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Positive intercept of the regression line in Wr/Vr graph (Fig.
2a) for flag leaf weight indicated the absence of complete
dominance but partial dominance with additive gene action. Array
points displayed that Pak. 81 contained the maximum recessive genes
for flag leaf weight while 4943 and 4072 had the maximum dominant
genes. Distribution of genes among the other parents was
intermediary. The negative correlation (-0.32) revealed the
involvement of dominant genes to increase the flag leaf weight
(Fig. 2b). That is why, 4943 and 4072 which
had the most dominant genes with lower Wr+Vr values were having
greater flag leaf weight. Lesser dominant genes in Pak. 81 produced
flag, leaves of smaller weight. However, awkward position of Fsd. 85
and Psbn. 90 gave an idea that dominant gene control for flag leaf
weight in these parents was not certain.
Wr/Vr graph (Fig. 3a) for specific flag leaf
area showed that the intercept was negative; the regression line cut
the Wr-axis below the origin, indicating ail overdominant gene
action. The position of array points in the graph throws light on the
distribution of dominant and recessive genes in the parents. Fsd. 85,
LU26S and 4943 were located closest to the origin thus, contained the
maximum number of dominant genes. Pak. 81 was located farthest from
the origin having lowest number of dominant genes. The correlated
response (0.41) of dominance and parental phenotype (Fig.
3b) indicated that recessive genes controlled specific flag leaf
area while the dominant alleles tended to reduce it. The position of
the parental points along the graph line affirmed this fact.
For specific flag leaf weight Wr/Vr graph (Fig.
4a) showed the presence of over dominance. Figure further
depicted that Fsd. 85 and LU26S being nearest to the origin contained
the maximum number of dominant genes while Pak. 81 which occupied the
farthest position from the origin contained the most recessive genes.
Wr+Vr/P graph (Fig. 4b) depicted that
specific flag leaf weight was under the control of dominant genes.
Negative correlated response (r=-0.29) between Wr/Vr and P also
agreed this point.
Heterosis studies
Flag leaf area is an effective yield related parameter. A larger FLA
helps to synthesize photosynthates in greater quantities which are
translocated to grains increasing their weight. Positive heterosis
for FLA is thus, important. Heterotic studies for FLA (Table
1) revealed that 25 cross combinations manifested a positive
increase over the mid- parent value. However, significant positive
heterosis was indicated in 8 of the crosses. The considerable
combinations in this respect included Fsd. 85 x LU26S, LU26S x Fsd.
85, 4943 x Fsd. 85 and LU26S x 4072, in descending order. Including
these crosses, heterobeltiosis was positive in 14 crosses but none of
them had significant values. Significant and negative heterobeltiosis
was shown by 7 crosses.
An overview of the Table 1 indicated that
23 crosses showed positive increase over mid-parent value for flag
leaf weight. Positive and significant heterosis was found in only 6
crosses. Maximum mid-parent heterosis (23.5%) was observed in Pak. 81
x LU26S, while the same cross also exhibited maximum positive and
significant increase (16.7%) over the better parent. Heterobeltiosis
was positive and significant in, only 4 of the crosses.
Out of 30 crosses 17. showed positive heterosis for specific flag
leaf area while significant positive heterosis (Table
1) was recorded in 3 of the crosses (4943 x 4072, Psbn. 90 x Pak.
81 and 4072 x Fsd. 85). Maximum increase (16.4%) was recorded in 4943
x 4072 hybrid. The cross Psbn. 90 x Pak.81 also showed significant
positive heterobeltiosis.
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