Analysis of Heterosis in some Bivoltine Silkworm Hybrids of Bombyx mori L.
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Date
2018-09
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Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Jammu
Abstract
The present investigation entitled “Analysis of Heterosis in some Bivoltine Silkworm Hybrids of Bombyx mori L.” was carried out at Division of Sericulture, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu at Udheywalla to evaluate and identify heterotic bi x bi silkworm hybrid combinations. Six indigenous bivoltine silkworm breeds, ND2, ND3, NSP, U1, CSR2 and JD6 were reared during autumn 2017 and seed of thirty hybrid combinations was prepared. Hybrid CSR2 × CSR4 were taken as control. During spring 2018, rearing of six parents and thirty-one hybrid combinations was conducted in a completely randomized design (CRD). Thirty-one treatments including control were replicated thrice with 200 worms per replicate post III rd moult. The evaluation of parents and hybrids was analyzed and heterosis worked out on mid parent value. Ranking of heterotic hybrids was done by Multiple Trait Evaluation Index (E.I.) method. For all the thirty hybrids, estimates for heterosis were worked out as per cent deviation from mid parent value. Different hybrids combinations exhibited significant and desirable heterotic estimate at egg, larval, cocoon and post cocoon stages when compared to check hybrid. Six hybrids viz., ND2 × NSP, ND2 × U1, ND2 × JD6, ND3 × ND2, ND3 × JD6 and NSP × JD6 recorded positive heterosis for egg traits. For larval traits, eight hybrids viz., ND2 × CSR2, ND3 × NSP, ND3 × CSR2, ND3 × JD6, U1 × JD6, CSR2 × ND2, CSR2 × ND3 and JD6 × ND2 were found to be heterotic. For commercially important cocoon parameters like coon yield by weight, by number, good cocoon and pupation percentage, significant heterosis was observed in twenty-three hybrids. Only one hybrid i.e. CSR2 × ND3 exhibited heterosis above than control for single cocoon weight, single shell weight and shell ratio percentage. At post cocoon stage, only three hybrids viz., NSP × ND3, NSP × U1 and CSR2 × ND2 were significantly heterotic. Based on the cumulative E.I. values for fifteen commercial characters, ranking of hybrids was conducted and eight hybrids qualified E.I. value > 50. Hybrid ND2 × CSR2 ranked 1st with maximum E.I. value of 55.53 followed by ND3 × NSP (55.33) and ND2 × NSP (53.93). The control hybrid CSR2 × CSR4 remained at a cumulative E.I. value of 47.16. Thus, based on relative heterosis and Multiple Trait Evaluation Index values for qualitative and quantitative traits, three hybrids ND2 × CSR2, ND2 × NSP and ND3 × NSP were shortlisted and found promising for exploitation at commercial level after validation by multi location field trial.
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