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Combining Ability Yield Attributing Characters in Line x Tester Inter specific Hybrids Confirmation
15
introducing slight modifications in the procedures to
suit the crossing system of self pollinated crops. In
present study heterotic box was developed by
involving barbadense and hirsutum varieties and it
was exploited by creating recombinational variability
for combining ability.
If two lines A and B are found to give potential
crosses with testers T
1
and T
2,
it is possible to increase
the genetic distance between these opposite pairs A, B
vs
, T
1
and T
2
by following population improvement
scheme for improving combining ability defined in
cross pollinated crops by introducing suitable changes
to match the crossing system seen in self pollinated
crops. The ongoing study at ARS, Dharwad on
evaluation of interspecific hybrids led to formation of
a heterotic box of two barbadense lines DB 533 and
DB 534 and hirsutum testers DH 98-27, ZCH 8,
178-24 and DH 18-31.
The main objectives of this study are 1) development
of hirsutum
vs
barbadense heterotic groups 2) To
determine combining ability effects (
gca
and
sca
),
variances (GCA and SCA), combining ability patterns
of these barbadense and hirsutum lines.
1 Results
1.1 Analysis of variance for combining ability
The Analysis of variance for combining ability done
with respect to hybrids are summarized in Table 1 for
eight characters. Among the lines (males), the mean
sum of squares (MSS) were not significant for all
characters except mean boll weight and seed cotton
yield which showed highly significant. Testers
(females) exhibited significant difference for four
characters seed index, ginning outturn, lint index and
seed cotton yield which showed highly significant.
Whereas, line x tester interactions were highly
significant for all characters except plant height and
number of sympodia per plant which recorded not
significant differences.
The estimates of variance due to general combining
ability (GCA), variance due to specific combining
ability (SCA), the magnitude of SCA variance were
greater than GCA variance for all 8 characters and the
variance ratio was less than half in these traits (Table 2).
1.2 Combining ability effects
The estimates of general combining ability effects of
females and males are presented in Table 3 and their
specific combining ability effects are presented in
Table 4 for all the characters.
1.3 Seed cotton yield (kg/ha)
The estimates of
gca
effects of tester parents (Figure 1)
in the population based crosses were found to be
significant differences for sixteen testers, of which ten
testers recorded positive significant
gca
effects and
the tester DH 98-27 showed maximum value of
gca
effect for seed cotton yield trait (333.42). Three
barbadense lines recorded significant
gca
effects
(Figure 1), of which two lines exhibited positive
significant
gca
effects recorded by the line DB 533
(242.92) and DB 534 (75.54). Among 92 crosses,
seventeen crosses differed significantly for
sca
effects
and the hybrid DH 11-8 × DB 534 (565.35) recorded
highest positive
sca
effect.
1.4 Plant height (cm)
The estimates of general combining ability effects
among hirsutum testers recorded significant negative
value in the tester DH 75- 23 (-21.36) and the highest
positive
gca
effect was exhibited by the tester DH
45-23 (9.60). All four barbadense lines exhibited not
significant
gca
effects and the line DB 531 showed
highest positive
gca
effect (2.88). Four crosses
differed significantly for
sca
effects, of these two had
positive
sca
effects showed by the crosses DH 18-31 x
DB 532 (52.60) and DH 31-2 × DB 531 (43.87),
whereas the crosses DH 23-4 × DB 533 (-44.04) and
DH 18-31 × DB 531 (-67.46) recorded significant
negative
sca
effects for plant height.
1.5 Number of sympodia per plant
The estimates of general combining ability effects
indicated not significant differences among all
hirsutum testers and four barbadense lines. Three
crosses expressed significant
sca
effects, of these one
hybrid exhibited positive
sca
effect showed by the
cross DH 31-2 × DB 532 (5.06) and two hybrids
recorded negative
sca
effects DH 23-4 × DB 533
(-5.64) and DH 31-2 × DB 534 (-5.97).