GENETIC DIVERSITY STUDIES IN SIX BIVOLTINE RACES OF BOMBYX MORI L., BASED ON PHENOTYPIC CHARACTERS.

Abstract

Comparative studies of phenotypic characters in some developmental stages of mulberry silkworm, Bombyx mori. L was carried out in order to access their genetic diversity. Three Jam and three Pam races evolved in J&K were selected for the study. The egg, larvae and cocoon stage were studied for the various phenotypic and economic parameters; these qualitative and quantitative characters were put into various statistical analysis like correlation studies of length and weight changes during V instar and clustering on the basis of UPGMA, Ward's method and Single linkage analysis. Results indicated highly significant differences for all the studied characters; high positive correlation between larval length and weight change during the V instar larval stage, Also, the races were divided into few clusters/groups on the basis of weight gain characteristics. The present study will help in selection of parents for various breeding programmes and evolving new locally acclimatized, high yielding superior quality silk producing races. Introduction:-The silkworm B. mori was domesticated over 5000 years ago (Nagaraju and Goldsmith, 2002) and is well known for its industrial importance in sericulture (Goldsmith et al., 2005). It has a number of varieties viz; univoltine, bivoltine, and polyvoltine. B.mori has become a model organism for studying other lepidopteron insects that cause serious agricultural damage and is also an important model for scientific discovery in the areas of microbiology, physiology and genetics. silkworm breeds play a vital role in the success of sericulture industry. Thus the breed development and improvement is a continuous process which aims at providing suitable genotypes with desired traits (Datta, 1984; Rao et al., 2006). Enrichment of silkworm breeds / hybrids have always been one of the important factors contributing to increase the productivity in sericulture sector. Continuous development, evaluation, renewal and change of existing breeds/hybrids with new superior varieties and their commercialization is the prime factor to increase silk quality and quantity (Chandrashekharaiah and Ramesh Babu, 2003).