This study was conducted to analyze genetic parameters in six commercial Iranian silkworm pure lines including Japanese origin pure lines of 31, 103 and 107 and Chinese origin ones of 32, 104 and 110. All stages of rearing, recording and collecting data were performed over four rearing periods. Quantitative traits of Cocoon Weight (CW), Cocoon Shell Weight (CSW) and Cocoon Shell Percentage (CSP) were evaluated in this study. Covariance components of the characters are estimated by means of REML method. It is estimated heritability, phonotypical, environmental and genetical correlations using DFREML software package. From obtained results, genetic parameters including heritability and genetic correlation for economical trait were different significantly; hence it must be applied appropriate breeding strategies in each pure line. Cocoon weight and CSW heritability was higher than CSP one. Additive genetic correlation between CW-CSW, CSW-CSP and CW-CSP was high, medium and low, respectively. From obtained results, response to selection for cocoon weight and cocoon shell weight are higher than cocoon shell percentage since latest trait had lower heritability. Therefore, it is expected correlated traits improve using selection based on cocoon shell weight. Furthermore, genetic trend of traits were negative and significant at non-selected populations. Phenotype trend of traits also were negative and significant at selected and non-selected populations which is cleared environmental conditions decline at improvement generations.
