PERFORMANCES OF SOME BIVOLTINE AND MULTIVOLTINE SILKWORM RACES IN BIRBHUM DISTRICT OF WEST BENGAL

Rearing performances of four bivoltine silkworm e.g. Pampore-5 (p-5), Kalimpong-B (KPG - B), NB-7 and NB-18, two multivoltine Nistari and G, two bivoltine F1 hybrids e.g. KPG-Bx P-5 and P-5x KPG-B, one multix bi i.e. Nx bi (P-5) and one multix multi (NXG) were compared to examine their suitability in both favourable and unfavourable climatic conditions in Birbhum district. The important economic traits e.g. single cocoon and shell weight, silk ratio, effective rate of rearing and cocoon yield per 100dfis, were improved in the favourable season. The bivoltine Fihybrids P-5XKPG-B and its reciprocal KPG-BXP-5 showed greater value in all economic characters than the pure races which were found to be profitable. Multix Bivoltine cross NX B (P-5) may be reared for higher economic return whereas N x G may be adopted in the unfavourable seasons to a satisfactory level but rearing of pure Multivoltine race was found to be uneconomic. Performance of pure bivoltine race, bivoltine F1 hybrids and multix bivoltine showed a dismal picture in all the above economic characters in the unfavourable seasons as revealed from experimental results.