INDUCTION OF THERMAL STRESS ON MULBERRY SILKWORM, BOMBYX MORI L. FOR SYNTHESIZING NEW LINES

In West Bengal the rearing of high yielding bivoltine silkworm varieties is a problem owing to the prevalence of high temperature and high humidity. Multivoltine breeds, though better in survival yet have poor economic traits and are unable to fetch better returns. As such, a scheme has been framed to evolve temperature tolerant bivoltine lines with moderate technological traits, suitable for the plains of West Bengal. Therefore, six genetically diverged bivoltine silkworm breeds viz. P5, JD-6, YS-3, SF-19, NB-18 and KPG-B reared alternatively under thermal stress followed by normal rearing for 18 generations. They were then screened under high temperature and high humidity, Three new temperature tolerant lines viz. BHR-1, BHr-2 and BHR-3 with moderate economic traits could be evolved out of the study.