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Results and
Discussion
Analysis of variance revealed significant differences among
parents and hybrids and parents vs hybrids for all the characters in
both the environments except for number of grains per ear in stress
environment and grain yield in both the environments. This indicated
sufficient amount of genetic variability in the present material.
This was further substantiated by the fact that D2 values
for 990 combinations ranged from 3.32 between HD 1925 and HD 1925 x
HD 2122 to 439.91 between NP 846 and HD 1925 x
Sonalika in normal
environment and from 2.23 between WG 377 x Sonalika and HD 1981 x Raj
821 to 462.75 between NP 846 and Sonalika in stress environment. Such
a range among parental combinations varied from 15.69 between HD 1925
and Sonalika to 428.26 between NP 846 and HD 2122 in normal
environment and from 6.64 between Raj 821 and Sonalika to 462.75
between NP 846 and Sonalika in stress environment.
On the basis of degree of divergence (D2), 45 populations
could be grouped into 9 and 8 clusters in normal and stress
environments, respectively (Table
1). Clusters I
and II were the largest and included 5 parents and 20 hybrids in
normal environment and 4 parents and 18 hybrids in stress
environment. Rest 4 parents and 16 hybrids, and 5 parents and 18
hybrids scattered over 7 and 6 groups in normal and stress
environments, respectively, mainly added to the divergence. This
corroborated the findings of Srivastava and Arunachalam (1977), Behl
and Singh (1986), that only few hybrids could add substantial
variation in the population. Groups VI, VII, VIII and IX in normal
and VII and VIII in stress environment were
monogenotypic and comprised of genotypes which were extraordinary for
one or more characters. In general, intracluster distances
(Table
2) were almost
equal and lower than the intercluster distances in both the
environments. Therefore, the genotypes included within a cluster
tended to diverge less from each other possibly due to large
similarity in parentage or selection of genotypes. The intercluster
distances varied from 6.65 between group III and VIII to 20.69
between VI and IX in normal environment and from 6.06 between III and
V to 18.78 between III and VII in stress environment. On overall
basis, clustering pattern over the environments showed only 45 per
cent similarity. Such inconsistencies for clustering pattern in
different environments have also been reported earlier (Somayajulu et
al 1970; Jatasra and Paroda 1978). The clustering pattern of hybrids
is known to be influenced by the parentage affinity between the
parents and progeny (Chaudhary and Singh 1975). In this regard,
mainly three grouping trends were evident in the present study. Out
of 36 hybrids, 17 and 16 were grouped in different clusters than both
the parents in normal and stress environments, respectively. Such a
grouping behaviour of F1 hybrids may be explained on the
basis of genic interactions among parents. In other 17 cases in
normal as well as stress environment, hybrids were found to be
grouped with one of the parent which showed dominance in its favour.
In rest 2 and 3 cases in normal and stress environments,
respectively, F1s
and their parents were clustered together. Such cross combinations
exhibited relatively low genetic divergence among parents.
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