Abstract

                                A study on the cocoon size variables and reeling traits was carried out with 101 bivoltine silkworm germplasm based on single cocoon reeling data with the objectives (i) to analyze the degree of correlation of cocoon length, width and L / W ratio on total filament length, non_x0002_broken filament length, (ii) to understand whether the shape of cocoons influences the reeling process, (iii) to find the cocoon shape uniformity among the accessions and (iv) to group the best accessions based on cocoon shape uniformity and longest filament length with less breakage during reeling cycle. The results revealed that 13 accessions (BBE-175, BBE-178, BBE-179, BBE-180, BBE-181, BBE-182, BBE-185, BBE-186, BBE-187, BBE-192, BBE-197, BBI_x0002_205 and BBE-270) showed more uniformity for cocoon shape, as its standard deviation and co_x0002_efficient of variation for cocoon length, width and L/W ratio were less than the overall mean values 1.886, 1.90 and 21.727; and 5.620, 9.990 and 12.360 respectively. These accessions also showed an average total filament length more than 1000 meters and less breakage during reeling cycles, indicating the superiority in filament strength. Correlation analysis showed that cocoon length, width and L/W ratio do not have statistically significant positive or negative correlation with total filament length or non-broken filament length. These 13 silkworm germplasm have elongated and oval cocoon shape and this study suggests that cocoon shape (especially oval or elongated) should be given more importance in breeding plan than considering the cocoon size (i.e., cocoon length, width).

Key words : Bombyx mori, Silkworm germplasm, Cocoon shape