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Development Heterotic Groups Based Combining Ability Inter specific Hybrids Performance Yield Fiber Quality Traits
39
higher fiber micronaire values than MRC 6918 (2.60).
1.3.9 Fiber strength (Tenacity) (g/tex)
The tenacity values ranged from 30.60 [DH 11-8 x DB
531] to 22.70 [DCH 32]. One hybrid DH 11-8 x DB
531 showed higher tenacity value than MRC 6918
(27.40), thirty hybrids exhibited high performance
with respect to tenacity value as compared to RAHB
87 (24.90) and sixteen hybrids had higher values of
tenacity than DCH 32 (22.70).
1.3.10 Fiber elongation (%)
Fiber elongation values ranged from 6.70 [DH 22-76 x
DB 534] to 5.60 [177-24 x DB 531], the results
recorded that one hybrid DH 22-76 x DB 534
exhibited higher fiber elongation value than RAHB 87
(6.40), ten hybrids had high performance with respect
to fiber elongation than DCH 32 (6.10) and twenty
hybrids showed higher values of fiber elongation than
MRC 6918 (5.80).
2 Discussion and Conclusion
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. A study of set of
hybrids involving the line as a common parent gives
an idea about the combining ability pattern of the
concerned line. The higher or lower performance of
the hybrids is itself taken as reflection of genetic
distance existing between the parents. It has been
possible to identify heterotic combinations (potential
crosses) based on their per cent superiority over the
commonly used check. When these crosses show up to
be consistently potential, they are considered while
forming heterotic groups involving parents of such
crosses.
The exercise of identifying diverse groups is a
continuous process because the new breeding lines
developed and stabilized and those lines obtained
from other sources are included in developing crosses
and these lines could be added in different heterotic
groups after studying their combining ability behavior
(pattern) by crossing with representative genotypes of
different groups. Thus the grouping of genotypes is
continuously revised and refined. In the recent years,
the concept of developing heterotic groups is put to
test in self pollinated crops like cotton. Segregating
populations based on diverse pairs of genotypes can
be the ideal base material required for implementing
procedures like reciprocal selection for improving
combining ability (Patil and Paltil 2003, Patil
et al.,
2011).
2.1 Line x Tester for confirmation of interspecific
heterotic groups
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. 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. The Line x Tester study
Cotton Genomics and Genetics