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.Copy Right, IJAR, 2016,. All rights reserved. …………………………………………………………………………………………………….... 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).The state of Jammu and Kashmir is known for producing bivoltine silk of international quality. Being one of the traditional agro-based industries of the state producing high quality bivoltine silk comparable to international quality helps in improving the economic conditions of landless farmers and weaker sections of the society and providing employment opportunities during pre-and post cocoon activities. Realizing the importance of sericulture, the

Implications of genetic diversity in the improvement of silkworm Bombyx mori L.

“…Genetic diversity is a fundamental criterion of animal and plant breeding programs because inter-and intra-population variability can be determined by recognizing the number of different forms of genotype expression and presented as information repositories in the form of genes, alleles and chromosomes (Pérez, 2010); the greater the variability found, the greater is the opportunity to find characteristics of interest, which in turn make up the genetic base, from which purpose-made, specific selection processes can be carried out for the objectives of an improvement program (Nezhad et al, 2010;Anuradha et al, 2012;Kumari and Tripathi, 2017).…”

“…These can give rise to hybrid combinations, descendants with high hybrid vigor, or transgressive individuals that can originate hybrids or commercial varieties (Lagos et al, 2003); it also allows estimation of rates of variation among genotypes, making it an effective tool for calculating increases in genetic potential in breeding programs (Nagaraju and Singh, 1997). Therefore, making a selection of genetically pure and divergent parental, knowing the genetic distances, and the nature and magnitude of the genetic diversity that exists among the available breeds of B. mori are critical activities because they determine the improvement of quantitative and qualitative traits linked to the production of cocoons (Sen et al, 1996;Nagaraju and Goldsmith, 2002;Maqbool et al, 2015;Kumari and Tripathi, 2017). Maqbool et al (2015) studied genetic divergence by analyzing quantitative traits in B. mori bivoltines and the results showed that 99.4% of the total divergence is represented by quantitative traits such as duration of fifth instar, total duration of larval cycle, weight of mature silk gland, cocoon weight, cocoon yield/10000 larvae, and denier.…”