Analysis of genetic variability among bivoltine and multivoltine silkworm genotypes using inter simple sequence repeat and simple sequence repeat markers

The silkworm is an ideal lepidopteran model for the study of genetics and genetic diversity. In this study, inter-simple sequence repeats (ISSR) and Simple Sequence Repeats (SSRs) were used to investigate genetic relationships among 32 mulberry silkworm genotypes which included bivoltine and multivoltine silkworm breeds. Genomic DNA was isolated from the silkmoth samples and six polymorphic ISSRs were utilized to screen the genotypes. A total of 641 scorable alleles were identified among 32 silkworm genotypes utilizing six polymorphic ISSR markers and size ranged from ~ 100 to ~ 1400 bp. The percent polymorphism for six ISSR primers ranged from 46.15 to 63.63%. A total of six monomorphic alleles were observed, accounting for 8.57%. Similarly, three thermotolerant SSR markers were screened which revealed a total of 108 alleles with a polymorphism of 69.44%. The molecular mass of the alleles ranged from ~ 190 bp to ~ 250 bp. The chi square based similarity index represents a clear genetic similarity of the silkworm breeds BMV2 and BM22 (0.23) and the maximum genetic distance for breeds TMS knob and CSR27SL (1.32). Cluster dendrogram utilizing distance matrix classified the genotypes into two clusters with five sub clusters representing highest polymorphism with 21 genotypes. Thus, ISSRs and SSRs polymorphic markers are informative for estimating the extent of genetic diversity as well as to determine the pattern of genetic relationships between different silkworm genotypes and provide unique molecular identity based on the identified monomorphic bands. ISSR and SSR marker-based barcodes could be an effective tool for the selection of parentage in silkworm breeding programs. Graphical Abstract