Study of multiple-trait selection in new Iranian silkworm genotypes- Chinese-shape parents

Introducing new lines to produce high-quality silkworm hybrids is one of the ongoing tasks of the silkworm breeding centers. Five lines of Y, 124, 154, 104, and 32 with Chinese-shaped cocoons were selected from the gene bank. Based on the diallel cross, 20 genetic compounds were reared massively over three generations. After establishing the basic generation with 14 genetic combinations, the multi-trait selection was performed for five generations by the independent culling levels method. To compare the performance of parental lines and their combinations, data on the four traits of cocoon weight, cocoon shell percentage, good cocoons percentage, and cocoon number/liter (cocoon size) statistically analyzed in each year and the overall five years. The mean of cocoon weight and cocoon shell percentage of all genetic combinations were higher than the parental lines (p < /em><0.05). The average response to selection for cocoon shell percentage was more than one percent in the three genetic combinations compared to the maternal parent. For the good cocoons percentage, the best combinations had no significant difference with the best lines (104 and Y). While cocoon size in one genotype (IRA14) was very large (94 cocoons/ liter), other genotypes of large cocoons did not show significant differences with those lines with large cocoons (154 and 124). Genetic improvement of cocoon weight was positive for 12 out of 14 genetic combinations, but only one of them increased more than 0.1 g. The best lines will select finally after doing the crossbreeding program of Chinese with Japanese lines.