (17) d e s c r ib e d the e s tim a tio n of h e r ita b ility fr o m the r e g r e s ­ sio n of o ffsp r in g on the fe m a le p a ren t in the c a s e of a n im a ls . R ob in son e t a l. (29). by u sin g data fr o m F p la n ts and p ro g en y p lo ts of " b ip a r e n ta l" p a r e n ta l p a ren t c r o s s e s in F^ popu­ la tio n s , obtained th r e e d iffe r e n t e s t im a t e s o f h e r ita b ility fo r eig h t d iffe r en t c h a r a c t e r s in c o r n . p a r e n t-o ffsp r in g Two of the e s t im a t e s r e s u lte d fr o m r e g r e s s io n s , and the th ird w as d e r iv e d fr o m the com p on en ts of v a r ia n c e fr o m the a n a ly s is o f the F^ p ro g en y data. H e r ita b ilit ie s fo r plant h eig h t, e a r h eig h t, husk e x te n sio n , and husk s c o r e w e r e r e la t iv e ly h igh . T h o se fo r n um ber of e a r s p er plant, e a r len gth , e a r d ia m e te r , and y ie ld w e r e c o n sid e r a b ly lo w e r . W orking w ith s o y b e a n s, W e is s e t a l. (37) found that s in g le plant m a tu r ity d e te r m in a tio n s w e r e h ig h ly in d ic a tiv e o f.th e m a ­ tu rity date of su b seq u en t p r o g e n ie s . g r e e of h e r ita b ility . T h is s u g g e ste d a high d e ­ A v e r y high h e r ita b ility v alu e fo r m a tu r ity in so y b e a n s (86 p e r cen t) w a s r e p o r ted by W eber (35). M ahmud and K ram er (18), in studyin g s e g r e g a tio n fo llo w ­ ing a so y b ea n c r o s s , c a lc u la te d h e r ita b ility e s t im a t e s in th ree 12 d iffe r en t w a y s. V a lu es fo r h eig h t, and 92 to ran ged fr o m 69 to 7 7 fo r y ie ld , 74 to 91 100 fo r m a tu r ity w hen the e s t im a t e s w e r e b a se d on g e n e r a tio n s "grow n in the sa m e season . When d iffe r e n t sp a c in g s and s e a s o n s w e re in v o lv ed , h e r ita b ility e s t im a t e s w e r e n e g lig ib le fo r y ie ld and ranged fr o m tu r ity . Burton 35 to 50 fo r h e ig h t and m a ­ (2), in stu d ie s of p e a r l m ille t c r o s s e s , ob tain ed r e la t iv e ly high h e r ita b ility v a lu e s fo r m a tu r ity . In e x a m in in g the lit e r a tu r e f o r d om in an ce r e la tio n s h ip s in co n n ectio n w ith e a r d ry w eigh t o r y ie ld of c o r n , the p r o b le m of h e t e r o s is w a s im m e d ia te ly e n co u n te r e d . In c r o s s e s am ong in b red lin e s of c o r n , h e t e r o s is of va ry in g d e g r e e s fo r g ra in y ie ld u su a lly o c c u r s (36, 32, 28). The natu re of the g en e a c tio n fo r y ie ld of c o m c e iv e d c o n s id e r a b le stu d y. en ts and F . and F ten double c r o s s e s . actu al and p r e d ic te d N e a l (20) h as r e ­ r e p o r ted y ie ld s fo r the p a r ­ g e n e r a tio n of ten s in g le , fo u r th r e e -w a y , and V e ry c l o s e y ie ld s . a g r e e m e n t w a s found b etw een The p r e d ic te d F^ y ie ld s w e r e c a lc u la te d u sin g the fo r m u la by C a s tle and W right (3), w h ich is b a se d on a r ith m e tic gen e a c tio n . K inm an and Sprague (14) have p r e s e n te d ad d ition a l data on the o b s e r v e d and p r e d ic te d y ie ld s of f o r t y - f iv e s in g le c r o s s e s and the F^ g e n e r a tio n s of th e se 13 com b in ation s in w hich gene a ctio n appeared to be predom inantly a r ith m e tic . P o w e r s (22) r e c a lc u la te d N e a l's data in o rd er to d e ­ term in e w hether or not it could a ls o be exp lain ed on a g e o m e tr ic h y p o th e sis. H ow ever, i t w as found to a g r e e only w ith the a r ith ­ m e tic sc h e m e . Jenkins (13) p r ese n te d data on the r e la tiv e e ffic ie n c y of four m eth od s of p red ictin g the p erfo rm a n ce of d o u b le -c r o s s c o m ­ bin ation s. The m ea n value of the four nonparental s in g le - c r o s s com b in ation s gave the b e s t a g r eem e n t w ith the a ctu a l d o u b le -c r o s s p e rfo r m a n ce . T h is m ethod a s s u m e s a r ith m e tic gene a ctio n . O ther w o rk ers found that p red icted d o u b le -c r o s s p erfo rm a n ce a g reed c lo s e ly with a ctu al p erfo rm a n ce (5. 1, 12). The author did not find any lite r a tu r e reporting the prob a­ ble num ber of g e n e s in v olved in d eterm in in g ear w eigh t or y ie ld ­ ing a b ility of co rn . a r e in v o lv ed . It i s g e n e r a lly b e lie v e d that n u m erou s g en e s H e r ita b ility estim ates^ fo r y ie ld of corn have been rep o rted by R obinson et a l. (29). (20.1, 9 .5 , R ather low p ercen ta ge v a lu es 15.5) w ere obtained fo r the th ree d ifferen t m eth od s used fo r estim a tio n . MATERIALS AND METHODS T hree e a r ly and th ree la te inb red lin e s of co rn w e r e u sed in the s ix d ifferen t c r o s s e s rep orted h e r e in . MS206, R53, and A158 w ere c la s s if ie d a s e a r ly lin e s , and W10, Oh40B, and W23 w ere c la s s if ie d a s la te . A ll s ix lin e s had b een inbred fo r a long period of tim e and w e r e of d iv e r s e o r ig in . The s ix d ifferen t c r o s s e s w ere (MS206 X W10), (MS206 X Oh40B), (R53 X Oh40B), (R53 X W23), (A 158 X Oh40B), and (A158 X W23). The data r e ­ ported w ere obtained in a fie ld ex p er im en t conducted during the su m m er of 1951 at the M ichigan State C o lleg e F a rm C rops fa rm . A ll s e e d s of the d ifferen t populations w er e produced in the su m ­ m e r of 1950. H e r e a fte r , the sym b ol B^ i s u sed to sig n ify that the p ro g ­ eny in d icated r e su lte d from b a c k c r o ssin g the F j gen era tio n to the d esign ated parent. P j and a r e em ployed to in d ica te an e a r ly or late inbred parent, r e s p e c tiv e ly . F o r each c r o s s , the e x p e r i­ m en t included a ll of the d ifferen t populations that could be ob­ tained from the two p a ren ts and the F j gen era tton - b y - c r o s s in g ____ and se lf-p o llin a tio n : P^, B^ to P^, F^, F^» to P^, and P^. A sp lit plot d e sig n w as u sed "in w hich the c r o s s e s w ere the m ain 15 p lo ts and the g e n e r a tio n s w ithin ea ch c r o s s w e r e su b p lo ts. r e p lic a tio n s w e r e u se d . E ig h t C om p lete ra n d o m ization o f the m a in p lo ts and su b p lots w a s p r a c tic e d , e x c e p t that the two p a ren ta l in b r e d s of e a c h c r o s s w e r e grow n in a d ja cen t p lo ts . e a ch of the P ^ , P^, and B. to P , and F One row and two row s ea ch of the g e n e r a tio n s co n stitu ted a p lot. s is t e d of tw e n ty -fiv e h ills sp a c e d 1 fo o t a p a rt. h ill w e r e planted on M ay 19. to P^, E ach row co n Two s e e d s p er When the a v e r a g e h eig h t o f the s e e d lin g s w as a p p r o x im a te ly 1 foot, the p lan ts w e r e thinned to one sta lk p e r h ill in su ch a m an n er a s not to b ia s the r e s u lt s of the e x p e r im e n t. A good stand w a s obtained fo r a ll of the popu­ la tio n s . W eather co n d itio n s w e r e g e n e r a lly unfavorable during the la tte r part of the grow ing s e a s o n fo r n o rm a l m a tu r ity o f corn . The la tte r p a rt of A ugust and the m a jo r p a rt of S ep tem b er w er e cloudy, c o o l, and w et. K illing f r o s t o c c u r r e d on S ep tem b er 29, 133 d ay s a fte r planting. E ach plant w a s tagged fo r silk in g date wh-en the s ilk of the m ain ea r w a s a p p ro x im a tely o n e -h a lf in ch in len gth . G om - p le te c b v er a g e ^>f the e x p e r im e n t w a s m ade each day during the p erio d of m o s t rapid silk in g and on a lte r n a te d a ys during p e r io d s 16 of in freq u en t s ilk in g . D a te s of silk in g w e r e tr a n sfo r m e d to v a lu e s fo r the n um ber of d a y s fr o m p lanting to s ilk in g . B e fo r e h a r v e s t, p la n ts w h ich w e r e n o tic e a b ly d am aged by in s e c t s o r d is e a s e s w e r e e x c lu d e d . terns w e r e u se d . Two d iffe r e n t h a r v e s tin g s y s - S ix r e p lic a tio n s of the e x p e r im e n t w e r e h a r v e s te d at a u n iform tim e fr o m planting (S ep tem b er 18 to 2 1 )--w h e n the m o r e advanced e a r s a p p ea red to have m a tu r ed s a t is f a c t o r ily so that a r a th e r w ide m o is tu r e co n ten t b etw een pop u lation s o f the c r o s s e s w ould be ob ta in ed . The tim e of h a r v e s t w a s b e fo r e f r o s t and a p p r o x im a te ly fifty d a y s a fte r 50 p e r c e n t o f the p la n ts in the e n tir e e x p e r im e n t had s ilk e d . A se c o n d s y s t e m of h a r v e stin g w a s fo llo w e d w ith tw o a d ja cen t r e p lic a tio n s w h ere ea ch e a r w a s h a r ­ v e s te d e x a c tly fifty d a y s a fte r s ilk in g . In both s y s t e m s , h a r v e s t w a s a c c o m p lis h e d by husking the e a r of ea ch plant and p la cin g the e a r and s ilk in g date tag in a p ap er bag m a rk ed w ith row and plant n u m b er. The pap er bag had s m a ll h o le s to f a c ilit a te a ir m o v e m e n t in d ry in g . G reen w eig h t in g r a m s fo r ea ch e a r w a s r e c o r d e d soo n a fte r h a r v e s t. A fte r dryin g to co n sta n t w eig h t in a s t e e l o ven s e t a t a p ­ p r o x im a te ly 155* F ., the d ry w eig h t o f e a c h e a r w a s d e te r m in e d . The o v e n s red u ced the m o is tu r e con ten t of & e e a r F t i r ^ p e r cent; 17 p ro p er a d ju stm en ts w e r e m ade fo r the m o istu r e data r e p o rted . Data on e a r w eig h t a r e re p o r ted a s o v e n -d r y w eig h t, containing a p p ro x im a tely 2 p er cent m o is tu r e . w eight, the te r m In d is c u s s in g the data on e a r ’’d ry w e ig h t” is u se d in th is study, even though the w eig h ts a r e a c tu a lly o v e n -d r y w e ig h ts. M eans and v a r ia n c e s w e r e c a lc u la te d fr o m individ ual p lan t data in a ll c a s e s . In the c a lc u la tio n of the to ta l population v a r ­ ia n c e s , the e ffe c t of r e p lic a tio n w as rem o v ed . The sig n ific a n c e of m ean s w a s te s te d by the standard '' t *’ t e s t (31). B e c a u se of the la r g e en v iro n m en ta l v a r ia b ility am ong the p a ren t lin e s fo r silk in g date and m o istu r e content, the v a r ia n ce of the F j w a s u sed as an e s tim a te of en v iro n m en ta l v a r ia n c e fo r the se g r e g a tin g g e n e r a tio n s of e a ch c r o s s . The w ithin g en era tio n v a r ia n c e o f the F j population w as su b tra cted fro m that of the F^, B. X to P . , X and B 1 to P to g e n e r a tio n s in e stim a tin g the g en etic v a r - ia n ce o f the r e s p e c tiv e p op u la tion s. F o r m u la s r ep o r ted by P o w e r s and Lyon (25) w e r e u sed to c a lc u la te the th e o r e tic a l m ea n s to d eter m in e w hether the nature of gene action w as m o re n e a r ly a r ith m e tic or g e o m e tr ic . fo r m u la s a r e shown in T able 1. T h ese 18 TA BLE 1 FORMULAS FOR ESTIMATING ARITHMETIC AND GEOMETRIC MEANS A r ith m e tic M ean P o p u la tio n F, 2 00 0 P 1 + 2 F 1 + P 2* G e o m e tr ic M ean A n tilog of p i + 4 F Bj to P j 1 + P 1 1 + P 2 B 1 *° P 2 Log A n tilog of • Log Anti lo g of 2 * P j, + L og P 2 4 2 F 2L og F j p i + Log P j 2 Fi + L og P 2 2 F^, and P^ r e p r e s e n t the m ea n of the e a r ly p aren t, F j , and la te p aren t, r e s p e c tiv e ly . 19 To t e s t the a g r e em e n t betw een o b se r v e d and c a lcu la ted a rith m e tic or g e o m e tr ic m e a n s of the F £ tio n s, the a n a ly s is of v a ria n ce w as u sed . and b a c k c r o ss populaD e g r e e s of freed om for the a n a ly s is of v a r ia n c e for e a ch c o m p a riso n betw een the s ix obtained and ca lcu la ted m e a n s for the F^, B^ to P^, or to populations w ere a s follow s: Source of V ariation total D e g r e e s of F reed o m 11 betw een m ea n s 1 betw een c r o s s e s 5 e r r o r ( c r o s s e s x m e a n s) 5 The form u la supplied to Burton (2) by S ew all W right w as u sed to e stim a te the m in im u m num ber of g e n e s con trollin g the e x ­ p r e s s io n of a sin g le c h a r a c te r . An e r r o r w as m ade in the printing of the form u la in that the v a ria n ce of the m ean of the F^ end F^ in the denom inator of the form u la should have been the varian ce of the F^ and F^ populations. The form ula a s used w as a s fo llo w s = the m ean of the s m a lle r parent pz P1 p 2 = the m ean of the la r g e r parent = the m ean of the population = the m ean of the population A ccord in g to Burton (2), th is form u la w ill fu rn ish an unbiased e s ­ tim ate of the gene num ber if the follow ing a ssu m p tio n s apply: 1. no linkage e x is t s b etw een p ertin en t g e n e s, 2. one parent su p p lies only plus fa c to r s and the oth er only m in u s fa c to r s am ong th o se in w hich th ey d iffer, 3. a ll g e n e s a r e equally im portant, 4. the d e g ree of dom inance of a ll plus fa c to r s i s the sam e 5. no in te r a c tio n e x is t s betw een p ertin en t n o n a lle lic g e n e s. for a ll, When th ese a ssu m p tio n s do not apply, the form ula g iv e s a value that m ay be m uch s m a lle r than the true gene num ber. 21 E s t i m a t e s of h e r it a b ilit y fo r e a c h c r o s s w e r e m a d e by the fo r m u la , V a r ia n c e F - V a r ia n c e F v a r ia n c e in e a ch c a s e / V a r ia n c e F , w h e r e the X C* £0 r e p r e s e n te d the to ta l population v a r ia n c e w ith the e f f e c t o f r e p lic a tio n r e m o v e d . A s pointed out by Wright (39), the u s e of the d iffe r e n c e b e tw e e n the v a r ia n c e of the F^ and F^ a s an e s t im a t e of g e n e tic v a r ia n c e i s a c tu a lly an e s t im a t e o f the su m of the fo llo w in g v a r i ­ ances: 1. T o ta l g e n e tic v a r ia n c e including: a. additive g e n e tic v a r ia n c e , b. v a r ia n c e due to d om in a n ce d e v ia tio n s fr o m the a d ­ d itiv e schem e, c. v a r ia n c e due to the in t e r a c tio n of n o n a lle lic g e n e s . 2. V a r ia n c e due to in te r a c tio n of the g e n o ty p e s and the en v ir o n m e n t. T h u s, the e s t i m a t e s obtained m u s t be c o n s id e r e d a s m a x im u m h e r i t a b il it i e s b e c a u s e the add itive part of the to tal g e n e tic v a r ia n c e i s the only portion c o n s id e r e d h e r it a b le . EX P E R IM E N T A L RESULTS ON CORN MATURITY D a y s F r o m P la n tin g to S ilkin g M e a n s, stan d ard d e v ia t io n s , and to ta l and g e n e t ic v a r i a n c e s fo r the num b er of d a y s fr o m planting to silk in g fo r p opu lation s of the s i x d iffe r e n t c r o s s e s a r e show n in T able 2. Frequency d is ­ tr ib u tio n s and the total n u m b er of p lan ts in e a c h population a r e p r e s e n t e d in T a b le 3. In T able 2 i t can be o b s e r v e d that the total v a r i a n c e s o f the in b r e d p a r e n ts in m o s t c a s e s w e r e la r g e . in b r e d s w e r e a ffe c te d m o r e by e n v ir o n m e n t than the F ^. The Thus, the v a r ia n c e of the F^ population w a s u se d a s an e s t im a t e of e n ­ v ir o n m e n ta l v a r ia n c e in the c a lc u la tio n o f g e n e tic v a r ia n c e s . D om in ance r e l a t i o n s h i p s . In the study of dom inance r e l a ­ tio n s h ip s , both g e n ic and phenotypic d om in an ce (9, 23) a r e c o n ­ s id e r e d . G en ic d om in a n ce d e n o te s the d e g r e e of e x p r e s s i o n of one or the o th er of the two c o n tr a ste d a l l e l e s of the h e te r o z y g o u s gene p air (Aa) plus the a c tio n of the e n v iro n m en t, in w hich A r e p ­ r e s e n t s any gene and a i t s a l l e l . T hus, an i n t r a - a l l e l i c i n t e r a c ­ tion of A and a m a y be in v o lv e d a s w e ll a s an in te r a c tio n with the en v ir o n m e n t. P h e n o ty p ic d om in an ce d e n o te s the d e g r e e of 23 TABLE 2 MEANS AND THEIR STANDARD DEVIATIONS. TOTAL AND GENETIC VARIANCES FOR N U M BER O F DAYS FROM PLA NTIN G TO SILKING P o p u la tio n Mean D ays S .D. of Mean T otal V a r ia n c e G e n e tic V a r ia n c e MS206 x W10 MS206 7 2.8 0 .3 5 16.90 B x to MS206 71.4 0 .1 7 10.77 73.3 0 .2 5 11.41 7 6 .2 0.21 16.81 5.40 80.3 0 .2 5 20.91 9 .5 0 9 2 .2 0 .3 3 15.00 Fi F2 B j to W10 W10 - 0 .6 4 MS206 x Oh40B MS206 72.1 0 .3 2 15.41 Bj 68.9 0 .1 6 8.13 ' 71.0 0 .2 0 7.21 to MS206 F1 0 .9 2 FZ B j to Oh40B 72.6 0 .20 1 3.98 6 .7 7 77.0 0 .2 2 17.49 10.28 OH40B 85.0 0 .3 2 13.75 R53 x OH40B R53 7 3.9 0 .2 4 10.29 B j to R53 7 0.7 0 .1 4 7.34 72.4 0 .2 3 9 .56 F1 - 2 .2 2 F2 B j to Oh40B 73.6 0 .1 8 11.25 1.69 75.6 0 .1 7 11.34 1.78 OH40B 85.4 0 .3 5 17.57 24 TABLE P op u lation Mean D ays 2 (C on tin ued) S.D . of Mean Total V a r ia n c e G e n e tic V arian ce R53 x W23 R53 to R53 F1 FZ B j to W23 W23 73.4 0 .2 2 7.95 70.4 0 .1 5 7.53 73.5 0 .2 5 10.85 74.7 0.20 15.28 4 .4 3 76.2 0 .1 9 13.37 2.52 86.8 0.31 16.46 - 3.32 A l 58 x Oh40B A l 58 76.3 0 .2 8 12.73 Bj 73.9 0 .1 7 10.16 74.2 0 .2 3 8.92 to A l 58 F1 1.24 F2 B j to OH40B 75.1 0.21 14.63 5.71 78.4 0.21 15.95 7.03 Oh40B 86.6 0 .3 3 15.51 A l 5 8 x W23 A l 58 75.3 0 .2 8 12.48 B x to A l 58 72.3 0 .1 4 7.17 73.3 0 .26 10.41 73.3 0 .19 11.75 1.34 77.5 0.20 14.24 3.83 85.6 0 .2 8 11.89 F1 F2 B j to W23 W23 - 3.24 25 TABLE 3 FREQUENCY DISTRIBUTION FOR NUMBERS O F DAYS FROM PLANTING TO SILKING FOR POPULATIONS OF CORN CROSSES _ Population N u m b er of D ays fr o m P la n tin g to Silking ______________________________ ____________________ _____________ _ 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 MS206 x W10 MS206 B to M5206 1 1 8 4 6 4 1 2 10 18 32 56 36 27 72 42 23 10 13 2 4 6 1 7 16 1 1 3 3 2 5 Fi 2 F2 B to W10 W10 5 8 15 4 18 18 17 9 1 2 18 16 16 31 25 19 1 2 6 1 3 2 3 2 5 3 1 9 33 37 39 28 57 31 25 14 13 19 11 12 7 16 1 2 5 13 17 16 21 29 24 21 23 38 35 31 1 MS206 x Oh40B MS206 B to M5206 1 3 5 20 1 1 5 26 18 13 6 5 8 22 43 31 45 47 46 7 21 19 15 3 6 8 16 29 32 11 29 17 14 5 7 4 1 1 5 60 53 42 19 21 4 5 7 2 Fi F2 B to OH40B Oh40B 3 1 8 5 8 1 10 10 12 26 44 1 3 3 7 3 5 1 2 1 1 7 1 5 25 37 38 48 45 23 42 25 22 15 2 18 1 3 5 4 18 2 19 3 10 27 28 22 22 1 1 13 13 6 6 3 3 R53 x OH40B R53 B to R53 f i to On40B Oh40B 4 3 8 27 38 54 52 49 70 18 17 1 3 3 4 3 3 2 3 3 12 13 37 16 59 64 51 24 31 13 14 6 7 3 2 2 3 31 56 44 4 8 77 21 31 24 6 5 7 5 7 10 8 5 24 1 5 20 34 3 11 9 10 1 9 40 22 13 11 7 3 1 1 1 26 TABLE 3 (C on tin ued) N um ber of D ay s f r o m P la n tin g to Silkin g T otal 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 MS206 x W10 1 136 1 363 1 8 11 1 1 4 6 3 1 1 9 13 12 12 2 179 2 3 10 10 14 2 2 379 1 9 10 13 1 1 1 6 21 15 5 7 6 1 2 2 343 1 139 MS206 x Oh40B 150 318 181 * 1 3 2 6 7 21 1 1 4 5 21 1 1 3 2 19 336 1 1 4 1 1 3 1 1 1 369 1 137 R53 x Oh40B 1 1 175 1 364 1 2 2 2 24 179 1 1 1 1 1 1 3 15 1 3 25 362 2 4 1 2 380 1 3 2 1 1 1 145 TABLE 3 (C on tin ued) N um ber of D ays fr o m P lan tin g to Silking la tio n 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 R53 R53 B to R53 1 1 5 11 X W23 7 19 28 23 26 12 12 13 2 3 2 1 2 1 1 7 10 8 4 5 11 23 36 63 60 36 35 17 20 F1 2 *V B to W23 W23 7 3 2 4 1 4 5 10 15 21 30 23 16 17 1 4 1 2 2 5 27 17 20 61 38 38 34 33 23 17 13 13 8 6 4 1 2 4 18 32 31 52 41 47 28 23 18 10 16 8 17 1 6 2 6 6 23 7 15 14 21 20 15 16 9 13 6 7 4 3 5 4 2 6 2 2 4 1 4 9 13 12 49 31 42 39 44 14 21 15 9 5 6 10 A l 58 x Oh40B A l 58 B . to A l 58 1 3 15 21 35 61 53 48 34 29 17 10 4 F1 1 1 1 4 B to Oh40B Oh40B 6 18 24 28 22 16 12 12 1 3 9 17 19 29 56 43 49 48 19 17 10 19 2 4 4 7 2 19 2 12 18 18 27 16 12 19 6 4 5 7 2 3 5 10 29 39 60 72 39 38 17 17 15 4 3 2 1 2 2 3 2 2 1 6 8 2 4 1 A15S A l 58 B . to A l 58 3 1 2 F1 f 2 B^ to W23 W23 3 9 5 X W23 8 16 20 39 14 14 10 8 9 5 7 23 28 31 60 44 38 23 22 20 13 1 8 12 20 31 42 55 42 28 27 10 22 12 14 3 3 1 10 10 13 28 TABLE 3 (C ontinued) N um ber of Days fro m Planting to Silking ----------------------------------------------------------------------------------------------------------------------------------------------------T o t a i (4 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 R53 x W23 3 5 4 1 2 170 1 327 2 180 1 2 3 1 2 7 26 16 17 9 1 2 21 1 8 5 10 1 379 1 8 2 1 8 3 1 1 2 1 361 1 169 A l 58 x OH40B 2 4 2 3 1 1 157 3 1 1 355 1 1 164 6 1 2 337 5 1 1 2 9 2 2 21 4 25 3 2 2 3 22 5 3 1 1 1 378 8 1 4 1 2 139 A158 x W23 2 2 1 159 354 ' 1 1 2 7 157 1 4 5 5 1 1 342 4 4 13 20 17 11 10 1 4 7 3 351 4 1 154 29 e x p r e s s io n of one or the oth er of two c o n tr a ste d c h a r a c t e r s in the gen eratio n a s c o m p a red to the e x p r e s s io n in the two p a r ­ ents; th e r e fo r e , both i n t r a - a l i e i i c and in t e r a ll e iic in t e r a c tio n s m a y be involved, a s w e ll a s in te r a c tio n s betw een the g e n e s and e n ­ vironm ent. The follow ing th e o r e tic a l s itu a tio n s w e r e u sed a s g u id e s in the in te r p r e ta tio n of dom inance r e la tio n s . phenotypic dom inance i s in d icated when the No (in te r m e d ia te ) m e a n for a c h a r ­ a c te r eq u als the a v e r a g e of the m e a n s of the two p a r e n ts. If g en ic dom inance i s a ls o in te r m e d ia te and th e r e i s no in t e r a l l e i i c i n t e r ­ action of g e n e s , the F^ m e a n would not be exp ected to d eviate s ig n ific a n tly fro m the m e a n , and the m e a n o f e a c h b a c k c r o s s would be e x p e c ted to fa ll h a lf-w a y betw een the F j m e a n and the m ea n of the parent to which the b a c k c r o s s w a s m a d e . C om plete phenotypic dom inance i s indicated when the m e a n d o e s not differ sig n ific a n tly fr o m the m e a n of one of the paren ts in the c r o s s . The m e a n would be ex p e c ted to f a ll betw een the two b a c k c r o s s m e a n s and should differ sig n ific a n tly from the F^ m e a n . The m e a n of the b a c k c r o s s to the dominant parent should not d iffer sig n ific a n tly fr o m the m e a n of the F j or dominant parent. The m e a n o f the b a c k c r o s s to the r e c e s s i v e 30 parent sh ou ld f a l l b e t w e e n the m e a n o f the and the r e c e s s i v e paren t but c l o s e r to the m e a n o f the F ^ . P a r t i a l p h e n o ty p ic d o m in a n c e i s in d ic a t e d w h en th e F^ m e a n f a lls b e tw e e n the m e a n o f one o f the p a r e n t s and the a v e r a g e o f the two p a r e n ta l m e a n s . The F^ m e a n sh o u ld f a l l b e t w e e n the two b a c k c r o s s m e a n s and sh o u ld m o r e n e a r l y a p p r o a c h the m e a n o f the F^ a s the d e g r e e o f d o m in a n c e b e c o m e s l e s s . In d e t e r m in in g g e n ic d o m in a n c e , th e c a lc u la t e d g e n e t i c v a r i ­ a n c e s of the s e g r e g a t i n g p o p u la tio n s w e r e u s e d . C o m p le te g e n ic do m in a n ce i s in d ic a t e d w hen the g e n e t ic v a r ia n c e o f the b a c k c r o s s to one p a r e n t i s n e g l i g i b l e and that o f the F^ and b a c k c r o s s to the other p a r e n t i s la r g e . I n t e r m e d ia t e (no) g e n ic d o m in a n c e i s i n d i ­ ca ted i f the g e n e t i c v a r i a n c e s o f the two b a c k c r o s s p o p u la tio n s a r e a p p r o x im a te ly e q u a l. A ny s it u a t io n not f a llin g in to the c a t e g o r y of c o m p le te o r i n t e r m e d i a t e g e n ic d o m in a n c e w ould be p a r t ia l g e n ic d o m in a n c e . H e te ro sis i s e x h ib ite d w h en the F^ m e a n f o r a c h a r a c t e r f a l ls s ig n if ic a n t l y b ey on d the m e a n o f e i t h e r p a r e n t o f a c r o s s . If the F j g e n e r a t io n s h o w s h e t e r o s i s , the b a c k c r o s s to the p a r e n t m o r e c l o s e l y a p p r o a c h in g the F^ sh o u ld a l s o e x h ib it h e t e r o s i s . 31 The m e a n sh o u ld f a l l h a l f - w a y b e tw e e n the m e a n o f the and the a v e r a g e of the two p a r e n t s . A s u s e d in the p r e s e n t s t u d i e s , the t e r m f e r s to the i n t e r a l l e i i c i n t e r a c t i o n " e p ista sis" re­ o f g e n e s in w h ic h a dom inan t gen e o f one a l l e l i c p a ir te n d s to m a s k the e f f e c t s of double r e ­ c e s s i v e g e n e s of o th e r a l l e l i c p a i r s a f f e c t in g the s a m e ch aracter. If c o m p le te e p i s t a s i s i s in v o lv e d , one d o m in a n t g e n e p r o d u c e s a s g r e a t an a f f e c t a s a l l o th e r d o m in a n t g e n e s a ffe c tin g the c h a r a c t e r in a g e n o ty p e . d o m in a n c e a r e When e p i s t a s i s , p h en oty p ic d o m in a n c e , and g e n ic co m p lete, v e r y s m a ll d iffe r e n c e s sh ould be o b ­ s e r v e d b e tw e e n the m e a n s of the d om in an t p a r e n t, b a c k c r o s s to the d o m in a n t p a r e n t, F ^, F ^, and b a c k c r o s s to the r e c e s s i v e p a r ­ ent. With c o m p le t e p h en o ty p ic and g e n ic d o m in a n c e and no e p i s ­ t a s i s , the m e a n s o f the F sh o u ld d e v ia t e £ and b a c k c r o s s to the r e c e a s i v e p a r e n t s i g n if ic a n t ly f r o m the F^ m e a n - - t h e d eg ree of d e ­ v ia tio n d epending c o n s i d e r a b l y upon the n u m b e r o f g e n e s a ffe c t in g the c h a r a c t e r . D if f e r e n t d e g r e e s o f e p i s t a s i s m a y be in d ic a te d when the s itu a tio n s u g g e s t s n e it h e r c o m p l e t e , n o r the a b s e n c e o f, e p ista sis. A s u m m a r y o f the d o m in a n c e r e la t io n s h ip s f o r the n u m b er of d a y s f r o m p lan tin g to s ilk in g i s p r e s e n t e d in T ab le 4. The 32 TABLE 4 SUMMARY O F DOMINANCE RELATIONSHIPS F O R N U M B E R O F DAYS FROM P L A N T IN G TO SILKING FO R CORN CROSSES MS206 x W10 R53 x W23 C om plete p h en o ty p ic d o m in a n ce C om p lete g e n ic d o m in a n c e No e p i s t a s i s C o m p le te p h en oty p ic d o m in a n c e C o m p le te g e n ic d o m in a n ce P a r tia l e p is ta s is MS206 x Q h40B A 158 x Qh40B Slight h e t e r o s i s C om p lete g e n ic d o m in a n c e No e p i s t a s i s S lig h t h e t e r o s i s C o m p le te g e n ic d o m in a n c e P o ssib le e p ista sis R53 x Qh40B A l 58 x W23 Slight h e t e r o s i s C om p lete g e n ic d o m in a n c e Strong e p i s t a s i s Slig h t h e t e r o s i s C o m p le te g e n ic d o m in a n c e P o ssib le e p ista sis 33 lom inance r e l a t i o n s h i p s o f the c r o s s e s w e r e g e n e r a l l y s i m i l a r , n the c r o s s (M S206 X W 10). the F^ m e a n did n o t d if f e r cantly f r o m that o f MS 2 0 6 (T a b le 2), s o that c o m p le t e p h e n o ty p ic dom inance w a s in d ic a t e d fo r e a r l i n e s s of s ilk in g . do m in a n ce w a s in d ic a t e d by the n e g a t iv e C o m p le te g e n ic e s t i m a t e d g e n e t ic v a r i ­ a n ce of the b a c k c r o s s to M S206 and by the g e n e tic v a r ia n c e of the sig n ifi­ r e l a t i v e l y la r g e and the b a c k c r o s s to W10. of the b a c k c r o s s to M S206 w a s s ig n if ic a n t l y l e s s T he m e a n than that o f the F j and M S 2 0 6 - - in d ic a t in g that i n t r a - a l l e l i c and i n t e r a l l e i i c g en e in t e r a c t i o n s m u s t have o c c u r r e d . E p i s t a s i s o f the e a r l y s ilk in g dom inan t g e n e s did not a p p e a r to be in v o lv e d , a s e v id e n c e d by the f a c t that the m e a n s o f tlie F^ and b a c k c r o s s to W10 w e r e c o n s id e r a b ly g r e a t e r than that o f the F ^ . S lig h t h e t e r o s i s w a s e x h ib ite d in the c r o s s (M S206 X Oh40B) s i n c e the m e a n o f the F^ w a s s ig n i f ic a n t ly l e s s than that of M S206. A l m o s t c o m p le t e g e n ic d o m in a n c e fo r e a r l i n e s s of s i l k ­ ing w a s in d ic a t e d in that the e s t i m a t e d g e n e t ic v a r ia n c e of the b a c k c r o s s to M S206 a p p r o a c h e d z e r o and w a s s m a l l in c o m p a r is o n to that o f the F and the b a c k c r o s s to O h40B . P r o b a b ly no e p i s - t a s i s o f d o m in a n t g e n e s o c c u r r e d , s in c e the m e a n of the b a c k c r o s s to O h40B w a s c o n s id e r a b ly l a r g e r than that o f th e F j o r the F ^. 34 In the c r o s s (R53 X O h40B ) the m e a n s o f the b a c k c r o s s to R53 w e r e both s ig n i f i c a n t l y l e s s R53. D e fin ite h e t e r o s i s w a s e x h ib ite d . and the than the m e a n of T he n e g a t iv e g e n e t i c v a r i ­ ance c a lc u la t e d f o r the b a c k c r o s s to R53 s u g g e s t e d that c o m p le t e g e n ic d o m in a n c e w a s i n v o lv e d f o r e a r l i n e s s o f s i lk in g . In t h is c r o s s i t a p p e a r e d th a t d o m in a n t g e n e s fo r e a r l y s ilk in g w e r e e p i s tatic to double r e c e s s i v e genes, s in c e t h e r e w e r e s m a ll d iffe r ­ e n c e s b e tw e e n the m e a n s of the F ^ , F^» and b a c k c r o s s to O h 40B . The low g e n e t ic v a r i a n c e s e s t i m a t e d fo r the F^ and b a c k c r o s s to Oh40B fu r th e r su p p o r t the h y p o t h e s is of e p i s t a s i s . S e g r e g a t io n for e a r l y s ilk in g b ey o n d that o f R53 o r the F^ o c c u r r e d in the b a c k c r o s s to R53 (T a b le 3), in d ic a tin g i n t r a - a l l e l i c and i n t e r a l l e i i c gene i n t e r a c t i o n s . C o m p le te p h e n o ty p ic d o m in a n c e w a s in d ic a te d f o r the c r o s s (R53 X W 23), b e c a u s e the m e a n o f the F^ did n o t d if f e r s i g n i f i ­ c a n tly f r o m the m e a n of R 53. The n e g a t iv e g e n e t ic v a r ia n c e of the b a c k c r o s s to R53 in d ic a te d c o m p le t e g e n ic d o m in a n c e fo r e a r l i n e s s o f s ilk in g . F £ The g e n e t ic v a r i a n c e s c a lc u la t e d f o r the and b a c k c r o s s to W23 p o p u la tio n s w e r e r a th e r low but w e r e la r g e r than that c a lc u la t e d f o r the b a c k c r o s s to R 53. Som e degree of e p i s t a s i s o f d o m in a n t g e n e s f o r e a r l y s ilk in g s e e m e d p r o b a b le 35 iv th is c r o s s , b eca u se there w ere m e a n s of the f i r s t f iv e p o p u la tio n s . s m a l l d i f f e r e n c e s b e tw e e n the The f r e q u e n c y d is t r ib u t io n (Table 3) s u p p o r ts the h y p o t h e s i s o f p o s s i b l e th ere w a s v e r y l i t t l e s e g r e g a t i o n fo r la t e e p ista sis, s in c e s ilk in g in the F £» and B J. to W23, beyond that of the F^. S lig h t h e t e r o s i s fo r e a r l i n e s s o f s ilk in g w a s in d ic a t e d in the cross (A158 X O h40B ) in th at the m e a n of the F^ w a s s ig n i f ic a n t ly l e s s than that of A 1 5 8 . s in c e A high d e g r e e o f h e t e r o s i s did n o t o c c u r , the F^ m e a n f e l l c l o s e r to that o f the F j been e x p e c t e d . than w ould h a v e T h e r e w a s a l m o s t c o m p le t e g e n ic d o m in a n c e fo r e a r l i n e s s o f s ilk in g a s sh ow n by the s m a l l g e n e t ic v a r ia n c e o f the b a c k c r o s s to A 158, w hen c o m p a r e d w ith that o f the F c r o s s to O h40B . c* o r the b a c k - The m e a n of the b a c k c r o s s to Oh40B f e l l s o m e ­ what c l o s e r to the m e a n o f the F^ than to that o f O h40B, s u p p o r t­ ing the h y p o t h e s is o f d o m in a n c e o f g e n e s fo r e a r l y s ilk in g . Som e d e g r e e o f e p i s t a s i s w a s in d ic a t e d by the c l o s e n e s s o f the F^ and F £ m eans. H o w e v e r , the r e l a t i v e l y la r g e d if f e r e n c e b e tw e e n the m e a n of the F^ and B^ to Oh40B s u g g e s t e d . that e p i s t a s i s m a y not have b e e n in v o lv e d . H e t e r o s i s fo r e a r l y s ilk in g w a s e x h ib ite d by the c r o s s (A 158 X W23) s i n c e the F j w a s e a r l i e r than the in b r e d A 1 5 8 . The 36 fact that there was no difference betw een the F and F. M suggests plete that genic variance ances a high dom inance calculated estim ated sm all, but degree larger was for for of indicated the the than F heterosis of the backcross to WZ3 was m ean of t h e F ^, epistasis was not F m eans I In a l l or slight or alm ost cross. indicated of t h e com plete, The in s i l k i n g was backcross than the to F j or for (R53 would m ust com plete earliness have that also than the the equal parent in all early populations silking in e v e r y beyond c r o s s - - m o re the and crosses that early of the noticeably ( A 1 5 8 X WZ3) observed in e v e r y significantly to th e interalleiic dom inance C om plete, indicated early to g iv e the silking the intra-allelic occurred was of was X O h 4 0 B ). (A158 X Oh40B) . and appear Since phenotypic parent for obtained rather H ow ever, early slight was va r i­ w ere larger the I n b a c kc r o s s parent significantly dom inance (A158 X O h40B) . segregation genetic to A 1 5 8 apparent either noted genic The genetic epistasis crosses, heterosis to 1 Com­ negative WZ3 p o p u l a t i o n s B backcross and highly and of t h e M invoked to A 158. m ean F the not backcross w that by was m eans L gene results for earlier e xc e p t parent, F j or in the (Table early crosses 3) It interactions the backcrosses 37 o the early >robably parent. H ow ever, of g e n e ac t i o n »umption of a r i t h m e t i c jackcross populations cases ■nean, the there ind that was of th e m eans F B and 1 slightly How ever, for are less to for presented than also the as - cross, the F and 5. the Be­ m ean arithm etic w ere In calculated in a l l c r o s s e s the calculated on in T a b l e either betw een populations the based action e a r ly silking of e a c h populations, was analysis betw een sum ption cross w ere parent in e v e r y there An all was the oft h e and sam e. geom etric F ^ geo­ In t h e m eans w ere M less the m eans crosses was or geom etric c ase than very little of v a r i a n c e obtained of a r i t h m e t i c reported obtained of h e t e r o s i s m eans gene little d iffe re n c e of th e to P M values geom etric m eans very early C alculated of e a c h obtained m etric ment and indicating- d o m in a n c e cause degree involved N ature ill som e for the F^ significantly m eans. was to d e t e r m i n e m ade and it w a s and the those gene evident two the calculated that that of th e m eans two. the, a g r e e ­ on the From the backcross m ean the action. different fro m H ow ever, arithm etic betw een geom etric: 5. calculated difference m eans or in T a b l e the m ean the F of t h e populations of the as­ for arithm etic geom etric m eans 38 TABLE 5 O B T A IN E D AND C A L C U L A T E D A R IT H M E T IC A N D G E O M E T R IC M EA N S FO R N U M B E R O F DAYS F R O M P L A N T IN G TO SILKING F Population w C alculated C ross O btained Mean (.days) M ean A rithm ctu (days) Geom etric (days) MSZ06 x WIO 76 Z 77 9 77 5 MSZ06 x Oh40B 7Z.-6 74 8 74.6 73 6 76.0 75.8 74 7 76 8 76 6 75.1 77 8 77 7 73 3 76.9 76.7 74.3 76.7 76 5 85.8- ! 59.9 R 5 3 x Oh40B R53 x WZ3 .................................. A 158 x O h 4 0 B A 1 5 8 x WZ 3 Me an F value . . . .............................. . . . Significant ....................... t the 1% l e v e l 39 TABLE 5 (Continued) — B to P O btained Mean (days) A r i t li­ m e t ic (days) .• B Population C alculated f " C alculated M ean Geo­ m etric (days) to P j P o p u l a t i o n O htained M ean (days) A rith­ m etic (days) Mean Geo­ m e t ric (days) 71 4 73 1 73. 1 80.3 82 8 82 2 68 9 7 1. 6 7 1.6 77.0 78 0 77 7 70.7 73 2 73 2 75 6 78 9 78 6 70.4 73 5 73 5 76.2 80 2 79.9 73 9 75.3 75 3 78 4 80.4 80 2 72 3 74 3 74 3 77 5 79 5 79 2 71.3 73.5 73 5 77.5 80.0 79 6 71.3** 71.3** 3 2 . 6 ** 24.4** 40 « for the ment F , and b w ith the B 1 to studied scale. the Both populations than the concluded was types of g e n e m ean that follow ing was of t h e the either action slightly arithm etic genetic the m ay closer m eans. variability arithm etic have to a g r e e - been or in the involved the geom etric in all of crosses. Gene calculation sented num ber of gene in the how form ula based. allelic is genes observed m eans should be gives num ber. The differ and the a the data was the am ount of se g reg a tio n all that when m ay that m inus quite be one appeared in a l l parent the w hich the betw een involving non­ R53 Some because the arithm etic m eans. It sm aller do than supplies those of the extrem es be crosses among because pre­ not to e x is t assum ptions much factors on the are It c o u l d c rosses calculated true beyond w hich for invoiced interactions in t h e the used assum ptions of n o occurred the form ula M ethods. the valid to fit that only to be and epistasis assum ption appeared not likely failed value lit The assum ptions assum ption m ost other the M aterials The of and on rem em bered form ula tors well interactions heritability num ber probably WZ3 b e c a u s e gene and section determ ined and fa obtained It c a n n o t b e crosses P not apply the gene only p lu s fac­ in w h i c h they relatively of the true the parents. sm all 41 R esults the d i f f e r e n t were of t h e crosses calculated and (R53 for num ber. It c a n b e was crosses covery for noted recovery of e a r l y far low er silking was num bers Lowest the gene with frequency extrem es and based crosses the of th e 6. m aturity in the F T able gene gene ( A t 5 8 X O h 4 0 B ) . ( MS < i 0 6 for from in the w hich the in crosses successful obtained of m i n i m u m shown Selection m ore 3) t h a t b e t t e r are the X W23) sh o u ld be ents calculation in B . to X num bers good in a l l on the num bers X Oh40B). of far of the gene (Table late population were silking sm aller distributions silking P date for in t h o s e calculated. c rosses par­ regardless Re­ of g e n e numbe r . E stim ated reported values \ariance used nonallelic are in the gene environm ent, heritability and form ula in a d d itio n w ere (A158 X O h40B). crosses the considered interactions, heritability \a lu e s gene (R53 b i l i t y of 4 8 p e r as and the genetic for expected, of th e the cross w ere genotypes the H ighest values X Oh40B) for rather high. X Oh40B) The genetic and (MS206 relatively (MS206 the 6. to d o m i n a n c e , variance heritability w ere due c rosses ( A 1 5 8 X WZ3) in T a b le because variability interactions obtained presented a m axim um included in b o t h c r o s s e s cent for are to a d d itiv e As X Oh40B) num bers values the low b e c a u s e H erita­ suggested J j | 42 TABLE 6 ESTIM ATED G E N E N U M BER AND H E R IT A B ILIT Y VALUES N U M B E R O F DAYS F R O M P L A N T IN G TO SILKING C ros M inim um Gene N u m b er Maxi m um He r ita b ility <%) 12.6 32 5.2 48 17 6 15 R53 x W 2 3 7 5 30 A 15 8 x O h 4 0 B 4 6 39 19 4 11 MS206 x W10 MS206 x O h40B R53 x O h 4 0 B A I 58 x W 23 Mean FOR 29 43 that c o n s i d e r a b l e could be m ade generation the early progress these progress w ithin studied parent in all progenies. w ithin the relatively large im ately date by variances C o n t e n t of E a r s H a r v e s t e d a t a P e r i o d F r o m D ate of P la n tin g replications of the experim ent after half of t h e and before frost had occurred. that d o u b le - c r o s s corn days after then it w o u l d silking. this harvest be parent hybrids If t h i s expected w ould have w ere plants reached condition that F backcross to if a n y , be m ade could be w ithin m ade because of th e is U niform harvested approx­ in the e x p e r i m e n t Shaw and T hom (30) had showed m aturity approxim ately generally true approxim ately reached the little, could progress late to the very selection obtained fifty d a y s silked of selection the by sim ilar that considerable to date variance indicated populations genetic silking progenies genetic crosses H ow ever, M oisture Six low silking backcross altering segregating The in a l t e r i n g in m aturity at for h a lf of th e the tim e all ears fifty corn, in of h a r v e s t indicated. M eans, for m oisture standard content of deviations, ears and harvested total and genetic at a uniform variances period from 44 planting for the distributions six for the D om inance lationships for period fro m WTO) , the plete less than m ated than that for that the of dom inance of m o i s t u r e . crosses and of the F^ The Slight segregation that was In t h i s the 7) m ean for of the of for considerably probably and to to genetic betw een beyond interallelic gene (M S206 the F - and M cross (MS£06 was but not low er that m ean 1 to MS206 the com ­ of e a r MS£06 the w ere dom inance esti­ much less genic percentage of the of t h e and X sig­ was partial a re­ significantly of d o m i n a n t B that it w a s interactions X W10) uniform Thus, no e p i s t a s i s in th e a variance affecting from at percentage H ow ever, fell dom inance less MS206 W10. 8 indicating a low er percentage cross slightly MS£06, genes F In t h e was backcross the harvested 9. C onsiderable occurred m oisture i n t r a - a l l e i ic involved. m ean deviated there of Table backcross Frequency A sum m ary MSZ06 population. and 7 Table existed of the indicated that a low er the T able in of e a r s in in reported (Table Fj B j to cating for F^ from m ean the was given dom inance The are content is of the different m oisture. reported relationships. planting phenotypic are populations m oisture m ean nificantly crosses back- F j, indi­ genes. (Table F^. 8) show ing probably relationships TABLE 7 MEANS AND THEIR STANDARD DEVIATIONS, TOTAL AND GE NETIC VARIANCES FOR MOISTURE CONTENT OF EARS HARVESTED AT A UNIFORM PERIOD FROM PLANTING P op u la tion M ean D ays S.D . of Mean T ota l V a r ia n c e Genetii Varianc MS206 x W10 MS 20 6 to MS206 F1 F2 B x to WTO W10 43.4 0 .44 19.99 41.1 0 .2 7 19.81 42.6 0 .3 2 13.79 47.1 0 .34 32.61 18.82 5 3.8 0.41 4 4 .3 6 3 0.57 75.3 0.64 4 6 .6 2 6.02 MS206 x Oh40B MS206 4 1 .8 0.34 12.76 Bj 40.4 0.24 13.85 4 2 .5 0.24 8.17 4 4 .2 0 .2 8 19.64 11.47 50.2 0.34 3 3 .3 6 2 5 .19 60.5 0 .5 6 32 .13 to MS206 F1 F2 B j to Oh40B Oh40B 5.68 R53 x OH40B R53 4 7 .8 0 .3 2 14.36 B t to R53 43.0 0.16 7.33 4 4 .9 0 .2 8 11.05 4 6.2 0.25 17.29 6.24 4 8 .3 0.26 19.99 8.94 61.0 0.55 3 3 .3 9 F1 F2 B j to Oh40B Oh40B - 3.72 46 TABLE P opulation Mean D ays 7 (C on tin ued) S.D . of Mean T otal V a r ia n c e G en etic V a r ia n c e R53 x W23 R53 4 7 .8 0 .3 3 14.78 Bj to R53 4 2 .2 0 .2 2 12.33 4 3 .9 0 .3 5 16.91 Fi - 4 .5 8 FZ B j to W23 4 6 .0 0 .3 6 3 6.5 3 19.62 4 5 .6 0 .3 5 3 3 .23 16.32 W23 62.4 0 .9 2 112.00 A l 58 x Oh40B A 1 58 4 9 .0 0.41 20.71 B j to A l 58 4 7 .4 0 .2 8 2 0 .5 2 4 7 .9 0 .3 3 13.99 4 9 .2 0 .30 22.71 8.72 53.2 0.31 27.01 13.02 6 1 .8 0.54 30.90 F1 F2 B j to Oh40B Oh40B 6.53 A 158 x W23 A l 58 4 9 .0 0 .4 0 18.95 B j to A158 4 4 .4 0 .2 2 12.90 4 4 .9 0 .3 3 13.18 4 5 .5 0 .3 2 2 5 .8 9 12.71 4 9 .4 0 .3 5 3 1.7 5 18.57 5 8.2 0 .8 7 9 4 .2 2 F1 F2 B j to W23 W23 - 0 .2 8 47 TABLE 8 FREQUENCY DISTRIBUTION FOR MOISTURE CONTENT OF EARS HARVESTED AT A UNIFORM PERIOD FROM DATE OF PLANTING FOR POPULATIONS OF CORN CROSSES C la s s C e n te r s fo r P e r lation 32 34 36 38 40 42 44 46 Cent M o istu r e 48 50 52 54 56 58 MS206 x W10 MS206 B . to MS206 3 Fi 2 F2 B . to W10 W10 1 3 10 20 22 17 8 7 7 4 2 12 29 46 63 41 31 25 8 7 2 1 2 1 2 4 17 31 26 19 20 8 2 3 1 1 1 8 6 19 28 37 57 38 29 14 12 11 7 2 11 6 17 26 27 33 28 35 20 1 MS206 x Oh40B 1 MS206 B j to MS206 1 8 13 23 22 22 11 5 2 5 23 67 53 49 22 13 3 3 1 15 30 38 31 14 5 2 7 40 57 61 38 16 9 11 2 28 49 48 45 44 19 12 9 8 25 10 F1 B . to OR40B Oh40B 3 1 2 1 4 1 5 3 R53 x Oh40B R53 B . to Rb 1 1 ] 1 9 Fi FZ B ,1 to J 1 Oh40B ] Oh40B 3 4 11 16 29 24 19 15 17 41 66 73 44 14 9 1 1 13 23 44 26 13 6 6 3 2 4 16 34 60 65 33 19 16 12 6 3 8 18 45 57 49 35 39 13 11 6 1 6 10 14 16 9 4 3 1 48 TA BLE 8 (Continued) C la s s C e n te r s fo r P e r Cent M oistu re Total 0 62 64 66 68 70 72 74 76 78 80 82 84 86 88 MS206 x W10 1 102 1 1 1 274 134 6 5 4 7 11 7 9 5 3 2 5 4 10 285 1 2 6 10 5 13 15 14 1 6 14 5 258 1 114 MS206 x Oh40B 111 242 139 1 9 9 12 1 1 3 1 1 3 6 12 4 5 . 2 249 1 1 2 1 1 1 284 103 V R53 x OH40B 1 1 137 276 137 1 4 1 3 12 8 1 9 1 1 1 8 8 274 1 4 1 289 1 1 112 49 TABLE Population 8 (C on tin u ed ). C l a s s C e n t e r s f o r P e r Cent M o is t u r e ______________________________________________________ 32 34 36 38 40 42 44 46 48 50 52 54 56 58 R53 x W23 R53 B . to R53 1 3 12 20 22 28 21 10 8 4 9 29 51 68 42 22 9 7 1 2 2 1 2 9 26 32 27 14 12 8 2 1 1 1 8 15 28 41 44 41 35 20 23 5 10 4 3 3 9 21 45 67 47 28 14 11 10 7 3 1 2 1 2 1 5 4 6 5 7 9 11 2 F, B? to W2 3 W23 2 <0 A 158 x Oh40B A l 58 B . to A l 58 1 2 Fi 1 B . to Oh40B Oh40B 2 6 10 20 26 20 17 6 5' 2 12 23 39 58 59 20 20 11 6 4 3 4 18 32 32 12 10 9 4 5 7 39 36 46 38 31 17 15 11 1 4 4 17 39 39 58 38 24 23 2 4 6 10 13 A l 58 x W23 A l 58 B . to A l 58 2 4 Fi 1 l \ to W23 W23 4 7 1 2 13 26 24 20 12 10 3 3 11 24 47 63 58 30 15 8 2 3 1 1 10 32 27 21 13 8 3 3 1 7 21 33 57 39 34 22 14 8 4 3 4 3 20 24 44 51 29 31 24 11 5 4 1 2 2 5 6 12 8 10 8 8 50 TABLE Class 8 (C on tin ued) C enters for P e r Cent M oistur e Tota 64 66 68 70 72 74 76 R 53 x 78 80 82 84 86 88 W2 3 132 245 1 36 2 1 3 1 3 10 1 285 1 1 10 7 6 1 7 6 9 2 5 1 278 4 132 A l 58 x Oh40B 121 1 266 1 126 2 257 2 1 1 3 9 9 1 7 1 5 6 2 1 2 87 1 106 A l 58 x W23 1 1 118 268 120 1 1 4 2 2 5 10 9 258 1 5 2 4 3 266 2 1 124 51 TABLE 9 SUMMARY OF DOMINANCE RELATIONSHIPS FOR MOISTURE C ONTENT OF EARS HARVESTED AT A UNIFORM P ERIOD FROM PLANTING FOR CORN CROSSES MS206 x W10 R53 x W23 C om p lete phenotypic d om in a n ce P a r t i a l g en i c do m i na n c e No e p i s t a s i s D efinite h e t e r o s i s C om ple te g e n ic d om inan ce P ossib le ep istasis MS206 x Qh40B A l 58 x Qh40B C om ple te p h en ot ypic d omin an ce P a r t i a l g en i c do m i na nc e No e p i s t a s i s Slight h e t e r o s i s P a r t i a l ge n ic dom inance P ossib le ep istasis R53 x Qh40B A l 58 x W23 Definite h e t e r o s i s C om ple te g e n ic do m i na nc e P ossible ep istasis D efinite h e t e r o s i s C om ple te g e n ic do m inance P ossib le epistasis 5Z for ear date m oisture H ow ever, In t h e inance mean The was was not genetic that genic in t h i s pected if e p i s t a s i s silking of the cross deviated m oisture F w ere the this H ow ever, from heterosis exhibited F j, that of was not percentage th a t of the silking as great dom­ since the early parent. the b a c k c r o s s to M S 2 0 6 was and the b a c k c r o s s to O h 4 0 B so indicated for genes the means Fj mean som ewhat w ere less was than and B^ would have sim ilar dom inance not to been relationships very genic percentage probably of t h e F D om inance cross a low er Fj ex­ for to that was for indi­ ' Slight the for phenotypic cated. was that of involved for com plete of d o m i n a n t from to earliness m oisture was because m ore content date. variance Epi sta sis Oh40B ear a low er sim ilar for X Oh40B). dom inance m oisture. involved dom inance (MSZ06 for generally significantly different than that p a r t i a l w ere genic indicated less of e a r the c ross estim ated much content Bj R53. very close heterosis in t h e to R 53, for cross and Although generations significantly involved, m oisture (R53 X Oh40B) F^ approxim ation w ere a low er content because w ere the F^ m ean the F m e a n w ould the harvest m eans significantly different, of at the F m ean less was If a h i g h d e g r e e not be of expected of to than a 53 fall so c lo s e indicated to th a t in th a t to R 53 w a s of th e the C om plete estim ated negative and was to O h 4 0 B p o p u l a t i o n s the means som e of the degree content. cross E pistasis (R53 m oisture , and Bj that for mean erable sm aller relatively and Bj also sm all was backcross that of the F differences populations genes indicated for of the than to O h 4 0 B of d o m i n a n t cross (R53 X W23), was for low er early to th e late late rapid and betw een suggested ear silking than the inbred F. num ber m uch developed less and of th e W23 m oisture date m ust from of W23 w a s of t h e ears w ere in th is (due to l a t e --probably because the was noted of m o r e rapid dates). in the loss low er ear. The percentage shown a consid­ they w e re of th e of m o i s t u r e genes obtained since E xtrem e below dom inant The high? before R53, for earliness contained case B ^ to th at of R53 It w i l l b e rather a low er F j, segregated harvested silking than slightly have for of the cross. percentage percentage heterosis m eans W 2 3 had a d e p letio n of m o is tu r e m oisture in m o i s t u r e The significantly inbred at harvest silking definite exhibited. a n y of the p o p u l a t i o n s the a was to W23 w e r e of m o i s t u r e beyond F^, variance dom inance X Oh40B). content backcross much The of e p i s t a s i s In t h e F F j, genetic genic very variability W 23 i n b r e d from the e a r s 54 of p l a n t s culated genic that for silked the backc r o s s dom inance ture earliest content. for the H ow ever, percentage of m o i s t u r e W A rith­ m etic (%) M ean Geo­ m e t ric (%) 47. 1 51.0 49.4 44.2 46.8 46.2 R 5 3 x O h 4 0 B ............... 46.2 49-7 49.2 R53 46.0 49.4 48.9 49.2 51.7 51.3 A l 5 8 x W 2 3 ................... 45.5 49.3 49.0 M ean 46.4 49.7 490 W 1 0 ............... MS206 x MS206 x Oh40B x W23 ................... A l 58 x OH40B F value . . . .................................. . ........................... * Significant 179.7** at the 5% l e v e l . ** S i g n i f i c a n t a t t h e 1% l e v e l . 122.4** 58 TABLE B to P j P o p u la t ion C alculated O btained M ean (%) A rith­ m etic (%) 10 ( C o n t i n u e d ) B j to C alculated M ean Geo­ m e t ric Population O btained M ean <%) (%> A rith­ m etic <%) M ean Geo­ m e t ric (%) 41.1 43.0 43 0 53.8 59 0 56 6 40.4 42 2 42.2 50.2 51.5 50.7 43 0 46.4 46.3 48.3 53.0 52.3 42 2 45.9 45.8 45 6 53.0 52 2 47.4 48.5 48.5 53.2 54 9 54.4 44.4 47.0 46.9 49.4 516 511 43.1 45.5 45.5 50.1 53.8 52.9 35.0** 37.4** 14.6* 9.4* 59 As in the w ere s tu d y of less silking than e ith e r explained by the epistasis w hich w as ences w ere m eans for typic obtained the nificant means and m eans of th e tained and values indicated ever. this that not calculated (A 158 X W £3), in some From the to P j m eans rather involving inbred the B X £» poor m eans. m eans R53 w ere The B substantiated for the dom inant genes contributed it c a n n o t be concluded w hether the 1 to P the the How­ for the for observed betw een the From gene crosses. X Oh40B). hypothesis of th e ob­ F individual differences by R53. nature of the com parisons. obtained of t h e sig­ geom etric case in the large pheno­ obtained populations, in b o t h differ­ a highly (MS£06 X O h 4 0 B ). (A158 fits any the heterosis or In t h e to P with com plete of the arithm etic best geom etric slight m ean populations. close calculated of the of v a r i a n c e , the fit w a s crosses and analysis of the that H ardly and calculated to be along crosses the all c a s e s appeared arithm etic because found b etw een geom etric and the in earliness significant differen ce in t h e and th e o re tic a l obtained the populations m ean and tasis for calculated exam ple, crosses crosses. of e i t h e r For the in s o m e and did T his evident was a mean. m eans for noted difference obtained of g e n e s to P j in o t h e r s . the calculated dom inance dom inance observed date, two of e p i s ­ these action data affecting 60 t ear m oisture content H ow ever, the means than culated m eans m inim um are in c l o s e the able (A158 agreem ent that assum ptions one p a r e n t factors W£3 a ls o supplies those appeared content. true, values gene num ber. geom etric.* to the w here values the crosses X Oh40B) the values for the num bers due form ula the obtained two c a l ­ not in w h ic h to c o n ta in given w hich that valid. dates. For they differ. dom inant m ay be the crosses of the that indicated. a low er sm aller is only m in u s of the f o r m u la much prob­ involv­ assum ption other for w ere It s e e m e d As previously genes assum ptions num bers at le a s t one the (MS206 silking T his and W 10), w ere date. for X of e a r s num ber for silking content for gene gene to the fa c t was (MS206 for calculated calculated m oisture calculated only p lu s f a c to r s the for calculated calculated W henever are The For gene of the ture cases 11. have been among or closer heritability crosses those low W£3 m a y in a ll heritability. with th o se three than the m eans slightly and in T a b le and less and num ber rem aining much w ere arithm etic differed num ber reported m eans arithm etic gene X Oh40B), ing geom etric the Gene w as-predom inantly ear are th an the m o is­ not true 61 TABLE 11 EST IM A T E D G E N E N U M B E R AND HER1TAB1LITY V A LU ES M O ISTURE C O N T E N T O F EA R S H A R V E ST ED AT A U NIFORM P E R IO D FR O M PL A N T IN G C ross M inim um Gene Numbe r M axim um He r ita b ility (%) 10.5 58 MS<>06 x O h 4 0 B 5.4 58 R53 x OH40B 7 1 36 R53 x 3 0 54 A 158 x O h 4 0 B 4 0 38 A 158 x WZ3 * 3 49 M S£06 x W10 M ean WZ3 FOR 49 bl The m axim um to i n d i c a t e the F that ture content also be to the at of a n y of the the tim e expected fro m late 7) w e r e parent large O nly selection because the and genetic In c r o s s e s content w ere than based ear m oisture W23 was x m oisture content w ere larger in a l t e r i n g gating for involved. ear m aturity could be on the selection on crosses selection on date values silking for silking heritability w ere for the other expected of e a r the b a s i s from of s ilk in g date. m oisture M ore in the five that crosses for in the selection m oisture neg­ m aturity values obtained parent was dates early date expected early for (Table X W10), be other three could variances could p r o g r e s s for m ois- populations (M S^06 c o n te n t- - indicating basis of e a r to the values m oisture w ithin populations S im ilar silking selection Good p ro g re s s crosses obtained than H eritability populations than f r o m content 11 tended basis genetic W Z3 h e r i t a b i l i t y from Table backcross the of th e of the those expected and for (A158 X O h40B ). case since in from on the the (A158 X Oh40B) involving w ould be in w h i c h w ithin crosses, variance higher made indicated. the b a c k c r o s s progress on harvest in the be reported crosses selection within ative of in all (MS206 X O h40B ), Irom values good p r o g r e s s could generation w heritability ear cross crosses m ore progress w ithin segre­ content at harvest • M oisture In t w o harvested was adjacent fifty d a y s determ ined. late-silking be C ontent From rem em bered desirable early. season than som e ears silking riety or frost, have w eather it w a s m oisture silking had not ears to Shaw all reached m oisture c o n t e n t of e a r s only F j studies double-cross silked than ears data, late ears w ere of the of the of the w hich m aturing content som e interpretation ear of the it had should less of p la n ts prevailed during the portion. Frost occurred Thom (30), ears dry w eight m axim um In t h e on the b a s is that m a x im u m In th e and conditions. concluded cent. for ears later w hich part of th e before harvested. reached that Days experim ent, m oisture poor for earlier w ere and of p l a n t s w eather apparent content was conditions the of the silking, In th e the C ooler A ccording after after that during of t h e replications WlO. w eather silked of E a r s H a r v e s t e d F i f t y the D ate of Silking Pollination inbred 63 * of the full m aterial of i n c o m p l e t e ears harvested R ather w eight not was of S h aw hybrids was reduced and w ere used, and R ather until the and high after M arston obtained w hile and fifty d a y s and of v a ­ before denting to a p p r o x im a te ly Thom, fifty d a y s regardless harvested m aturity. dry harvested (27) the 40 p e r M arston, present study 64 included the F^, parental dition to the Fj single-cross hybrid days there after six silking. The tim e of m a x i m u m The m eans variances and the are total was H ow ever, the inbred obtained line follow ing that in th e for backcrosses sm aller that in t h e involved w eather betw een in d i f f e r e n t 1Z. not the total after populations num ber dis­ of the of p l a n t s uniform the was Frequency used harvest obtained crosses that m aturation to the late results m ay w ere Because conditions of t h e conditions The populations conditions The and fifty d a y s the 13. relationships. discussion w eather for T able agreem ent w eight fifty from m eans added for confidence results. D om inance differences in of e a r s m ature deviations Table in a d ­ single-cross not dry content in F^ w ere ear standard reported populations in the apparently m oisture num ber m uch the their ear are reported planting. to the and for crosses harvest sam e Even that crosses in t h i s hybrid ears the tributions backcross som e and genetic for and w ere determ ined. silking inbred, have m ost the considerably w ere with late of m entioned ears, the the know ledge influenced by le ss the previously m aturing is p r e s e n t e d affected of c o r n parents. for of th e the favorable parents results. w eather and the 65 TABLE 12 MEANS AND THEIR STAND AR D DEVIATIONS. TO TA L AND G ENETIC VARIANCES FOR MOISTURE C O N TEN T OF EARS H ARVESTED F I F T Y DAYS A F T E R SILKING Mea n Days P op u l a t io n S.D. of Mean To tal V a r ia n c e MS206 x W10 MS206 to MS206 F1 F2 B j to W10 W10 G e n e ti c V a r ia n c e • 45 ;8 0 .4 7 7.54 43.4 0.27 6.50 43 .8 0 .3 2 4 .5 5 46.1 0 .2 5 5.80 1.25 4 9 .8 0.38 12.02 7.47 63 .4 1.41 49.98 1.95 MS206 x O h40B MS206 44.0 0 .3 9 5.95 Bj 42.8 0 .2 6 5.04 43.7 0.28 3.40 45.2 0 .2 5 5.32 1.92 48.6 0.4 0 13.32 9.9 2 54.3 0 .5 7 11.14 to MS206 ' F1 F2 B j to O h4 0B Oh40B 1.64 R53 x Oh40B R53 Bj to R53 F1 F2 B j to Oh40B Oh40B 48.5 0 .4 3 7.06 45.6 0 .1 9 3.04 46.2 0 .2 8 3 .38 47.1 0 .3 8 12.71 9.3 3 48.3 0 .3 2 9 .3 3 5.95 5 4 .8 0 .6 8 15.31 - 0 .3 4 66 TABLE P o p u l a t io n Mea n Days 12 ( C o n t in u e d ) S.D . of Mean To tal V a r ia n c e G e n e ti c V a r ia n c e R53 x W23 R53 Bj to R53 Fi 47.3 0 .2 9 3.19 44.0 0 .2 0 3.32 43.1 0 .2 6 3.00 0.3 2 F2 B j to W23 43.8 0 .2 9 8.09 5.09 44.3 0 .2 5 5.06 2.0 6 W23 46.6 0 .9 8 35.40 A l 58 x O h40B A l 58 49.3 0 .45 7.20 B ^ to A 15 8 47.5 0 .3 5 10.67 48.1 0.4 0 5.97 49.2 0.34 9.15 3.1 8 50.6 0 .3 2 9.20 3.23 55.8 0.6 2 12.71 Fi F2 to OH40B Oh40B 4.7 0 A l 58 x W23 A l 58 47.6 0 .4 6 8.75 Bj 45.4 0.21 3.74 45.4 0 .2 6 2.46 46.1 0 .42 14.51 12.05 47.2 0 .3 8 12.42 9.96 49.6 1.40 59.15 to A 1 58 F1 F2 B l to W23 W23 1.28 67 TABLE 13 FREQUENCY DISTRIBUTION FOR MOISTURE CONTENT OF EARS HARVESTED F I F T Y DAYS FROM THE DATE OF SILKING FOR POPULATIONS O F CORN CROSSES _ Populat ion P e r Cent M o istu re __________________________ _______________________ 33 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 MS206 x W10 1 MS206 B . to ] MS206 ] 1 r i U B .to W10 W10 1 2 4 5 1 2 8 1 4 9 12 11 9 9 5 5 4 2 1 6 4 13 15 12 12 11 6 3 5 1 1 3 2 1 2 1 7 5 8 4 5 10 12 9 21 13 1 3 ], j 8 6 1 3 8 7 1 5 3 3 6 2 1 2 MS206 x Oh40B MS 20 6 B to ] MS206 ] Fi 3 1 2 4 3 3 10 8 15 10 10 12 3 1 2 3 7 1 3 9 12 16 20 4 B? to 1 On40B ] Oh40B 4 2 7 7 5 9 7 1 1 2 3 6 2 1 2 1 1 2 7 6 2 1 5 10 10 15 12 8 3 5 4 1 3 • 4 2 8 3 1 4 4 R53 x Oh40B R53 B to RS Z 4 ] ] 3 F1 F 2 B to ] Oh40B ] Oh40B 1 6 6 7 8 3 2 7 23 16 23 6 5 2 2 1 3 6 1 1 4 6 5 2 1 9 12 5 2 2 4 2 8 3 3 3 5 8 17 4 5 15 8 11 15 2 2 7 9 9 5 18 12 1 1 2 68 TABLE 13 (C o n tin u e d ) P e r Cent M o is t u r e To tal 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 MS206 x W10 34 89 45 94 1 1 ' 1 1 2 3 85 1 3 1 2 1 1 3 2 25 MS206 x OK40B 39 76 42 87 1 3 1 1 2 1 85 1 1 34 R53 x OH40B 1 38 88 42 1 1 3 1 88 1 1 4 91 1 1 1 1 33 TABLE 13 ( C o n t i n u e d ) P e r Cent M o is tu r e __________________________________ Popu- 33 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 R53 x W23 R53 B . to R53 4 ] ] 1 ] ] 1 1 1 4 8 10 2 4 16 17 16 14 10 5 7 8 4 4 4 1 1 1 4 2 1 4 9 12 12 10 16 15 7 3 2 1 9 11 16 12 14 8 8 2 2 3 2 2 5 1 1 4 3 3 2 1 8 2 3 3 5 2 1 1 8 13 15 13 1 1 3 9 5 3 3 3 1 2 7 14 3 5 1 9 13 11 13 7 2 2 4 4 3 F1 F2 B to W23 W23 3 7 10 2 1 2 1 A158 x Oh40B A 158 B . to AI58 3 ] ] 1 1 4 F1 4 F, B^ to ] Oh40B ] OH40B 5 3 3 3 9 5 5 6 2 6 3 14 13 4 4 8 12 4 * 1 3 3 2 2 2 1 A158 x W23 A 158 B . to A158 2 ] ] 1 Fi 1 1 B ?to W23 W23 ] ] 1 1 1 5 7 1 5 3 2 13 12 24 12 10 5 3 1 1 2 10 10 6 4 3 5 7- 5 10 16 13 7 4 6 4 1 4 4 12 15 10 10 9 5 3 1 3 1 3 4 1 7 1 6 2 1 1 3 5 1 2 1 2 2 2 70 TABLE 13 ( C o n t i n u e d ) P e r Cent M ois tur e - — ■ ■ ■-------------------------------------------------------------------------------------------------56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 Total R53 x W23 38 82 44 1 94 83 37 A 1 5 8 x OH40B 36 1 1 89 38 1 3 2 3 1 80 1 1 3 4 1 91 1 1 1 33 A 1 5 8 x W23 1 • 41 86 37 1 1 1 1 1 1 1 1 84 85 2 30 71 A content T able sum m ary of e a r s 14. For hibited fo r as cross to for low er Since than did (MSZ06 the that there m oisture of t h e dom inance not a p p e a r date one (Table days Septem ber 3) after 29 - the Fj degree of g e n i c for the of t h e it F was in th is of the F .. F i M w was X in m o i s t u r e . to e x t r e m e lateness in s ilk in g , silking. show s silking that The the conditions frequency ears to d e v e lo p for before to to MS<£06. that no large This condition ear-drying killing fro s t dif­ Inbred differences from W10, dom inance tVlO. distribution o f W 10 h a d back- Fpistasis relatively B early slightly le s s cross. variable w eather by believed . and the of the contributed ex­ silking high genes in was with variance and varying after rather because in heterosis backcross for m oisture presented of the MS£0h population, high the that estim ated m eans is days of genetic involved due with d iffe re n c e s the to b e the fifty m ean involved extrem ely and content actually W10 pollination, slight was betw een probably to a W10). for than content variance Bj less was silking of the Since much after X m oisture 12) . was ferences was ear relationships days a com parison genetic was cross (Table ear that genic the MS206 it a p p e a r e d dom inance fifty by MS206 the harvested a low er evidenced parent of on thirty in e a r associated silking to fifty - occurred on 1L TABLE 14 SUM M ARY O F DOM INA NCE R E L A T IO N SH IPS FO R M O ISTU R E C O N T E N T O F EARS H A R V E S T E D F IF T Y DAYS A F T E R SILKING F O R C O R N C RO SSES MS206 x W10 R53 x WZ3 Slight h e t e r o s i s No genic d o m i n a n c e No e p ista sis D efinite h e te r o s is P a r t i a l genic d o m in a n c e P ossible epistasis MSZ06 x Q h 4 0 B A 158 x O h 4 0 B C o m p le te phenotypic. dom inance P a r t ia l genic d o m in a n c e No e p is ta s is Slight h e te r o s i s (E vidence for o r against genic d o m in an ce not clear) Possible epistasis R53 A 158 x x Qh40B Slight h e t e r o s i s C o m p le te genic d o m in a n ce Possible epistasis W^3 Slight h e te r o s i s A lm o st c o m p le te genic dom inance P ossible epistasis 73 In t h e to c ross MS<£06 w e r e plete close phenotypic content. The sm aller genetic variance of the m ore is b e lie v e d that m oisture dom inance than for there the Oh40B, epistasis in 13) b e y o n d ing F the B^ backcross betw een not to b e to MS£06 fo r that of the or MS£06 and ear (MS£06 interallelic m oisture X Oh40B) and e a r gene content w ere m oisture for was than the Altho ugh be low er Because in th is Com­ ex­ ear-drying, for Fj of the and B^ Seg­ ear m oisture indicated that considerable sim ilar to a (Table occurred. after- silking fo r results uniform obtained period rel­ to cross. have it ear low er m ust B j m oisture probably of the fifty d a y s at ear to O h 4 0 B . interactions content low er to M S£06 can involved backcross Fj MS£06. sm aller MS£06. m ean and of dom inance by the a conditions genic contributed of th e m ean m uch to O h 4 0 B slight appeared the and the for date genes m ean backt ross in w e a t h e r was difference int r a - a l l e l i c cross the of of the for for the indicated fo r of the variation large R esults that estim ated atively regation was variance variability plained by X Oh40B), approxim ations genetic slightly part (MS206 for from the silk­ date of p lan tin g . in th e Slight heterosis cross (R53 was X Oh40B), exhibited since for the F^ a low er m ean m oisture was content significantly 74 less than lations for that of w ere high e a r m oisture riod date from ability was and in th e of th e of g e n e s of e a r for contributed by that m eans was later ditions betw een in for the low er F 6 and silking and a in t h e uniform studies earliness com plete genic of pe­ was genetic days and harvest negative fifty F^ it a p p e a r e d in t h e for The content B^ contributed genetic B . to 1 m ean revealed w ere the Because of Fj fifty d a y s two p a r e n t s m eans both p a re n ts The two p a r e n t s drying. the at suggested m oisture of the of m o i s t u r e of t h e R53 Also, popu­ segregation distribution, of e p i s t a s i s R53. little five vari­ dom inance after silking R53. of th e percentage to ear A com parison with degree first observed cross. content involving backcross very frequency in t h i s of t h e and was m oisture crosses m eans the of the som e a low er the together beyond involved planting, exhibited close populations epistasis silking Because relatively B j to O h 4 0 B that R53 the had there was and dom inant of the less not B^ (R53 heterosis date approxim ately ears W23 in d icated cross definite after to R 53 variance of t h e of equal. w eather significant to W23, Bj R53 c o m p a re d degree The observed of g e n ic W23 con­ difference it a p p e a r e d to the som e a low er H ow ever, genes to for silking. favorable a X W23) that heterosis. to t h a t of dom inance for the g e n e s contributed for low er e a r m oisture indicated interm ediate p aren tly contained the inheritance dom inance. of th e have F been data and and m o re In t h i s days rapid cross, after date, the days the The have means for due realized ear for and w e re in e a r genic m eans that ear silked con­ date earlier harvested at a from som e fifty uniform planting m oisture to m ay m oisture in s i lk in g harvest slight of e a r m oisture indicated by the F ^ and A158. F the harvested m asked on of e p i s t a s i s of e a r s rapid ap­ depletion extent by silking. (A158 X Oh40B), and the ears those uniform W 23 g e n e s betw een variability from of R 5 3 f o r e a r l y of t h e variability 13) content, critical degree content (Table both p a r e n ts to be som e in th e segregation m oisture differences m oisture In t h e Since low er to the different of the silking--as the b a c k c r o s s e s sm all sim ilar populations expected of m o i s t u r e planting. cross for extrem e been a low er percentage after genes backcrosses, results genes dom inance. of the loss effects In t h e for genic the had not b e e n fully dom inant in b o t h b a c k c r o s s silking w e re period fro m H ow ever, could not be involved te n t of W23 m a y R53. dom inant Because , F by w ere for heterosis ears fifty difference the genetic approxim ately exhibited harvested significant Because was the betw een variances sam e, the of 76 evidence for or segregation against for low er and A 158 o c c u r r e d ear and closeness means epistasis m ay Slight the cross less lor have of th e been for backcross of A 1 5 8 to A 158 w a s five the of t h e and much --indicating occurred. The indicated that was exhibited in Fj was significantly dom inance was indicated A158 b ecau se sm all F Fj cross m ean genic SI i g h t t h a t of th e populations m o i s t u r e - content C om plete c o n trib u te d by interactions in t h i s low er not c le a r. to A 158 and the first since was content beyond gene involved (A158 X W23). the g e n e s m oisture interallelic heterosis than that dom inance in t h e b a c k c r o s s th at int r a - a l l e l i c of t h e genic the less genetic variance than that of t h e of F and Cm backc r o s s dom inant were to genes low er segregation tions (Table to l e s s that F^, H ow ever. for rapid for m oisture low e a r 13) The large w eather Some relatively sm all relations m oisture content late. and W23 m o s t in m o i s t u r e favorable silked of t h e W23. harvest occurred conditions m ay differences in the depletion b e ca u se than som e several A158. and ears sim ilar in th e b a c k c r o s s popula­ v a r i a b i l i t y of W 23 m a y h a v e b e e n epistasis the b a c k c r o s s e s . obtained at likely co n trib u ted The for drying have betw een been the characteristics stu d y of the of e a r s m oisture due on plants involved b e c a u se means of the of t h e Fj, dom inance con ten t of e a r s 77 h a r v e s t e d by the two m e t h o d s w e r e so m e w h a t d ifferent. h a r v e s t of e a r s at a unif or m p e r io d f r o m planting, of the g e n e s for At the the full e ff e c t rapid e a r m o i s t u r e depletion contained by W2 3 had not be en f ully r e a l i z e d . A c o m p a r i s o n of the do m inance m atu ri ty st u d i e s r e la ti o n s h ip s for the thr e e r e v e a l e d that s o m e d e g r e e of h e t e r o s i s for e a r l i ­ n e s s was ex h ibi t e d in the c r o s s e s and (A158 X W23) (R53 X O h 4 0 B ) , (A158 X Oh40B). in e v e r y c o m p a r is o n . The c r o s s showed c o m p l e t e phenotypic dom inance for e a r l i n e s s (MS206 X W10) in the stu d i e s of s ilk in g date and e a r m o i s t u r e content at a uniform har ve st p e r i od f r o m planting. H o w e v e r, slight h e t e r o s i s the e a r h a rv es t fifty da ys a f t e r silking. inance f o r low m o i s t u r e w a s Oh40B) f o r both e a r m o i s t u r e was exhibited C om plete phenotypic d o m ­ indicated fo r the c r o s s st u d ie s. w as e x hi b i t ed fo r e a r l y s i l k i n g . in H ow ever, In the c r o s s (MS206 X slight h e t e r o s i s (R53 X W23), c o m ­ plete phenotypic do mi nanc e w a s indicated for e a r l y silking and d e f ­ inite h e t e r o s i s f o r the two e a r m o i s t u r e s t u d ie s . The c h a n g e s of e n vir on m en t during the gr owing s e a s o n may have been an i m p o r ­ tant f a c t o r in d e t e r m i n i ng whe ther a p a r t ic u la r c r o s s exhibited phenotypic d o mi nanc e o r h e t e r o s i s fo r the three m aturity st u d ie s . In m atu ri t y s t u d i e s of t o m a t o e s . P o w e r s ( 2 2 ) showed that phenotypic 78 dominance may heterosis may evidence and was be be upon all indicated three plete on silking period alter silking was genic vested vest lor cross was content dominance and indicated lor harvest dominance lor earliness for of genic silking uniform m oisture date silking, genu cross studies dominance' for period after in the both and from moisture date content was and ex­ partial cross earliness was indicated planting for uni- the m oisture dominance a For only partial (A158 silking com­ filty d a y s genic for content X Oh40B). for dominance earliness (R53 of e a r s However, genic was However, in studies at Complete X Oh40B) WZ3 ) the harvested in the are earliness (A158 X ear (MS^06 and for for c ross heterosis ( MSci Ob X WTO) , of e a r s However that processes X Oh40B) the This phenomena genetic genic earliness m oisture hypothesis identical that season. dominance Complete silking the and genic fifty d a y s hibited. lor of (R53 For season intermediate studies a crosses p l a n ’T n g complete at of complete studies. and dominance the alm ost the from in the X WZ 3 ) . m or exhibited. hibited support physiological same dominance lorm in in o n e in a d i f f e r e n t the for date indicated degrees maturity genic by a i ro s s represent Complete was clearly presented dominance dependent exhibited har­ the har­ was ex­ indicated partial genic 79 % dominance lor a uniform period dominance was In a l l the two lower from not m oisture planting, clear three crosses ear for involved possibly However, was exhibited v ol v i n g fifty inbred in the or days no e p is ta s is against was MS^06 degree harvest after genu evident in degree of the in t h e at silking Some rem ainder stronger the crosses. crosses 111 - R53 Nature of gene sumption of a r i t h m e t i c backc r o s s populations silking are means were between less the two small differences were of t h e arithmetic For or the ear the geometric means in a l m o s t a means means to P for the and populations, com parisons and and mean F^ the and after the obtained differences The calculated The difference Bj calculated B^ of t h e P ^ means. of the as­ and the significant the the cas-es b e c a u s e Fj the on the fifty days small all highly for action means were between based content In a l l calculated revealed obtained 15. means means gene moisture* Table obtained B Calculated geometric identical X geometric in than of v a r i a n c e mean or calculated means analysis a c t ion for presented to P j the early to a for e\ idem c for studies, the was exhibited harvest involving of e p i s t a s i s it and the m aturity was between calculated to P j populations arithmetic and b differed very little, and the mean of t h e obtained 80 TABLE 15 O B T A IN E D AND C A L C U L A T E D A R IT H M E T IC AND G E O M E T R IC MEANS FOR MOISTURE CO N TEN T O F EARS H A RV ESTED F I F T Y DAYS A F T E R SICKING F^ Population Calculated Obta mod Mean C ros s <%) Mean A r it h m e tit Geo­ m e t ric (%) { % ) 46 1 49 I 48 6 MS<£06 x O h 4 0 B 45 L 46 4 46 2 R 5 3 x Oh40B 47. 1 48 9 48 8 R53 4 3.8 45 0 45 0 A I 58 x O h 4 0 B 49 I 50 3 50 3 A 158 46. I 47 0 47 0 46 3 47 8 47 6 MSZOo x W10 x WZ3 x W23 Me an F value 2 1 8 Significant at the 5% l e v e l Significant at the 1% l e v e l * - * 3 0 . 2 ’' 81 TABLE Bj to P j Population 15 (C on tin u ed ) B j . Calculated Obtained Mean (%) to P ^ Population Calculated Arith m e tic Geo­ m e t ric (%) (%) Obtained Mean <%) Arith m e tic <%) Geo­ m etric (%) 43 4 44 8 44 8 49 8 53 6 5Z.7 4<£ 8 43.9 43 9 48.6 49.0 48 7 45.6 4 7,4 47.3 48.3 50 5 50.3 44 0 4 5. 0 ESTIM A TED G E N E NU M BER AND H ERITABILITY VALUES WEIGHT O F EARS HARVESTED AT A UNIFORM PERIOD FROM TIME OF PLANTING CrOSS MSZ06 x W10 MSZ06 x OK40B R53 x OH40B R53 x WZ3 M inimum G e n e xr Numw ber Z1 I 19.Z FOR Maximum He r ita b il ity <%) - 10 14 -30 11 A 158 x O h 4 0 B - -54 A I 58 x WZ3 - -48 j j |l 98 Weight Ears days after of were harvested silking, and standard deviations, in T a b l e 21 period those that dry and are ears were harvested to earlier eighty-three days after development after silking 133 d a y s after obtained for and b a c k c r o s s in a l l crosses. 22. toward the and later Ears of p l a n t s did not ear it that have frost the harvesting later a fifty-day of a k i l l i n g for rem em ­ conditions silked reported numbers of t h e weather their ar^ should be part fifty means, variances total Again different replications The genetic quite because heavier ear populations In the to the the were that the heterosis means significantly la r g e r In a l l weight. crosses dominant were and Table relationships apparent MS206 b e c a u s e total planting O h 4 0 B ) . it w a s genes determined. From than than period for which o c c u rre d planting D o m in a nce was weight in harvested subjected two adjacent distributions reported Days from the Frequency populations bered E ars H arvested Fifty th e D a t e of Silk in g The larger for means X W10) parents ear to MS206, of t h e heterosis Fj. F . of b o t h p a r e n t s and had weight of t h e b a c k c r o s s e s than those decided than those (MS206 late crosses, (MS206 X contributed than the to the It i s late more early parent parent reasonable to 99 TABLE 21 MEANS AND THEIR STANDARD DEVIATIONS, TOTAL AND GENETIC VARIANCES FOR WEIGHT OF EARS HAR­ VESTED FI FTY DAYS FROM DATE OF SILKING P op ul atio n Mean Gram s 3.D. of Mean Total V ariance G ene tic Va ria n c e MS206 x W10 MS206 Bj to MS206 Fi F2 B t to W10 W10 55.9 3. 12 331.75 126.4 3.41 1034.49 179.5 4.80 1035.79 139.4 2.93 806.28 -229.51 151.8 3.85 1259.61 223.82 54 .'5 4.67 545.63 - 1.30 MS206 x Oh40B MS206 B l to MS206 F1 F2 B j to Oh40B Oh40B 56.8 2.70 285.00 122.2 3.51 934.70 187.8 3.72 580.83 127.3 3.65 1160.92 580.09 139.6 3.82 1239.73 658.90 104.1 4.43 668.33 353.87 R53 x Oh40B R53 Bj to R53 F1 F2 B j to Oh40B OH40B 78.9 2.91 322.71 162.0 2.91 745.27 195.0 5.16 1117.74 138.6 3.19 893.20 -22 4.5 4 143.8 3.18 918.87 - 1 9 8 .8 7 100.6 5.73 1082.95 -3 7 2 .4 7 100 TABLE P op ula tio n Mean Days 21 (C on tin u ed ) S.D. of Mean Total Variance G ene tic Varia n c e R53 x W23 R53 Bj to R53 F1 F2 B j to W23 W23 87.3 1.68 107.80 165.8 2.20 396.82 2 0 1. 5 2.86 359.42 156.5 3.24 989.29 629.87 168.2 3.08 787.46 428.04 104.8 5.31 1044.88 A1 58 x Oh40B A158 Bj to A158 F1 F2 B j to Oh40B OH40B 37.40 • 90 .6 4. 18 629.66 141. 2 3.58 1143.26 194.4 4.66 824.97 143.8 3.42 934.59 109 62 150.8 3.82 1324.66 499.6 9 9 2.2 4.99 823.11 318.29 A158 x W23 A158 B j to A 15 8 Fi r 2 B to W23 W23 95 .7 3.81 594.30 147.6 2.96 753.03 2 0 5 .5 4.62 789.84 148.0 3.85 1247.25 457.41 158.6 4.85 2002.04 1212.20 91.5 6.71 1350.55 - 36.81 10 1 TABLE 22 F R EQUEN CY DISTRIBUTION FOR WEIGHT O F EARS H A R VESTED F I F T Y DAYS FROM TIME O F SILKING FOR P OPU LA TIO N S O F CORN CROSSES C lass Centers in G r a m s f o r E a r W eight P o p u la t io n 15 25 35 45 55 65 75 85 95 105 115 125 135 145 8 11 8 15 MS206 x: W10 3 MS206 to MS206 4 6 6 9 3 1 2 2 1 1 3 2 2 5 1 1 Fi F, 2 Bj to W10 W10 1 1 3 4 2 5 5 MS206 2 7 4 to MS206 3 3 1 12 13 15 17 3 3 3 1 2 6 6 5 1 2 1 1 4 12 7 3 3 3 6 2 3 1 MS206 Bj 6 Oh40B X ' 3 6 8 9 8 8 3 F1 F2 B to Oh40B 3 1 1 Oh40B 3* 3 1 2 1 1 3 5 4 2 6 9 12 8 14 3 6 4 7 10 10 4 5 7 2 4 2 2 1 11 9 R53 x: OH40B R53 Bj 2 1 2 2 9 10 9 3 1 1 2 to R53 F2 B j to Oh40B Oh40B 1 2 F1 1 1 1 1 1 2 1 1 2 1 2 4 3 1 3 4 11 17 15 1 6 7 8 7 13 4 4 2 4 3 2 TABLE C la ss 22 (C on tin u ed ) Ce nt e rs i in G r a m s fo r Ear Weight Total 175 155 165 185 195 205 215 225 235 245 255 265 275 MS206 x W10 34 13 10 2 5 3 7 5 8 4 5 8 4 7 6 1 2 1 94 13 11 12 7 6 4 2 85 89 2 1 45 25 MS206 x Oh40B 39 76 14 2 4 4 2 5 6 10 7 2 1 13 12 7 5 8 4 4 5 1 1 42 1 87 1 2 85 1 34 • R53 x Oh40B 38 10 12 15 10 8 1 4 1 1 1 5 5 5 8 3 6 7 11 7 5 17 10 11 4 1 1 3 88 1 4 42 1 88 1 91 33 TABLE C lass 22 (C on tin u ed ) Centers in G r a m s fo r E a r Weight copulation 15 25 35 45 55 65 75 85 95 105 • R53 2 R53 B 115 125 135 145 * W23 X 6 14 10 6 1 1 8 4 4 11 17 2 7 4 6 6 3 2 1 2 to R53 Fi 1 F ?. 1 1 1 1 B j to W23 2 W23 1 5 5 4 4 A l 58 x Oh40B A 1 58 1 B j to A158 1 3 1 2 2 5 7 6 2 6 1 4 3 8 5 9 13 1 F, 1 F2 B to OH40B 1 3 Oh40B 1 2 1 3 2 1 6 2 2 2 1 11 8 13 1 1 2 2 1 6 5 15 3 6 4 4 2 4 1 1 3 2 B j to A158 W23 W23 X 4 9 8 4 1 2 7 8 5 10 9 1 ■ Fi F2 B to W23 1 1 1 1 2 1 3 2 1 2 1 2 A l 58 A 1 58 11 1 3 1 3 5 5 9 10 1 1 4 2 2 3 3 3 1 5 4 5 3 1 2 104 TABLE C l a ss 22 (C ontinued) Ce nte rs in G r a m s for Ear Weight Total 155 165 175 185 195 205 215 225 235 245 255 265 275 R53 W23 X 38 19 14 10 9 1 2 1 7 10 7 10 13 11 10 4 3 5 9 19 11 9 4 16 3 1 8 3 82 5 1 44 2 4 1 1 1 94 83 37 1 A158 x Oh40B 36 12 6 4 6 3 1 1 I 1 89 4 2 4 5 3 2 4 6 6 38 16 7 6 4 4 10 16 16 5 2 1 1 80 1 2 1 A l 58 1 91 ■ 33 W23 X 1 41 5 16 • 5 3 1 1 1 3 6 4 2 5 11 10 7 9 6 1 5 8 13 10 11 9 14 2 86 7 1 2 2 5 1 2 • 37 84 85 30 1 05 assum e been th at the even by f r o s t means larger before if s o m e harvest velopm ent b efo re In t h e R53 w a s for cross that larger In t h e X WZ 3 ) , a revealed that ever, the would have on the F £ values the equal of the Thus relative to h e t e r o s i s for e a r of g e n e and b a ck c ro ss it i s under action. O btained populations r e p o r t e d at the b o tto m are of th e in e a c h late w eather to m a k e distributions three presented for-large How­ probably conditions any definite two p a r e n ts of a crosses. and calculated table (A158 cross. parents of the con­ harvest dom inant genes equal in t h e s e genes sam e and frequency im possible contributions weight The ear to to O h 4 0 B - - of d o m i n a n t R53. for both p a re n ts larger de­ of W10 (A158 X O h 4 0 B ) . and to the ear of t h e b a c k c r o s s reported of f a v o r a b l e have in d e v e l o p m e n t backcross inbred means backc ro s s e s somewhat mean contribution early backcross low m e a n t h a t of th e a larger the N ature than the stopped would and inco m p lete to the X Oh40B), contribution developm ent conclusions cross been pollination (R53 X W23). alm ost means Poor the p r e v i o u s l y s t u d y of the to O h 4 0 B had not been from crosses w'eight w a s for e a r was for the W10 a n d ears higher weight made to contributed (R53 there ear clusion was ear frost significantly mdic a ti n g of B j in means Table 23. for F in d ic a te d th a t f o r the 106 TABLE 23 O BTA IN ED AND C A L C U L A T E D A R ITH M ETIC AND G E O M E T R IC M EAN S FO R W EIGH T O F E A R S H A R V E S T E D F IF T Y DAYS A F T E R SILKING F z P o p u l at ion C alculated O btained M ean (gm s.) C ros s A rithm etic (gm s ) M ean Geom etric (gm s ) MS206 x W 1 0 ............................... 1 39 4 1 17 4 99 5 MS206 x Oh40B 127 3 1 34 1 120.2 138 6 142.4 1318 156 5 148 8 138.8 R53 x Oh40B R53 x W2 3 . x Oh40B 143.8 142/9 133.3 A I 58 x W 2 3 ....................................... 148.0 149 6 1 38 7 142 3 139 2 127 1 M ean F value . . . . . . . . ....................... 0.51 ! Significant at the 5% lex el Significant at the 1% l e v e l 00 xn A 158 107 TABLE 23 B j to P j P o p u l a t i o n Calc u lated O btained Me an (gms ) A rith­ m etic (gms ) (Continued) Bj M ean Geo­ m e t r ic (gms ) O btained M ean (gm s.) to P opulation C alculated M ean --------------------------------A rithGeometic m etric (gms ) ( g m s .) 1 <£6.4 117.7 100 2 1518 11 7 0 98 9 12 2 2 122 3 103 3 139 6 14 6 0 139 8 16 2 0 137 0 124 0 143 8 147 6 140 1 16 5 8 144 4 1 32 6 168 2 153.2 145 3 14 1 .2 142 5 132 7 1 50 8 14 3 3 1 33 9 147.6 150.6 140.2 158 6 148 5 137 1 144 2 135 8 12 2 2 152 1 14 2 .6 132 5 2.89 18.1: * 2 44 6 50 108 and backcross betw een the arithm etic m ean m e a n , of lor the the com parison the For tdditive. md of conclusion Sprague the num bers of gene and could oubtedly of be the much and that in num bers at low er high (R53 and that w ere The F oi the calculated obtained of the betw een geom etric \alue geom etric data fit the car in dry m eans obtained m eans of t h e hypothesis weight agreem ent h e r i t a b il i t y F^ made and existed for 13 ^ t o w ere with th at the ef- predom inantly that o: {20} Neal (14) are than to the Since crosses could not estim ates given harvest form ula R elatively [ Oh40B.) was heritability im m aturity um ptions the determ ining that ;ene and differences significance harvests, and X Oh40B) ects obtained num ber R53 m eans differences m eans approached and than ulations the genes Gene jreater Significant of T his K inm an significant B ^ to P ^ p o p u l a t i o n s . both of th e no obtained obtained and population ects of the m eans the P populations* in and the real heritability be for crosses 24 gene and M inim um for In v i e w of o n e w-as w hich of the of the b a s ic num bers c al - are efas- un- values. values X W<3 3) i n d i c a t e d variance c alc u l a t e d Table these Fj ( MS^) (E^ X L>^) type b e ­ c a u s e o f a lo w e r f r e q u e n c y o f g e n e s of the la t e in b r e d s , w h ich p ossess o u tsta n d in g c o m b in in g a b ilit y f o r y ie ld . 1 16 H y b rid s e e d p r o d u c tio n by the p r o p o s e d m e th o d w ould be m u c h l e s s d if f ic u lt and e x p e n s i v e than by the c o n v e n tio n a l m e th o d . F o r the p r o d u c tio n o f e q u a l q u a n tit ie s o f d o u b l e - c r o s s seed, the p r o p o s e d m e th o d w ould r e q u ir e a s m a l l e r a m o u n t of s e e d o f the i n b r e d s and a m u c h s m a l l e r q u an tity of s i n g l e - c r o s s s e e d (E X L.) than that r e q u ir e d f o r the m e th o d ( E . X L . ) X (E X L _ ). * A m (b s m a l l e r a m o u n t of s i n g l e - c r o s s m e th o d i s seed r e q u ir e d fo r the The su ggested e s p e c i a l l y im p o r t a n t b e c a u s e of the d if f ic u lt y o f m a t c h ­ in g e a r l y and la te i n b r e d s f o r s e e d p r o d u c tio n . In the s u g g e s t e d m e th o d the b a c k c r o s s e s to the e a r l y p a r e n t s w ould be m a d e by d e t a s s e l i n g the e n t. and u s in g the e a r l y in b r e d a s the p o lle n p a r ­ T h e r e f o r e , a m u c h g r e a t e r y i e l d o f foundation b a c k c r o s s s e e d p e r a c r e w ould be o b ta in ed fo r c o m b in in g the two b a c k c r o s s e s than w ould be o b ta in ed by p r o d u c in g found ation s i n g l e - c r o s s f o r m a k in g the c o n v e n tio n a l doub le c r o s s . The b a c k c r o s s seed seed w ould be p r o d u c e d on v i g o r o u s F^ p la n ts w h ile the s e e d fo r the m a k in g o f the n o r m a l double c r o s s i s p r o d u c e d on in b r e d p la n t s . It cou ld not be c o n c lu d e d w h e th e r the n a tu r e o f the g e n e a c t io n f o r s ilk in g date and m o i s t u r e a r ith m e tic or g e o m e tr ic . c o n te n t w a s p r e d o m in a n tly H o w e v e r , in a l l c a s e s w h e r e the two 117 c a lc u la t e d m e a n s d if f e r e d , the t h e o r e t i c a l g e o m e t r i c m e a n s w e r e c l o s e r to a g r e e m e n t w ith t h o s e o b ta in e d . G en e n u m b e r s c a l c u l a t e d f o r the c r o s s e s 19 fo r s il k in g d a te, 2 to 11 fo r m o i s t u r e ra n ged fr o m 5 to c o n te n t o f e a r s h a r v e s t e d a t a u n ifo r m p e r io d f r o m p la n tin g , and 1 to 5 4 f o r m o i s t u r e te n t o f e a r s h a r v e s t e d f ifty d a y s a f t e r s i lk in g . con­ A ll of the a s s u m p ­ t io n s of W r ig h t's f o r m u la did not a l w a y s a p p ly to the d ata i n t h e s e stu d ie s. H ow ever, it is b e l i e v e d that the v a l u e s o b ta in e d m a y be o f s o m e v a lu e in in d ic a tin g the r e l a t i v e p r o g r e s s that m a y be e x ­ p ected fro m s e l e c t i o n fo r e a r l y s ilk in g d a te o r low e a r m o i s t u r e in the s e g r e g a t in g p o p u la tio n s of the c r o s s e s . M ore ra p id p r o g ­ r e s s w o u ld be e x p e c t e d fo r the c r o s s e s w h e r e lo w e r g e n e n u m b e r s w e r e in v o lv e d . F o r the fo u r c r o s s e s in v o lv in g R53 and A 1 5 8 , th e m u c h lo w e r g e n e n u m b e r s o b tain ed f o r the m o i s t u r e c o n te n t of e a r s h a r v e s t e d f ifty d a y s a f t e r s ilk in g than f o r s ilk in g date m a y in d ic a t e that s o m e o r a l l of the d o m in a n t g e n e s a f f e c t in g s ilk in g d ate w e r e not a c t i v e f o r e a r m o i s t u r e d e p le tio n . H e r it a b i li t y v a l u e s m u s t be c o n s i d e r e d a s a m a x i m u m b e ­ c a u s e g e n e t ic v a r i a b i l i t y o t h e r than that w h ic h i s w a s in c lu d e d . s t r i c t l y a d d itiv e H ig h e r a v e r a g e h e r i t a b i li t y v a l u e s w e r e o b ta in ed f o r 1 18 ear m o istu r e c o n te n t a t both h a r v e s t s than fo r s ilk in g d a t e - - i n d i ­ c a tin g that m o r e p rogress the b a s i s o f e a r m o i s t u r e d a te . From c o u ld be e x p e c t e d f r o m s e l e c t i o n on c o n te n t than on the b a s i s of s ilk in g a p r a c t i c a l sta n d p o in t, s e l e c t i o n fo r e a r m a t u r i t y sh o u ld n o r m a ll y be done a t a m u c h l a t e r u n ifo r m h a r v e s t date than the one r e p o r te d in t h is in v e s t ig a t io n ; i t p r o b a b ly w ould not be done fif t y d a y s a f t e r s ilk in g o f in d iv id u a l p la n t s . The i m m a t u r it y of e a r s a t both h a r v e s t p e r i o d s m a y h ave in f lu e n c e d the a c c u r a c y o f the c o n c l u s i o n s or y ield . r e a c h e d on e a r w e ig h t A high d e g r e e o f h e t e r o s i s w a s e x h ib ite d f o r h e a v i e r e a r d r y w e ig h t in a l l c r o s s e s in both h a r v e s t s . A lth ou g h the la te i n b r e d s W10, O h40B , and W23 c o n tr ib u te d m u c h to the o b ­ s e r v e d h e t e r o s i s , the e a r l y in b r e d R53 w a s n o te w o r th y in i t s c o n tr ib u tio n . T hus R53 sh o u ld be a good e a r l y in b r e d fo r u s e in the d e v e lo p m e n t of h i g h - y i e ld i n g and e a r l y h y b r id s . The c o n c lu s io n that the g e n e s a f f e c t in g e a r w e ig h t f o llo w e d the a r i t h m e t ic s c a l e w a s in a g r e e m e n t w ith the r e s u l t s o f N e a l (20) and K inm an and S p ra gu e (14). c r o s s e s from s in g le - c r o s s y ie ld s i s a r i t h m e t i c g e n e a c tio n . P r e d i c t i n g y i e l d s o f double b a s e d on the a s s u m p t i o n o f 1 19 G ene n u m b e r s that could be c a lc u la te d for e a r w eig h t w e r e p robably m u c h too low b e c a u s e at l e a s t one of the b a s ic a s s u m p ­ tio n s of the f o r m u l a - - t h a t one p a ren t s u p p lie s only plu s f a c t o r s and the o th e r , only m in u s f a c t o r s - - w a s o b v io u sly not tr u e . Both p a r e n ts contributed to the o b s e r v e d h e t e r o s i s . The low h e r it a b ilit y v a lu e s fo r the e a r h a r v e s t at a u n i­ fo r m p e r io d f r o m planting in d ic a te d that v e r y lit t le , if any, p r o g ­ ress could be e x p e c te d fr o m w ithin the s e l e c t i o n fo r h e a v ie r e a r w e ig h t s e g r e g a t in g p r o g e n ie s of any of the c r o s s e s H o w e v e r, fo r the e a r h a r v e s t fifty d a y s a f t e r s ilk in g , stu d ied . r a th er good h e r it a b ilit y v a lu e s w e r e c a lc u la te d fo r the c r o s s e s (MS206 X Oh40B), (R53 X W23), and (A158 X W23). F o r e a r w e ig h t and e a r m o i s t u r e content at both h a r v e s t s , h ig h e r h e r i t a b i l i t i e s w e r e obtained fo r the c r o s s e s (R53 X W23), (MS206 X Oh40B), and (A 158 X W23). SUMM ARY The in h e r it a n c e of m a t u r ity and e a r w eig h t w e r e i n v e s t i ­ gated w ith s i x d iffe r e n t c r o s s e s of e a r ly X la te in b red l in e s of co rn . D om inance r e la t io n s h ip s , gen e n u m b e r s , nature of gene action , and h e r it a b ilit y w e r e stu d ied . Silking date, m o is t u r e c o n ­ tent of e a r s h a r v e s t e d at a u n ifo rm p e r io d fr o m tim e of planting, and e a r m o is t u r e con ten t fifty d a y s a fte r s ilk in g w e r e u se d a s m e a s u r e s of m a tu r ity . Data on e a r w eig h t w e r e obtained at two h a r v e s t p e r io d s . 1. In e a c h c r o s s , e ith e r c o m p le te phenotypic d om inan ce o r s lig h t h e t e r o s i s fo r e a r l i n e s s w a s in d ic a te d in a l l m a tu r ity s t u d ie s . S om e d e g r e e of h e t e r o s i s fo r e a r l i n e s s w a s p robab ly i n ­ v o lv e d in e a c h c r o s s . H o w e v e r , the m a jo r portion of the o b s e r v e d e a r l i n e s s a p p e a r e d to be due to d om inance of g e n e s . 2. C om p lete g e n ic d om inance for e a r ly s ilk in g , p a r tia l to c o m p le te g e n ic d o m in a n ce for lo w e r e a r m o is t u r e at a uniform h a r v e s t p e r io d f r o m planting, and v a r ia tio n s fr o m none to c o m p le te g e n ic d om in a n ce fo r lo w e r e a r m o is t u r e fifty da ys a fte r s ilk in g w e r e in d ic a te d fo r the c r o s s e s . The data s u g g e s t that the c l a s ­ s if ic a t io n of in b r e d l in e s e n t ir e ly on the b a s i s of silk in g date m a y 121 not fu r n is h the d e s i r e d in fo r m a tio n on m a tu r a tio n . Som e in b r e d s c o n tain ed dom inant g e n e s fo r e a r ly silk in g that did not appear to e f f e c t e a r m o i s t u r e d e p le tio n . O ther in b r e d s w e r e la te in s ilk in g but con tain ed d om inant g e n e s fo r rapid e a r d ryin g. 3. E pi s t a s i s fo r e a r l i n e s s a p p e a r e d to be exh ib ited by the d om inant g e n e s con trib u ted by the e a r l y inbred R53 and p o s s ib ly by A 158. E a r l y in b r e d s containing dom inant e p is t a t ic g e n e s for e a r ly m a t u r it y should p r o v id e m o r e u n ifo r m ity of m a tu r ity in a double c r o s s of the type (E^ X L.^) X (E^ X L.^) than an e a r ly in b red with dom inant but n o n e p ista tic g e n e s for e a r l i n e s s . E p is- t a s i s of dom in ant g e n e s m a y aid in ex p la in in g r e p o r ts that c r o s s e s of the type (E . X L, ) X (E X i X L ) w e r e no m o r e v a r ia b le than 6 M that of the type (E^ X E^) X (L^ X L^). 4. In the m a tu r ity s t u d ie s , it could not be concluded w h eth er gen e a c tio n w a s fo llo w in g e ith e r the a r ith m e tic o r the g e o m e tr ic s c h e m e s . from m ent In a l l c a s e s w h e r e c a lc u la te d m e a n s d iffe r ed the a c tu a l m e a n s , the g e o m e t r ic m e a n s Were w ith the obtained. c l o s e r to a g r e e ­ It w a s p robable that both ty p e s of gene a c tio n w e r e in v o lv e d . 5. M in im u m g en e n u m b e r s ranged fr o m 5 to 19 fo r s ilk in g data, f r o m 2 to 11 fo r m o is t u r e content of e a r s h a r v e s t e d at a 1L I u n ifo rm p e r io d f r o m planting, and f r o m 1 to 54 for m o i s t u r e c o n ­ tent of e a r s h a r v e s t e d fifty d ays a f t e r s ilk in g . 6. to M a x im u m h e r it a b ilit y v a lu e s ranged fr o m 48 p e r c e n t fo r s ilk in g date, m o is t u r e 11 p e r cent 36 p e r c e n t to 58 p er c en t for con ten t of e a r s h a r v e s t e d at a u n ifo rm p e r io d fr o m planting, and 22 p e r c e n t to 83 p e r c en t fo r m o is t u r e conten t of e a r s h a r v e s t e d fifty da y s a fte r silk in g . m o is t u r e H e r it a b ilit ie s for e a r con ten t a v e r a g e d h ig h e r than h e r it a b ilit y of s ilk in g date. T h e r e w a s an in d ic a tio n that silk in g date w as a ffe c te d m o r e by e n v ir o n m e n t than e a r m o i s t u r e content. 7. C o n s id e r a b le h e t e r o s i s w a s exh ib ited for h e a v ie r ea r w e ig h t in a l l c r o s s e s . in i t s Of the e a r ly in b r e d s , R53 w as e x c e p tio n a l co n trib u tion of fa v o r a b le g e n e s fo r h e a v ie r e a r w eight. G e n e s a ffe c tin g e a r w eig h t fo llo w e d the a r it h m e t ic 8. M a x im u m h e r it a b ilit y v a lu e s c a lc u la te d in d ic a te d that v e r y l i t t le , i f any, p r o g r e s s s e l e c t i o n fo r h e a v y e a r s w ithin the schem e. for e a r w eight could be e x p e c ted fr o m se g r e g a tin g p r o g e n ie s of any o f the c r o s s e s at the u niform h a r v e s t p e r io d . H o w e v e r, good p r o g r e s s could be e x p e c te d fr o m s e l e c t i o n within the F tion of the c r o s s e s genera­ (MS206 X Oh40B), (R53 X W23), and (A158 X W23) in the c a s e of a h a r v e s t fifty d ays a fte r silk in g . 1^3 9. It w a s p r o p o se d that an com b in ation of e a r ly lin e s con taining dom inant e p i s t a s t i c g e n e s with late l in e s p o s s e s s i n g e x c e p tio n a l c om b in in g a b ility for y ie ld m a y be m ad e a s fo llo w s: [ ( ( E j X L j ) E j ) X « E 2 X E ) E 2 )]. 'if LITERATURE CITED 1. A n d e r so n , D. C. The r e la tio n b e tw e e n s i n g l e - and d o u b lec r o s s y i e l d s in co r n . Jour. A m e r . Soc. A gron . 30: 209-11. 1938. 2. Burton, G. W. Q uantitative in h e r ita n c e in p e a r l m i l l e t (P e n n is e t u m g la u c u m ). A gron . Jour. 4 3 :4 0 9 -1 7 . 1951. 3. C a s t le , 4. C h a r le s , D. R ., and Sm ith, H. H. D istin g u ish in g b e tw e e n two ty p e s of g en e a c tio n in quan titative in h e r it a n c e . G e n e t ic s 2 4 :3 4 -4 8 . 1939. 5. D o xta to r, C. W., and Johnson, I. J. P r e d ic t io n of doub lec r o s s y i e l d s in c o r n . Jour. A m e r . Soc. A gron . 28: 460-62. 1936. W. E ., and W right, S. A m ethod of e s tim a tin g the num ber of g e n e tic f a c t o r s in c a s e s of blending i n ­ h e r it a n c e . S c ie n c e N. S. 54:223. 1921. • 6. E ck h a rt, R. C ., and B rya n , A. A. E ffe c t of m ethod of c o m ­ bining two e a r l y and two la te in b r e d s of c o r n upon the y ie ld and v a r ia b ilit y of the r e s u ltin g double c r o s s e s . Jour. A m e r . S o c. A gron . 3 2 :6 4 5 -5 6 . 1940. 7. E m e r s o n , R. A ., and E a s t , E. M. The in h e r ita n c e of q uan ti­ ta tiv e c h a r a c t e r s in m a i z e . Neb. A g r. Exp. Sta. R e s . B u i. 2. 1913. 8. F r e e m a n , W. H. The in h e r ita n c e of husk length, e a r length, and d a y s to s ilk in g in m a i z e . Unpublished P h .D . t h e s i s , U n iv e r s it y of I llin o is lib r a r y , C ham pagne-U rbana, 111. 1945. 9. G o ld sc h m id t, R. P h y s i o l o g i c a l G e n e t ic s . Y ork and London. 1938. 375 pp. i l l u s . New 1 25 10. Goodwin, R. H. The in h e r ita n c e of flo w e r in g t im e in a s h o r t day s p e c i e s Soli dago s e m p e r v i r e n s L.. G e n e t ic s 2 9 :5 0 3 19. 1944. 11. H a y e s , H. K., and Johnson, I. J. The b reed in g of im p r o v e d s e lf e d li n e s of co r n . Jou r. A m e r . Soc. A gron. 31 :7 1 0 24. 1939. 12. H a y e s , H. K., Johnson, I. J., and Rinke, E. H. A c o m p a r is o n of the a c tu a l y ie ld of double c r o s s e s of m a iz e with th e ir p r e d ic te d y ie ld fr o m s in g le c r o s s e s . Jou r. A m e r . S oc. A gron. 3 5 :b 0 -6 5 . 1943. 13. J en k in s, M. T. M eth od s of e s tim a tin g the p e r fo r m a n c e of double c r o s s e s in co rn . Jou r. A m e r . S o c . A gron. 26: 1 9 9 -2 0 4 . 1934. 14. Kinman, M. L,., and S p ra gu e, G. F . R elatio n b etw een num ber of p a ren ta l l in e s and t h e o r e t ic a l p e r fo r m a n c e of s y n ­ thetic v a r i e t i e s of c o rn . Jour. A m e r . Soc. A gron. 37: 3 4 1 -5 1 . 1945. 15. L.eng, E . R. T i m e - r e l a t i o n s h i p s in t a s s e l d e v e lo p m e n t of in b red and hybrid co rn . A gron . Jour. 4 3 :4 4 5 -5 9 . 1951. 16. E in d s tr o m , E . W. E x p e r im e n t a l data on the p r o b le m o f quan­ tita tiv e c h a r a c t e r in h e r ita n c e in m a i z e and t o m a to e s . G e n e t ic s 2 8 :8 1 -8 2 a b s. 1943. 17. E u sh , J. JL. H e r ita b ility of q uan titative c h a r a c t e r s in fa rm a n im a ls . H e r e d it a s , Suppl. v o l ., pp. 3 5 6 - 7 5 . 1949. 18. Mahmud, Im an, and K r a m e r , H. H. S e g r e g a tio n for y ie ld , h eig h t, and m a tu r ity fo llo w in g a so y b ean c r o s s . A gron. Jour. 4 3 :6 0 5 -0 8 . 1951. 19. M a n g e lsd o r f, P . C., and F r a p s , G. S. A d ir e c t q uantitative r e la tio n sh ip b etw een V itam in A in c o rn and the n u m ­ ber of g e n e s fo r p ig m en ta tion . S c ie n c e 7 3 :2 4 1 -4 2 . 1931. 126 20. N e a l, N. P . The d e c r e a s e in y ie ld in g c a p a c ity i n advanced g e n e r a t io n s of hybrid c o rn . Jour. A m e r . S oc. A gron. 2 7 : 6 6 6 -7 0 . 1935. 21. P in n e ll, E. L. The v a r ia b ilit y of c e r t a in quantitative c h a r ­ a c t e r s of a d o u b l e - c r o s s hybrid in co rn a s r e la te d to the m eth o d of com b ining the four in b r e d s . Jour. A m e r . S oc. A g r o n ., 3 5 :5 0 8 -1 4 . 1943. 22. P o w e r s , L. I n h e r ita n c e s of quan titative c h a r a c t e r s in c r o s s e s in v o lv in g two s p e c i e s of L y c o p e r s i c o n . Jour. A g r. R e s . 6 3 :1 4 9 -7 4 . 1941. 23. . An e x p a n sio n of J o n e s' th e o r y for the exp lanation of h e t e r o s i s . A m e r . N at. 7 8 :2 7 5 -8 0 . 1944. 24. P o w e r s , L ., L o c k e , L. F . , and G a r r e tt, J. D. P a r titio n in g m ethod of g e n e tic a n a ly s is applied to quan titative c h a r ­ a c t e r s of tom ato c r o s s e s . USDA T ech. B ui. No. 998. 1950. 25. P o w e r s , L ., and L yon, C. B. In h e r ita n c e s tu d ie s on duration of d e v e lo p m e n ta l s t a g e s in c r o s s e s w ithin the genus L y c o p e r sic o n . Jou r. A g r . R e s . 6 3 :1 2 9 -4 8 . 1941. 26. R a s m u s s o n , J. S tu d ies on the in h e r ita n c e of quantitative c h a r a c t e r s in P i s u m . H e r e d it a s 2 0 :1 6 1 -8 0 . 1935. 27. R ather, H. C ., and M a rston , A. R. A study of c o rn m a tu r ity . M ich. A g r . Exp. Sta. Q u a r te r ly B ui. 2 2 :2 7 8 -8 8 . 1940. 28. R ic h e y , F . D. H ybrid v ig o r and c o r n b r e e d in g . S oc. A g ron . 3 8 :8 3 3 -8 4 1 . 1946. 29. R obinson, H. F . , C o m sto c k , R. E ., and H a r v e y , P . H. E s t i m a t e s of h e r it a b ilit y and the d e g r e e o f dom inance in co rn . A gron . Jou r. 4 1 : 3 5 3 -5 9 . 1949. 30. Shaw, R. H ., and Thom , H. C. S. On the phenology of fie ld corn, silk in g to m a tu r ity . A gron. Jour. 4 3 :5 4 1 -4 6 . 1951. Jou r. A m e r . 127 31. S n e d e c o r , G. W. S t a t is t ic a l m e th o d s . 4th ed. C o lle g ia te P r e s s , In c., A m e s , Iowa. 1946. 32. Spragu e, G. F . The e x p e r im e n ta l b a s i s for hybrid m a i z e . B io . R e v ie w s 2 1 : 1 0 1 -2 0 . 1946. 33. S tr in g fie ld , G. H ., and T h a tch er, L. E . Corn row s p a c e s and c ro p s e q u e n c e s . A gron. Jou r. 4 3 :2 7 6 -8 1 . 1951. 34. T h a y er, J. W. The e f f e c t of v a r ia b ilit y in the d o u b l e - c r o s s corn hybrid of p a r e n ta l in b r e d s d iffe r in g in m a tu r ity and oth er plant c h a r a c t e r i s t i c s . Unpublished P h .D . th esis. M ich ig an State C o lle g e L ib r a r y , E a s t L a n sin g , M ichigan. 1949. 35. W eb er, C. R. In h erita n ce and in t e r r e la t io n of so m e a g r o n o m ic and c h e m ic a l c h a r a c t e r s in an i n t e r s p e c if i c c r o s s in s o y b e a n s , G ly c in e m a x X G . u s s u r i e n s i s . Iowa A g r. Exp. Sta. R e s. Bui. 374. 1950. 36. W haley, W. G. 37. W e is s , M. G ., W eber, C. R., and Kalton, R. R. E a r ly g e n e r ­ ation te s tin g in s o y b e a n s. Jour. A m e r . Soc. A gron. 3 9 :7 9 1 -8 1 1 . 1947. 38. W illia m s , L. F . In h erita n ce in a s p e c i e s c r o s s in s o y b e a n s. (an a b s tr a c t) G e n e t ic s 3 3 :1 3 1 -3 2 . 1948. 39. 40. W right, S e w a ll. H ete ro sis. Bot. R ev. S y s t e m s of m a tin g . 1 0 :4 6 1 -9 8 . 1944. G e n e tic s 6 :1 1 1 -7 8 . Yang, Y. Study on the nature of g e n e s c o n tr o llin g hybrid v ig o r , a s it a f f e c t s silk in g tim e and plant h eigh t in m a iz e . A g ro n . Jou r. 4 1 :3 0 9 -1 2 . 1949. 1921. CO RRELA TIO N C O E FFIC IEN TS B ETW EEN W EIGHT AND M A TU RITY C orrelation w eight and ear and n u m b e r system s. m oisture of d a y s characteristics w ere (2) b y som e C om stock cv that heavy * covariance weight the expression of a c r o s s , relationship is genetic form ula correlation they of two do n o t heritable. To correlations supplied to B u r t o n cvX Y F2 - cvXYFj = - * = = - = - - = = = - - ----V(vXF2 - v X F j)(v Y F 2 - vYFj) and v = variance. coefficients and betw een e a r ear Although betw een The dry dry for both h a rv e stin g (31). effects, ear ear used: correlation correlations used m easured crosses. fo r both h a rv e s t p e rio d s ative silking generation nonheritable the and betw een relationship of th e was C orrelation percentage the of the calculated betw een to was segregating calculated for G enetic w here in a how m u c h elim inate planting procedure m easure w ere percentage from Standard coefficients indicate coefficients EAR w ere betw een weight and are ear days w eight and e a r from planting 25. Significant n e g ­ sh o w n in T a b le o b t a in e d in a l m o s t all weight was associated m oisture cases, with e a r l y to s i l k i n g indicating silking and with low ear m oisture the selection content. of h e a v y of the p o p u la tio n s tained for for the m ature the ear ears the G enetic V alues variability F . at a uniform heavy ears w ere for early ability ears this the crosses in within any was were planting num ber than of im been largely show n in than that sim ilar, produced for re Table heavy selection the of t h e indicating percentage the m aturity m oisture ob­ calculated because in m o i s t u r e and e arly with low are greater cases program w ere h a rv e st period. could not be F^ larger m ay have for in m o s t In a b r e e d i n g correlations The harvest correlations relatively low w ith high yielding select heavy values crosses genetic percentage period from silking. ear w e i g h t of th e silked vest periods. after uniform som e In g e n e r a l , w hich to harvest higher in e a r in m o i s t u r e encountered crosses. correlations for plants low should be higher negative a t the for difficulty slightly h a r v e s t fifty days sponsible 26. ears of the In g e n e r a l , No ears a t the that and har­ of plants it w o u ld be p o ss ib le , content. TABLE 25 CORRELATION C O EFFIC IEN TS B E T W E E N EAR A N D M A T U R I T Y IN C O R N C R O S S E S Population E a r H arv est at U niform P e rio d F r o m Planting W EIGHT E ar H arvest Fifty Days A fte r Silking j“ XZ XY XZ XY M S 2 0 6 x W10 Bj to M S 2 0 6 B J to W10 •0 . 5 * * -0.4** ■0. 4** -0.3** - 0 . b** - 0 . 9 ** •0.5** - -O.c** -0.7** 0.4** _0.5** ** -0.7** -0.9** •0.3** •0.5** 0 . 8** •0.5** • 0 . b * * 0.4** - 0. 5 * * ■0. L * * 0.5** 0.7** -0.7** •O . o * * 0.7** - 0 . b** • O . o 0 . 8* * R53 x O h40B Bj to R53 •0.4** -O.t ** Bj to O h 4 0 B - A158 x Oh40B B t to A 158 B ] to O h 4 0 B • O. u * * -0.5** •0 . * 0.3** -0.7** -0.7** ■0 . L * * 0.6** -0.5** -0.5** 0.5** 0.4** -0.7** -0.7** •0.7** 0.7** 0* T A B L . E 25 ( C o n t i n u e d ) E a r H a rv e s t at Unit o r m P e r i o d F r o m Planting Population XZ XY MS206 B B^ to MS20 6 to O h 4 0 B E ar H arvest Fifty Days A fte r Silking XY XZ x Oh40B _o . 6 * * - 0. 5 * * - - 0. e * * -0.7** +0.1 -0.4** -0.5*+ - -0.4** -0.4** - 0. 8** 0 . ' * * -0.7** 0.2 - 0.2 - 0 . 8* * - 0. 8* * 0. 1 - 0. 1 R53 x W23 Bj to R53 - 0 4 *+ - 0 i ■* * + 0 .6 * * -0.7** -0.3* -0.5** - 0 . L* y' -0.7** -0.3** _0.3** -0.5** -0.7** - - Bj to W2 3 0.2 -0.5** A 1 5 8 x W23 B x to A 158 -0.3** -0.4** -0.4** - 0.2 0 . 8** -0.9** -0.4** - 0.8** -0.3** -0.4** -0.5** -0.4** 0 . 5** - 0 . 3 ** -0.5** - - B } to W23 - 1 number X = e a r d ry weight; Y = e a r m o is tu r e of d a y s f r o m p l a n t i n g to s i l k i n g . * S ig n ifican t at the 5% l e v e l . ** S i g n i f i c a n t a t t h e 1% l e v e l . percentage; 0. 6 * * * Z = GENETIC C O R R E I.A iH W S B E T W E E N EAR W EIGHT M A T U R I T Y IN C O R N C R O S S E S C ross MSZO . x E a r H a r v e s t at U nitorra P v r.o d F r o m i ’l a n : i n g E ar H arvest Fifty Days A fte r Silking XY* XZ XV XZ -0.4 ^-0.5 -0.9 -0.5 -0.~ -0.9 -0.3 0 0 +0.Z -0.7 +0.Z W10 MS ZOo x O h 4 0 B R53 x Oh40B R53 x WZ3 A 15o x O h 4 0 B -A158 x AND WZ3 * X = e a r y d ry weight; Y = e a r m o is tu r e n u m b e r of d a y s f r o m p l a n t i n g t o s i l k i n g . content; Z =