Basic HTML Version
Heterosis Performance Seed Cotton Yield Physiological Parameters F
1
Inter Specific Hybrids Cotton
62
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 mean per se performance of seed cotton yield and
physiological parameters in inter specific crosses.
1 Results and Discussion
Heterosis is the superiority of F
1
over the mean of the
parents or over the better parent or over the standard
check (Hays et al., 1956), with respect to
agriculturally useful traits. The primary objective of
heterosis breeding is to achieve a quantum jump in
yield and quality of crop plants.
Cotton improvement programmes primarily lay
emphasis on development of hybrids, which have
contributed in improving the productivity of cotton.
Hybridization is the most potent technique for
breaking yield barriers. Selection of parents on the
basis of phenotypic performance alone is not a sound
procedure, since phenotypically superior lines may
yield poor combinations. It is therefore essential that
parents should be chosen on the basis of their
combining ability. Combining ability analysis is the
most widely used biometrical tool for identifying
prospective parents and for formulating breeding
procedures most likely to succeed.
The two barbadense lines DB 533 and DB 534 were
selected for creating recombinational variability for
combining ability. Twenty eight F
4
lines derived from
this cross were utilized to assess recombinational
variability for combining ability by crossing them
with 4 hirsutum testers. These results are presented
below.
1.1 Analysis of variance (RBD)
The preliminary RBD analysis was carried out for
four characters under study for all genotypes involved
in the present investigation viz., 112 crosses (Line x
Tester), 28 lines, 4 testers , two commercial checks
(MRC 6918
Bt
check and DCH 32 non
Bt
check) and
eight bench mark crosses. Mean sum of squares for
four characters are presented in Table 1. ‘F’ test
indicated highly significant variation among the
genotypes for all the characters.
1.2 Mean per se performance and estimation of
heterosis
Mean per se performance of four hirsutum females
and 28 barbadense males (Table 2) and derived F
1
crosses and commercial checks (Table 3). Further,
results of heterosis values over mid parent and
commercial checks for various characters were
studied to assess the variability for combining ability
were given in Table 4.
Table 1 Analysis of variance for seed cotton yield and physiological parameters
Source
D.f.
Mean Sum of Square
Seed cotton yield
(kg/ha)
Photosynthetic rate
(μmol CO
2
m
-2
·s
-1
)
Stomatal condu ctance
(μmol m
-2
·s
-1
)
Transpiration rate
(mmol H
2
O m
-2
·s
-1
)
1
2
3
4
Replications 1
470122.81
35.94*
0.00009
18.10**
Geotypes
153 575226.37**
75.21**
0.16**
8.16**
Error
153 134348.79
5.94
0.01
1.36
S.E d
273.03
1.64
0.05
0.55
CD@ 5%
765.14
4.60
0.14
1.55
C.D. 1%
1011.98
6.09
0.18
2.05
Table 2
Per se
performance of 28 barbadense lines and 4 hirsutum testers for seed cotton yield and physiological parameters
Sl.
No.
Parents
Seed cotton yield
(kg/ha)
Photosynthesis rate
(μmol CO
2
m
-2
·s
-1
)
Stomatal conductance
(μmol m
-2
·s
-1
)
Transpiration rate
(mmol H
2
O m
-2
·s
-1
)
1
2
3
4
1 DB 533 x DB 534 F
5
IPS 44 893.52
21.36
1.05
9.58
2 DB 533 x DB 534 F
5
IPS 62 697.10
24.76
0.92
9.56
3 DB 533 x DB 534 F
5
IPS 105 1052.42
21.89
0.73
16.66
4 DB 533 x DB 534 F
5
IPS 26 766.91
24.45
0.74
9.14
Cotton Genomics and Genetics