Genetics of yield and yellow vein mosaic virus (YVMV) resistance in okra [Abelmoschus esculentus (L.) Moench]
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Date
2019
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DIVISION OF VEGETABLE SCIENCE ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Okra is an important vegetable crop of India ranking first across the world in terms
of area and production. However, average productivity of okra has remained very
low and almost stagnant over the last few decades. Moreover, prevalence of serious
yellow vein mosaic virus (YVMV) disease has affected fruit yield and quality
drastically. The present investigation was undertaken to understand the genetics of
yield and yield related traits; and YVMV resistance through generation mean
analysis (GMA). ANOVA revealed the presence of significant variation among
generations for all the yield and related traits across the eight crosses. The scaling
and joint scaling test indicated that inadequacy of additive–dominance model to
explain the gene effects. Six parameter model explained complex pattern of
inheritance for yield and related traits. Gene effects viz., additive (d), dominance (h)
and epistatic effects (i, j, l) found to be significant across the eight crosses. While,
the magnitude of dominance effect (main effect) and dominance × dominance
(interaction effect) was larger than additive gene effects for traits such as yield per
plant, first fruiting node, days to 50% flowering, inter-nodal length, plant height,
fruit diameter, fruit length, number of fruits per plant and average fruit weight,
thereby indicating importance of population improvement approaches particularly
reciprocal recurrent selection. Duplicate type of epistasis revealed for yield and
related traits suggesting that positive alleles of traits dispersed in the parents that
nullifying the influence. GMA for 15 biochemical traits led to identification of major
proportion of non-additive gene effects over additive and epistatic gene effects. Out
of 14 okra genotypes screened against YVMV resistance revealed highly resistant
(DOV-12 and DOV-66), two moderately resistant (DOV-62 and DOV-64) and ten
susceptible genotypes. Chi-square analysis in F2 and back cross populations (BC1P1
and BC1P2) suggested involvement of single dominant gene that followed typical
Mendellian monogenic ratio of 3:1 in resistant × susceptible cross. In resistant ×
resistant cross, presence of duplicate dominant epistasis (15:1 ratio) for resistance
was evident through chi-square analysis. Non-allelic relationship existed among the
different dominant genes contributed by different resistant sources. Analysis of interspecific crosses has proved that Abelmoschus caillei was better and more compatible
with Abelmoschus esculentus (cultivar: Pusa A-4) compared to Abelmoschus
tetraphyllus and Abelmoschus moschatus considering characters such as fruit setting,
average number of seeds per fruit and germination of F1 seeds.
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T-10157
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