Molecular evaluation of bivoltine, polyvoltine and mutant silkworm (Bombyx mori L.) with RAPD, ISSR and RFLP-STS markers

Mulberry silkworm (Bombyx mori L.), the most important silk producing insect, exhibits wide diversity in morphological and biometric characters. Characterization of vast genetic resources based on the morphological and quantitative traits is not solely dependable as the phenotypic traits are influenced by environment. In order to study genetic relatedness of the selected and varied genotypes, six each of the bivoltine, polyvoltine silkworm accessions and mutant stocks, were studied with RAPD, ISSR and RFLP-STS markers. Twelve RAPD primers generated 172 markers of which 161 were polymorphic, generating 93.60% polymorphism. Pair-wise genetic divergence varied from 0.209 between Mysore Princess and Rong Diazo to 0.588 between Boropolu and TMS-35. The ISSR primers generated 156 markers of which 132 were polymorphic thus generating 84.62% polymorphism. The pair-wise genetic diversity among the genotypes varied from 0.189 between Rong Diazo and BL-23 to 0.438 between MU-10 and TMS-35. Similarly, 10 RFLP-STS primers produced a total of 69 bands, out of which 53 were polymorphic thus realizing 75.6% polymorphism. Genetic distance varied from 0.242 between Nistari-M and BL-23 to 0.730 between Fengshong and TMS-17. On clustering with UPGMA and principal component analysis (PCA), RAPD and ISSR markers clearly discriminated the bivoltines and multivoltines and a multivoltine Tamil Nadu white occupied the positions among bivoltines, since it has bivoltine parentage. Boropolu, an original land race from North East India, and Feng shong, a Chinese silkworm strain, also showed a closer genetic relationship.