INHERITANCE OF AND INTERRELATIONSHIPS OF TRYPTOPHAN,
NIACIN, PROTEIN,'AND KERNEL WEIGHT
IN CORN

by
Kuo, Chun-yen

A THESIS
Submitted, to th e School o f G rad u ate S tu d ie s o f M ichigan
S ta te C o llege o f A g ric u ltu re and A pplied S cien ce
i n p a r t i a l f u l f i l l m e n t o f th e re q u ire m e n ts
f o r th e d eg ree o f
DOCTOR OF PHILOSOPHY

D epartm ent o f Farm Crops
1953

ACKNOlrfLSDGMaSIT
The w r i t e r w ishes to e x p re ss h is s in c e re th a n k s
and a p p r e c ia tio n to D r. E. C. Rossman f o r h i s guidance in
o u tlin in g t h i s re s e a rc h and f o r h is a d v ice i n th e p re p a ra ­
t i o n o f th e m a n u sc rip t.

G ra te fu l acknowledgment i s a ls o

due to D r. R. W. Luecke and D r. E. J . Benne f o r t h e i r v a l­
u a b le a s s is ta n c e and to M rs. Jean V in cen zi f o r h e lp in g w ith th e
a ss a y s re p o rte d h e r e in .

The w r i t e r i s a ls o in d e b te d to th e

M ichigan C e r tif ie d H ybrid Seed Com P ro d u cers A sso c ia tio n
f o r g r a n tin g th e funds w hich made t h i s s tu d y p o s s ib le .

TABLE O F CONTENTS

Page
INTRODUCTION ..................................................................................................

1

REVIEW OF LITERATURE..................................................................................

3

MATERIALS AND METHODS........................................

11

EXPERIMENTAL RESULTS ANDD I S C U S S I O N .....................................

23

A Survey of Tryptophan a n d N i a c i n C o n t e n ts o f
Sixty Inbred l i n e s .........................................

23

Interrelationships o f T r y p t o p h a n , N i a c i n , P ro­
t e in and Kernel W eight. . . . . . . . . . . . . .

27

Inheritance Study o f N i a c i n , T r y p t o p h a n , P r o te in
and Kernel Weight
......................................................

43

SUMMARY.............................................. .................................................

59

LITERATURE CITED..........................................................................................

62

INTRODUCTION
Improvement i n n u t r i t i v e v a lu e o f c o m f o r human and
anim al consum ption i s one o f th e o b je c tiv e s i n some co m
b re e d in g program s.

A pproxim ately e ig h ty - f iv e p e rc e n t o f th e

t o t a l corn p ro d u c tio n i n th e U nited S ta te s i s u sed f o r l i v e ­
s to c k fe e d in g .

I n o th e r p a r t s o f th e w o rld , m illio n s o f

p eople depend upon c o m f o r a p r i n c ip a l p a r t o f t h e i r d i e t .
Com p r o te in i s low i n try p to p h a n and l y s i n e , two o f
th e e s s e n t i a l amino a c id s f o r norm al grow th.
low i n n ia c in c o n te n t.

Corn i s a ls o

Lack o f n i a c i n i s m ainly re s p o n s ib le

f o r p e lla g r a i n th e h ig h co rn d i e t a r e a s .
S ince th e e a r l y work o f Hopkins (2 1 ), a number o f
i n v e s t ig a ti o n s have shown t h a t th e chem ical co m p o sitio n o f
th e co m i s u n d er th e c o n tr o l o f g e n e tic f a c t o r s .

T h e re fo re ,

improvements i n p r o te in , try p to p h a n and n ia c i n c o n te n ts o f
c o m a re p o s s ib le by p la n t b re e d in g te c h n iq u e s .
P r o te in , try p to p h a n and n i a c i n c o n te n ts i n co rn a re
a l l q u a n tita tiv e ly in h e r ite d .

The su c c e ss o f a b re e d in g

program to im prove th e q u a n tity o f th e s e c o n s ti tu e n t s may be
im proved w ith more in fo rm a tio n co n cern in g th e mode o f
in h e r ita n c e and th e i n t e r r e l a t i o n s h i p s o f th e s e c o n s ti t u e n ts .
The o b je c tiv e s o f t h i s s tu d y w ere:
(l)

To su rv ey s i x t y in b re d s a s so u rc e m a te r ia ls f o r

2

b re e d in g h ig h n ia c i n and h ig h try p to p h a n c o rn .
(2 )

To s tu d y th e i n t e r r e l a t i o n s h i p s o f try p to p h a n ,

n i a c i n , p r o t e i n and k e r n e l w eight i n c o m .
(3 )

To o b ta in in fo rm a tio n on dominance r e l a t i o n s h i p s ,

n a tu r e o f gene i n t e r a c t i o n s , gene numbers and d egree o f
h e r i t a b i l i t y o f try p to p h a n , n ia c i n , p r o te in and k e r n e l w eight
in com ,

REVIEW OF LITERATURE

F eeding ex p erim en ts w ith co rn (2 , 7, 26, 29) showed
t h a t i t s p r o te in was o f low b io l o g ic a l v a lu e , due p r i n c i p a l l y
to i t s low try p to p h a n c o n te n t.

I n t h e i r m e ta b o lic stu d y o f

amino a c id s , W ilcock and Hopkin (48) d e m o n strated t h a t
try p to p h a n was d i r e c t l y u t i l i z e d as th e norm al p re c u rs o r o f
some s p e c i f i c hormone o r o th e r su b sta n c e s e s s e n t i a l to grow th.
Matsuyama and Mori (2 8 ) i n t h e i r q u a n tita tiv e stu d y o f
try p to p h a n i n v a rio u s p r o te i n s found o n ly t r a c e s o f try p to p h a n
i n co rn p r o te in a s compared t o 0 .8 3 $ , 1.33$> and 1 .0 0 $ o f
try p to p h a n i n th e p r o te in s o f soybean, r i c e and w heat, re s p e c ­
tiv e ly .
M ish le r e t a l . (32) and Powick e t aL. ( 3 8 ) s t a t e d t h a t
c o rn d i e t was low i n n ia c in c o n te n t.

Supplem enting th e co m

d i e t w ith s y n th e tic n ia c i n cu red th e d e f ic ie n c y and in c re a s e d
grow th i n t h e i r fe e d in g experim ents w ith ch ick en s and p ig s ,
re s p e c tiv e ly .
B urkholder (4 ) r e p o rte d t h a t co rn meal c o n ta in e d 10 to
15 m icrogram s o f n ia c i n p e r gram .

An a d u lt would have to e a t

1 ,0 0 0 grams o f c o m m eal p e r day i n o rd e r to meet th e d a ily
n ia c i n re q u ire m e n t o f 1$ m illig ra m s p e r day .

He su g g ested

b re e d in g a s t r a i n o f co rn w hich c o n ta in e d a t l e a s t 35 microgram
p e r gram f o r use by p eo p le whose d i e t a r y i s p e lla g r a p ro d u c in g .

4

K reh l e t a l . (24) showed t h a t e i t h e r 50 mg. o f
try p to p h a n o r 1 .0 mg. o f n ia c i n p e r 100 gram o f r a t i o n com­
p l e t e l y c o u n te ra c te d th e n ia c in d e f ic ie n c y caused by th e
in c lu s io n o f 40$ corn g r i t s i n a low p r o t e i n r a t i o n .

In

t h e i r s tu d ie s o f s ig n if ic a n c e o f try p to p h a n i n human n ia c in
m etabolism , Holman and DeLange (20) gave ev id en ce t h a t p r o te in
d e f ic ie n c y and p a r t i c u l a r l y try p to p h a n d e f ic ie n c y m ight p la y
a s ig n ific a n t ro le in p e lla g ra .
Elvehjem (13) found an in c r e a s e o f n ia c in and n ia c i n
m e ta b o lite e x c r e tio n when r a t s were fe d try p to p h a n .

He s t a t e d

t h a t th e lo n g re c o g n iz e d r e l a t i o n s h i p betw een th e consum ption
o f co m and p e lla g r a was m ain ly due to th e d e f i c ie n c i e s o f
try p to p h a n and n ia c i n i n c o m .
I n t h e i r su rv e y o f G uatem alan corn v a r i e t i e s f o r
try p to p h a n and n ia c i n , A g u irre and Bressam ( l ) found t h a t
q u a n t i t i e s o f try p to p h a n s u p p lie d by c o m p ro v id e d 50 to 118$
o f t h a t re q u ire d f o r a d u lt human m ain ten an ce, w h ile th e same
c o m o n ly s u p p lie d an av erag e o f 73$ o f th e r e q u ire d n ia c i n .
They concluded t h a t th e c o n v e rsio n o f some try p to p h a n in to
n ia c i n and th e r e l e a s e o f u n a v a ila b le o r bound n ia c i n i n
" T o r t i l l a s " p re p a re d by so ak in g co rn meal i n lim e w a te r,
acco u n ted f o r th e low in c id e n c e o f p e lla g r a i n G uatem ala.
Bonner and Yanofsky (3 ) u s in g m utant s t r a i n s o f
N eurospora s tu d ie d th e b io s y n th e s is o f try p to p h a n and n i a c i n .
They s t a t e d t h a t try p to p h a n ap p eared t o s e rv e a s p re c u rs o r o f

5

n ia c i n and a ls o proposed th e fo llo w in g h y p o th e s is .

■COO*,- i'H-duOH
A

i

Oi'-j-,Anfhr,tr{;lt OH - Ktyv^cQn'.n-z

fNi i cLC; i'l
C5 lU»-v>.£; j C. H / ;/1
I n o rd e r to determ in e w h eth er th e tr y p to p h a n -n ia c in
r e l a t i o n found i n N eurspora a ls o e x is te d i n h ig h e r p la n ts ,
Nason (33) d em o n strated i t by stu d y in g th e m ature e x c ise d
c o m embryo grown i n s t e r i l e c u l t u r e .

He found t h a t th e

a d d itio n o f try p to p h a n to th e n u t r i e n t s o lu tio n r e s u lt e d i n
a s i g n i f i c a n t in c r e a s e o f n ia c i n i n th e m ature e x c is e d c o m
embryo.
Flynn e t a l . (14) a n aly z e d in d iv id u a l s e lf e d e a rs
from an open p o llin a te d v a r i e t y f o r crude p r o te in and n ia c i n .
As th e p e rc e n ta g e o f crude p r o te i n in c r e a s e d , th e y observ ed a
marked d e c re a se i n n i a c i n .

The k e r n e ls o f medium p r o te in c o m

c o n ta in e d 3 4 .1 m icrogram s o f n ia c in p e r gram and th o s e o f h ig h
p r o t e i n co rn c o n ta in e d 2 7 .3 m icrogram s p e r gram.
S a rk a r (42) found a s i g n i f i c a n t n e g a tiv e c o r r e la ti o n
betw een p r o te in and n ia c in c o n te n t.

R odriguez e t a l . (41)

6

a ls o r e p o rte d a sm all n e g a tiv e c o r r e la ti o n ( " r " = -0 .2 4 9 )
between p r o te in and n ia c in c o n te n t o f 39 in b re d l i n e s o f
c o m i n O hio.

F rey (17) found h ig h ly p o s i t i v e c o r r e l a t i o n

betw een p r o t e i n and try p to p h a n i n two c ro s s e s o f c o m .
E a rle y e t a l . ( l l ) r e p o rte d t h a t a heavy a p p lic a tio n
o f n itr o g e n to th e s o i l r e s u l t e d i n an in c r e a s e i n th e con­
c e n tr a ti o n o f p r o te in and a d e c re a se i n n i a c i n .
M ille r .et a l . (31) r e p o r te d t h a t n ia c i n c o n te n t
appeared to be e s s e n t i a l l y in d ep en d e n t o f th e p r o te i n and
p r o te in components s tu d ie d .
I n 1899, Hopkins (21) showed t h a t i t was p o s s ib le to
in flu e n c e th e co m position o f c o m by p ro p e r e a r-ro w s e l e c t i o n .
The f i r s t e x te n s iv e p r o te in s e le c ti o n i n co rn was in a u g u ra te d
by th e I l l i n o i s A g r ic u ltu r a l Experim ent S ta tio n a t t h a t tim e .
A fte r f i f t y y e a rs o f s e le c t io n , Woodworth r e p o r te d (49) t h a t
th e h ig h p r o te in s t r a i n c o n ta in e d 19.45!* and th e low p r o te in
s t r a i n had 4 .9 1 ^ .

The s h i f t was ra p id a t f i r s t b u t became

slow er i n succeeding g e n e r a tio n s .
E a s t and Jo n es (12) a ls o r e p o rte d t h a t th e p r o te in
c o n te n t o f c o rn was an in h e rite d " c h a r a c t e r i s t i c .

They l i s t e d a

number o f o th e r f a c t o r s , such a s te m p e ra tu re , m o is tu re , and
f e r t i l i z e r , t h a t m ight a ls o a f f e c t p r o te in c o n te n t.
P rev io u s in v e s t ig a t i o n s (10, 12, 34) have shown th e
e f f e c t s o f n o n -g e n e tic f a c t o r s in flu e n c in g p r o te in c o n te n t o f
com .

S e a so n a l e f f e c t s , lo c a t io n e f f e c t s and s ta g e o f m a tu r ity

7

caused v a r i a t i o n s i n p r o t e i n c o n te n t.
I n h e r ita n c e stud;je*of p r o t e i n c o n te n t i n c o rn g r a in
(15, 19) have shown t h a t th e number o f h e r e d it a r y f a c t o r s
a f f e c t i n g p r o t e i n c o n te n t m ust be l a r g e , and low p r o te i n was
found to be dom inant i n most c a s e s .

Chem ical c o m p o sitio n o f

th e e n t i r e k e r n e l was in flu e n c e d by h e t e r o s i s s in c e h y b rid
v ig o r in c re a s e d th e c arb o h y d ra te f r a c t i o n o f c o m more th a n
th e p r o te in f r a c t i o n , th u s te n d in g t o low er th e p r o te i n p e r­
c e n ta g e .
Osborne e t a l . (35) and S h o w alter and C arr (4 3 , 44)
r e p o r te d t h a t z e in , which c o n s t i t u t e s a p p ro x im a te ly one h a l f
o f c o m p r o t e i n , was d e f i c i e n t i n try p to p h a n .
I t has a ls o been proven (2 1 , 30) t h a t s e l e c t i o n o f
co rn k e rn e l having la r g e germ s iz e would g iv e b o th s u p e r io r
q u a l i t y and q u a n tity o f c o m p r o te in and try p to p h a n s in c e
th e germ p o r tio n o f co rn k e rn e l c o n ta in s a h ig h p r o te i n p e r­
c en ta g e and a lo w er z e in p e rc e n ta g e th a n t h a t o f th e endosperm
p o r ti o n .
F o r im provem ents i n p r o te in q u a l i t y , F rey (17)
su g g este d t h a t i t m ight be more d e s i r a b le t o s e l e c t d i r e c t l y
f o r in c re a s e d p e rc e n ta g e try p to p h a n i n c o m g r a i n .

He found

com plete dominance f o r low try p to p h a n i n I l l i n o i s h ig h x
I l l i n o i s low , w h ile Hy x 1198 showed no dom inance.

P r o te in

p e rc e n ta g e i n th e I l l i n o i s h ig h x I l l i n o i s low fo llo w e d th e
a ssum ptions o f a r ith m e tic gene i n t e r a c t i o n w h ile try p to p h a n ,

8

le u c i n e , is o le u c in e and v a lin e in h e r ita n c e fo llo w e d e i t h e r
in te ra c tio n e

P r o te in p e rc e n ta g e and try p to p h a n were con­

d itio n e d a t l e a s t by 22 and 15 g e n es, r e s p e c t i v e l y .
In one c y c le o f r e c u r r e n t s e le c tio n , F re y (16) found
t h a t th e p e rc e n ta g e o f try p to p h a n was r a is e d 0 . 013%, w hich
was an in c r e a s e o f 1 2 .7 9 $ o v e r th e o r i g i n a l F2 p o p u la tio n .
S e v e ra l w orkers (20 , 25, 39, 45) have shown t h a t th e
n i a c i n c o n c e n tra tio n i n co rn was a f u n c tio n o f th e g e n e tic
c o n s t i t u t i o n w ith v e ry l im it e d in f lu e n c e o f en v iro n m en t.
They r e p o r te d t h a t s ta r c h c o rn e x h ib ite d a wide ran g e o f
n ia c i n c o n te n t when th e d i f f e r e n t v a r i e t i e s grew on th e same
s o i l i n th e same l o c a l i t y d u rin g th e same s e a so n .
M ather and B arton-W rig h t (27) n o te d t h a t th e s ta r c h y
Su gene was dom inant f o r lo w er n i a c i n c o n te n t o v e r i t s su
a lle le .

They found t h a t sw eet corn had tw ic e a s much n ia c i n

a s s ta r c h y c o rn .

G o rfin k e l (18) a ls o r e p o r te d p r a c t i c a l l y a

com plete dominance o f Su gene f o r low n ia c i n .

He found th e

n ia c i n c o n te n t o f e a r l y v a r i e t i e s to be h ig h e r th a n th e medium
and l a t e v a r i e t i e s .
Teas et_ a l . ( 4 6 ) found try p to p h a n and n i a c i n were con­
s i s t e n t l y h ig h e r i n su g ary th a n i n s ta r c h y i n th e l a t e d e v elo p ­
ment p e rio d o f k e r n e l, b u t th e y were e s s e n t i a l l y e q u a l i n th e
two g en o ty p es a t e a r l i e r s ta g e s o f k e r n e l developm ent.
R ichey and Dawson (40) showed t h a t th e mode o f i n h e r ­
i ta n c e f o r n ia c i n c o n te n t was m u ltip le f a c t o r in h e r i ta n c e

9

in v o lv in g th e j o i n t a c tio n o f many genes o f sm all in d iv id u a l
e f f e c t s w ith dominance la c k in g .

They found t h a t s in g le and

double c ro s s h y b rid s te n d e d to be in te r m e d ia te betw een th e
p a r e n ta l in b re d s i n n ia c in c o n te n t.
I n a s e r i e s o f h ig h and low n ia c in c r o s s e s , G o rfin k e l
(18) o b serv ed t h a t where th e p a r e n ts had a c o n te n t o f 22 m ic ro grams p e r gram o r l e s s , th e n ia c i n c o n te n t o f th e h y b rid s
ap p eared t o be a d d i t i v e l y d e term in e d and exceeded t h a t o f b o th
p a r e n ts .

When th e p a r e n ta l in b re d s had more th a n 22 microgram s

p e r gram th e n ia c i n c o n te n ts o f th e h y b rid s were in te rm e d ia te
betw een th e p a r e n t s .

H ybrids h ig h i n n ia c i n came from c ro s s e s

o f h ig h n ia c in in b r e d s .
I n v e s tig a t io n s by t h e Ohio S ta tio n (8 , 22, 23) have
shown t h a t g e n e tic and e n v iro n m e n ta l f a c t o r s , such a s s o i l and
sea so n , in flu e n c e d th e n ia c i n c o n te n t o f co rn h y b rid s .

D itz le r

e t a l . (9 ) found t h a t h ig h and medium n i a c i n c o n te n ts were
dom inant i n a l l th e c ro s s e s s tu d ie d and th e n i a c i n v a lu e s o f
th e h y b rid s f e l l betw een th e l i m i t s e s ta b li s h e d by th e p a r e n ta l
in b r e d s .
R ichey and Dawson (40) found t h a t th e seed p a re n t had
tw ic e th e in f lu e n c e o f th e p o lle n p a re n t on n ia c i n c o n te n t.
M ille r e t a l . (3 0 ) i n t h e i r o i l in h e r ita n c e stu d y a ls o showed
t h a t th e genotype o f th e e a r b e a rin g p a re n t had a p red o m in atin g
in flu e n c e on th e o i l p e rc e n ta g e o f th e g r a in p ro d u ced .

Source

o f p o lle n had a c o n s is te n t though r e l a t i v e l y sm all e f f e c t .

10

Norden (34) found no r e la ti o n s h ip betw een k e r n e l
w eig h t and p r o t e i n c o n te n ts .

However, he found t h a t th e

k e r n e l w eight was s i g n i f i c a n t l y a f f e c t e d by sea so n , h y b rid s ,
m a tu r iti e s and lo c a t i o n .
Leng (2 $ ) and R ichey and Dawson (4 0 ) found no c lo se
r e l a t i o n s h i p betw een k e r n e l s iz e and n ia c i n c o n c e n tra tio n .

MATERIALS AND METHODS
S ix ty in b re d s were a n a ly z e d f o r ty r to p h a n and n ia c in
c o n te n ts .

Two c r o s s e s , W23 x Oh 51 A and W23 x R53 were a v a i l ­

a b le f o r in h e r ita n c e s tu d ie s o f try p to p h a n and n i a c i n .

F£ and

b a c k c ro ss s e e d s were produced i n th e g reen h o u se d u rin g th e
w in te r 1951-1952.

The p a t t e r n s o f th e s e two c ro s s e s w ere:

(1)

High n ia c in -lo w try p to p h a n (W23)
x
Low niacin-m edium try p to p h a n (R53)

( 2)

High n ia c in -lo w try p to p h a n (W23)
x
Medium n ia c in - h ig h try p to p h a n (0h51A)

The sym bols, Pj_ and P2 , r e f e r to th e two p a r e n ta l in b r e d s ;
Bc-^ d e s ig n a te s th e b a c k c ro ss t o P-^, and Bc^ r e f e r s to th e b a c k c ro s s t o P £.
Two

rows each o f th e P-j_, Pg and

*2> B°1 and

BC2 were p la n te d on May 19,

n u rse ry .
a p a rt.

Each row c o n s is te d
The

F^_ and fo u r rows
1952 i n th e c o rn

o f tw e n ty p l a n t s spaced one

p la n ts were hand p o l l i n a t e d

each o f
b re e d in g

fo o t

t o e lim in a te p o s s ib le

e f f e c t s o f so u rc e o f p o lle n on t h e im m ediate g e n e r a tio n .

E ig h t

p la n ts o f one s in g le c ro s s were o u tc ro s s e d w ith sw eet corn
p o lle n .
A ll e a r s were m ature a t h a r v e s t.
seed c o m d r i e r a t 100 d e g re e s F .

11

They were d r ie d i n a

One hundred k e r n e ls o f each

12

e a r were counted and w eighed.

About tw o t h i r d s o f th e k e r n e ls

on each e a r were ground i n a W eber's hammer mi 11 u sin g a 20
mesh s ie v e .

Random sam ples o f th e ground co rn w ere ta k e n f o r

m o istu re d e te r m in a tio n .

These were fo u n d to be q u ite u n ifo rm

i n m o istu re c o n te n t, ap p ro x im a te ly 1 0 ^ m o is tu re .

A ll th e

v a lu e s re p o rte d a re on th e a i r - d r y b a s i s .
P r o te in A n a ly s is —One gram o f th e ground co rn was ta k e n
f o r p r o t e i n d e te rm in a tio n .

N itro g e n was d eterm in ed by

th e s ta n d a rd K jeldahl-G urm ing Method a s d e s c rib e d by th e
A s s o c ia tio n o f O f f i c i a l A g r ic u ltu r a l C hem ists ( 5 0 ) .
v a lu e s a re K je ld a h l n itr o g e n x 6 .2 5 .

P r o te in

One d e te rm in a tio n was

made on each sam ple.
M ic ro b io lo g ic a l A n a ly s is —M ic ro b io lo g ic a l methods a re
b ased on th e o b s e rv a tio n t h a t c e r t a i n m icro o rg an ism s r e q u ir e
s p e c if ic amino a c id s and v ita m in s f o r g ro w th .

U sing a b a s a l

medium com plete i n a l l r e s p e c ts e x ce p t f o r th e amino a c id s
and v ita m in s under t e s t , grow th re sp o n se s o f th e organism a re
compared q u a n t i t a t i v e l y i n s ta n d a rd and unknown s o lu tio n s .

The

a c id produced by th e organism i s m easured to d e term in e th e
amount o f grow th w hich i n d i c a t e s th e amount o f v ita m in o r amino
a c id s i n th e t e s t s o lu tio n .

The p ro c e d u re i s b r i e f l y summarized

a s fo llo w s :
T e st o rg an ism :

L a c to b a c illu s a ra b in o s u s 1 7 -5(8014) was

u sed f o r b o th try p to p h a n and n ia c i n d e te r m in a tio n s .

The

co m p o sitio n o f inoculum and s ta b f o r c u ltu r in g t h i s organism
i s shown on T able 1 .
T able 1 .

C om position o f medium f o r inoculum ( L a c to b a c illu s
a r a b in o s u s )

I n g r e d ie n ts

P r o p o rtio n

Amount r e q u ir e d f o r
200 m l.
500 m l.

B acto -p ep to n e

0.8%

1 .6 gm.

4 .0 gm.

Y east e x t r a c t

0.1% .

0 .2 gm.

0 .5 gm.

Sodium a c e ta te
(an h y d ro u s)
G lucose

0 .1 %

0 .2 gm.

0 .5 gm.

1.0%

2.G gm.

5.0 gm.

S a lt A

0.5%

1 .0 m l.

2 .5 m l.

S a lt B

0.5%

1 ,0 m l.

2 .5 m l.

2 .0 gm.

5 .0 gm.

For making s ta b ,
add 1% Bacto a g a r

S ta n d a rd c u rv e :

The s ta n d a rd s to c k s o lu tio n s f o r

try p to p h a n and n i a c i n were p re p a re d w ith 2ug/ml. and 0 . lu g /m l,
re s p e c tiv e ly .

T r i p l i c a t e tu b e s were s e t up f o r each o f th e

e ig h t l e v e l s f o r th e s ta n d a rd c u rv e s .

T able 2 shows th e

amount o f s ta n d a rd s to c k s o lu tio n i n each tu b e and F ig u re s 1
and 2 show sample s ta n d a rd cu rv es when th e v a rio u s l e v e l s o f
s ta n d a rd s o lu tio n s were t i t r a t e d w ith 0.1N sodium h y d ro x id e .
A new s ta n d a rd curve was p re p a re d f o r each new group o f a s s a y s .

14

T able 2 .

m l. o f
s ta n d a rd

Amount o f s ta n d a rd try p to p h a n and n ia c i n on th e
e ig h t d i f f e r e n t l e v e l s

u g ./m l. t r y p t .

u g ./tu b e N.A.

ml.H20

m l.B .
medium

0 .0

0 .0

0 .0 0

5 .0

5 .0

0 .5

1 .0

0 .0 5

4 .5

5 .0

1 .0

2 .0

0 .1 0

4 .0

5 .0

1 .5

3 .0

0 .1 5

3 .5

5 .0

2 .0

4 .0

0 .2 0

3 .0

5 .0

2 .5

5 .0

0 .2 5

2 .5

5 .0

3 .0

6 .0

0 .3 0

2 .0

5 .0

3 .5

7 .0

0 .3 5

1 .5

5 .0

*Each t e s t tu b e i s th u s f i l l e d up to 10 m l. m ark.

B asa l medium:

The co m p o sitio n o f b a s a l medium f o r

b o th try p to p h a n and n ia c i n d e te rm in a tio n s i s g iv e n i n T able 3 .

15

T able 3#

C om position o f 100 m l. o f b a s a l medium f o r
try p to p h a n and n i a c i n d e te rm in a tio n s

I n g r e d ie n ts

Amount

C asein h y d ro ly s a te lOOmg./ml.

10 m l.

1 - c y s tin e 4m g./m l.

10 m l.

B io tin 0 . l u g ./ m l .

0 .4 m l.

p-am inobenzoic a c id lO O ug./m l.

0 .2 m l.

Thiam ine, c alc iu m p a n th o th e n a te p y rodoxine lOQugy&l•

0 ,2 m l.

R ib o fla v in lO O ug./m l.

0 .4 m l.

A denine, G uanine, U r a c il Im g ./m l.

2 .0 m l.

S a lts A

1 .0 m l.

S a lts B

1 .0 m l.

G lucose

4.0gm .

Sodium a c e t a t e (an h y d ro u s)

4.0gm .

d -1 try p to p h a n 4m g./m l. ( f o r n ia c i n d e te rm in a tio n )

1 0 .0 m l,

N ia c in lO O ug./m l. ( f o r try p to p h a n d e te rm in a tio n )

1 4 .0 m l,

-KThe m ix tu re i s a d ju s te d t o pH 6 .6 - 6 . 8 and d i lu te d to
100 m l, -with d i s t i l l e d w a te r.

J. V

F ig u re

i_ j

S a m p le ;s t a n d a r d

ug.

p e r tu b e

— —x

j

u <-» j j i i a . i l

c u rv e

f o r ”' t r

:.i 1.:r ^ .d^ .:]LQ:
o f try p to p h a n

*±“ -1. / — v>*j

optiari: a s s a y

'iirM

17

F ig u re

2 S a m p le

N ia c in

1 -2 3 -5 3

c u rv e , f o r n i a c i n

assay

i

■025 - r G 5

-.-075 .1 0 :
ug.

!- . - 2 0 :
p e r tu b e o f n i a c i n

-130

-r^ 5

13

T ryptophan a n a l y s i s :

S in c e th e u n n a tu ra l D -fo ra s o f

c e r t a i n o f th e e s s e n t i a l amino a c id s a re n o t u t i l i z e d i n
n u t r i t i o n , th e v a lu e s e x p re sse d i n t h i s s tu d y a re f o r L try p to p h a n .

T ryptophan v a lu e s a re g iv e n a s th e p e rc e n ta g e s

i n th e whole co rn k e r n e l.

S ix te e n m i l l i t e r s o f 4N NaOH were

added t o 0 .5 grams o f th e ground sample and th e m a te r ia l was
a u to c la v e d a t 250° F . w ith 15 pounds o f p re s s u re f o r e ig h t
ho u rs to in s u r e com plete d ig e s t i o n .

C o n cen trated h y d ro c h lo ric

a c id was used to a d ju s t th e sample to pH 7 and d i s t i l l e d w a ter
was added t o d i l u t e th e sample to 100m l,

A fte r f i l t e r i n g , th e

sample was covered w ith a few d ro p s o f to lu e n e and s to r e d i n
th e r e f r i g e r a t o r u n t i l a ssa y e d .
N ia c in a n a l y s i s ;

V alues f o r n ia c i n a re e x p re sse d i n

micrograms p e r gram o f g r a i n .

One gram o f th e ground sample

mixed w ith 50 m l. o f 0.1N HCL was h y d ro ly zed i n th e a u to c la v e
f o r 30 m inutes a t 15 pounds o f p r e s s u r e w ith a te m p e ra tu re o f
121° C.

A fte r th e sample had been d ig e s te d , i t was c e n tr if u g e d

f o r 15 m in u tes a t 3500 R.P.M .

T w en ty -fiv e m l. o f th e su p e r­

n a ta n t was drawn, a d ju s te d t o pH 4 .6 w ith NaOH, and d i lu te d to
50 m l.

A fte r f i l t e r i n g , th e sample was co v ered w ith a few

drops o f tol.dene and k e p t i n r e f r i g e r a t o r u n t i l a ssa y e d .
T ryptophan and n ia c i n a s s a y s :

When th e p re p a re d sam ples

reach ed room te m p e ra tu re , d i l u t i o n s were made to g e t th e p ro p e r
c o n c e n tra tio n .

D u p lic a te sam ples o f 1 , 2, and 3 m l. were

p ip e tte d in to t e s t tu b e s and k> 3* and 2 m l. o f d i s t i l l e d w a ter

19

were added t o b rin g th e tu b e s to th e 5ml. m ark, r e s p e c t i v e l y .
F ive m i l l i t e r s o f th e b a s a l medium were added to each tu b e o f
b o th unknown and s ta n d a rd sam p les.

The tu b e s were covered

w ith m e ta l caps and s t e r i l i z e d i n an a u to c la v e f o r 12 m in u tes
a t 15 pounds o f p re s s u re a t 121° C.

The tu b e s were th e n

in o c u la te d w ith one drop o f L a c to b a c illu s su sp e n sio n which had
been t r a n s f e r r e d from th e s ta b c u l tu r e a b o u t 18 h o u rs p re v io u s ly
and had been t r e a t e d w ith a s e r i e s o f d i l u t i o n s by s t e r i l e
s a li n e s o lu tio n .

A fte r in c u b a tin g 72 h o u rs a t 37° C ., th e tu b e s

were t i t r a t e d to pH7 w ith 0.1N NaOH.

A s ta n d a rd cu rv e was p r e ­

p a re d , from which th e c o n c e n tra tio n s o f th e unknown sam ples
were d e term in e d .

The same p ro ced u re was a p p lie d f o r b o th t r y p t o ­

phan and n ia c i n d e te rm in a tio n s e x c e p t t h a t th e b a s a l medium u sed
f o r try p to p h a n a ss a y c o n ta in e d no try p to p h a n and th e b a s a l medium
f o r n ia c in a ss a y c o n ta in e d no n i a c i n .
Methods o f In h e r ita n c e S tu d y :
(1 )

H e te ro s is and dominance r e l a t i o n s h i p s :

The i n t e r ­

p r e t a t i o n o f th e d a ta f o r h e t e r o s is and dominance r e l a t i o n s h i p s
was based on th e p a tte r n s o u tlin e d by Powers (36, 3 7 ) .

Genic

v a ria n c e s and means o f th e p o p u la tio n were u sed to d eterm in e
w hether h e t e r o s i s , p h en o ty p ic dom inance, g e n ic dom inance, o r
no dominance e x is t e d .
(2 )

N ature and i n t e r a c t i o n s o f g e n e s :

The form ulas

by Powers (3 7 ) were used f o r e s tim a tin g th e e x p ec te d means on

the assumption of arithmetic and geometric gene interactions
These formulas are shown in Table 4»

T able 4®

Form ulas f o r e s tim a tin g th e e x p ec te d means on
th e assum ption o f a r ith m e tic and g eo m etric
gene i n t e r a c t i o n s

P o p u la tio n

A rith m e tic Mean

*2

P i + 2Fj_ + P2

G eom etric Mean

lo g pi + 21ogF]_ + lo g P 2
a n til o g o f

4
logFx t lo g pi
FX + PX

Be-,

a n tilo g o f

2
logF-L f lo g P 2
Be,

a n tilo g o f

* px> p2 and F^ a r e th e means o f two p a r e n ts and F^
p o p u la tio n s , r e s p e c tiv e ly .

(3 )

Gene num bers:

The form ula by C a s tle and W right (6 )

was used f o r e s tim a tin g gene num bers.
.2
(F2 ran g e)
N =
~T
8 (SF2 - S F .^)
N * th e number o f gene p a i r s
F2 range = th e h ig h e s t F2 in d iv id u a l minus th e lo w e st
Ey in d iv id u a l
2
SF0
2 == th e v a ria n c e o f th e F0
2
SFth e v a ria n c e o f th e F^

The assumptions underlying this formula are:
1.

A ll gene e f f e c t s a re a d d i t i v e .

2.

A ll genes a r e e q u a lly im p o rta n t and have
equal e f f e c ts .

3.

No dominance i s p r e s e n t.

4.

The F^ v a ria n c e r e p r e s e n ts o n ly e n v iro n m e n ta l
v a r ia n c e s .

5.

One p a re n t c o n ta in s o n ly p lu s genes and th e
o th e r p a r e n ts c o n ta in o n ly minus genes f o r th e
c h a r a c te r s i n q u e s tio n .

(4 )

H e rita b ility :

e s tim a te h e r i t a b i l i t y .

W arners method (4 7 ) was used to

In t h i s m ethod, h e r i t a b i l i t y e s tim a te s

a r e b a se d on th e v a ria n c e s o f th e t h r e e s e g r e g a tin g p o p u la tio n s ,
th e F2 and th e summed b a c k c ro sse s t o each p a r e n t.

The method

h as th e advantage o f n o t r e q u ir in g an e s tim a te o f e n v iro n m e n ta l
o r o f t o t a l g e n e tic v a ria n c e s , b u t u s e s o n ly t o t a l -w ithin popu­
l a t i o n v a r ia n c e s .
H e r i t a b i l i t y i s c a lc u la te d a s :
H e rita b ility
where (1 /2 ) D =

=

( 1 /2 ) D
y
-----

th e a d d itiv e g e n e tic component
o f th e F2 v a ria n c e ,

VFg

a

(l/2 )D

t o t a l w ith in F2 v a r ia n c e , and
a

2(VF2)

-

(VBc]_ +

VBC2 ) where

VBc}_ and VBC2 a re th e t o t a l w ith in v a ria n c e s

22

o f th e b ack ci'o sses o f th e F-^ t o th e r e s p e c t­
iv e p a r e n ts .
The assum ptions u n d e rly in g t h i s fo rm u la a r e :
1.

Genic e f f e c t s a r e a d d iti v e , lo c u s t o lo c u s (no
e p is ta s is ).

2.

G enotypic and e n v iro n m e n ta l v a ria n c e s a re
in d e p e n d e n t.

3.

The en v iro n m e n ta l components o f F^ and b a ck c ro ss
v a ria n c e s a re o f com parable m ag n itu d e.

EXPERIMENTAL RESULTS AND DISCUSSION
A Survey o f T ryptophan and N ia cin C ontents f o r S ix ty In b re d L in es
T ryptophan and n ia c i n c o n te n ts f o r s i x t y in b re d l i n e s
a re shown i n T able 5.

The av erag es were 2 3 .5 4 u g ./g m . f o r

n ia c i n and 0 .0 7 2 $ f o r try p to p h a n .

N ia c in c o n te n ts ranged

from 1 3 .4 5 u g ./g m . to 3 3 .5 4ug ./g m . a d if f e r e n c e o f 149.7$*
T ryptophan c o n te n ts ranged from 0 .0 5 0 $ to 0 .0 8 9 $ , a d if f e r e n c e
o f 78$.

K ern el w e ig h ts f o r th e s e in b re d s av erag ed 2 4 .0 4 grams

p e r 100 k e r n e ls and ranged from 1 3 .1 0 grams t o 35.00 g ram s.
C o n sid e ra b le d if f e r e n c e s i n n ia c in and try p to p h a n con­
t e n t s were e v id e n t among in b re d l i n e s t h a t had no p re v io u s
s e l e c t i o n f o r th e s e c h a r a c t e r i s t i c s .

A n a ly sis o f i n d iv id u a l

e a r s o f th e p a r e n ta l l i n e s used i n th e fo llo w in g in h e r ita n c e
s tu d ie s showed c o n s id e ra b le v a r i a b i l i t y f o r try p to p h a n and
n ia c i n c o n te n ts w ith in lo n g -tim e in b re d l i n e s o f c o m (T ab le 7 ) .
S in ce th e s e in b re d s had no s e le c tio n f o r try p to p h a n and n ia c i n ,
i t i s p o s s ib le t h a t th e in b re d s m ight be q u ite v a r ia b le f o r
th e s e c h a r a c t e r i s t i c s .

23

T able 5 .

A Survey o f N ia c in and Tryptophan C ontent o f 60 In b re d L in es Grown i n M ichigan
Experim ent S ta tio n , 1950
* (The w eight i n grams p e r 100 k e r n e ls o f each in b re d i s a ls o re c o rd e d )

In b re d s

N ia c in
ug./gm .

Tryptophan
0 /0

K ern el Weight
gm./lOO

In b re d s

N ia c in
u g ./g m .

Tryptophan
0 /0

K ern el Wei^
g m ./l0 (

R53
W?
ND230
49
W-D

18.11
28.78
27.53
24.73
18.19

.0 6 0
.056
.072
.064
.066

3 0 .8 8
1 8 ,1 0
2 0 .3 0
24.00
19.40

MS42
L317
WR3
MS4
R 9 -2 -1 -1 -1

20.41
16.93
1 8 .5 8
27.02
22.20

.087
.082
.082
.073
.077

28.10
1 4 .0 0
2 2 .5 0
20.80
29.30

M13
Ia l5 3
W25
WF9
Ohio 51A

31.09
2 6 .5 6
2 7 .6 6
27.46
27.67

.067
.082
.065
.073
.063

25.20
2 1 .1 0
28.90
22.80
27.39

MS113
MSI
P 4 4 -4 -2 -6 -2
MS24A
MS64

27.68
2 4 .9 7
14.73
20.13
3 3 .5 4

.069
.089
.076
.089
.081

25.70
22.50
3 2 .3 0
2 7.10
1 7 .8 0

M14
W23
Hy2
W10
L289

25.90
3 2 .1 4
23.05
19.91
26.56

.0 7 2
.050
.066
.074
.076

1 6 .8 0
20.61
1 9 .4 0
24.70
19.80

F 1 4 -3 -3 -7 -2
P 4 4 -4 -6 -1 -1
P 4 4 -4 -3 -6 -1
0 9 5 -4 -6 -1 -1
P87-6-14-1

16.82
2 6 .8 4
14.89
25.76
3 2 .8 8

.075
.063
.066
.078
.064

25.50
2 6.50
3 0 .7 0
2 2.90
22.80

C105
MS14
A385
MS17
0h43

21.78
25.32
14.86
20.65
23.72

.074
.062
.076
.0 6 2
.067

27.40
28.60
21.90
23.10
28.30

F 1 4 -3 -8 -5 -1
0 9 5 -4 -5 -1 -1
P 4 4 -2 -1 -5 -1
G l l - l -2 -2 -3
0 9 5 -4 -5 -6 -1

1 7 .9 7
21.45
28.91
20.39
2 4 .7 7

.076
.073
.069
.072
.080

1 9 .2 0
27.00
2 5 .8 0
2 3.70
2 7 .6 0

Table 5.

In b re d s

(continued)

N ia c in
u g ./g m /

Tryptophan
0 /0

K ern el Weight
gm./lOO

In b re d s

N ia c in
u g ./g m .

Tryptophan
0 /0

K ern el Weight
gm./lOO

W146
NS40
Oh45
3D105
187-2

22.70
2 8 .34
20.41
1 9.31
23.28

.0 7 0
.078
.064
.080
.0 7 0

24.40
23.50
24.30
1 8 .8 0
3 1.80

F 5 0 -2 -3 -2 -1
F 1 3 -3 -5 -6 -1
P 4 4 -2 -4 -8 -1
F 1 6 -2 -4 -2 -2
P 7 -1 -3 -3 -3

13.43
25.83
25.01
20.85
26.75

.070
.074
•071
.077
.069

3 3 .8 0
2 2 .0 0
3 5 .0 0
2 3.90
2 5 .9 0

W8
MS206
MS50
MS12
MSI 5

2 8 .0 3
17.55
16.12
2 1.38
26.53

.082
.083
.078
.079
.081

1 8 .5 0
1 9 .8 0
23.60
24.20
3 0 .7 0

P 7 -1 -1 -4 -1
G 100-5-2-7-1
Kan K R
ML5-58-3
N

1 9 .1 8
28.56
2 5 .6 8
24.42
3 0 .5 6

.069
.069
.063
.080
.073

2 4 .0
1 5 .8
2 4 .0
2 4 .6
1 3 .1 0

26

C o r r e la tio n c o e f f i c i e n t s f o r try p to p h a n , n ia c i n , and
k e r n e l w eig h t a r e p re s e n te d i n T able 6 .
T able 6 .

C o r r e la tio n c o e f f i c i e n t s " r" f o r try p to p h a n , n ia c i n
and k e r n e l w eight o f th e s i x t y in b re d l i n e s

C o r r e la tio n betw een

" r" v a lu e

Tryptophan and n ia c i n

-0 .2 4 3 8

T yrptophan and k e r n e l w eight

-

N ia c in and k e r n e l w eight

-0 .2 6 5 3 *

0.1098

•^ S ig n ific a n t a t 5%
A ll th e " r" v a lu e s were n e g a tiv e , b u t o n ly th e c o r r e la ­
t i o n betw een n ia c i n and k e r n e l w eig h t was s i g n i f i c a n t a t 5%
l e v e l o f p r o b a b i l i t y and i t was to o sm all to be o f any im p o rtan ce
in s e le c tio n .

However, th e r e was a s l i g h t t r e n d tow ard h ig h e r
i
n ia c i n i n sm a ll k e rn e ls and v ic e v e r s a . There was no r e l a t i o n ­
s h ip betw een try p to p h a n c o n te n t and k e rn e l w eig h t f o r th e 60
in b re d s s tu d ie d .

Even though th e n e g a tiv e c o r r e l a t i o n betw een

try p to p h a n and n ia c i n c o n te n ts was n o t s i g n i f i c a n t , th e r e were
s e v e r a l in b re d s t h a t were above a v erag e f o r b o th try p to p h a n and
n ia c i n , and some l i n e s were low i n b o th .

Thus, i t ap p ears

p o s s ib le t o develop l i n e s w ith h ig h e r th a n av erag e c o n te n ts o f
b o th try p to p h a n and n ia c i n .

.-,00
1 ' /.$

27

I n t e r r e l a t i o n s h i p s o f T ryptophan, N ia c in , P r o te i n and K ern el
W eight
Two c ro s s e s , W23 x R53 and. W23 x 0h51A, were u sed i n
stu d y in g try p to p h a n and n i a c i n .

W23 x R53 was a c ro ss o f h ig h

n ia c in -lo w try p to p h a n x low niacin-m edium try p to p h a n .

W23 x

Oh$lA was a c ro s s o f h ig h n ia c in -lo w try p to p h a n x medium n i a c i n h igh try p to p h a n .

P r o te in p e rc e n ta g e s were d eterm in ed o n ly f o r

W23 x R$3 p o p u la tio n s .
c ro sse s.

K ern el w e ig h ts were d eterm in ed f o r b o th

Means, s ta n d a rd d e v ia tio n s o f means and ra n g e s f o r

p r o te in , try p to p h a n , n ia c i n and k e r n e l w eig h t a re p re s e n te d i n
Table 7*
Large d if f e r e n c e s i n try p to p h a n , n ia c i n , p r o te in and
k e rn e l w eight were o bserved w ith in th e n o n -s e g re g a tin g P^, ? 2
and Fp p o p u la tio n s o f b o th c ro s s e s ,

C o e f f ic ie n t s o f v a r i a t i o n s

o f a l l th e c h a r a c t e r i s t i c s f o r each p o p u la tio n were c a lc u la te d
(T able 8 ) .

D e sp ite th e sm a ll number o f in d i v id u a l s i n th e Pl>

P2 and F-j_ p o p u la tio n s , i t appeared t h a t th e n o n -s e g re g a tin g
p o p u la tio n s were a s v a r ia b le as th e s e g r e g a tin g p o p u la tio n s i n
a l l th e c h a r a c te rs s tu d ie d .

V a r i a b i l i t y i n th e n o n -s e g re g a tin g

p o p u la tio n s , P^, P2 and F^, i s commonly a t t r i b u t e d to e n v iro n ­
m ental f a c t o r s .

In b re d l i n e s o f c o rn te n d t o be more s u s c e p tib le

to non h e r i t a b l e f a c to r s th a n th e more v ig o ro u s Fp, F2 and b a ck c ro s s p o p u la tio n s .

S ince th e s e in b re d s had n o t been p re v io u s ly

s e le c te d f o r th e se c h a r a c t e r i s t i c s , i t i s a ls o p o s s ib le t h a t
th e r e was some g e n e tic v a r i a t i o n among in d iv id u a ls w ith in a l i n e .

Table 7. Means and Ranges of Niacin, Tryptophan and Kernel Weight for each population in the Cross of
W23 x R53 and W23 x Ohio 51A

W23 x R53
N ia cin
ug./gm .

Tryptophan
0 /0

Mean
Range
S.D . o f Mean

3 2 .1 4
2 3 .7 3 -4 1 .3 9
1 .3 5

.050
.0 4 2 -.0 5 9
.0011

1 0 .0 0
7 . 63 - 1 2 .8 1
0 .3 1

20.61
1 6 .3 6 -2 5 .5 0
1 .0 0

15

Mean
Range
S.D . o f Mean

1 8.11
1 3 .2 5 -2 5 .6 4
0.86

.060
.0 5 3 -.0 6 9
.0015

1 2 .5 7
1 0 .4 4 -1 4 .0 6
0 .2 6

3 0 .8 8
2 2 .9 0 -3 6 .6 4
1 .0 5

15

Fi

Mean
Range
S.D . o f Mean

2 7.97
2 1 .7 7 -3 4 .0 1
1 .0 3

.056
.0 5 1 -.0 6 2
.0008

11.23
8 .6 9 -1 4 .1 3
0 .3 9

24.11
1 3 .6 5 -3 0 .1 5
1 .3 0

15

F2

Mean
Range
S.D . o f Mean

2 4.88
1 6 .4 8 -4 1 .7 5
0 .7 6

.060
.0 4 9 -.0 7 0
.0007

1 2 .2 4
9 .0 6 -1 5 .3 8
0 .2 2

24.16
1 3 .7 6 -3 0 .4 5
0 .5 2

47

Bc^

Mean
Range
S.D . o f Mean

3 0.28
2 1 .8 2 -4 2 .7 2
0 .8 2

.053
.0 4 5 -.0 6 1
.0006

11.06
8 .6 3 -1 3 .6 9
0 .2 1

25.56
1 5 .0 0 -3 2 .1 5
0 .5 8

43

Bc2

Mean
Range
S.D . o f Mean

21.78
1 2 .8 1 -3 4 .9 0
0 .7 6

.059
.0 4 9 -.0 6 9
.0007

11.95
9 .5 0 -1 5 .1 9
0 .2 0

26.83
1 7 .4 7 -3 8 .8 5
0 .5 6

49

r x*

*P l

a

W23

P2

-

R53

P r o te in
0 /0

K ern el Weight
gm./lOO

Number o f Samples

Table 7.

(continued)
W 23 x Ohio 51A
N ia c in
u g ./g m .

T ryptophan
0 /0

K ern el W eight
gm./lOO

Number o f Samples

Mean
Range
S.D . o f Mean

32.14
23.7 3 -4 1 .3 9
1 .3 5

.0.50
.0 4 2 -.0 5 9
.0011

2 0 .6 1
1 6 .3 6 -2 5 .5 0
1 .0 0

15

p2*

Mean
Range
S.D . o f Mean

27.67
2 9 .8 1 -2 4 .3 4
0.39

.063
. 0 5 5 -.0 8 2
.0016

27.39
2 3 .6 4 -2 9 .3 2
0 .9 5

15

F1

Mean
Range
S.D . o f Mean

3 2 .6 4
2 7 .3 3 -3 8 .6 6
0 .8 1

.056
.0 4 9 -.0 6 5
.0012

29.54
1 9 .7 2 -3 6 .5 0
1 .0 4

15

F2

Mean
Range
S.D . o f Mean

32.94
2 0 .2 4 -4 9 .7 2
0.8 9

.056
.044—.066
.0008

26.29
1 5 .8 5 -3 4 .1 5
O.5 6

58

Bc^

Mean
Range
S.D . o f Mean

3 2 .5 0
2 2 .9 0 -4 8 .4 3
0 .6 8

.0 5 0
.0 4 1 -.0 6 0
.0004

2 3 .5 7
1 2 .9 0 -3 1 .8 6
0 .5 8

62

Bc2

Mean
Range
S.D . o f Mean

3 0 .8 6
1 7 .9 0 -5 5 .9 4
0 .8 7

.056
.0 4 7 -.0 7 4
.0007

28.81
1 6 .0 4 -3 4 .0 7
0 .4 7

61

Fl *

r

¥23

P2

*

Ohio 51A.

Table 8.

Coefficient of Variability of all the characters studied in each populations of the crosses
W 23 x R 53 and W 23 x Ohio 51A
W 23 x R 53

W 23 x Ohio 51A

•

K ern el Weight

Tryptophan

N ia cin

K ern el Weight

Average
%

•
•

P o p u la tio n s :P r o te in

Tryptophan

N ia cin

P1

: 11.96

8 .7 0

1 6 .6 1

1 5 .5 7

8 .7 0

1 6 .6 1

1 5 .5 7

13.39

P2

:

7.88

7.98

1 9.02

1 3 .2 4

10.03

5.53

7 .81

1 0 .2 1

F1

: 13.45

5.38

1 4 .7 0

20.90

8 .1 8

9 .5 6

1 3 .6 4

1 2 .2 6

F2

: 1 2.34

7.82

20.86

1 4 .6 5

1 0.25

20.38

1 6 .1 7

14.63

Bc-l

: 1 2 .75

7.30

18.16

1 4 .9 1

6 .9 2

16.49

1 9 .9 8

13.79

Bc2

: 1 1 .8 0

9 .1 4

24.70

1 4 .5 0

10.09

21.94

1 2 .8 4

1 5 .0 0

•
•

Vjo

o

31

Long-tim e in b re d l i n e s a r e commonly assumed to be homozygous,
b u t a c t u a l l y th e y may be homozygous o n ly f o r th e c h a r a c te rs
s e le c te d and may be v a r ia b le f o r u n s e le c te d c h a r a c te r s .

Only

e a rs w ith good seed s e t were s e le c te d f o r t h i s s tu d y so i t i s
n o t l i k e l y t h a t s p a r s e - p o llin a ti o n was a f a c t o r i n th e r e s u l t
o b ta in e d .
The freq u e n cy d i s t r i b u t i o n s t a b l e s f o r tr y p to p h a n ,'
n ia c i n , p r o te in and k e r n e l w eight a r e shown i n T ab les 9 , 10,
11, and 12, r e s p e c tiv e ly .

The wide ra n g e s covered by p a re n ts

a g a in in d ic a te d t h a t th e y w ere r e l a t i v e l y h etero zy g o u s f o r
th e f a c t o r s a f f e c t i n g th e s e c h a r a c t e r i s t i c s .

The d i s t r i b u t i o n

o f Fj_ in d iv id u a ls f o r try p to p h a n , n ia c i n and p r o t e i n were w ith ­
i n th e l i m i t s s e t by b o th p a r e n ts and th e two b a c k c ro ss popu­
l a t i o n s te n d ed t o s h i f t tow ard t h e i r r e s p e c tiv e p a r e n ta l s id e
and few extrem es a p p e a re d .

For a l l th e c h a r a c te r s s tu d ie d ,

th e F 2 p o p u la tio n had a w id e r d i s t r i b u t i o n th a n t h a t o f th e
F^.

T his le a d s to th e c o n c lu sio n t h a t th e s e c h a r a c te r s were

q u a n tita tiv e ly in h e rite d .

W ithout lin k a g e , th e g r e a t e s t

amount o f v a r i a b i l i t y sh ould be p r e s e n t i n Fg p o p u la tio n s .
The range o f s e g r e g a tio n i n F 2 p o p u la tio n s f o r a l l th e s e
c h a r a c te r s , alm ost covered th e ran g e o f some o f th e p a r e n ta l
lin e s .

T his s u g g e s ts t h a t r e l a t i v e l y few genes w ere re s p o n s i­

b le f o r th e s e c h a r a c t e r i s t i c s .

These freq u en cy d i s t r i b u t i o n

ta b le s a ls o in d i c a t e th e p re se n c e o f dominance r e la t io n s h ip s
o f th e s e c h a r a c te r s .

The d e t a i l e d stu d y o f th e s e a p p ea rs i n

32

Table 9.

Frequency Distribution of Tryptophan Percentage in each
Population of Two Corn Crosses

C la ss C en ters f o r T ryptophan P e rc e n ta g e
P o p u la tio n *038 .040 .042 .044 .046 .048 .0 5 0 ,.052 .054 . 056 .058 .060 .062
W23 x R53
Px (W23)

1

Bc^CW ^cFi)

1

3

2

2

3

2

1

2

6

5

8

8

9

2

2

1

2

5

1

4

1

1

2

3

1

4

7

10

11

3

4

4

5

11

5

4

1

2

2

1

F1
F2
Bc2 (E53xF1 )
P2 ( r 53)

1

W23 x Oh 51A
P1 (W23)

1

1

3

2

2

3

2

Bc1 (W23xF1 )

2

1

11

12

11

12

11

1

3

2

1

1

3

3

1

4

6

6

7

10

8

3

3

8

4

8

9

8

6

5

6

2

2

2

1

F1
F2
Bc2 (0h51A x F j)
P2 (0h51A)

1

1

1
1

33

Table 9

(C ontinued)

.064 .0 6 6 .068 .070 .072 .074 .076 .07S .080 .082 .084 .086 T o ta l

15
43
15
4

1

2

2

47

3

5

3

2

49

2

1

1

10

15

62
1

15

4

2

1

3

2

1

5

1

1

1

1

$8

1

61
1

15

34

Table 10.

Frequency Distribution of Niacin Content in each
Population of Two C o m Crosses

C lass C en ters f o r N ia c in C ontent
P o p u la tio n . 10

12

14

16

18

20

22

ug ./gm »

24

26

28

30

32

34

1

1

3

3

1

2

7

7

5

6

3

5

6

3

2

1

W23 x R53
PX(W23)
Bc1 (W23xF1 )

1

F1

<£
1 3

F2
Bc2 (R53xF1 )
P2 (R53)

2

6

8

11

4

6

2

3

1

4

1

2

2

2

7

7

4

9

4

5

2

5 ' 3

2

1

1

1

1

1

3

3

1

2

2

7

8

9

10

2

2

1

7

2

W23 x 0h51A
Pi (W23)
Bcx(W23xFi)

1

F1
F2
Bc2 (Oh51xF1 )
P2 (0h51A)

1

1

3

2

6

6

4

7

6

1

1

4

11

11

7

9

5

2

2

8

3

35

T able 10

36

3

(C o n tin u ed )

38

40

42

1

1

2

15

2

3

43

1

44

46

48

50

52

54

56

1

58

T o ta l

15
1

1

47
49
15

1

1

2

12

4

4

1

1

2

9

6

3

1

1

4

15
1

62

1

15
2
2

1

1

2
1

58
1

61

15

36

Table 1 1 .

Frequency d i s t r i b u t i o n o f p r o te in p e rc e n ta g e i n each
p o p u la tio n o f c ro s s W23 x R53

C lass c e n te r s f o r p r o te in p e rc e n ta g e s
P o p u la tio n

7 .0

7 .5

8 .0

8 .5

9 .0

9*5

1 0 .0

1 0 .5

1 1 .0

1 1 .5

1

1

3

4

2

1

1

Bc1 (¥23xF1 )

3

1

5

6

5

2

6

F1

1

2

2

1

1

3

1

2

2

4

6

3

3

5

4

6

W23 x R53
P1 (W23)

F2
Bc2 (R53xF1 )
P2(R53)

f e

1

2

1

3

37

Table 11 (C ontinued)

1 2 .0

1 2 .5

1 3 .0

1 3 .5

1 4 .0

1 4 .5

1 5 .0

1 5 .5

1
3
2

43

1

1

1

15

6

6

8

2

2

3

2

7

7

6

2

3

2

1

7

2

1

1

T o ta l

15
2

7

1 6 .0

1

47
49
15

38

Table 12.

Frequency of distribution of kernel weights in each
population of two corn crosses

C lass c e n te r s f o r k e r n e l w eig h t
P o p u la tio n : 13

15

16

17

PX(W23)

1

1

1

Bc1 (W23xF1 )

1

14

18

19

20

gm./lOO k e r n e ls

21

22

23

1

3

2

24

25

4

8

1

1

W23 x R53

2

1

F1

1

1

F2

1

Bc2(R53x Fx )

4

3

1

1

1

1

2

4

1

3

3

6

10

2

1

5

5

1

1

1

1

1

P2 (R53)

W23xQh51A
P-l(W23)
B c ^ V ^ x F i)

1
2

3

1

1
2

1
1

1

1

3

2

7

8

6

9

1

F1
F2

1

Bc2(Oh51AxF1 )

1

P2 (OH51A)

1

3

3

1

1
1
2

3

5

10

4

2

1

3

1

39

T able 12

26

27

28

(C on tin u ed )

29

30

31

32

33

34

35

36

37

1

T o ta l

10

5

3

1

5

5

1

1

1

1

1

3

15

4

5

3

2

2

47

5

4

8

9

2

2

1

3

1

1

43

2
2

1

2

1

1

49

1

1

15

10
1

2

3

2

2

5

2

1

2

3

3

4

5

3

4

5

2

1

1

1

2

7

9

7

7

7

5

3

3

1

1

1

2

3

62

1

1

3

1

15
58

1

61
5

40

th e fo llo w in g s e c tio n on dominance r e l a t i o n s h i p s .
C o r r e la tio n c o e f f i c i e n t s a re shown i n T able 1 3 .

In

W23 x H53> s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s betw een p r o te in
and try p to p h a n c o n te n t, and betw een p r o t e i n and k e r n e l w eig h t
were found i n a l l th r e e p o p u la tio n s , w h ile c o r r e l a t i o n be­
tw een p r o te in and n i a c i n were a l l s i g n i f i c a n t l y n e g a tiv e .
C o rre la tio n s between try p to p h a n and n i a c i n were a l l n e g a tiv e
b u t o n ly two o f th e th r e e c o r r e l a t i o n s w ere s i g n i f i c a n t l y
n e g a tiv e .

There was a s l i g h t ten d en cy f o r n ia c i n to be nega­

t i v e l y c o r r e la te d w ith k e r n e l w eight b u t th e r e l a t i o n s h i p was
s i g n i f i c a n t i n o n ly one o f th e th r e e p o p u la tio n s .

T ryptophan

te n d ed to be p o s i t i v e l y c o r r e la te d w ith k e r n e l w eig h t b u t a g a in
o n ly one o f th e th r e e p o p u la tio n s was s i g n i f i c a n t .
I n W23 x Oh^lA, th e n e g a tiv e c o r r e l a t i o n s o f try p to p h a n
w ith n ia c in was n o t s i g n i f i c a n t i n any o f th e p o p u la tio n s .
n e l w eight and try p to p h a n were p o s i t i v e l y c o r r e la te d .

Ker­

C orre­

l a t i o n s o f k e rn e l w eight w ith n i a c i n w ere s i g n i f i c a n t l y n e g a tiv e
i n two o f th e th r e e p o p u la tio n s .
The p o s i t i v e c o r r e l a t i o n o f p r o te i n w ith try p to p h a n and
th e n e g a tiv e c o r r e l a t i o n betw een p r o t e i n and n ia c i n a s shown i n
W23 x R53 were i n c lo s e agreem ent w ith th e p re v io u s i n v e s t ig a ­
ti o n s by F rey (17)> Flynn e t a l . (1 4 ) , S a rk a r (4 2 ), Rodriguez
e t a l . (41) and E a rle y e t a l . ( 1 1 ) .

Thus, th e n e g a tiv e c o rre ­

l a t i o n found betw een try p to p h a n and n i a c i n i n ¥23 x R 53 seemed
p o s s ib le s in c e th e p r o te in w ith try p to p h a n and th e p r o t e i n w ith

Table 13„

C o rre la tio n C o e f f ic ie n ts in v o lv in g th e P r o te in and T ryptophan P e rc e n ta g e s , N ia c in Con­
t e n t , and K ern el Weight i n each p o p u la tio n o f th e C ross VI 23 x R53 and W23 x 0h51A.

Tryptophan

P r o te in
Bc]_

F2

BCl

:
Bc2

Bc2

:

Tryptophan

+.5439** +.6044** +.3965*

:

N ia c in

-.5 8 3 1 * * -.5 4 0 1 * * -.4 5 4 7 * *

:

-.5 5 3 9 * *

-.1 5 8 0

-.3 0 2 7 *

K ernel Weight

+.3238* +.3484*

:

+.3887**

+.0175

+.0898

-.0 4 1 4

F2

:

N ia cin
f2

Bcj_

Bc2

W 23 x R53

+.3176*

-.2 0 0 3

-.2 0 0 0

-.3 4 3 9 *

-o l3 9 5

-.7 1 5 3 * * -.2 4 8 7 *

W23 x 0h51A
Tryptophan

:

N ia c in

:

-.1 2 8 7

- .2 2 6 0

K ernel Weight

:

+ . 3236 *

+,3360**+.2208

** S ig n if ic a n t a t 1% l e v e l
* S ig n if ic a n t a t 5% l e v e l

42

n ia c i n were p o s i t i v e l y and n e g a ti v e ly c o r r e l a te d , r e s p e c t i v e l y .
T h is p o s i t i v e c o r r e l a t i o n o f p r o te i n w ith try p to p h a n and th e
n e g a tiv e r e l a t i o n s h i p s betw een p r o te in and n ia c i n and betw een
try p to p h a n and n ia c i n a g re e w ith th e h y p o th e s is o f try p to p h a n —
n ia c i n b io s y n th e s is p o s tu la te d by Bonner e t a l . ( 3 ) and Nason ( 3 3 ) Tryptophan may be a p r e c u r s o r o f n ia c i n ( l , 13, 20, 2 4 ) .
T ryptophan i s tra n s fo rm e d t o n i a c i n d u rin g grow th by means o f
gene a c tio n , th u s th e l a r g e r th e amount o f n ia c i n formed th e
s m a lle r th e amount o f try p to p h a n re m a in in g .

I n W23 x 0h51A,

th e ev id en ce i n fa v o r o f t h i s b io s y n th e s is h y p o th e s is was n o t
a s s tro n g as i t was i n th e c r o s s W23 x R53 s in c e th e n e g a tiv e
c o r r e la tio n s betw een try p to p h a n and n ia c i n were n o t s t a t i s t i ­
c a lly s ig n ific a n t.
The b io s y n th e tic r e l a t i o n s h i p s o f try p to p h a n and n ia c in
may im ply t h a t i t would n o t be p o s s ib le to o b ta in a c o m v a r i ­
e ty t h a t i s h ig h i n b o th n ia c i n and try p to p h a n .

However, d a ta

i n T able $ show t h a t some in b re d l i n e s were h ig h e r th a n average
i n b o th n ia c i n and try p to p h a n .
S ig n i f ic a n t p o s i t i v e c o r r e l a t i o n was found betw een
k e r n e l w eight and p r o te in i n a l l th r e e p o p u la tio n s o f W23 x
R$3.

I n a s e l e c t i o n program f o r h ig h p r o t e in i n th e c ro s s ,

th e p la n t b re e d e r m ight ta k e ad v an tag e o f t h i s sm all c o rre ­
l a t i o n and s e l e c t th e l i n e s w ith la r g e k e r n e l s .

C o rre la tio n s

o f k e r n e l w eig h t w ith try p to p h a n and w ith n ia c i n showed a
s l i g h t ten d en cy f o r h ig h try p to p h a n to be a s s o c ia te d w ith

43

la r g e k e r n e l w eight and f o r h ig h n ia c i n t o be a s s o c ia te d
w ith low k e r n e l w e ig h t.

W hile one h a l f o f th e s e c o r r e l a t io n s

w ere s i g n i f i c a n t , th e r e l a t i o n s h i p s ap p eared t o be sm a ll and
o f l i t t l e v a lu e i n b re e d in g f o r n ia c i n and try p to p h a n .

P re ­

sum ably, th e k e rn e l w eig h t co u ld be e a s i l y a f f e c t e d by th e
en v iro n m e n ta l f a c t o r s a s re p o rte d i n th e p re v io u s i n v e s t ig a ­
t i o n s (10, 3 4 )•
I n h e r ita n c e Study o f N ia c in . T ryptophan, P r o te in and K ern el W eight
The in h e r ita n c e s tu d ie s w ith th e s e c h a r a c te r s sh o u ld be
i view ed w ith some r e s e r v a tio n .

S ince th e s e a re a l l q u a n t ita t iv e

c h a r a c te r s a f f e c t e d d i r e c t l y o r i n d i r e c t l y by a la r g e number
o f g e n e tic f a c t o r s , hundreds o f sam ples o f s e g re g a tin g p o p u la­
t i o n s sh o u ld be u sed t o make in h e r ita n c e s tu d ie s more e f f e c t i v e .
S in ce chem ical d e te rm in a tio n s o f try p to p h a n and n ia c i n a re
c o s tl y and tim e consuming, a c o m p a ra tiv e ly sm all number o f
sam ples was u s e d .
Dominance R e la tio n s h ip s
Means, s ta n d a rd d e v ia tio n s o f means, t o t a l v a ria n c e s
and g e n e tic v a ria n c e s f o r n ia c i n , try p to p h a n , p r o te in and
k e r n e l w eig h t o f each p o p u la tio n i n th e two c ro s s e s a re p re ­
s e n te d i n T able 1 4 .

The t o t a l v a ria n c e o f th e

p o p u la tio n

was used a s an e s tim a te o f en v iro n m e n ta l v a ria n c e i n th e
c a lc u la tio n o f g e n e tic v a r ia n c e .

G en etic v a ria n c e i s e q u al

44

T able 1 4 .

Means, S ta n d a rd D e v ia tio n s o f Means, T o ta l V arian ces and
G enetic V arian ces f o r N ia c in , T ryptophan, P r o te in and K ern el
Weight o f each p o p u la tio n i n th e c ro s s e s W23 x R53 and
W23 x Oh$lA

W23 x R53
Mean

S ta n d a rd D e v ia tio n o f

•

P o p u la tio n

•

Wo. o f ;
T ry p to K e rn e l:
T ry p to S am p les:N iacin phan
P r o te in W eight rN iacin phan
P r o te in
:u g ./g m . %
%
gm /lO O :ug./gm
%
%
oU-N
o•

1 0 .0 0

2 0 .6 1

•
•

1 .3 5

.0011

0 .3 1

.060

1 2 .5 7

3 0 .8 8

•

0 .8 6

.0015

0 .2 6

: 27.97

.0 5 6

1 1 .2 3

24.11

•
♦

1 .0 3

.0008

0 .3 9

47

: 2 4.88

.0 6 0

1 2 .2 4

24.16

*
•

0 .7 6

.0007

0 .2 2

Bcj_

43

: 3 0 .2 8

.053

11.06

2 5 .5 6

0 .8 2

.0006

0 .2 1

Bc2

49

: 2 1.78

.059

1 1 .9 5

26.83

«

0 .7 6

.0007

0 .2 0

•

1 .3 5

.0011

0 .3 9

.0016

Pl(W23)

15

: 3 2 .1 4

P2 (R53)

15

: 1 8 .1 1

*1

15

F2

*

W23 x Oh51A
P1 (W23)

15

: 3 2 .1 4

.0 5 0

20.61

P 2 (0h51A)

15

: 2 7.67

.063

27.39

F1

15

: 3 2 .6 4

.036

2 9 .5 4

•
•

0 .8 1

.0012

F2

58

: 3 2 .9 4

.0 5 6

26.29

»
•

0.8 9

.0008

Bc-^

62

: 3 2 .5 0

.0 5 0

2 3 .5 7 •• 0 .6 8

.0004

Bc2

61

: 3 0.86

.0 5 6

28.81 •• 0 .8 7

.0007

45

Table 1 4 .

Mean

(C ontinued)

T o ta l V arian ces

G e n etic V arian ces

•

•

K e rn e l:
T ry p to K e rn e l:
T ry p to K ern el
W eig h t:N iacin
phan P r o te in W eight:N ia c in phan
P r o te i n W eight
: ug ./g m
/
%
gm /lO O :ug./gm
$
/
gro/lOO
1 .0 0 :28.49 .000019

1 .4 3

1 0 .3 0

•

-.05

s l l .8 7 .000023

0 .9 8

1 6 .7 3

•
•

1 .3 0 :16.91 .000009

2 .2 9

25.42

•
•

0 .5 2 :26.92 .000022

2 .2 8

1 2.53 :1 0 .0 1 .000013

-0 .0 1

-1 2 .8 9

0 .5 8 :3 0 .2 7 .000015

1 .9 8

1 4 .5 0 :1 3 .3 6 .000006

- 0 .3 1

-1 0 .9 2

0.56 :28.91 .000029

1 .9 8

1 5 .1 5 :1 2 .0 0 .000020

- 0 .3 1

-1 0 .2 7

1 .0 0 :28.49 .000019

1 0 .3 0

•
•

0.95 : 2 .3 4 .000040

4 .5 8

•
*

1 .0 4 : 9 .7 5 .000021

1 6 .2 1

•
«

0 .5 6 :45.53 .000033

18.09 :3 5 .7 8 0.000012

1 .8 8

0 .5 8 :2 8 .7 7 .000012

2 2 .1 8 :1 9 .02-0000009

5 .9 7

0 .4 7 :45.83 .000032

1 3 .6 8 :36.08 0000011

-2 .5 3

46

to th e t o t a l v a ria n c e minus th e F]_ v a r ia n c e .
N ia c in c o n te n t:

I n th e c ro s s W23 x R53> no h e te r o s i s

f o r n ia c i n was observed s in c e th e F^ mean d id n o t s i g n i f i c a n t l y
exceed th e mean o f e i t h e r p a re n t o f th e c r o s s .

No g e n ic domi­

nance was in d ic a te d s in c e th e g e n e tic v a ria n c e s o f th e two
b a c k c ro ss and Fg p o p u la tio n s were o f s im ila r m ag n itu d e.

The

F-|_ mean f e l l betw een th e mean o f one o f th e p a r e n ts and th e
average o f th e two p a r e n ta l means, so t h a t p a r t i a l p h en o ty p ic
dominance was in d ic a te d f o r h ig h n i a c i n .

E p i s t a s i s o f h ig h

n ia c in dom inant genes was n o t a p p a re n t, a s ev id en ced by th e
f a c t t h a t th e means o f th e F2 and Bc2 ( to R53) were c o n s id e r­
a b ly l e s s th a n t h a t o f th e F^.
I n th e c ro s s W23 x 0h51A, th e r e was a ls o no in d ic a tio n
o f h e te r o s is s in c e th e F-^ mean d id n o t s i g n i f i c a n t l y exceed
e i t h e r p a r e n t.

P a r t i a l g e n ic dominance o f genes c o n trib u te d

by W23 f o r a h ig h n ia c in v a lu e was in d ic a te d i n t h a t th e
g e n e tic v a ria n c e e stim a te d f o r th e b a c k c ro ss to W23 was con­
s id e r a b ly l e s s th a n t h a t o f th e Fg and th e b a c k c ro ss to 0h51A.
Evidence f o r com plete p h en o ty p ic dominance f o r h ig h n ia c in
was in d ic a te d by th e f a c t t h a t th e mean o f th e F-j_ d id n o t
d i f f e r s i g n i f i c a n t l y from th e h ig h n ia c in p a r e n t, W23.

The

r e l a t i v e l y sm all d if f e r e n c e s betw een th e means o f th e F^,
? 2 > Bc-j_, and BC2 in d ic a te d t h a t e p i s t a s i s o f dom inant gene
may have o c c u rre d .

S lig h t s e g r e g a tio n o c c u rre d i n t h e Fg and

47

Be t o W23 (T ab le 10) f o r a h ig h n i a c i n v a lu e beyond W23 and
th e F^, showing t h a t i n t r a - a l l e l i c and i n t e r - a l l e l i c gene
i n t e r a c t i o n m ight be p r e s e n t .
Tryptophan p e r c e n ta g e :

No h e t e r o s i s and no pheno­

ty p ic dominance ( I n te r m e d ia te ) f o r try p to p h a n p e rc e n ta g e was
e x h ib ite d i n th e c ro s s W23 x R$3 s in c e th e mean o f th e F-^
showed no s i g n i f i c a n t d if f e r e n c e from th e a v erag e o f two p a r ­
e n t m eans.

G en etic v a ria n c e s o f th e s e g r e g a tin g p o p u la tio n s

in d ic a te d th e p re sen c e o f p a r t i a l g e n ic dominance f o r low
try p to p h a n , a s evidenced by th e f a c t t h a t th e g e n e tic v a ria n c e
o f Bc-]_ to W23 was c o n s id e ra b ly lo w er th a n t h a t o f BC2 and F£.
No e p i s t a s i s was o bserved s in c e th e means o f F2 , Bc^ and BC2
d i f f e r e d c o n s id e ra b ly from th e F^ mean.
In t h e c ro s s W23 x 0h51A, th e mean o f th e F^_ was a ls o
c lo s e to th e average o f th e two p a re n t means, i n d i c a t i n g no
h e t e r o s i s and no p h e n o ty p ic dom inance.

The g e n e tic v a ria n c e

o f th e b a c k c ro ss to W23 was n e g a tiv e a s compared to t h a t o f
th e F2 and BC2 and th e r e may have been com plete g e n ic dominance
f o r low try p to p h a n by genes c o n tr ib u te d by W23.

E p i s ta s is was

p ro b a b ly n o t p re s e n t s in c e th e mean o f Bc^ was s i g n i f i c a n t l y
d i f f e r e n t from t h a t o f th e F-j_.
P r o te i n p e rc e n ta g e ;

I n th e c ro s s W23 x R53> th e r e was

no i n d i c a t i o n o f h e te r o s is and p h en o ty p ic dominance s in c e th e
F-^ mean c lo s e ly approached th e av erag e o f th e two p a re n t m eans.
F u r th e r ev id en ce f o r no p h en o ty p ic dominance was i n d ic a te d by
th e f a c t t h a t th e mean o f e i t h e r b a c k c ro ss p o p u la tio n d id n o t

48

d i f f e r s i g n i f i c a n t l y from, th e av erag e o f th e F^_ and th e
a p p ro p ria te p a r e n t.

No g e n ic dominance was in d ic a t e d s in c e

th e g e n e tic v a ria n c e s o f th e two b a c k c ro ss and F 2 p o p u la­
tio n s were o f s im ila r m agnitude.

The means o f F-]_, F2, Bc^

and Bc2 d e v ia te d c o n s id e ra b ly so t h a t no e p i s t a s i s was
in d ic a te d .
K ernel w e ig h t;

I n th e c ro s s W23 x R53* no h e t e r o s i s

and no p h en o ty p ic dominance (I n te r m e d ia te ) w ere e x h ib ite d a s
i n d ic a te d by th e r e l a t i v e sm all d if f e r e n c e betw een th e F-^
mean and th e av erag e o f th e two p a r e n t s .

The g e n e tic v a ria n c e s

f o r F2 j Bc^ and Bc2 were a l l n e g a tiv e and o f th e same m agnitude
so t h a t no g e n ic dominance was i n d ic a t e d .

No e p i s t a s i s was

a p p a re n t s in c e no h e t e r o s i s and no dominance were o b serv ed f o r
t h i s c h a r a c te r .
The com parison o f th e F^_ mean o f th e c ro s s W23 x 0h51A
w ith t h a t o f th e two p a r e n ts showed s l i g h t h e t e r o s i s f o r la r g e
k e r n e l w eight s in c e th e
c o n s id e ra b ly .

mean exceeded th e mean o f Oh$lA

Complete g e n ic dominance was p o s s ib le , s in c e

th e g e n e tic v a ria n c e o f th e b a c k c ro ss to 0h51A was n e g a tiv e
as compared w ith th e g e n e tic v a ria n c e o f Bc-j_ and F2 .

This

in d ic a te s some d eg ree o f g e n ic dominance f o r la r g e k e rn e l
w eight by th e genes c o n trib u te d by 0h51A.

No e p i s t a s i s o f

th e s e dom inant genes f o r la r g e k e r n e l w eig h t was observ ed
s in c e th e r e were wide d if f e r e n c e s betw een F^ mean and th e
means o f th e s e g re g a tin g p o p u la tio n s .

49

A summary o f th e dominance r e l a t i o n s h i p s f o r th e
c h a r a c te r s s tu d ie d i n th e s e two c ro s s e s i s g iv e n i n T able 1 5 .
The p h e n o ty p ic dominance f o r h ig h n ia c i n found i n
b o th c ro s s e s was i n agreem ent w ith th e r e s u l t by Ohio w o rk ers
(9 ).

T his le a d s to th e c o n c lu s io n t h a t a c ro s s o f h ig h

n ia c i n x low n ia c in may be u sed i n a b re e d in g scheme t o im­
prove th e n ia c i n c o n te n t o f th e low n ia c i n p a r e n t.

R ichey

and Dawson (4 0 ) concluded t h a t n ia c i n v a lu e was in te rm e d ia te
betw een two p a re n ts w ith dominance la c k in g .

T his d if f e r e n c e

i n agreem ent i n d ic a te s t h a t th e b e h a v io r o f dominance r e l a t i o n ­
s h ip s m ight be d i f f e r e n t i n d i f f e r e n t in b re d s in v o lv e d i n a
c ro s s a s r e p o rte d by G o rfin k e l (1 8 ) .
Both try p to p h a n and p r o te i n have shown no p h e n o ty p ic
dom inance.

However, some d eg ree o f i n t r a - a l l e l i c gene i n t e r ­

a c ti o n was o b serv ed s in c e th e r e was g e n ic dominance f o r low
try p to p h a n i n b o th c r o s s e s .

F rey (17) found t h a t low p r o te in

and low try p to p h a n w ere dom inant c h a r a c te r s and o th e r s ( 1 9 )
have a ls o found low p r o t e i n to be dom inant o v er h ig h p r o t e i n .
The d if f e r e n c e betw een t h e i r r e s u l t s and th o s e o f th e p re s e n t
s tu d y m ight be a t t r i b u t e d to th e sm all d if f e r e n c e s o f tr y p t o ­
phan and p r o te in v a lu e s betw een th e p a re n ts u sed i n t h i s stu d y
and a ls o to c o n s id e ra b le v a r i a t i o n caused by e n v iro n m en tal
fa c to rs .

W23 was found to c o n tr ib u te dom inant h ig h n ia c i n

genes and th e c ro s s e s in v o lv in g i t would p ro b a b ly be low i n
try p to p h a n s in c e th e r e were n e g a tiv e c o r r e l a ti o n s betw een
try p to p h a n and n ia c i n .

Table 15«

Summary of the characters studied with respect to heterosis and dominance relationships

C h a ra c te r

W23 x R53

W23 x 0h51A

N ia c in

No h e te r o s is
P a r t i a l ph en o ty p ic dominance
No g e n ic dominance
No e p i s t a s i s

No h e te r o s is
P o s s ib le com plete p h e n o ty p ic dominance
P a r t i a l g e n ic dominance
P o s s ib le e p i s t a s i s

Tryptophan

No h e te r o s is
No ph en o ty p ic dominance (In te rm e d ia te )
P a r t i a l g e n ic dominance
No e p i s t a s i s

No h e t e r o s i s
No p h e n o ty p ic dominance (I n te r m e d ia te )
P o s s ib le com plete g e n ic dominance
No e p i s t a s i s

P r o te in

No
No
No
No

h e te r o s is
ph en o ty p ic dom inance' (In te rm e d ia te )
g e n ic dominance
e p is ta s is

K ernel w eight

No
No
No
No

h e te r o s is
p h en o ty p ic dominance (In te rm e d ia te
g e n ic dominance
e p is ta s is

S lig h t h e te r o s is
P o s s ib le com plete g e n ic dominance
No e p i s t a s i s

51

K ern el w eig h t was v a r i a b le and, th e r e f o r e , no d e f i ­
n i t e c o n c lu s io n co u ld be draw n.

However, p o s s ib le h e te r o s is

and dominance f o r la r g e k e r n e l w eight was in d ic a te d i n W23 x
0h51A.

T his m ight be due t o th e f a c t t h a t th e k e rn e ls o f F-^

and s e g re g a tin g p o p u la tio n s te n d to be l a r g e r th a n t h e lo n g ­
tim e s e lf e d in b r e d s .
Among th e fre q u e n c y d i s t r i b u t i o n t a b l e s , o n ly th e
n ia c in c o n te n t i n ¥23 x 0h51A d e se rv e d some a t t e n t i o n .

In

b a c k c ro ss p o p u la tio n to th e h ig h n ia c i n p a re n t and i n Fg
p o p u la tio n , s l i g h t s e g r e g a tio n f o r h ig h n ia c i n v a lu e beyond
t h a t o f th e p a re n t and Fj_ was o b s e rv e d .

This p ro b a b ly i n d i ­

c a te d t h a t i n t r a - a l l e l i c and i n t e r a l l e l i c gene i n t e r a c t i o n
was p r e s e n t.

The i n t r a - a l l e l i c gene i n t e r a c t i o n m ight be o f

some im p o rtan ce i n a f f e c t i n g t h e com plete p h en o ty p ic dom inance.
N ature o f Gene I n t e r a c t i o n
The o bserved means and th e c a lc u la te d mean b ased on
th e a ssu m p tio n o f a r ith m e tic and geftnetric gene i n t e r a c t i o n s
f o r n ia c i n , try p to p h a n , p r o te in and k e r n e l w eig h t i n th e two
c ro s s e s a re shown i n T able 1 6 .

I t was im p o s sib le to d eterm in e

w hether th e observed means f o r th e s e c h a r a c te r s f i t t e d e i t h e r
th e a r ith m e tic o r g e o m etric scheme o f gene i n t e r a c t i o n s in c e
th e c a lc u la te d v a lu e s were s i m i l a r .

F rey (17) found a r ith m e tic

gene i n t e r a c t i o n f o r p r o te in i n one c ro s s b u t h is try p to p h a n
d a ta d id n o t f i t e i t h e r o f th e c a lc u la te d v a lu e s .

Table 1 6 .

Observed means and c a lc u la te d a r ith m e tic and g eo m etric means f o r N ia cin C o n ten t, Tryptophan
p e rc e n ta g e and P r o te in p e rc e n ta g e i n th r e e s e g re g a tin g p o p u la tio n s o f th e two c r o s s e s .

Tryptophan %

N ia cin ug./gm .
I C a lc ilia te d Meanj
P o p u la tio n O bserved‘A r ith Mean :m etic

P r o te in P e rc e n ta g e
C a lc u la te d Mean

C a lc u la te d Mean

Geo- ‘Observed A rith ­
m etic
m e tr ic : Mean

K ern el Weight gm./lOO

Geo­ Observed A rith ­
m e tic
m e tric
Mean

C a lc u la te d Mean

Geo­ O bserved A rith ­
Mean
m e tric
m e tic

Geo­
m e tric

W23 x R53

vn

F2

: 2 4 .8 8

: 26.55

25.98

•

.0 6 0

: .056

.056 : 1 2 .2 4

: 1 1 .2 6

1 1 . 2 2 : 2 4 .1 6

: 24.92

2 4.65

Bc1

: 3 0 .2 8

: 3 0 .0 6

29.99

*
•

.053

: .053

.053 : 1 1 .0 6

: 1 0 .6 2

1 0 . 6 0 : 2 5 .5 6

: 2 2 .3 6

2 2 .3 0

B c2

: 21.78

: 23.04

22.51

•
•

.059

: .058

.0 5 8 : 1 1 .9 3

: 1 1 .9 0

1 1 . 8 8 : 2 6 .8 3

: 27.50

2 7.29

•
•

.0 5 6

: .056

.057 :

: 26.29

: 26.77

26.49

: 2 3 .5 7

: 2 0 .0 8

2 4 .6 7

: 28.81

: 2 8 .4 7

28.45

1 1 .2 3 : 2 5 .8 7

: 25.02

25.64

W23 x 0h51A
F2

: 3 2 .9 4

: 3 1 .2 7

3 1 .2 1

Bcx

: 3 2 .5 0

: 32.39

32.40 :

.0 5 0

: .053

.053 :

B c2

: 30.86

: 3 0 .1 6

3 0 .0 6

•
•

.056

: .0 6 0

.059

•
*

Average

: 2 8 .8 7

: 28.91

28.69 :

.055

: .056

.056 : 1 1 .7 5

: 11.26

fo

53

E stim a te d Gene Number
The e s tim a te d number o f genes a f f e c t i n g n ia c i n and
try p to p h a n i n th e two c ro s s e s a re shown i n T able 1 7 .

No

e s tim a tio n on gene numbers f o r p r o t e in and k e rn e l w eig h t
co u ld be made b ecause th e v a ria n c e o f th e

p o p u la tio n s f o r

th e s e two c h a r a c te r s were g r e a t e r th a n th e v a ria n c e s o f t h e i r
r e s p e c tiv e F2 p o p u la tio n .

The e s tim a te d number o f genes f o r

n i a c i n and try p to p h a n were low i n b o th c r o s s e s .

T h is i s e v i­

dence t h a t i t would be r e l a t i v e l y e asy to s e l e c t h ig h t r y p t o ­
phan and h ig h n ia c i n l i n e s i n th e s e g re g a tin g p o p u la tio n s .
S in ce a l l o f th e a ssu m p tio n s i n th e form ula f o r e s tim a tin g
gene numbers nay n o t alw ays be f u l f i l l e d , th e c a lc u la te d gene
numbers a re c o n sid e re d a s minimum numbers o f genes w ith m ajor
e f f e c t s and th e r e may be many more genes in v o lv e d w ith sm all
e ffe c ts.
T able 17.

E stim a te d number o f genes a f f e c t i n g f o r n ia c i n and
try p to p h a n i n th e c ro s s e s W23 x R53 and W23 x 0h51A.

C h a ra c te rs

W23 x R$3

W23 x Oh$lA

N ia cin

8

3

Tryptophan

5

5

H e r i t a b i l i t y Study
T able 18 p r e s e n ts th e e s tim a te d h e r i t a b i l i t y v a lu e s f o r
n ia c i n , try p to p h a n , p r o te in and k e rn e l w eight f o r th e two c r o s s e s .

54

T able 18.

E stim ated p e rc e n t o f H e r i t a b i l i t y f o r N ia c in ,
T ryptophan, P r o te in and K ern el W eight b y means
o f t o t a l w ith in v a ria n c e s i n each s e g re g a tin g
p o p u la tio n o f th e two c ro s s e s W23 x R$3 and
W23 x Oh$lA.

T o ta l W ith in V arian ces f o r
P o p u la tio n

:N ia cin

Tryptophan

P r o te in

K ern el Weight

F2

: 26.92

0 ,0 0 0 0 2 2

2 .2 8

1 2 .5 3

BC]_

: 3 0.27

0.000015

1 .9 8

1 4 .5 0

Bc2

: 28.91

0.000029

1 .9 8

1 5 .1 5

00

26

37

i
to
o

% o f E stim a te d
H e rita b ility

••

W2J . x R £

¥23 x Oh51A
F2

: 45.53

0.000033

1 8 .0 9

Bc^_

: 28.77

0 .0 0 0 0 1 2

2 2 .1 8

Bc2

: 45.83

0 .0 0 0 0 3 2

1 3 .6 8

66

1 .7

% o f E stim ated
H e rita b ility
:

36

55

In W23 x H$3, two n e g a tiv e v a lu e s and a zero v a lu e
f o r h e r i t a b i l i t y were found f o r n ia c i n , k e rn e l w eig h t and
try p to p h a n , r e s p e c t i v e l y .

These n e g a tiv e and z e ro h e r i t a ­

b i l i t y v a lu e s show t h a t th e en v iro n m e n ta l v a ria n c e s were
g r e a t e r th a n th e F£ g e n e tic v a r ia n c e s .

Thus, th e r e was no

encouragem ent f o r s e le c tio n f o r try p to p h a n , n i a c i n and k e r ­
n e l w eight i n t h i s c r o s s .

P r o te in p e rc e n ta g e i n W23 x R53

showed 26% h e r i t a b i l i t y , o f f e r i n g some encouragem ent f o r
s e le c tio n .
In th e c ro s s W23 x 0h51A, h e r i t a b i l i t y f o r n i a c i n and
try p to p h a n was 36% and 66 %, r e s p e c t i v e l y .

Thus,- th e r e were

p o s s i b i l i t i e s f o r s e le c tio n i n th e F2 s e g re g a tin g p o p u la tio n .
Low h e r i t a b i l i t y f o r k e r n e l w eight was a g ain o b serv ed i n t h i s
c ro ss.
L a rg e r p o p u la tio n s o f s e g re g a tin g m a te r ia l a re needed
to g iv e more a c c u ra te e s tim a te s o f h e r i t a b i l i t y .

From th e r e ­

s u l t s o f t h i s stu d y , i t a p p e a rs t h a t t h e m agnitude o f h e r i t a ­
b i l i t y e s tim a te s f o r a c h a r a c te r d i f f e r e d from c ro s s to c ro s s
and th e r e was more o p p o rtu n ity f o r s e l e c t i o n f o r try p to p h a n and
n i a c i n i n W23 x 0h51A th a n i n W23 x R53«

I

56

Study o f th e R e la tiv e E f fe c t o f th e Source o f P o lle n on th e
N ia c in and T ryptophan C ontent o f Corn
E ig h t F-j_ p la n ts o f th e c ro s s I a l5 3 x R53 w ere p o l l i ­
n a te d w ith sw eet c o m p o lle n and a n o th e r e ig h t
th e same c ro s s were s e l f p o l l i n a t e d .

p la n ts o f

Com parisons o f n ia c i n

c o n te n t and try p to p h a n p e rc e n ta g e f o r th e s e lf e d and o u tc ro s s e d e a r s a r e shown i n T able 1 9 .

The d if f e r e n c e i n n ia c in

c o n te n t was n o t s i g n i f i c a n t and th e d if f e r e n c e i n try p to p h a n
p e rc e n ta g e was s i g n i f i c a n t a t 5% le v e l*

These d if f e r e n c e s

in d i c a t e t h a t th e h ig h n ia c in c o n te n t o f sweet co rn was r e c e s ­
s iv e to th e s ta r c h y c h a r a c te r , a s shown by p re v io u s i n v e s t i g a ­
t i o n s (25, 4 0 ) .

T h e re fo re , th e h ig h n ia c i n c o n te n t o f sweet

co rn does n o t a p p e a r prom isin g f o r im proving th e n ia c i n c o n te n t
o f s ta r c h y c o rn th ro u g h b re e d in g .
Lower try p to p h a n v a lu e s were o b serv ed i n th e o u tc ro s se d
p l a n t s th a n th e s e lf e d p l a n t s ,

H e te r o tic d i l u t i o n m ight be a

p o s s ib le e x p la n a tio n f o r t h a t , however, o th e r f a c t o r s co u ld
a ls o a f f e c t i t s in c e th e d if f e r e n c e was n o t h ig h ly s i g n i f i c a n t .
In fo rm a tio n on dominance r e l a t i o n s h i p s , h e r i t a b i l i t y ,
gene numbers, g e n e tic and en v iro n m en tal v a r i a b i l i t y a re im por­
t a n t to p la n t b r e e d e r s .

The ty p e o f b re e d in g program , o p p o rtu ­

n i t y f o r s e l e c t i o n , and r a t e o f improvement may be d eterm in ed
a s more in fo rm a tio n o f t h i s ty p e i s accu m u lated .
R e s u lts p re s e n te d i n t h i s s tu d y in d ic a te t h a t try p to p h a n ,
n ia c i n and p r o te in a r e n o t e q u a lly am enable to s e l e c t i o n .

57

T able 1 9 .

Comparison o f th e av erag e n i a c i n and try p to p h a n
c o n te n ts o f s e lf e d and sw eet co rn p o lle n c ro s s e d
e a r s i n I a l5 3 x R53 p l a n t s .

C h a ra c te r

S e lfe d e a r s
Av.

Sweet c o m p o lle n
c ro s se d e a r s Av.

D iffe re n c e

2 1 .2 6

0 .4 7

N ia c in , u g ./g m . 21.73
T ryptophan, %

0 .0 5 7

0.053

0.004*

* S i g n i f ic a n t a t 5% l e v e l

In h e r ita n c e o f th e s e c h a r a c t e r i s t i c s a p p ea rs t o d i f f e r some­
what depending upon th e p a r t i c u l a r p a re n ts u sed and t h i s f a c t
c o m p lic a te s a b re e d in g program .

These chem ical c o n s t i t u t e n t s

were complex i n t h e i r in h e r it a n c e and, i n some c a s e s, th e y
were a f f e c t e d more by e n v iro n m e n ta l v a r i a t i o n .
S ince chem ical a n a ly s e s o f th e la r g e number o f sam ples
needed i n a p la n t b re e d in g program a re so ex p en siv e and tim e
consuming, any s i g n i f i c a n t r e l a t i o n s h i p t h a t m ight e x i s t among
th e c h a r a c t e r i s t i c s sh o u ld be o f v a lu e i n re d u c in g th e amount
o f chem ical a n a ly s e s needed i n a s e l e c t i o n program .

T h e re fo re ,

more e f f o r t sh ould be d ev o ted t o fin d in g more e a s i l y d eterm in ed
c h a r a c te r s t h a t may be a s s o c ia te d w ith th e s e chem ical c o n s ti tu ­
e n ts .
W ith th e expanded p ro d u c tio n o f s y n th e tic v ita m in s by
chem ical i n d u s t r i e s , i t a p p e a rs t h a t a d d itio n o f n ia c in to th e
fe e d may bea-more p r a c t i c a l s o lu tio n th a n a tte m p tin g to c o r r e c t

58

th e d e f ic ie n c y by p la n t b re e d in g .

However, where a n u t r i t i o n a l

d e f ic ie n c y can be c o r r e c te d by improvement i n th e n a t u r a l fe e d ­
s t u f f , dependence on th e human elem ent can be red u ced .

Cost

o f adding s y n th e t ic try p to p h a n to fe e d r a t i o n s a t p re s e n t i s
alm o st p r o h i b i t i v e , so improvement i n try p to p h a n c o n te n t o f co rn
would be a d e f i n i t e c o n tr ib u tio n .

I t was re p o rte d by Elvehjem

( 1 3 ) t h a t i t would c o s t 400 tim es a s much to use s y n th e tic
try p to p h a n a s to u se n i a c i n .

F urth erm o re, th e p resen ce o f

try p to p h a n i n th e fe e d can be c o n v erted to n ia c i n by rum inant
a n im a ls.
S ince h ig h n ia c i n was found to be dom inant i n th e p re s ­
e n t stu d y , i t a p p e a rs p o s s ib le to o b ta in b o th h ig h n ia c i n and
h ig h try p to p h a n c o n te n ts by b a c k c ro ssin g a h ig h n ia c i n l i n e to
a h ig h try p to p h a n p a re n t a s th e r e c u r r e n t p a r e n t.

R e c u rre n t

s e l e c t i o n a p p ea rs t o be a pro m isin g b re e d in g scheme to improve
n ia c i n c o n te n t o f corn i n th e m a te r ia l s in c e th e d a ta in d ic a te d
p a r t i a l to com plete dominance f o r n i a c i n .

No dominance was

in d ic a te d f o r try p to p h a n and p r o te in and, th e r e f o r e , r e c u r r e n t
s e l e c t i o n does n o t appear to be a p ro m isin g p ro ced u re to im­
prove th e s e c o n s t i t u e n t s .

M

■

SUMMARY
S ix ty in b re d l i n e s and two c ro s s e s , W23 x R53, and
W23 x Oh^lA, were a n a ly z e d f o r try p to p h a n and n ia c in c o n te n ts .
P r o te in a n a ly s e s were made f o r W23 x R53 and k e rn e l w eig h t was
d eterm in ed f o r b o th c r o s s e s .
c h a r a c te r s were in v e s t ig a te d .

I n t e r r e l a t i o n s h i p s o f th e s e
The in h e r ita n c e o f th e se c h a r­

a c te r s c o n cern in g dominance r e l a t i o n s h i p s , n a tu r e o f gene
a c tio n , gene numbers and h e r i t a b i l i t y were s tu d ie d .
C o n sid e ra b le d if f e r e n c e s i n n ia c i n and try p to p h a n con­
t e n t s were e v id e n t among th e s i x t y in b re d l i n e s .

The d i f f e r ­

ences betw een h ig h and low f o r n i a c i n and try p to p h a n were
1 4 9 .7 $ and 78$, r e s p e c t i v e l y .

S e v e ra l in b re d s were above

av erag e f o r b o th try p to p h a n and n ia c i n and some l i n e s were
low i n b o th .
I n c ro s s W23 x R53, s i g n i f i c a n t p o s i tiv e c o r r e la tio n s
were found betw een p r o te in and try p to p h a n and s i g n i f i c a n t
n e g a tiv e c o r r e l a t i o n s betw een p r o te in w ith n i a c i n and tr y p t o ­
phan w ith n i a c i n .

T his seemed to a g re e w ith th e try p to p h a n -

n ia c i n b io s y n th e s is .

N egativ e c o r r e la t io n s betw een try p to p h a n

and n ia c in were n o t s i g n i f i c a n t i n th e c ro s s W23 x OhfJIA.

In

bo th c r o s s e s , th e r e was a s l i g h t ten d en cy f o r h ig h try p to p h a n
t o be a s s o c ia te d w ith la r g e k e r n e l w eight and h ig h n ia c i n to
be a s s o c ia te d w ith sm all k e r n e l w e ig h t.

W hile a few o f th e s e

60

c o r r e la tio n s w ere s i g n i f i c a n t , th e r e la t i o n s h i p s were sm all
and o f l i t t l e v a lu e i n a p la n t b re e d in g s e le c tio n program .
S ig n i f ic a n t p o s itiv e c o r r e la ti o n s f o r p r o te in w ith k e rn e l
w eight were fo u n d .
High n ia c i n was dom inant o v e r low n ia c in on b o th
c ro sse s.
n an ce,

T ryptophan and p r o t e i n showed no p h en o ty p ic domi­
K ernel w eight was v a r i a b l e .

There was no dominance

f o r k e r n e l w eight i n th e c ro s s ¥23 x R53* w h ile i n ¥23 x 0h51A
s l i g h t h e te r o s is o r com plete dominance was in d ic a te d f o r la r g e
k e r n e ls .
I t was n o t p o s s ib le t o d eterm in e w hether th e observ ed
mean f o r th e s e c h a r a c te rs f i t t e d e i t h e r th e a r ith m e tic o r
g eo m etric scheme o f gene i n t e r a c t i o n s in c e th e v a lu e s were
s im ila r.

P ro b ab ly , b o th ty p e s o f gene i n t e r a c t i o n were i n ­

volved ,
E stim a te d gene numbers f o r try p to p h a n and n ia c i n were
low .

H e r i t a b i l i t y o f th e s e c h a r a c te r s d if f e r e d i n each c r o s s .

More encouragem ent f o r s e l e c t i o n f o r try p to p h a n and n ia c i n was
p re s e n t i n W23 x 0h51A th a n ¥23 x R$3*
There was c o n s id e ra b le v a r i a b i l i t y i n th e n o n -s e g re g a tin g
p o p u la tio n , ?1> P 2 ' and F-j_ f o r a l l th e c h a r a c te r s s tu d ie d .
E nvironm ental f a c to r s m ight have caused p a r t o f t h i s v a r i a t i o n .
S ince th e s e c h a r a c te r s had no p re v io u s s e le c ti o n , i t i s p o s s ib le
t h a t th e r e was some g e n e tic v a r i a t i o n among in d iv id u a ls w ith in
th e p a re n ts u sed i n th e s e s t u d i e s .

....

|

61

N ia c in c o n te n t was n o t a f f e c t e d by sw eet c o m p o lle n .
S l i g h t l y lo w e r try p to p h a n c o n te n t was found i n th e e a r s o f
p la n ts o u tc ro s s e d w ith sw eet c o m th a n i n th e s e lf e d p la n ts *

LITERATURE CITED

1 . A g u irre , F ., and B ressam , R. The n u t r i t i v e v a lu e o f C e n tra l
American co rn s (try p to p h a n , n ia c i n , th ia m in e and r ib o ­
f l a v i n c o n te n t o f 23 v a r i e t i e s i n G uatem ala) Food
R esearch 1 8 : 273-279. 1933.
2 . B oas, M. A ., and Jac k so n , H. M. The b i o l o g i c a l v a lu e of
p r o te in s o f w heat, m aize and m ilk . Biochem. J o u r . 26:
1923. 1932.
3 . Bonner, D. M., and Y anofsky, C.
The b io s y n th e s is o f t r y p t o ­
phan and n ia c i n and t h e i r r e l a t i o n s h i p s . J o u r, o f
N u tr it io n 4 4 : 603-16. 1931.
4 . B u rk h o ld er, P . R.
N ia c in i n maize ( A b s tra c t)
Med. A ss. J o u r . 105: 306. 1944*.

Amer. V et.

5 . Cameron, J . W., and T eas, H. J .
The r e l a t i o n betw een n ic o ­
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8 . C u r tis , J . J . , and E a r le , F. R.
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64

24o K re h l, ¥ . A., T eply, L. J . , Sarma., P . S ., and Elvehjem , C. A.
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Supple­
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3 0 . M ille r , P . A ., and B rim h a ll, B.
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3 3 . Nason, A.
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i n c o rn . S cience 109: 1 7 0 -1 . 1949.
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E f f e c t o f lo c a t io n , seaso n , s ta g e o f
m a tu rity and v a r i e t y on p r o te in c o n te n t o f c o rn .
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M. S.

3 5 . O sborne, T ., and Mende, L. B.
N u t r it iv e p r o p e r tie s o f
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1

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Powers, L.
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c ro s s betw een Lycopersicum e scu lan tu m and L. p im p in e lifo liu m . J o u r, o f G e n e tic s 3 9 : 1 3 9 -7 0 . 1939.

37»

_________ •
In h e r ita n c e o f q u a n t ita ti v e c h a r a c te r s i n
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R es. 63: 149-74. 1941.

38.

Powick, W. C .j E l l i s , N. R ., and D ale, C. N.
R e la tio n s h ip
o f corn d i e t s to n i c o t i n i c a c id d e f ic ie n c y i n growing
p i g s . J o u r, o f Animal S cien ce 6 : 3 9 5-400. 1947*

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R ichey, F. D ., and Dawson, R. F.
Survey o f th e p o s s i b i l i t i e s
and methods o f b re e d in g h ig h n i a c i n c o rn . P la n t P h y sio lo g y
23: 238-54. 1948.

40.

_________ , and ____________.
E xperim ents on th e in h e r ita n c e o f
n ia c in i n c o rn . P la n t P h y sio lo g y 26: 4 7 5 -9 3 . 1951.

41.

R odriguez, L. D ., Hunt, C. H ., B ethke, R. M.
The p r o t e in ,
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42.

S a rk a r, B. C. R.
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p a n th o th e n ic a c id c o n te n t. M c h . Agr. Exp. S ta . Q. B u i.
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43*

S h o w a lte r, M. F ., and C arr, R. H.
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44*

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Teas, H. L ., and Newton, A. C.
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__________, _____________ , and Cameron, J . W.
T ryptophan,
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47* W arner, J . N.
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m
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W illco ck , E. G. and Hopkin, F. G.
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Woodworth, C. M.
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and o i l i n c o rn . Agron. J o u r . 44: 6 0 -5 . 1952.

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A s s o c ia tio n o f O f f i c i a l A g r ic u ltu r a l C hem ists, Methods o f
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W isco n sin . 6th ed. 1945

INHERITANCE OF AND INTERRELATIONSHIPS OF
TRYPTOPHAN, NIACIN, PROTEIN, AND KERNEL
WEIGHT IN CORN

by
Kuo, Chun-yen

AN ABSTRACT
Subm itted to th e School o f G rad u ate S tu d ie s o f
M ichigan S ta te C o lleg e o f A g ric u ltu re and
A pplied S cien ce i n p a r t i a l f u l f i l l m e n t
o f th e re q u ire m e n ts f o r th e d e g re e o f
DOCTOR OF PHILOSOPHY
D epartm ent o f Farm Crops
1953

Approved,

Kuo, Chun-yen

ABSTRACT

1

The success o f a breeding program t o improve th e
q u a n tity o f the n u t r i t i v e const.i-fc-u.ents o f co rn may b e ach iev ed
w ith more in fo rm atio n concerning -th e mode o f in h e r ita n c e and
i n t e r r e l a t i o n s h i p s o f th e se c o n s t i t u e n t s .
S i x t y inbred l i n e s and t^ n o c ro s s e s , ;.v'23 x R53 and W23
x 0 h 51 A, w ere analyzed f o r try p t0 p h a n and n ia c i n c o n te n ts ,
u s in g m ic ro b io lo g ic a l assay.

P r o t e i n a n a ly s e s were made f o r

423 x R53 an d kernel w eig h t was (d eterm in ed f o r b o th c r o s s e s .
I n t e r r e l a t i o n s h i p s o f th e se c h a r a c t e r s w ere in v e s t i g a t e d .

The

i n h e r i t a n c e o f these c h a r a c t e r s c o n c e rn in g - dominance r e l a t i o n ­
s h ip s , n a t u r e of gene action, g ^ x ie numbers and h e r i t a b i l i t y
were s t u d i e d .
C onsiderable d iffe re n c e s

i n n ia c in and try p to p h a n con­

t e n t s w ere evident among the s 2J c t ,y in b re d l i n e s .

The d if f e r e n c e s

betw een h ig h and low f o r n ia c in a_nd try p to p h a n were 14 9 .7 $ and
78$, r e s p e c tiv e ly .

S e v e ra l inbj>e cls were above a v erag e f o r b o th

try p to p h a n and n ia c in and some l i n e s were low in b o th .
I n cross W23 x R'53» s ig rd L fic a n t p o s i t i v e c o r r e l a t i o n s
w ere fo u n d between p r o t e i n and t r y p t o p h a n and s i g n i f i c a n t neg­
a t i v e c o r r e la tio n s betw een p r o t e i n w ith n i a c i n and try p to p h a n
w ith n i a c i n .

This seem ed to agr»e e w ith try p to p h a n - n ia c in

b io s y n th e s is .

N e g a tiv e c o r re la tio n s betw een try p to p h a n and

n ia c i n w ere not s ig n if ic a n t in t i n e cro ss W23 x Oh31 A.

In b o th

ABSTRACT

2

c r o s s e s , th e r e was a s l i g h t te n d en c y f o r h ig h try p to p h a n to be
a s s o c ia te d w ith la r g e k e r n e l w eig h t and h ig h n ia c i n t o be
a s s o c ia te d w ith s m a ll k e r n e l w eight*

While a few o f th e s e

c o r r e l a t i o n s were s i g n i f i c a n t , th e r e l a t i o n s h i p s were sm all
and o f l i t t l e v a lu e i n a p la n t b re e d in g s e le c ti o n program*

S ig ­

n i f i c a n t p o s i t i v e c o r r e l a t i o n f o r p r o te in and k e r n e l w eight were
fo u n d .
High n ia c i n was dom inant o v e r low n ia c i n i n b o th c r o s s e s .
T ryptophan and p r o te in showed no p h en o ty p ic dom inance.

There

was no dominance f o r k e rn e l w eight i n th e c ro s s W23 x R53, w h ile
i n W23 x OhplA s l i g h t h e te r o s is o r com plete dominance was i n d i ­
c a te d f o r la r g e k e r n e l s .
I t was n o t p o s s ib le to d e te rm in e w hether th e o b serv ed
mean f o r th e s e c h a r a c te r s f i t t e d e i t h e r th e a r ith m e tic o r geo­
m e tric scheme o f gene i n t e r a c t i o n s in c e th e v a lu e s w ere s i m i l a r .
E stim a te d gene numbers f o r try p to p h an and n ia c in were
low , i n d ic a tin g th e r e l a t i v e l y h ig h p o s s i b i l i t y o f s e le c tin g
th e s e c h a r a c te r s i n th e s e g r e g a tin g p o p u la tio n s .
o f th e s e c h a r a c te r s d i f f e r e d i n each c r o s s .

H e rita b ility

More encouragem ent

f o r s e l e c t i o n f o r try p to p h a n and n ia c i n was p r e s e n t i n V/23 x
OhplA th a n W23 x E53*
There wa3 c o n s id e ra b le v a r i a b i l i t y i n t h e n o n -s e g re g a tin g
p o p u la tio n s , P-j_, P 2 , and

f o r a l l th e c h a r a c te r s s tu d ie d .

E nvironm ental f a c t o r s m ight have caused p a r t o f t h i s v a r i a t i o n .
S in ce th e s e c h a r a c te r s had no p re v io u s s e le c ti o n , i t i s p o s s ib le

Kuo, Chun-yen
ABSTRACT

3

t h a t th e r e was some g e n e tic v a r i a t i o n among in d iv id u a ls w ith in
th e p a re n ts u sed i n th e s e s t u d i e s .
N ia c in c o n te n t was n o t a f f e c t e d by sw eet c o rn p o lle n
and s l i g h t l y lo w er try p to p h a n c o n te n t was found i n th e e a r s
o f p la n ts o u tc ro s s e d w ith sw eet c o m th a n i n t h e s e lf e d p l a n t s .