DNA Polymorphism and Genetic Variation among Bivoltine Silkworm (Bombyx mori L.) Genotypes Revealed by RAPD Markers

Background: In breeding programs, the selection of parental lines based on their phenotypic traits along with genetic variation at their DNA level is the better option in directional breeding as specific DNA profiles would be useful in producing reliable estimates of genetic identity and diversity at their genomic levels. In this context, Random amplified polymorphic DNA (RAPD) marker approach was used to ascertain genetic diversity and relationship among 12 bivoltine silkworms (Bombyx mori L.) genotypes for the identification of diverse genotypes to be used as parents for the improvement of quantitative traits in silkworms.

Results: RAPD analysis with 12 silkworm genotypes revealed high polymorphism of 88.88%. Ten RAPD primers utilized in this study generated PCR products in the range of 202-2876 bp across 12 silkworm genotypes. The Polymorphism information content (PIC) ranged from 0.295 to 0.493%. Based on Nei’s similarity coefficients, the genetic distance among the studied silkworm genotypes ranged from 0.93 to 0.99. Of the pairwise combinations, CSR18 and SH6, showed the highest similarity (0.99) whereas, SKAU-R-6 and DUN6 showed the lowest similarity (0.93) among the genotypes. The dendrogram generated, using Unweighted pair group method using the arithmetic average (UPGMA) from this marker, grouped the 12 silkworm genotypes into five main clusters, which corroborates the differences in their phenotypic characters.

Conclusion: The study clearly indicated the potential use of RAPD markers in differentiating silkworm genotypes based on their characters. The information generated on genetically divergent genotypes identified in this study would be useful in future silkworm breeding programmes for modifying the yield potentials of silkworms so as to boost up bivoltine silk production in the interest of temperate sericulture industry.