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Crop Biotech Update

Insect Resistance Transgenes Reduce Herbivory and Enhance Fecundity in Rice

June 3, 2011

Fudan University scientist Xiao Yang and colleagues tested the effect of genetically-engineered insect resistance on the herbivory and fecundity of insects in advanced generations of crop-weed hybrids of rice. They created two filial generations (F2 and F3) of crop-weed hybrid lineages of GM rice using lines with two transgene constructs, cowpea trypsin inhibitor (CpTI) and a Bt transgene linked to CpTI (Bt/CpTI).

Results showed that CpTI had no significant effect on the insects' ability to reproduce, but decreased forage of the insects on the plants. On the other hand, Bt/CpTI significantly decreased insect damage to almost 80% and greater fecundity compared to non-GM controls and weedy parent. Slight fitness cost was observed in F3 progeny with Bt/CpTI when grown under conditions of low insect pressure and direct competition with transgene-negative controls.

Based on the results, the researchers concluded that Bt/CpTI transgenes may introgress into co-occurring weedy rice populations and contribute to greater seed production when target insects are abundant. However, the net fitness benefits that are associated with Bt/CpTI could be temporary if there is not enough insect pressure in the surroundings.

Read the abstract at