Abstract

In order to estimate genetic parameters of the cocoon weight (CW), cocoon shell weight (CSW) and cocoon shell percentage (CSP) of three industrial lines of silk-worm (number 31, 103 and 107), data were collected from three successive generations. (Co)variance components were as follows: additive genetic variation (δ²_g) and environmental variation (δ²_e) of traits and additive genetic covariance (cov_{g1, 2}) and environmental covariance (cov_{e1, 2}). Heritability of traits was estimated with maximum likelihood procedure (REML) by using algorithms (DFREML) based on a three trait animal model. Data were from half-sibs and the heritability and genetic, phenotypic and environmental correlation were estimated between traits. The highest heritability for CW was estimated in lines 31 and 107 (0.58 and 0.58, respectively) and the lowest heritability for CW was in line number 103 (0.28). The highest and lowest heritability for CSW was in lines 107 and 103 (0.70 and 0.01, respectively). Also, the highest heritability for CWP was in line 31 (0.48) and the lowest value was in line 103 (0.077). The highest δ²_g for CSP was estimated in line 103 (0.004) and lowest δ²_g was estimated in line 107 (0.001). The highest and lowest δ²_g for CW were estimated in lines 103 and 31 (0.0004 and 0.00003, respectively). The δ²_g for CW was high in line 31 (0.604) but low in line 103 (0.257). The highest and lowest δ²_e for CW were in lines 103 and 107 (0.02 and 0.01, respectively). Furthermore, the highest δ²_e for CSW was estimated in line 103 (0.0013) but minimum δ²_e was in line 107 (0.0007). Maximum cov_{g1, 2} for CW-CSW was estimated in line 103 (0.00087) and minimum value was estimated in line 31 (0.00012). A high cov_e1,2 for CW- CSP was estimated in line 103 (0.093) but it was low in line 31 (0.00026). The highest cov_{g1, 2} for CSW-CSP was in line 103 (0.002) but it was low in line 31 (0.00079).

Key words: Cocoon, correlation, heritability, genetic (Co) variance.