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Results and Discussion
The variance analysis for all the nine metrical traits is
given in Table 1. Genotype mean
squares for these polygenic traits were significant at 1%
and 5% level of probability (except 1000-kernel weight)
which provided the evidence for the significant genetic
variability for these traits among the genotypes. Among
varieties/mutants, mutant 35-Nayab, 115-Nayab, A-6 and B-6
took significantly (P>=.01) lesser time to flowering as
compared to Pak-70 and other mutant strains (Table
2). Rest of the mutant strains do not show significant
genetic variation for heading duration. Heading date which
directly influences the maturity is a polygenic character,
under present investigation is altered by induced mutation.
Early maturity in wheat is associated with escape from
pests, drought, heat and other stress injuries that occur
late in the growing season (EDWARDS et al. 1976).
Plant height (Table 2) in all the
mutant strains have generally displayed non-significant
reduction over Pak-70. However, mutant 35 and 115-Nayab are
even taller than the mother cultivar Nayab. It is obvious
from the data that all the mutants which are nearly equal to
the height of check variety Pak-70 or even taller than the
mother cultivars have produced significant yield than did
relatively shorter ones. This situation is well supported by
LAW and WORLAND (1973) and SHAKOOR et al. (1977).
They demonstrated that taller wheat had larger grains as
compared to shorter ones. Height reduction through induced
mutat ions generally also results in a reduced grain weight
(KONZAK 1973). Mutant 115-Nayab and A-6 produced
significantly more number of tillers per unit area than the
commercial variety Pak-70 (Table
2). Some of the mutants though produced more number of
tillers per unit area but the difference were statistically
non-significant. Increase in the number of tillers per unit
area is desirable character from breeders point of view
because of its direct influence on crop yield (LARIK et
al. 1980b).
Evidence of the modification of spike characteristics is
presented in Table 2. Significant
(P>=.01) increase in spike length, spikelets per spike,
grains per spike and grain yield per spike were observed in
mutant strains 35-Nayab, B-6, B-33, C-43 and D-28 when
compared with their respective controls and check variety
Pak-70. These results are in confirmation with SIDDIQUI
et al. (1978) and LARIK (1979a). These authors have
observed positive shift in the mean values for these
characters. These components have made effective
contribution in enhancing grain yield.
Grain yield performance of all the mutants and mother
cultivars is depicted in Table 2.
These results further confirm the yield superiority of all
the mutant strains over Pak-70 and their mother cultivars.
These mutants have theoretical and practical significance as
they produce higher yields than the mother cultivars under
fertilizer stress condition (SIDDIQUI 1976). The genetic
modification of allopolyploids (SIDDIQUI 1972) offered
varied opportunities of redesigning of crop ideotypes for
the changing agricultural environments. The high
productivity of these mutants under tight supplies of
fertilizer (SHIELDS 1975) might be due to induced genetic
alterations with respect to nitrogen fixation (DOBEREINER
1977).
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