Elucidating genetic divergence of silkworm (Bombyx mori) using internal transcribed Spacer1 (ITS1)

The silkworm Bombyx mori is one of the prominent molecular model system, being continuously evaluated through genetic approaches, since decades to better the best in silk production. DNA profiles provide reliable estimates of genetic diversity within and between genotypes. This is important both for the maintenance of genotypes as well as selection of parents for the development of elite hybrids. To ascertain genetic diversity and phylogenetic relationship among 23 bivoltine silkworm strains, DNA barcoding of ITS1 region and Mahalanobis D2 analysis was carried out. Neighbour-joining analysis grouped 23 strains into five clusters based on sequence variation of ITS1 region. Based on seven quantitative traits, the D2 values were obtained and the selected strains were grouped into three clusters using Tocher’s method. Cocoon yield by number (44.27%) and shell ratio (41.5%) recorded maximum contribution towards divergence. The clustering pattern revealed agreement for divergence as SKUAST-1 and SKUAST-22 formed an outgroup cluster at both molecular as well as genetic level. The current study clearly demonstrated that ITS1 sequences of B. mori were useful in studying intra specific nucleotide variations and can be used as DNA barcode for future B. mori studies. The divergent strains identified in this study could be used in future breeding programmes for quality silk production.