Analysis of genetic variability and character association in bivoltine Silkworm (Bombyx mori L.) and their hybrids

Abstract

The present work was taken up, with the view, to study the direct and indirect effect of yield and their components and correlation coefficient of six metric trails of bivoltine silkworm (Bombyx mori L.) Six newly evolved breeds viz., SK-27, SK-28, SK-29 and SK-30 along with two commercial races NB4D2 and SH6 were utilized as the parental stock in the present study. Each of the six breeds were crossed in all possible combinations, to get fifteen hybrids The parents and hybrids were reared as suggested by Dar and Singh [1] in two environments E1 and E2 i.e. spring and summer season. After third moult, three replications of 250 worms each were retained. Observations were recorded for weight of 10 grown larvae (g) cocoon yield (no.)/10,000 larvae, cocoon yield (kg.)/10,000 larvae, single cocoon weight (g), single shell weight (cg) and shell ratio (%). The methodology was adopted by using formula in which the direct contribution of each of different components as well as indirect effect through the other yield components were analysed. The phenotypic and genotypic correlation coefficient were calculated for six quantitative traits, using the formula suggested by AI-Jibouri et al. [2].. Heritability (broad sense) was computed from the components of genetic variance. Expected genetic gain based on full sib family selection was calculated at 5% selection intensity (k = 2.06).