Studies on the combining ability, heterosis and gene action in some bivoltine silkworm (Bombyx mori L.) genotypes

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Date
2003
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SKUAST Kashmir
Abstract
Studies on the combining ability, nature and extent of different gene actions ; heritability; Genetic advance and nature and extent of heterosis involving a 7 x 7 diallel set of Bivoltine silkworm (Bombyx mori L.) were carried out for thirteen traits viz., Total larval duration ; 5th age larval duration ; weight of mature larvae ; cocoon yield by Number and cocoon yield by weight, single cocoon weight, single shell weight, shell ratio, pupation rate, average filament length and weight, raw silk recovery and Denier. Analysis of variance revealed significant difference in parents, for total larval duration, 5th age larval duration, single cocoon weight, shell ratio, Raw silk recovery, in hybrids for total larval duration, 5th age larval duration, cocoon yield by number, cocoon yield by weight, denier and parents vs hybrids for total larval duration, 5th age larval duration, weight of mature larval. Cocoon yield by number, cocoon yield by weight, pupation rate, average filament length, average filament weight and raw silk recovery except for few traits indicating presence of considerable variability in the materials understudy. Mean squares due to gca revealed significant difference for all the traits except weight of mature larvae, shell weight, pupation rate average filament length, average filament weight and Denier. Mean square due to sca effects were also significant for all the traits except Denier. Dominance component of genetic variance (2D) was greater in magnitude than additive component (2A) for all the traits. The degree of dominance was in the range of over dominance (More than 1). None of the parents was found to be a good general combiner for all the traits. SKUAST-27, SKUAST-28, SKUAST-29, SKAU-R-1 and NB4D2 were found to be good general combiners for many economically important traits. No cross was found to be good specific combiner for all the traits while SKUAST-29 x SKUA-R-1, SKUA-R-1 x SKUA-R-6 and SKUAST-27 x SKUAST-1 were found to be good specific combiners for five viz. average filament length, average filament weight and raw silk recovery & single shell weight and shell ratio out of the thirteen traits. Estimates of heritability (bs) were moderate to high for all the traits except Denier. However heritability (n.s) for all the traits was low to fairly high. Out of thirteen traits ten were found to have low genetic advance and for three traits viz. 5th age larval duration, cocoon yield by number and weight was found to be moderate. SKUA-R-1 x SKUA-R-6 and SKUAST-28 x SKUAST-29 displayed desirable and significant heterosis over mid and better parents in 3 traits viz., cocoon yield by weight, raw silk recovery and single cocoon weight and 4 traits viz., total larval duration, single shell weight, average filament weight and Denier out of 13 traits respectively.
Description
M.Sc Thesis submitted to SKUAST Kashmir
Keywords
bivoltine silkworm (Bombyx mori L.), heterosis and gene, bivoltine silkworm, Sericulture
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