Genetic Studies for Heat Stress Tolerance in Bread Wheat (Triticum aestivum L. em.Thell.) Through Diallel Analysis
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Date
2022
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Abstract
The present investigation was conducted to analyse combining
ability, heterosis, heterobeltiosis, inbreeding depression, components
of genetic variance and heat stress tolerance for grain yield and its
contributing traits in bread wheat (Triticum aestivum L. em. Thell.) in
two varying environments created by two dates of sowing viz., normal
sown and late sown conditions at Agricultural Research Farm of
Rajasthan Agricultural Research Institute (Sri Karan Narendra
Agriculture University, Jobner), Durgapura, Jaipur (Rajasthan). The ten
genetically diverse parents viz., DPW 621-50, DBW 90, PBW 502, Raj
1482, Raj 4037, UP 2425, Raj 3765, PBW 550, HI 1563 and Raj 4079
crossed in half-diallel fashion (excluding reciprocals) in rabi 2018-19
and for the advance generation F1‟s seed was grown at Wellington
(Tamil Nadu), IARI regional sub-station in kharif 2019. The ten parents
along with their 45 F1‟s and 45 F2‟s were evaluated in a randomized
block design with three replications each in two environments during
rabi 2019-20 for grain yield and its contributing traits. The observations
were recorded for days to heading, days to maturity, plant height, tillers
per plant, flag leaf area, spike length, grains per ear, 1000-grain
weight, biomass per plant, grain yield per plant, harvest index, canopy
temperature and protein content.
The analysis of variance exhibited significant differences
among the parents and generations in both the environments for all the
studied characters which suggested the presence of sufficient genetic
diversity. The G x E interaction revealed significant for all the
characters under investigation. Significance of GCA and SCA for all the
studied characters in both generations revealed the importance of both
additive and non-additive gene action. The ratio of GCA/SCA variance
(predictability) indicated the preponderance of non-additive gene action
for all the studied characters.Overall estimation revealed that parents viz., Raj 4037, Raj
3765, PBW 502 and Raj 4079 were good general combiner and the
crosses DBW 90 x Raj 4037, DPW 621-50 x Raj 4037 and Raj 4037 x
Raj 4079 good specific cross combination for grain yield and its
contributing traits in both environments. These crosses should be
recommended for the handling of segregating generations to obtain the
transgressive segregants.
Sufficient degree of heterosis and heterobeltiosis were found
for all the studied characters. The cross, DPW 621-50 x Raj 4037 in
both environments exhibited desirable heterosis and crosses Raj 4037
x Raj 4079 in E1 while, in E2 Raj 4037 x Raj 4079 and Raj 4037 x Raj
3765 showed desirable heterobeltiosis for yield and its all of the
contributing traits.
The assessment components of genetic variance revealed that
both additive (D) and dominance (H1 and H2) components were
significant for all the studied characters which showed both
components of genetic variance effective in these traits expression.
The graphical analysis showed partial to over-dominance for different
characters in both environments. The scattering of array points
revealed the presence of genetic diversity among the parents for most
of the characters.
The result of heat susceptibility index (HSI) exhibited that
parents viz., UP 2425, PBW 502, Raj 4037 and Raj 4079 were desired
for grain yield and some other traits. Among the crosses, DPW 621-50
x Raj 4037 and DBW 90 x Raj 4037 were found more desirable for heat
tolerance in most of the studied traits across the generations, should
be used as promising breeding material for development for heat stress
tolerant wheat cultivars.
An overall assessment on the basis of per se performance,
SCA effects and heterosis, the crosses viz., Raj 3765 x Raj 4079, Raj
4037 x Raj 4079 and Raj 4037 x Raj 3765 were found promising in
both environments for grain yield and its most of the contributing traits.
Hence, these crosses should be toss transgressive segregants for
grain yield in the segregating generation and they can be used in
further breeding programme.
An overall assessment of the results of this study suggested
that recurrent selection (Hull, 1945), diallel selective mating
(Jensen,1970) and bi-parental mating (Joshi and Dhawan, 1966) might
be effective breeding approaches for development of superior
genotypes and appreciable improvement of bread wheat in future.