Toxicity And Biological Effects Of Bt Rice Pollen On The Different Varieties Of Domestic Silkworm, Bombyx Mori (Lepidoptera: Bombyxidae)

The susceptibility of the different varieties of domestic silkworm, Bombyx mori Linnaeus (Lepidoptera: Bombyxidae) to the pollen of Huachi2000B 1, a transgenic Bacillus thuringiensis (Bt) rice line was measured using bioassay method, and the effects of Bt rice pollen on the biological characteristics of FengyixWusi, a hybrid variety for summer and autumn rearing, and its parent races were also studied under the laboratory conditions. The results are shown as follows:1. Susceptibility of different varieties of B. mori to Bt rice pollenExcept for Fengyi X Wusi, the neonates from the varieties of B. mori were relatively sensitive to both Bt rice pollen and purified CrylAb protein. The susceptibility of Jingsong larvae to Bt rice pollen was the highest, contrasted with the lowest that of Fengyi X Wusi, which the LC50 value of the latter was only about 1/10 of that of the former. After fedding with Bt rice pollen at the concentration of 0.05 g pollen/g artificial diet, i.e. 1.19±0.10ng CrylAb/g artificial diet, for 48 h, survival curves of the larvae of different varieties of B. mori showed a obvious different variation pattern among the varieties. There was no distinct difference in the larval survival curves of FengyixWusi between Bt rice pollen and non-Bt rice pollen treatments. In contrast, survival curves of the larvae of other varieties who exposed to Bt rice pollen were highly distinct different from those who exposed to non-Bt rice pollen. Larval survival rate of Fengyi X Wusi was highly significantly higher than that of other varieties including its parental races, such as Fengyi and Wusi, and JingsongxHaoyue, a hybrid variety of spring rearing, and its parental races, Jingsong and Haoyue after exposure to Bt rice pollen, which indicated that Fengyi X Wusi was much more resistant or tolerant to Bt rice pollen than other varieties. There was no distinct difference in larval survival curves of different varieties between non-Bt rice pollen exposure and the control, which suggested that non-Bt rice pollen at such a dosage probably posed no marked impact on the survival of silkworm larvae.2. Biological effects of Bt rice pollen on different varieties of B. moriThe neonates of Fengyi X Wusi and its parental races were continuously exposed to the pollen of Bt rice, Huachi2000Bl and its parent variety deposited on the mulberry leaves at the concentrations of 0.002g/ml and 0.050g/ml, the sublethal dosage for FengyixWusi larvae, until pupation, respectively. The treatment of Bt rice pollen, especially at the concentration of 0.050g/ml, resulted in significantly higher larval mortality, longer developmental time, less body weight of early instar larvae, lower pupation and emergence rate, poorer cocoon quality, lesser number of eggs laid and more number of eggs unlaid per female. It suggested that high concentration of Bt rice pollen has dramatically adverse effects on biological characteristics of the silkworm such as larval survival, growth and development, and cocoon traits under laboratory conditions.