physicochemical

COMBINING ABILITY ANALYSIS FOR YIELD AND YIELD COMPONENT TRAITS IN RICE
gene interactions in controlling these traits.
Predominance of non-additive gene action for grain
yield and components has also been reported
(Sanjeevkumar et al., 2007 and Sarma et al. 2007).
Hence, heterosis breeding is an appropriate and right
approach for yield improvement in rice.
The gca is generally attributed to the additive
effects of genes and is fixable (Sprague and Tautam,
1942). Hence selection of the parents based on gca
effects is of great importance in breeding programme.
The general combining ability (gca) effects of the
parents in the present study have brought to the light
suggesting them to use in successful breeding
programme, especially hybrid breeding. Three lines
(APMS 6A, PUSA 5A and CRMS 32A) and eight
testers (1096, 612-1, GQ-37-1, GQ-70, GQ-120, KMR
3, SC5 9-3 and SG 27-77) were found to be the good
general combiners for grain yield (Table 2). The lines
APMS 6A and CRMS 32A were also good general
combiners for yield components like panicle weight,
filled grains per panicle and per day productivity, while
PUSA 5A for dwarf plant stature, productive tillers
per plant and per day productivity, which is early to
flower indicating its usefulness in breeding for
earliness. The restorers 1096 and GQ-70 were found
good for dwarfnenss, early flowering, productive tillers
per plant, filled grains per panicle, spikelet fertility
per cent and productivity per day, while 612-1 and
KMR-3 contributed maximum favourable alleles for
earliness, productive tillers per plant, panicle length
and productivity per day.
SC5 9-3 and SG 27-77 can be used as good
source for panicle weight, filled grains per panicle
and productivity per day. For improving earliness in
days to 50% flowering, productive tillers per plant
and productivity per day, the line GQ 37-1 can be
used as it possessed desirable significant gca
effects. Extent of grains filling in hybrids is influenced
by the restoration ability of male parents. In respect
of spikelet fertility %, 1096, GQ-25, GQ-70, SG-26-
120, 124, 517 and IR 43 possessed significant positive
gca effects. These parents had low sterility and can
be used as potential donors in improving this
character. Mahadevappa (1985) reported spikelet
fertility in hybrids as one of the reasons for not
realizing the full yield potential in rice hybrids. Multiple
crossing among the above parents is also
recommended to get superior recombinants with
desirable traits along with grain yield.
The number of cross combinations
generated from parents having different types of gca
effects (viz., positive significant, negative significant
or non significant) and their corresponding Specific
Combining Ability effects were observed. Almost all
types of sca effects were obtained from any type of
parental combinations.(Table 3)
Instances where the gca effects of both the
parents were negative but the sca effect of the
resultant hybrid was positive was observed for grain
yield per plant in hybrids IR 58025A x 619-2, IR
58025A x IR 60, IR 58025A x SC5 2-2-1, IR 58025A
x SG 26-120 and IR 79156A x SG 26-120. Such
behaviour has been attributed to over dominance and
epistasis (Rahman et al., 1981)
Some crosses were derived from parents
having high gca resulted in high sca effects for grain
yield per plant in hybrids APMS 6A x 612-1, PUSA
5A x KMR-3 and APMS 6A x SC5 9-3 suggesting
the presence of additive x additive type of gene action.
This indicated that selection could be effective in F 2
generation and utilized in transgressive breeding.
Significant positive gca effect in any one of
the parents and negative or non significant effect on
the other parents leading to significant sca effect in
hybrids could be observed for grain yield per plant in
hybrids IR 79156A x 1096, APMS 6A x GQ-25,
PUSA 5A x IR 43 , IR 58025A x GQ 37-1, IR 58025A
x GQ-70, IR 79156A x SG 27-77, PUSA 5A x 611-1
, IR 79156A x GQ-70, IR 79156A x KMR-3, CRMS32A
X IR 43 and PUSA 5A x 124. The high yield potential
of cross combinations with high x low gca effects
was attributed to interactions between positive alleles
from good combiner and negative alleles from poor
combiner (Dubey, 1975). Similar results were also
obtained by Peng and Virmani (1999). All these
29