Abstract
New bivoltine lines (NBL’s) of the silkworm, Bombyx mori L. evolved employing heat shock technology were subjected for evaluation based on multiple traits evaluation index (E.I.) during winter, summer, and monsoon seasons keeping its parentage CSR2 and CSR27 as check breeds. The cumulative score was used to rank the silkworm breeds, and the value of a specific characteristic in a specific genotype was compared to the ranking. Interestingly, all NBL’s exhibited highest larval survivability and lesser larval duration compared to their parental breeds during all the three seasons of rearing. Notably, among different seasons, the larval weight (5.07 g), cocoon weight (2.18 g), cocoon shell weight (0.49 g), pupal weight (1.70 g), cocoon shell percentage (22.25%) and filament length (1, 054 m) were found to be highest during winter and monsoon seasons compared to summer season in NBL-5 being top on the list. Furthermore, the cocoon shell percentage of NBL-5 was 21.49, 21.91 and 22.25% which is highest as against 21.17, 21.89 and 22.02% in CSR2 during winter, summer and monsoon seasons respectively. Taken together, while NBL-5 has performed excellently with higher multiple trait E.I. value being first in the list in all the three seasons, NBL-9 and NBL-10A were also showed better performance with E.I. values greater than 50 irrespective of the seasons. As a result, we suggest NBL-5, NBL-9 and NBL-10A breeds as better parents while preparing disease free layings of cross breed or single and/or double bivoltine hybrids for commercial exploitation to enhance silk output in both tropical and temperate regions during all the seasons.
