Heat shock response in silkworm Bombyx mori L. and development of summer and autumn specific thermo-tolerant breeds

摘要

Like numerous organisms, silkworm when exposed to high tetrecerature exhibits a heat shock response involving new synthesis of heat shock protein. Due to production of heat shock protein silkworm shows the tolerance to high temperature. It is reported by different researchers that cell which is pre-exposed to thermal stress acquires a transient resistance against the killing effect of a subsequent thermal stress. Keeping this phenomenon as a base, a breedmg project was undertaken to develop thermo-tolerant bivoltine silkworm breeds at RSRS. Sahaspur, Dehradun in the year 1998 and Chinese method of breeding was adopted. Twenty bivoltme and eight Biv. x Multi crosses have served as breeding materials to isolate new breeds/hybrids. During developmentof new lines, breeding populations in filial generations (1998-2001) were exposed to high tenrature and high humidity by rearing them in summer seasons to infuse tolerance and also to facilitate the selection of hardy breeds tolerant to high temperatureand high humidity. Subsequently, three Chinese type lines viz. ATR6, ATR16 and ATR28 and three Japanese type viz. ATRU, ATR13 and ATR29 have been evolved. Hybrids of these thermo-tolerant breeds have the pupation rate around 90% with shell ratio between21-23% which is about 25% more than ruling hybrid. Among the six new hybrids. ATR16 x ATR29 has excelled over the others and subjected to hybrid testing during between 2003 to 2007 in Uttarakhand, H.R and in U.R An average cocoon yield in ATR16 x ATR29 was 38/100 dfls in hotter months whereas in control the yield was only 26 kg.