Genetic Variability of the Silkworm, Bombyx mori (L., 1758) (Lepidoptera: Bombycidae) of Different Geographical Origin as Revealed by mtDNA Gene Segment Sequencing Analysis

Genetic variability and phylogenetic relationships in eight strains of the economically important silkworm Bombyx mori of different geographical origin and belonging to the Bulgarian germplasm were examined for the first time using 12S rDNA mtDNA gene segment sequencing analysis. We found 58 variable sites. Intra-strain variability was detected based on neighbour-joining, minimum evolution, maximum parsimony, UPGMA and PCA analyses. Eight haplotypes were revealed corresponding to the eight strains studied. PCA analysis distinguished Plovdiv 14, Plovdiv 18 and Maiak 5 strains from the rest. Maximum parsimony and UPGMA trees demonstrated that the strain Plovdiv 14 showed a large sequence divergence as compared to the other studied strains. Our results could be applied in future conservation strategies and breeding programs for B. mori in Bulgaria. 12S rDNA mtDNA gene segment sequencing analysis could be used with isoenzyme analysis for discriminating of strains of different geographical origin in relation to their involvement in breeding programs and preserving their original characteristics.