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Combining Ability Yield Attributing Characters in Line x Tester Inter specific Hybrids Confirmation
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1.9 Ginning outturn (%)
Six hirsutum tester parents displayed significant
gca
effects, of which three testers exhibited significant
positive
gca
effects and highest value was recorded by
DH 98-27 (2.87). Among the barbadense lines, DB
532 (-0.61) exhibited significant negative
gca
effect.
Eighteen crosses expressed significant
sca
effects, of
these eight crosses showed positive
sca
effects and the
hybrid 178-24 × DB 533 recorded highest positive
sca
effect (6.70).
1.10 Lint index (g)
Seven hirsutum testers showed significant
gca
effects,
of which four testers had positive
gca
effects and the
tester DH 13-7 (0.84) recorded highest value of
gca
effect. There are no significant differences among all
barbadense lines and DB 534 (0.14) exhibited highest
value of
gca
effect. Out of 92 crosses studied, seven
crosses recorded significant
sca
effects for this
character, of which five showed significant in positive
direction and the cross 178-24 × DB 533 recorded
highest significant positive
sca
effect (1.91).
1.11 Pooled score for
gca
effects
Based on simple pooled
gca
score method (Table 5),
the hirsutum testers DH 13-7 and DH 98-27
(Decreasing order) are recognized as the most
potential parents. Among the barbadense lines, the
lines DB 534 and DB 533 based on simple pooled
gca
score method showed the most general combiner
parents. Based on per cent
gca
method, the hirsutum
testers DH 13-7, DH 98-27 and DH 45-23 (Decreasing
order) were the most potential combiners (Table 6).
Among the barbadense lines, the lines DB 5343 and
DB 533 based on per cent
gca
score method showed
the most potential parents. Similarly, based on
weighted
gca
method the most potential combiners
were found to be the hirsutum testers DH 13-7, DH
98-27 and DH 18-31. Among the barbadense lines, the
lines DB 534 and DB 533 based on weighted
gca
method is the most potential parents (Table 7).
2 Discussion and Conclusion
2.1 Combining ability for confirmation of heterotic
groups
In hybrid research study on cotton, large number of
crosses involving varietal lines are used for assessing
combining ability status. On constantly observing the
most potential crosses attempts are made to infer
about the causes of high heterosis. What are the
combinations that give potential crosses? What would
be the probable cause for high potentiality revealed by
the F
1
? What is the genetic base or is there any
physiological mechanism linked to high productivity
of F
1
etc., are the questions which are examined and
on the basis of the information available, heterotic
groups are developed (Patil et al., 2011). The most
potential crosses observed in present study have been
examined and based on this the combining ability
behavior (Pattern) of the line involved is determined.
With the help of this information diverse groups are
formed which are capable of giving potential hybrids
between them.
The research programme on development of hybrids
at UAS Dharwad has focused attention on developing
heterotic groups, meant for evolving intra hirsutum
hybrids and interspecific hybrids. Efforts are made to
develop different heterotic groups like Stay green x
Compact, Robust x Compact, Robust x Higher RGR
and Stay green x higher RGR
i.e.
(Patil and Patil,
2003). These studies have also shown ways of
exploiting heterotic groups by following novel
approaches of creating recombinational variability for
combining ability and exploiting the same through
reciprocal selection for combining ability (Mallikarjun,
2005 and Somashekar, 2006).
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 lines DH 98-27, ZCH 8, 178-24 and DH
18-31. To create recombinational variability DB 533
and DB 534 crossed was made and material was
advanced to F4 generation with an objective of
evaluating recombinational variability for combining
ability in F
4
generation. The Line x Tester study was
planned to assess the relative potential of these
barbadense and hirsutum lines and confirmed
appropriateness of the choice of this heterotic box of
two barbadense and four hirsutum lines. The objective
of this study was to determine the relative ranking of
the selected barbadense and hirsutum lines when
compared with the new lines developed during this
period.