Heat Shock Response of FC2 - A Bivoltine Hybrid of the Mulberry Silkworm, Bombyx mori

Recent trend in the sericulture industry is introduction of single or double bivoltine hybrids of the silkworm, Bombyx mori for commercial exploitation. Towards this, CSR breeds were suggested to rear in the field but their performance and success in all the seasons is a limiting factor. Hence, foundation combinations like FC1 and FC2 that represents a bivoltine hybrid origin have been used as male parent to cross with multivoltines for production of F1 hybrids. In view of this practical limitations and commercial interest, we have selected FC2 as experimental material to examine its tolerance to fluctuated environmental condition at the field. Different instars larvae were exposed to heat shock (HS) temperatures of 35 and 45°C for 2 h with 2 h recovery period. All the HS induced larvae were reared along with control in natural environmental condition. Interestingly, 45°C was determined as lethal temperature due to induction of more than 75% mortality in all the instars. Correspondingly, response to 35°C heat shock in all the instars found quite significant in terms of increased larval weight (2.51 g), ERR (87.77), cocoon weight (1.64 g), shell weight (0.35 g), pupal weight (1.28 g), and adult survivability (82 %) compare to control, which are statistically highly significant. With this, we inferred that FC2 had shown profound response to HS temperatures 35 and 45°C and the inbuilt acquired tolerance to overcome fluctuated environmental condition, which can be exploited as potent material for development of thermotolerant silkworm strains for the tropics, keeping global warming in view.