T h e o r . A p p l . G e n e t . 49 (1977) 117-122

9 by Springer-Verlag 1977

Combining Ability and Heterosis in Diallel Crosses of Maize * B . S . D h i l l o n and 3. Singh D i v i s i o n of G e n e t i c s , Indian A g r i c u l t u r a l R e s e a r c h I n s t i t u t e , New Delhi (India) S u m m a r y . The p r e s e n t i n v e s t i g a t i o n i n v o l v e d c r o s s e s a m o n g 20 e l i t e y e l l o w m a i z e p o p u l a t i o n s . T h e s e w e r e e v a l u a t e d in f o u r e n v i r o n m e n t s in a r a n d o m i z e d block d e s i g n with f o u r r e p l i c a t i o n s in e a c h e n v i r o n m e n t . V a r i e t y C u ba was o b s e r v e d to be t h e b e s t g e n e r a l c o m b i n e r f o r g r a i n y i e l d , f o l l o w e d by St C r o i x and P r o l i f i c . No c l e a r a s s o c i a t i o n c o u l d be d i s c e r n e d b e t w e e n g e n e r a l c o m b i n i n g a b i l i t y (GCA) e f f e c t s f o r g r a i n y i e l d and i t s c o m p o n e n t s , and m e a n g r a i n y i e l d p e r f o r m a n c e and GCA e f f e c t s . H e t e r o s i s was o b s e r v e d in g e n e r a l and all t h e c r o s s e s i n v o l v i n g Cuba y i e l d e d b e t t e r than t h e m i d p a r e n t . The f i v e h y b r i d s , K i s a n • Cuba, A n t i g u a 3D • St C r o i x , P r o l i f i c • St C r o i x , Vijay • A n t i g u a G r . I and A 23 • Cuba, y i e l d e d m o r e than t h e s t a n d a r d c h e c k . S i g n i f i c a n t y i e l d s u p e r i o r i t y of t h e s e v a r i e t a l h y b r i d s o v e r the b e s t c o m m e r c i a l c o m p o s i t e ( J a w a h a r ) s u g g e s t e d the p o s s i b i l i t y of their commercial exploitation. is e s s e n t i a l . The p r e s e n t study was u n d e r t a k e n a l o n g

Introduction Because

of the lack of proper

understanding

action involved in the expression mercial

use of varietal crosses

ed heterosis

of gene

of heterosis,

com-

has not received

attention in the past, even though Beal

(1878)

due

report-

to the extent of 40 per cent over the bet-

ter parent.

In recent studies on maize,

etic variance

has been shown

pollinated varieties,

additive gen-

to predominate

in the expression

in open

of yield and

other metric

traits (Gardner

1963; Gardner

quist 1966),

and successfully

exploited by employing

intrapopulation These

selection schemes

broadbased

comparable

Moreover,

composite

Promising

bined in varietal hybrids, developing

countries

tion. For

formulating

composite

would

population or gene

to

can be com-

are better suited to

due to convenient

seed produc-

an effective programme

varieties and their hybrids,

the combining

hybrids.

be amenable

composites

which

1969).

the possibility of

in yield to commercial

such populations

further selection.

and Lonn-

(Gardner

studies have suggested

synthesizing pools,

these lines.

ability of the materials

to breed

a knowledge

of

being handled

* P a r t of t h e t h e s i s s u b m i t t e d by t h e s e n i o r a u t h o r in the p a r t i a l f u l f i l m e n t of t h e r e q u i r e m e n t s f o r t h e Ph. D. d e g r e e

Materials

and Methods

Crosses among 20 yellow maize populations, eleven developed in India and nine obtained from Mexico, formed the material. The parental populations were selected primarily on the basis of their own performance as well as of hybrids involving them. The populations developed in India were five commercial composites (Amber, Jawahar, Kisan, Vijay and Vikram), three experimental composites (C 2, J 236 and Prolific) and three experimental synthetics (A 22, A 23 and E 13), while the populations obtained from CIMMYT, Mexico, were four composites (Antigua Group I, Caribbean Flint, Puerto Rico Group I and Yellow Tuxpeno) and five open pollinated varieties (Antigua 2D, Antigua 3D, Cuba 19, St Croix 4D and Francisco Flint). All possible crosses were made and bulked seed of crosses and reciprocals was laid out in a randomized block design with four replications during the rainy seasons of 1970 and 1971 at the Indian Agricultural Research Institute, New Delhi, and Gobind Ballabh Pant University of Agriculture and Technology, Pantnagar. These locations represented IndoGangetic plains and sub-montaneous Kamaon foot hills region, respectively. The two years and two locations were assumed to represent four random environments. Grain yield per plant and days to silk were based on whole plot observation. Plant height, ear height, ear length, ear diameter and number of kernel rows were recorded on 10 randomly selected plants and their means were used for analysis. At harvest, fresh ear weight was recorded for each plot and was adjusted to 15 per cent grain moisture and 80 per cent shelling.

118

Theor.

T a b l e 1. A n a l y s i s o f v a r i a n c e Source

d.f.

Mean squares D a y s to silk

Grain moisture

Plant height

178.0 11.0 19.2 7.4 5.7

77.0 ~ 6.0 ~ 15.5 ~ 5.4 5.0

13957.9 400.8 328.2 202.5 173.7

*, *~* S i g n i f i c a n t at 5 p e r c e n t a n d 1 p e r c e n t l e v e l ,

respectively

19 170 57 510 2268

3570.9 639.0 1461.4 478.2 315.0

~ ~ ~ ~

~ ~ ~ ~*

D a y s to s i l k w e r e r e c o r d e d a s d a y s t a k e n t o s i l k e m e r g e n c e o f 75 p e r c e n t o f p l a n t s i n a p l o t . M o i s t u r e p e r centage was determined using the' Universal Moisture T e s t e r ' in a g r a i n s a m p l e o b t a i n e d f r o m two r o w s of e a c h o f t h e f i v e e a r s s e l e c t e d at r a n d o m at t h e t i m e o f harvest. Combining ability analysis was based on the proc e d u r e s d e v e l o p e d by S i n g h ( 1 9 7 3 ) . M e t h o d 4 w a s employed assuming the fixed effects (Model I).

Ear height

~ ~ ~ ~

8536.4 272.2 339.7 113.9 96.4

~ ~ ~ ~

GCA • E interaction for grain yield,

Ear length

Ear diameter • 10

Kernel rows

23.6 ~ 3.2 ~ 3 . 2 ~* 1.6 1.6

18.8 0.8 1.2 0.5 0.4

44.6 ~ 1 . 6 ~* 0.9 ~ 0.5 0.5

~ ~ ~ ~

while SCA X E was significant

d a y s to s i l k , p l a n t h e i g h t , e a r h e i g h t

and ear diameter

o n l y . V a r i a t i o n a c c o u n t e d f o r by

combining ability effects, higher in comparison

in general,

was appreciably

with interaction

e f f e c t s of GCA

and SCA with environments. Only three varieties,

Cuba,

St C r o i x

had a GCA effect significantly greater Results and Discussion Analysis

of v a r i a n c e

among hybrids.

The combining

ability analysis of significant var-

(GCA) and specific combining

a b i l i t y ( S C A ) f o r all c h a r a c t e r s .

T a b l e 2. E s t i m a t e s Code

1 2 3 4 5 6 7

of g e n e r a l

Pedigree

9 10 11 12 13 14 15 16 17 18 19 20

Amber Jawahar Kisan Vijay Vikram C 2 J 236 Prolific A 22 A 23 E 13 Antigua Gr. 1 A n t i g u a 2D A n t i g u a 3D Caribbean Flint Cuba Puerto Rico Gr.I St C r o i x Yellow Tuxpeno Francisco Flint

S.E.

-_-(}i) +-

8

Significant

It w a s a l s o t r u e f o r

D a y s to silk

Grain mois-

-0.4 -3.9 ~ -1.4 0.8 -3.0 ~ -2.0 0.3

1.1 0.3 0.3 0.0 -0.3 -0.8 0.3 -1.1 -0.5 0.0 -0.9 -1.2 -0.4 0.3 1.2 1.0 -1.2 0.1 1.2 0.6

0.2 -0.3 ~ 0.2 -0.1 0.2 -1.0 ~ -0.1 -0.9 ~ 0.1 0.2 - 0 . 3 ~r -0.4 ~ 0.0 0.0 -0.3 ~ 1.4 ~ -0.3 ~ 0.2 0.5 ~ 0.7 ~

~

~

~ ~ ~ ~ ~

1.02 at 5 per

cent

level

higher GCA

effects than the others.

These three parents

good general combiners

for one or more yield com-

ponents.

However,

any clear association

yield and its components was a good combiner

was lacking,

for ear length,

were

between

though Cuba St C r o i x f o r e a r

combining ability effects

Grain yield

4.8 -1.3 1.1 -2.7 1.1 1.7 -1.4 -2.0 10.6 -2.0 5.1 -1.6 -3.9

and Prolific,

than zero for

grain yield (Table 2). Cuba haddistinctly

showed significant differences

( T a b l e 1) s u g g e s t e d t h e p r e s e n c e iation due to general

49 ( 1 9 7 7 )

for combining ability

Grain yield

GCA SCA GCA XE SCA X E Pooled error

Appl. Genet.

~ ~ ~ a ~ ~* ~ *r e ~ ~ ~ ~ ~ ~ ~

0.14

0.12

Plant height

5.7 -1.9 -1.7 3.3

Ear height

~ ~* ~ ~

-0.6

-7.2 2.7 5.7 -0.1 -4.9 -1.9 -15.0 -15.0 1.1 6.1 6.7 -2.5

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

2 . 8 ~" 13.9 ~ 2.9 ~ 0.76

Ear length

1.8 ~ -1.6 ~ 0.3 1.9 ~

0.3 ~ 0.2 ~ 0.2 ~ 0.1

0.0

0.3 ~

-8.4 1.5 0.7 1.4 -0.9 -2.2 -9.4 -10.6 1.5 5.4 3.3 -0.2 -1.4 14.9 2.0

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

0.56

0.1 0.0 -0.4 0.0 -0.6 -0.2 -0.4

~ ~ ~ ~

-0.2 ~ 0.0

0.1 0.7 ~ 0.2 ~ 0.0 -0.3 ~ -0.1 0.07

Ear diameter •

Kernel rows

0.1 0.0 -0.1 0.1

0.0 0.4 ~ -0.1 0.3 ~

-0.6 ~

-0.4 ~

-0.2 -0.1 -1.1 0.0 1.0 0.1 1.0

0.0 0.0 0.1 0,0 0.1 0.1 0.7 0.5 0.1 0.0 -0.8 -0.5 0.2 -0.8 0.0

~ ~ ~ ~

0.8 ~ 0.0

-0.7 0.0 -1.6 2.1 -1.0 0.1

~ ~ ~ ~

0.12

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

0.04

B . S . Dh i l l o n and J . Singh: C o m b i n i n g A b i l i t y and H e t e r o s i s in D i a l l e l C r o s s e s of M a i z e

d i a m e t e r and k e r n e l r o w s , and P r o l i f i c f o r k e r n e l

European

r o w s . Of t h e s i x p o o r c o m b i n e r s f o r g r a i n y i e l d ( F r a n -

lative oviposition for plant height. Further work on

c i s c o F l i n t , J a w a h a r , V i k r a m , E 13, C a r i b b e a n F l i n t

these lines is desirable.

particularly in correcting re-

Dhillon et at. (1977) reported mean

and P u e r t o R i c o G r . 1), f o u r w e r e g o o d c o m b i n e r s f o r one o r o t h e r y i e l d c o m p o n e n t , s u p p o r t i n g the ab o v e

corn-borer,

119

performance

of t h e s e p a r e n t a l p o p u l a t i o n s . Cuba w as d i s t i n c t l y d i f f e r e n t f r o m t h e o t h e r m a t e r i a l s , being the p o o r e s t

observation. T h e r e was an i n d i c a t i o n that the y i e l d s u p e r i o r i t y

y i e l d e r , h a v i n g the l o n g e st , t h i n n e s t c o b s and t a k i n g

of Cuba, and to a l e s s e r e x t e n t of St C r o i x , was due

m a x i m u m days to s i l k . In c o m b i n i n g a b i l i t y a n a l y s i s ,

to l a t e m a t u r i t y . S i m i l a r r e s u l t s w e r e a l s o r e c o r d e d

it had t h e h i g h e s t GCA e f f e c t f o r g r a i n y i e l d and e a r

in s i x d i a i l e l c r o s s e s ,

length, indicating complete agreement between mean

c o m p r i s i n g v a r i e t i e s of v a r y -

ing m a t u r i t y r a n g e , s t u d i e d by t h e All I n d i a C o o r d i n -

p e r f o r m a n c e and GCA e f f e c t f o r e a r l e n g t h but e x a c t l y

ated Maize I m p r o v e m e n t Scheme ( P r o g r e s s Report

the r e v e r s e for grain yield. Another divergent parent

1972). A c c o r d i n g l y , t h e r e is a n e e d f o r g r e a t e r c a r e

was A n t i g u a 2D, which had the s h o r t e s t p l a n t s , l o w e s t

to r e c o r d g r a i n y i e l d u n b i a s e d f o r m a t u r i t y , to o b t a i n

e a r p l a c e m e n t and m a x i m u m n u m b e r of k e r n e l r o w s .

e s t i m a t e s of GCA r e l e v a n t to p r a c t i c a l b r e e d i n g . Two

It was a l s o t h e b e s t c o m b i n e r f o r s h o r t plant type and

a p p r o a c h e s a r e p o s s i b l e : (i) to study g r a i n y i e l d p e r

s e c o n d b e s t f o r k e r n e l r o w s . St C r o i x , an a bove a v e r -

dayl and ( i i ) to a d j u s t y i e l d f o r a v e r a g e m a t u r i t y

ag e y i e l d e r , had the t h i c k e s t e a r s and was a l s o t he

through regression technique.

best g e n e r a l c o m b i n e r f o r e a r d i a m e t e r . A n t i g u a 3D,

The s e c o n d a p p r o a c h

J a w a h a r and A 22 w e r e b e t t e r y i e l d e r s and a v e r a g e

is b ei n g a p p l i e d to h o s t - p e s t r e s i s t a n c e s t u d i e s in the

Table 3. E s t i m a t e s of s p e c i f i c c o m b i n i n g a b i l i t y e f f e c t s of s o m e h y b r i d Pedigree a

Grain yield

Days to silk

Grain Plant m o i s t u r e height

Ear height

Ear length

Ear Kernel diameter rows

-0.4 0.9 -0.1 0.3 0 .1 1.7" -0.3 0.4 0 .1 1.9 ~ -0.6 0.4 0.4

-0.4* 0.5* -0.2 0.0 -0.3 -0.3 -0.5* 0 .2 0.3 0.1 -0.1 -0.2 0.2

0.7 -1.1"

0.0 -0.6*

Good S p e c i f i c C o m b i n e r For G r a i n Y i e l d 1 X 17 1 • 2 • 3 • 4 x12 4 • 18 6 • 6 X13 8• 9 x15 11 X 15 12 X 1 9 14 X1 8

17.1" 11.1" 10.1" 13.6" 13.4" 9.2* 12.6" 10.0" 14.1" 9.1" 11.2" 13.9" 16.6"

-1.8" 0.8 -1.2" 0.4 0.0 -0.5 0.0 -0.7 -1.3 ~ -1.0 0.1 -0.5 -0.8

-0.4 0.5 0.4 -0.5 0.1 0.8 -0.2 -0.2 0.8 1.2" -0.3 0.7 0.8

0.4 4.4 3.1 -0.2 -1.9 6.2* 3 .6 7.4* 3.0 0 .1 0.2 1 .4 9.2*

-1.8 0 .7 0.0 -0.2 -3.1 5.0* 0.5 7.0* 6.0" 1 .4 0.2 -2.4 1.7

1.1" 0.5 0.3 0.4 0 .1 0.3 -0.2 0.4 -0.3 0.2 -0.1 0.4 0.4

3.4 8.1"

-1.2 4.9*

0.8* 0.5

Poor Specific Combiner For Grain Yield 2 • 2 • 3 X9

4 x6 4 x8 5 X1 0 6 • 7 x18 9 X19 12 • 14 • 16 14 X 17 15 X 19 17 X 18 S.E.(sij)•

-8.5* -10.7"

-1.1 0.9

0.2 0.4

-8.5 ~

1.0

0.1

-0.7

-2.0

-0.1

-0.4

-0.6*

-11.2" -9.3* -11.9" -17.2" -8.8* -10.5" -22.8" -8.8* -9.2* -13.9 ~ -8.9*

-0.4 0.4 0.0 2.2* 2.0* 0.2 1.7" 0.6 -0.3 0.2 1.4

0.1 -1.0" 0.4 -0.7 -0.7 -0.4 -0.7 0.0 0.5 -0.1 0.4

-6.0 -5.7 -3.6 -2.1 1.1 -0.9 -13.7" -10.5" 4.1 -10.4" -12.9"

-1.3 -1.5 -1.2 -0.4 2.3 -1.9 -7.8" -0.8 -0.8 -7.5* -10.5"

-0.7* -0.1 -0.5 -0.5 0.0 0.4 -1.0" -0.8* -0.5 -0.9" -0.2

-0.4 -0.1 -1.1" -0.2 -1.1" 0.2 -2.4* -1.0" 1.6" -0.6 -1.0"

-0.2 0.2 -0.2 0.4* -0.6* -0.2 -0.1 0.2 0.5* 0.2 -0.3

0.56

0.51

3.12

2.32

0.30

0.48

0.17

4.20

* Significant at 5 per cent level a Pedigree code is given in Table 2

120

T h e o r . Appl. G e n e t . 49 (1977)

g e n e r a l c o m b i n e r s , e x c e p t f o r J a w a h a r which w as a

was t h e m o s t c o m m o n p a r e n t a m o n g s t t h e h y b r i d s

poor general combiner.

sh o w i n g s i g n i f i c a n t l y n e g a t i v e SCA e f f e c t s , w h i l e a

H y b r i d s with s i g n i f i c a n t p o s i t i v e SCA e f f e c t s f o r g r a i n y i e l d w e r e A m b e r • P u e r t o R i c o G r . I, A n t i g u a

p o o r g e n e r a l c o m b i n e r ( C a r i b b e a n F l i n t ) was the m o s t c o m m o n p a r e n t in t h e o t h e r g r o u p of h y b r i d s . It was

3D x St C r o i x , P r o l i f i c x F r a n c i s c o F l i n t , A n t i g u a

a l s o i n t e r e s t i n g that t h e h y b r i d of t h e b e s t g e n e r a l

Gr. 1 • YellowTuxpeno, KisanXCuba,

c o m b i n e r (Cuba) and b e s t y i e l d e r ( A n t i g u a 3 D ) s h o w e d

Gr.1, C 2 •

V ij a y x A n t i g u a

23, E 13 x C a r i b b e a n F l i n t , A m b e r •

s i g n i f i c a n t l y n e g a t i v e SCA e f f e c t s .

Francisco Flint, Jawahar x Caribbean Flint, C 2 •

Sixty-three hybrids showed significant superioity

A n t i g u a 2D, Vijay x St C r o i x and A 22 • C a r i b b e a n

in g r a i n y i e l d o v e r m i d - p a r e n t and t h e m a x i m u m h e t e r -

F l i n t (Table 3 ) . F i f t e e n h y b r i d s had s i g n i f i c a n t SCA

o s i s was 40 p e r c e n t f o r K i s a n x C u b a ( T a b l e 4 ) . I t w a s

e f f e c t s f o r e a r l y m a t u r i t y and, of t h e s e , A m b e r x

i n t e r e s t i n g t h a t all t h e c r o s s e s i n v o l v i n g C u b a y i e l d e d

P u e r t o R i c o G r . 1, J a w a h a r • C a r i b b e a n F l i n t and

b e t t e r t h a n the m i d - p a r e n t with a r a n g e of 6 to 40 p e r

Prolific • Francisco Flint combined desirable effects

c e n t . C u b a w as a l s o i n v o l v e d in s i x of t h e top eight h y -

f o r both y i e l d and m a t u r i t y . None of the h y b r i d s with

b r i d s . The p e r f o r m a n c e of Cuba, and i t s p r a c t i c a l i m -

p o s i t i v e SCA f o r y i e l d s h o w e d s i g n i f i c a n t SCA e f f e c t s

p l i c a t i o n s , h a v e b e e n d i s c u s s e d by D h i l l o n and Singh

e i t h e r f o r s h o r t s t a t u r e o r f o r low e a r p l a c e m e n t .

(i975).

H o w e v e r , the t h r e e h y b r i d s c i t e d a b o v e w e r e m e d i u m

t h e s e c o n d m o s t c o m m o n p a r e n t , but St C r o i x a n o t h e r

combiners for ear placement (except Prolific X F r a n -

good g e n e r a l c o m b i n e r , t r a i l e d b e h i n d A 23, A n t i g u a

c i s c o F l i n t ) and plant h e i g h t . F o u r t e e n h y b r i d s h ad

G r . 1, A n t i g u a 2D, Y e l l o w Tuxpeno and C 2. S i gni f i c a nt

s i g n i f i c a n t n e g a t i v e SCA e f f e c t s f o r g r a i n y i e l d and

h e t e r o s i s o v e r b e t t e r p a r e n t w as o b t a i n e d f o r 32 h y -

P r o l i f i c , a l s o a good c o m b i n e r l i k e Cuba, was

t h e s e w e r e , in g e n e r a l , a s s o c i a t e d with p o s i t i v e SCA

b r i d s . T h r e e h y b r i d s ( K i s a n X Cu b a, C 2 X Cuba and

e f f e c t s f o r s i l k i n g and n e g a t i v e SCA e f f e c t s f o r height

A 23 x Cuba) s h o w e d o n e - t h i r d g r e a t e r y i e l d than the

and e a r c h a r a c t e r s .

better parent.

Amber x Puerto Rico Gr.t, Jawahar X Prolific, Vijay x St C r o i x , C 2 x A n t i g u a G r . 1, J 236 •

Croix,

E i g h t e e n h y b r i d s w e r e h i g h l y h e t e r o t i c , as they p e r f o r m e d significantly better than m i d - p a r e n t for

A 22 x A n t i g u a 3D, E 13 x F r a n c i s c o F l i n t , A n t i g u a

four o r m o r e c h a r a c t e r s (Table 4 ) . H e t e r o t i c r e s p o n -

G r . I X A n t i g u a 2D, A n t i g u a 3D x C u b a , C a r i b b e a n

s e s of v a r i o u s t r a i t s e x h i b i t e d a d e f i n i t e a s s o c i a t i o n

F l i n t x Y e l l o w Tuxpeno, Cuba X P u e r t o R i c o G r . I,

b e t w e e n t h e m in t h e s e h y b r i d s . G r a i n y i e l d was a s s o -

P u e r t o R i c o G r . I x St C r o i x and St C r o i x • Y e l l o w

c i a t e d with y i e l d c o m p o n e n t s , p a r t i c u l a r l y e a r d i a -

Tuxpeno s h o w e d s i g n i f i c a n t SCA e f f e c t s f o r f o u r o r

m e t e r and k e r n e l r o w s . C o n t r a r y to p r e v i o u s i n d i -

m o r e t r a i t s . Of p a r t i c u l a r i n t e r e s t was the h y b r i d

cations, these hybrids combined heterotic responses

A n t i g u a G r . 1 x A n t ig u a 2D, which had t h e h i g h e s t

f o r high y i e l d and e a r l y m a t u r i t y . None of t h e s e h y -

n u m b e r of s i g n i f i c a n t SCA e f f e c t s ( f o r all t r a i t s e x -

b r i d s was h e t e r o t i c f o r l o w e r e a r p l a c e m e n t ( e x c e p t

cept g r a i n m o i s t u r e and k e r n e l r o w s ) . It had the

A n t i g u a G r 1 • C a r i b b e a n F l i n t ) and s h o r t plant h e i g h t .

l o w e s t SCA e f f e c t s f o r g r a i n y i e l d , plant height and

The b e s t g e n e r a l c o m b i n e r (Cuba) was a p a r e n t of

e a r d i a m e t e r . Such p o o r p e r f o r m a n c e was e x p e c t e d ,

50 p e r c e n t of t h e h i g h l y h e t e r o t i c c o m b i n a t i o n s . This

s i n c e t h e p a r e n t s a r e c l o s e r e l a t e d in o r i g i n .

w as e x p e c t e d as C u b a was t h e m o s t d i v e r s e p a r e n t .

C o n s i d e r a t i o n of GCA e f f e c t s of t h e p a r e n t s i n v o l v e d in t h e c r o s s e s showing s i g n i f i c a n t l y p o s i t i v e and n e g a t i v e SCA e f f e c t s f o r y i e l d i n d i c a t e d no a s s o c i a t i o n b e t w e e n e x p r e s s i o n of GCA and SCA e f f e c t s . None of t h e h y b r i d s showing s i g n i f i c a n t l y n e g a t i v e SCA e f f e c t s was e i t h e r a p o o r • p o o r o r a good • good c r o s s ; the s a m e was the c a s e f o r h y b r i d s with s i g n i -

The s e c o n d m o s t c o m m o n p a r e n t w as St C r o i x ( good g e n e r a l c o m b i n e r f o r y i e l d ) and it was i n v o l v e d in f i v e h y b r i d s . With r e g a r d to the c o n t r i b u t i o n of highly h e t e r o t i c h y b r i d s , t h e t h i r d good g e n e r a l c o m b i n e r f o r y i e l d ( P r o l i f i c ) w as o v e r t a k e n by A n t i g u a G r . I, V i j a y , C a r i b b e a n F l i n t and F r a n c i s c o F l i n t . In a p r a c t i c a l b r e e d i n g p r o g r a m m e ,

it would be

f i c a n t l y p o s i t i v e SCA e f f e c t s e x c e p t f o r two p o o r •

u s e f u l to t e s t t h e s u p e r i o r i t y of a h y b r i d o v e r a s t a n d -

c o m b i n a t i o n s ( J a w a h a r • C a r i b b e a n F l i n t and E 13 X

a r d c u l t i v a r . In t h e p r e s e n t study, J a w a h a r was t he

C a r i b b e a n F l i n t ) . A good g e n e r a l c o m b i n e r ( P r o l i f i c )

h i g h e s t - y i e l d i n g s t a n d a r d c u l t i v a r and only f i v e h y -

B.S.

Dhillon and J. Singh: Combining Ability and Heterosis

T a b l e 4. P e r f o r m a n c e parent (BP) Heterotic

in Diailel C r o s s e s

of Maize

of some promising hybrids as per cent of mid-(MP)

121

and better-

Hybrids For Grain Yield

Pedigree a

MP

BP

Pedigree

MP

BP

Pedigree

MP

BP

1 1 1 1 1 2 3 3 3 3 3 3 4 4 4 4 4 4 5 5 5

115" 117" 120" 118" 116" 120" 116" 113" 112 ~ 111" 140" 113" 113" 122 ~ 114" 119" 115" 113" 112" 116 ~ 115"

111 113" 113" 116" 113" 108 112 112 111 109 135" 112 106 114" 108 110 114" 106 107 116" 114 ~

5 6 6 6 6 6 6 7 7 7 7 8 8 8 8 8 8 8 8 8 8

122" 129" 122" 125" 133" 114" 114" 116" 113" 115" 115" 111" 124" 118" 119" 114" 128" 112" 120" 118" 125"

117" 127" 120" 121" 132" 112 110 111 105 105 109 105 121" 115" 117" 110 122" 108 116 ~ 116" 124"

9 10 10 10 10 10 11 12 12 12 13 13 13 14 15 15 16 16 16 16 18

119" 116" 112" 134" 113 ~* 112" 121" 128" 128" 115 ~ 126" 112" 112 ~ 116" 112" 111" 118" 125" 128 ~ 123" 111"

108 116" 110 131" 107 112 113" 125" 128" 113" 121 ~ 107 111 113" 104 110 110 115" 125 ~ 118" 105

Grain moisture

Plant height

Ear height

Ear length

Ear diameter

Kernel rows

96 98 93* 102 91" 99 92* 97 104 99 95 98 97 103 98 93* 94* 97

105 103 106 106 99 111 106 99 106 106 97 102 104 108 108 113 106 106

106 102 107 104 96 106 10 9 98 110 108 95* 97 108 107 110 113 105 107

102 99 102 104 99 102 102 107" 102 105" 103 100 102 101 101 104 96 97

105" 106" 107" 105" 104" 106" 106" 106" 104" 110" 106" 108" 105" 103 ~ 104" 106" 105" 105"

104" 104" 104" 106" 107" 105" 106" 104" 105" 104" 107" 109 ~ 106" 104" 106" 109" 102 106"

• 10 • 12 • 16 • 17 X 20 X 16 • 6 X8 X 10 X 12 • 16 • 19 • 10 X 12 • 13 • 16 X 18 X 19 • 6 • 8 X 13

• 16 x 10 • 12 • 13 • 16 X 19 • 20 • 8 X 12 • 13 X 16 X9 • 10 • 12 X 13 • 15 • 16 • 17 • 18 • 19 X 20

• 16 x 12 • 13 • 16 X 17 X 19 X 16 X 16 X 19 • 20 X 16 X 18 X 19 X 18 X 16 X 18 X 17 • 18 • 19 X 20 X 19

Highly Heterotic Hybrids (MP) Pedigree a

Grain yield

1 X 16 2 • 16 3 • 16 4 x 13 4 x 15 4 • 16 5 x 16 7 X 12 8 x 18 10 X 16 12 x 15 12 • 16 12 • 20 14 K 18 15 • 18 16 • 18 16 X 20 18 • 19

120" 120" 140 ~ 114" 101 119" 122" 113" 120" 134" 100 128" 115" 116" 111" 125" 123" 111"

D a y s to silk 96* 97* 95* 96* 96* 96* 96* 96* 97* 97* 97* 94 e 95* 98* 96* 94* 94* 97*

* The d i f f e r e n c e s b e t w e e n h y b r i d m e a n a n d p a r e n t m e a n s i g n i f i c a n t at 5 p e r c e n t a Pedigree code is given in Table 2

b r i d s ( K i s a n x C u b a , A n t i g u a 3D x St C r o i x , X St C r o i x ,

Prolific

V i j a y x A n t i g u a G r . 1 a n d A 23 • C u b a )

yielded significantly better than Jawahar i o r i t y b e i n g 11 t o 18 p e r c e n t ) .

(the super-

Extensive evaluation

edge over the standard inbred-hybrid venient seed production. base,

Because of the broad genetic

such hybrids are also expectedto be more stable

in t h e i r p e r f o r m a n c e

in t h e f a c e of w e a t h e r f l u c t u a t i o n s

of t h e s e f i v e v a r i e t a l h y b r i d s w o u l d b e d e s i r a b l e f o r

and pests and diseases.

commercial

further improvement

exploitation. Varietal hybrids have the

approach in con-

They a r e a l s o a m e n a b l e to

by s e l e c t i o n . It i s w o r t h w h i l e

122

Theor. Appl. G e n e t . 49 (1977)

adding that varietal hybrids are being commercially grown

and further improved

in Kenya

(Darrah

et ai.

1972).

Acknowledgements The a u t h o r s e x p r e s s t h e i r thanks to M r . A r u n Saxena for c o m p u t e r p r o g r a m m i n g and to Mr. Daijit Singh, Dr. J . S . S a m r a and Mr. A . S . Sethi. The f i n a n c i a l a s s i s t a n c e g i v e n by the R o c k e f e l l e r F o u n d a t i o n (to B. S. D. ) is s i n c e r e l y acknowledged.

Literature

Beal, W.J. : Rept. Mich. State Board Agri. 17, 445-457 (1878) Darrah, L.L. ; Eberhart, S.A.; Penny, L.H. : A maize breeding methods study in Kenya. Crop Sci. 12, 605-608 (1972)

R e c e i v e d J u l y 3, 1976 C o m m u n i c a t e d by B . R . M u r t y

Dhillon, B.S. ; Singh, J. : Cuba 19, a highly heterotic variety of maize and its possible utilization in varietal hybrids. Current Sci. 4_44, 479-480 (1975) Dhillon, B . S . ; Singh, J . ; Singh, N . N . : G e n o t y p e e n v i r o n m e n t a l i n t e r a c t i o n s and p e r f o r m a n c e of m a i z e v a r i e t i e s and t h e i r h y b r i d s . Maydical 2_22 ( i n P r e s s 1977) G a r d n e r , C . O . : E s t i m a t e s of g e n e t i c p a r a m e t e r s i n c r o s s f e r t i l i z i n g p l a n t s and t h e i r i m p l i c a t i o n s in plant b r e e d i n g . In: " S t a t i s t i c a l G e n e t i c s and P l a n t B r e e d i n g " ed. H a n s o n , W . D . and R o b i n s o n , H. F . 225-250 NAS-NRC 982, W a s h i n g t o n ( 1963 ) G a r d n e r , C . O . : The r o l e of m a s s s e l e c t i o n and m u tagenic t r e a t m e n t in modern corn breeding. Proc. 24th A n n . C o r n and S o r g h u m R e s . Conf. 24, 1521 (1969) G a r d n e r , C . O . ; Lonnquist, J . H . : S t a t i s t i c a l g e n e t i c t h e o r y and p r o c e d u r e s useful i n s t u d y i n g v a r i e t i e s and i n t e r v a r i e t i a l c r o s s e s i n m a i z e . CIMMYT R e s . B u l l . No. 2, P. 34 (1966) Singh, D. : Diallel c r o s s a n a l y s i s for c o m b i n i n g a b i l ity o v e r d i f f e r e n t e n v i r o n m e n t s . If. I n d i a n J. Genet. 3__33, 469-481 (1973)

B . S . Dhillon D e p a r t m e n t of P l a n t B r e e d i n g Punjab Agricultural University Ludhiana 141004 (India)

Joginder Singh Project Coordinator (Maize) Cummings ' Laboratory Indian Agricultural Research Inst. New Delhi 110012 (India)