s. z. mirhoseini

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.

The effect of mulberry leaves enrichment with riboflavin in 7, 37, 77 and 127ppm concentrations on larval growth and cocoon characteristics of Bombyx mori L., hybrid 103×104 was studied. Silkworm larvae were fed on fresh mulberry leaves of shin inche nevise enriched with riboflavin once a day. All biological and economical parameters were determined by using standard techniques in sericulture. The results showed that larval weight was greater in 77ppm among treatments on the 7th day of the fifth instar which had 47% increase compared to control. Maximum amount of female cocoon weight and female pupal weight were recorded 1.622g and 1.169g, respectively, in 127ppm while male cocoon weight and pupal weight were greater in 37ppm and recorded to be 1.169g and 0.895g, respectively. Maximum amount of cocoon shell weight and cocoon shell ratio were recorded in 77ppm for male (0.311g and 26.06%) and female (0.318g and 21.46%). Maximum weight of 50 eggs (0.027g) was recorded in 127ppm while high fertility and hatchability was recorded in 77ppm concentration. Effective rate of rearing was maximum in control treatment (72%) with no significant difference compared with other treatments. The overall results showed that riboflavin can be used at 77ppm concentration for the significant increase of cocoon weight, cocoon shell ratio and egg production of silkworm, Bombyx mori L.