همبستگی فنوتیپی بین صفات مرتبط با ابعاد پیله در کرم ابریشم

The generative traits in silkworm are complex and are controlled by several genes and the effects of their interactions. In the silkworm breeding, it is necessary to be aware of the response of traits to selection and their changes due to correlation with other traits. In the final evaluation of the silkworm, the combination of several traits is important, but it is necessary to consider the relationship between the traits and their magnitude and direction. The size and dimensions of the cocoon are among the traits of the cocoon that have been investigated in the present study. The dimensions of the cocoon consist of several sub-traits. These traits include cocoon length (L), cocoon width (W), length to width of cocoon ratio (L/W) and width to length of cocoon ratio (W/L). Number of cocoons per liter (N/Lit) is another trait that indicates the size of the cocoon. Phenotypic correlation coefficients were calculated by using SAS statistical program and CORR procedure. The data were obtained from a 8×8 diallel cross experiment and including direct and reciprocal crosses between Chinese lines (108, 110, 114, 118) and Japanese lines (107, 109, 111, 113) which was implemented in a complete randomized design with 3 replications. The results of this study showed that the number of cocoons per liter had no significant phenotypic correlation with other traits of cocoon dimensions. This indicates that the attribute of number of cocoons per liter can not be a suitable substitute for the other four attributes. In contrast, the correlation between other traits was significant at the level of one percent probability (P<0.01). The highest positive and significant phenotypic correlation was between W and W/L (r=0.888). In the second order, the positive and significant phenotypic correlation was between L and L/W (r=0.726). Therefore, these traits can well be substituted for each other. The highest negative and significant phenotypic correlation was between L/W and W/L (r= -0.981). In second, third and fourth degrees, the highest negative and significant phenotypic correlation were between W with L/W (r= -0.865) and L with W/L (r= -0.712) and L with W (r= -0.317), respectively. The results showed that the changes of these traits are in opposite directions to each other and therefore the manner of their changes should be considered in the breeding processes according to the desired policies.