Genetic Variability in Silkworm (Bombyx mori L.) Strains with Different Origin

Genetic diversity within and among ten silkworm Bombyx mori strains was investigated using isoenzymes of four metabolic enzymes viz., phosphoglucomutase (PGM), malate dehydrogenase (MDH), acid phosphatase (ACP) and aspartataminotransferase (AST) by polyacrilamide gel electrophoresis (PAGE). Three of the studied enzyme systems - PGM, MDH and ACP manifested intra- and inter-strain polymorphism with three or five alleles. AST was monomorphic in all strains tested. The observed heterozygosity was found to range from 0.000 to 0.266. Allele frequencies of all loci were used to estimate NEI'S (1972) genetic distance, which was found to range between 0.004 and 0.457 among the strains studied. A perusal of genetic diversity within and among strains indicated that 34.72% of the observed variation occurred among strains and the rest of the variation (65.28%) within strains. Genetic relatedness of ten strains revealed by UPGMA dendrogram, showed genetic grouping of strains in two clusters. Populations of silkworm strains Kinshu and E 29, and Asahi and Kinshu showed the highest percent of polymorphism and more number of alleles, respectively. Their rich genetic diversity needs to be exploited in conservation and breeding programme.