Studies on Seasonal Performance of Newly Developed Bivoltine Silkworm (Bombyx Mori L) Hybrids Tolerant To BMNPV and Effect of Temperature on Disease Induction

Season and region specific studies of silkworm Bombyx mori L. are of greater importance in identifying and understanding the adaptability of silkworm genotypes, which are largely influenced by climatic factors. The performance of the newly developed hybrid combinations was evaluated for twelve economic traits during pre-monsoon, monsoon and post-monsoon seasons of the year to understand genotype and environment interactions and their stability under fluctuating tropical environmental conditions with Bombyx mori Nuclear Polyhedro Virus (BmNPV) inoculation @ 2x106 PIB’s/larva. The data was subjected to two way analysis of variance and season-wise relative merit of individual hybrids was computed following Multiple Trait Evaluation Index method. The index values indicated that the hybrids BNR9 x BNR10 and BNR9 x BNR4 with higher average cumulative EI values were ranked I and II and establishing their superiority over multiple traits. Further the larvae soon after fourth moult were kept at room temperature (25ºC), low temperature (5ºC) and high temperature (32ºC) without feed for 6 hours and then inoculated perorally with BmNPV. The newly ecdysed fifth instar larvae when exposed to low temperature of 5ºC and starved enhanced larval susceptibility to BmNPV while the hybrids BNR9 x BNR10 and BNR9 x BNR4 exhibited higher tolerance to BmNPV at 25ºC and moderate tolerance at 32ºC.