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Wheat Information
Service
Number 72: 42-45 (1991)
Genetic
divergence in some wheat strains and their
hybrids
I. Singh and R. K. Behl
Department of Plant Breeding, Haryana Agricultural University,
Hisar-125 004, India
Introduction
Quite often genetic divergence among parents has been referred to
as a deterministic factor of the inherent potential of a cross in
terms of its per se, combining ability effects and
segregational ability. In that context it is belived that the high
genetic divergence would lead to heterotic response in F1
and high frequency of transgressive segregants in F2
generation. High genetic divergence was not found favourable for
heterotic response rather medium divergence among parents figured to
be more compatible level of divergence (Srivastava and Arunachalam
1977; Arunachalam. et al 1984; Behl et al 1985). Moreover, it is not
necessary that group distances measured by multivariate analysis,
especially refer to actual genetic divergence among parents entering
crosses (Behl et al 1985). Rather clustering pattern of F1
hybrids was found to be influenced by the dominace relationship for
few traits with major contribution to total D2-value among
parents entering crosses. Quantitative assessment of degree of
divergence among genotypes entering crosses and their hybrids in thus
essential. Present study was, therefore, conducted to determine
genetic divergence among 36 F1 hybrids and their 9
parents.
Materials and Methods
Nine cultivars, namely, 1. WL 711, 2. NP 846, 3. WG 377, 4. HD
1981, 5. UP 262, 6. HD 1925, 7. HD 2122, 8. Raj 821 and 9. Sonalika
of wheat (Triticum aestivum L.), suitable for different
agro-ecological conditions, were crossed in all possible combinations
(excluding reciprocals) to yield 36 F1 hybrids. The
parents and F1s were evaluated in a randomized block
design with three replications in two locations with centrasting
environments i.e., normal environment (irrigated) at Haryana
Agricultural University, Hisar and stress environment (rainfed) at
Dry Farming Research Centre (HAU) Bawal. The plot size consisted of a
3 m long single row for each parent and F1. The intra- and
inter-row plant distances being 15 cm and 30 cm, respectively.
Observations on tiller number (NT), number of grains per ear (NG),
1000-grain weight (GW) and grain yield (GY) were recorded on randomly
selected five plants from each entry per replications in each
environment.
Following the analysis of variance and covariance, the data were
subjected to multivariate analysis.
Mahalanobis'D2-statistic was used for assessing genetic
divergence among genotypes. Generalized statistical distances (TOCHER
Method) described by Rao (1952) were used to classify parents and
F1s into different clusters. Heterosis was estimated over
mid-parent.
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