Genetic variability and selection index of some quantitative traits of bivoltine silkworm (Bombyx mor; L.) genotypes

Abstract

Genetic variation among genotypes and relation between major yield contributing traits are of vital importance in the breeding programme that aim to· produce improved genotype [1]. The present investigation has been undertaken to estimate the genetic variability of some important economic characters of bivoltine silkworm genotypes and their evaluation based on selection index for use in the breeding programme. A total of 59 bivoltine silkworm germplasm stocks (Thirty genotypes of spin peanut shape cocoons. sixteen genotypes of spin oval shape cocoons, eleven genotypes of spin elliptical shape cocoons, and two genotypes of spin spindle shape cocoons) maintained at Central Sericultural Research and Training Institute, Berhampore, were reared during two favourable seasons viz., March-April, Nov-Dec (2001 to 2003) in completely randomized design (CRD). During rearing, the important quantitative traits having commercial value such as, fecundity, larval period (days), pupation rate (%), cocoon yield/10,000 larvae (wt), cocoon weight (g), shell weight (g), cocoon shell ratio (%), filament length (m) and denier were recorded. The data were subjected to analysis of variance, estimation of genotypic and phenotypic coefficients of variation (GCV %, PCV %), heritability (h2 in broad sense) and genetic advancement. The selection index for ranking the genotypes was done following smith [2], based on the criterion I and II (Table 1).