Characterization of indigenous silkworm (Bombyx mori L.) breeds on the basis of morphological traits

The morphological characterization among domesticated insect like silkworm (Bombyx mori L.) is an important aspect for selection of suitable parents for breeding programme. The present study was conducted on twenty bivoltine silkworm breeds to estimate the extent relationship by morphological characterization. Eighteen morphological traits both qualitative and quantitative viz., egg shape, chorion colour, colour of the newly hatched larva, larval marking, cocoon colour, cocoon shape, pupa colour and shape, colour of male and female moth, fecundity, hatching, larva weight 5th day, Vth instar duration, total larval period, percentage of malformed cocoons, pupation rate, single cocoon weight, single shell weight and shell percent were studied and data revealed significant variability among the breeds. Maximum Euclidean distance was observed between NB₄D₂ and CSR₁₉ (163.25) followed by CSR₁₉ and UDHEY-5 (145.13) and minimum between UDHEY-1 and UDHEY-3 (4.20). The dendrogram of phenotypic data grouped all breeds in two clusters; Cluster A and B. Cluster A was sub divided into two sub-clusters cluster AI and cluster A II. Cluster A I contained eight breeds and Cluster AII eleven breeds. Cluster B comprised of one breed CSR₁₉. In PCA the genetic divergence was maximum between NB₄D₂ and CSR₁₉, whereas it was minimum in UDHEY-7 and ND2. PCoA results depicted CSR₁₉ and SPO having greater divergence, whereas it was minimum between UDHEY-7 and ND2. On the basis of Euclidean distance metric the performance of the breeds; CSR₁₉, NB₄D₂, PO₃, UDHEY-8, SPO, UDHEY-4, ND2, CC1, UDHEY-2, UDHEY-5, UDHEY-7, UDHEY-6 have been identified as promising breeds and are recommended for further breeding to boost bivoltine silk production.