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Cotton Genomics and Genetics
74
Heterosis works as a basic tool for improvement of
crops in form of F
1
and F
2
populations, and economic
heterosis (over standard cultivar). It also contributes to
choose genotypes with desired genetic variance, vigor
and maternal effects. Therefore, it is essential to have
detailed information about desirable parental
combiners in any breeding program, which can reflect
a high degree heterotic response. In intra- and
inter-specific heterosis, yield increase over better
parent or greater than best commercial cultivar (useful
heterosis) has been documented (Baloch et al., 1993b;
Galanopoulou-Sendouca and Roupakias, 1999; Wei et
al., 2002; Yuan et al., 2001 & 2002; Khan et al., 2007;
Khan, 2011). Both positive and negative heterotic
values have been detected, demonstrating potential of
hybrid combinations for traits improvement in
breeding programs (Hassan et al., 1999; Khan et al.,
2009). F
1
hybrids with high heterosis were also
associated with higher inbreeding depression;
therefore, moderate type of heterosis has some
stability in segregating populations (Tang et al., 1993;
Soomro, 2000; Soomro and Kalhoro, 2000). Therefore,
heterotic studies can provide basis for exploitation of
valuable hybrid combinations in future breeding
program.
The main objective of this study to study the heterosis
and
per se
performance of new cotton intra hirsutum
hybrids in respect of kapas yield and its attributing
characters.
1 Results and Discussion
1.1 Analysis of variance
The mean sum of squares for kapas yield and its
attributing characters in 51 hybrids of cotton are
presented in Table 1. Mean sum of squares for hybrids
was highly significant for all the characters except
number of monopodia per plant, mean boll weight and
seed index indicating presence of significant
differences among the hybrids evaluated in respect of
these traits. The mean sum of squares for hybrids vs
checks was highly significant for plant height number
of sympodia per plant, number of bolls per plant,
kapas yield per plant and ginning outturn revealing
superiority of hybrids over checks and presence of
heterosis in respect of these traits.
1.2 Mean
per se
performance of hybrids
The mean
per se
performance of hybrids in respect of
kapas yield and its attributing characters (Table 2) are
briefly presented below.
1.2.1 Days to 50 per cent flowering
Among 51 hybrids evaluated, the hybrid RAH 97 x
SC 68 took minimum number of days for 50 per cent
flowering (66.50 days) followed by the hybrids RAH
318 x RGR 58, RAH 243 x RGR 32 and RAH128 x
RGR 24 (67.00 days), RAH 318 x SC 68, RAH 243 x
SC7 and BUNNY
Bt
(67.50 days), RAH128 x RGR
32 (68.00 days), RAH 318 x SC 7, RAH128 x SC 68
and RAH 97 x RGR 58 (68.50 days), RAH 243 x SC
14 and RAH 97 x RGR 24 (69.00 days) and RAH 318
x RGR 24, RCH2
Bt
, RAH 243 x RGR 24, RAH146 x
SC 7, RAH 97 x SC 7, RAH 97 x RGR 32, RAH 124
x SC 18 and RAH 124 x SC 7 (69.50 days) which are
statistically on par with one another. Contrary to this,
the hybrid RAH128 x SC 14 took maximum number
of days (72.50) followed by the hybrids RAH 243 x
SC 18, RAH128 x RGR 37, RAH146 x RGR 32,
RAH146 x RGR 37, RAH 97 x SC 14, RAH 97 x SC
18 and RAH 124 x RGR 37 (72.00 days).
1.2.2 Plant height (cm)
The hybrid RAH146 x RGR 24 recorded maximum
plant height (138.70 cm) followed by the hybrid
RAH128 x SC 14 (134.30 cm), while the hybrid RAH
318 x RGR 37 recorded minimum plant height of
(84.30 cm).
1.2.3 Number of monopodia per plant
Among the 51 hybrids, the hybrid RAH146 x RGR 37
recorded maximum number of monopodia per plant
(2.50) followed by RAH 318 x RGR 58 and RAH 97
x RGR 32 (2.40), RAH 243 x SC 68 and RAH 243 x
RGR 24 (2.30) and RAH 243 x SC 14 and RAH 124 x
RGR 32 (2.25) which are on par with each other. On
the other hand, the hybrid RAH 124 x SC 7 (1.20)
recorded minimum number of monopodia per plant.
1.2.4 Number of sympodia per plant
Maximum number of sympodia per plant were
observed in the hybrid RAH 124 x SC 18 (28.85)
followed by the hybrid RAH128 x SC 14 (28.40) and
RAH 243 x SC 68 (28.30) which are on par with one
another. On the other hand, the hybrid RAH 318 x SC
18 recorded lowest number of sympodia per plant
(16.30) followed by RAH 318 x RGR 37 (17.50).
1.2.5 Number of bolls per plant
The hybrid RAH146 x RGR 58 produced maximum
Cotton Genomics and Genetics