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Materials and methods
The studies were conducted on ten cultivars of bread wheat
(Triticum aestivum L.) of diverse geographical origin, namely,
Moncho, Pavon, Broohis, Chiroca, HD 2204, Raj 1482, WL 711,
Raj 821, Durgapura 65
and Kharchia 65. The parents were crossed in all possible
combinations, without reciprocals. The resulting 45 F1's
were grown to get F2's seeds. All 45 F2's and
ten parents were grown in a randomized block design with three
replications under early, normal and late sown environments at the
experimental field of the Department of Plant Breeding. Each plot
consisted of single 5 m row length of parent and 10 rows of
F2 with the spacing of 30 cm between rows and 15 cm
between plants. Ten competitive plants in parents and twenty plants
in F2 progenies were selected randomly for recording
observations for grain yield and its ten component characters (Table
1) under each environment, separately. Pooled analysis of variance
over the environments was done according to Panse and Sukhatme
(1967). The variance components analyses were done as suggested by
Hayman (1954).
Results and discussion
The pooled analysis of variance over the environments for the
experimental design (Table 1) showed
highly significant differences amongst genotypes for all the traits
studied. The genotype x environment interaction was also observed to
be high for all the traits and is in agreement with those of Sharma
and Singh (1982), Nanda et al. (1983), Sharma et al. (1986) and
Dasgupta and Mondal (1988) who revealed the significant role of
environments in the expression of yield and yield components in
wheat.
As emphasized by Hayman (1954), the first important part of the
analysis is testing the validity of the several assumptions
underlying diallel analysis, vis: (1) diploid segregation, (2)
homozygous parents, (3) no reciprocal differences, (4) no linkage,
(5) no epistasis and (6) absence of multiple alleles. The absence of
multiple allelism and independent distribution of genes are difficult
to be established (Kempthrone 1956). Though diallel analysis has
several limitations, the results obtained by many plant breeders do
indicate that at least some insight could be made on the inheritance
of relatively complex traits like yield even when only some of the
assumptions are satisfied (Hayman 1954).
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