Soybean plants expressing the Bacillus thuringiensis cry8-like gene show resistance to Holotrichia parallela

Cry8-like from Bacillus thuringiensis (Bt) encodes an insecticidal crystal (Cry) protein. Holotrichia parallela (Coleoptera: Scarabaeoidae), commonly known as the dark black chafer, is a troublesome pest of soybean (Glycine max). To test whether cry8-like can confer resistance against H. parallela to soybean, we introduced cry8-like from the Bt strain HBF-18 into soybean cultivar Jinong 28.

Quantitative reverse transcription-PCR analysis demonstrated that cry8-like was expressed most highly in soybean leaves. In addition, Southern blot assays revealed that one copy of the integrated fragment was present in the transformed plants. Eight independent cry8-like transgenic lines were subsequently fed on by H. parallela. Under H. parallela feeding stress, the survival rates of the non-transgenic plants were 92% lower than those of the transgenic plants. The mortality rate of H. parallela increased when the larvae fed on the roots of T₁ transgenic soybean plants. Moreover, the surviving larvae were deformed, and their growth was inhibited.

Collectively, our data suggest that transgenic soybean plants expressing the cry8-like gene are more resistant to H. parallela than non-transgenic plants and that transgenic expression of the cry8-like gene may represent a promising strategy for engineering pest tolerance. The events generated in this study could thus be utilized in soybean breeding programs.