Search

One of the main objectives of the new breeding programs for silkworms is to consider the ability to withstand environmental fluctuations. In this study, the performance of the Iranian commercial silkworm lines was investigated under heat and cold stress. Seven Iranian commercial silkworm lines including 31, 32, 103, 104, 151, 153, and 154 were reared under standard conditions at Iran Silk Research Center. To induce heat and cold stress, 300 larvae on the third day of the fifth instar including three replicates of 100 larvae, were placed in an incubator at 35 °C and for 2 and 12 hours, respectively, and then returned to the standard rearing conditions at 25 °C until the end of the breeding period. The characteristics of cocoon weight (cw), cocoon shell weight (csw), and cocoon shell percentage (csp) were investigated under control and stress treatments. The generalized linear model (GLM) procedure of SAS software was used for statistical analysis. The results of the variance analysis showed that the effect of all sources of variance including genotype, stress, sex, two-way interaction effects of genotype × stress, genotype × sex, and stress × sex and three-way interaction effect of genotype × stress × sex were significant for all investigated traits. Therefore, the averages related to the three-way interaction effect of genotype × stress × sex were considered and discussed. The results of the comparison of the means showed that in general, the larvae of the control group, especially lines 154 and 153, had better performance in all the examined traits compared to the larvae under heat and cold stress groups and a significant difference was observed between them (P < 0.001). In the same way, the larvae of the heat stress group had a higher performance than the larvae of the cold stress group, which indicates the thermal tolerance of silkworm to higher temperatures than to low temperatures. In conclusion, the performance of Iranian commercial silkworm lines is affected