Liu Qingsong,Romeis Jörg,Yu Huilin,Zhang Yongjun,Li Yunhe,Peng Yufa
We determined whether plant volatiles help explain why Cotesia chilonis (a parasitoid of the target pest Chilo suppressalis ) is less abundant in Bt than in non- Bt rice fields. Olfactometer studies revealed that C. chilonis females responded similarly to undamaged Bt and non- Bt rice plants. Parasitoids preferred rice plants damaged by 3 rd -instar larvae of C. suppressalis, but did not differentiate between caterpillar-infested Bt and non- Bt plants. According to GC-MS analyses of rice plant volatiles, undamaged Bt and non- Bt rice plants emitted the same number of volatile compounds and there were no significant differences in the quantity of each volatile compound between the treatments. When plants were infested with and damaged by C. suppressalis larvae, both Bt and non- Bt rice plants emitted higher numbers and larger amounts of volatile compounds than undamaged plants, but there were no significant differences between Bt and non- Bt plants. These results demonstrate that the volatile-mediated interactions of rice plants with the parasitoid C. chilonis were not disrupted by the genetic engineering of the plants. We infer that parasitoid numbers are lower in Bt than in non- Bt fields because damage and volatile induction by C. suppressalis larvae are greatly reduced in Bt fields.
Yaoyu Jiao,Xiaoyun Hu,Yufa Peng,Kongming Wu,Jörg Romeis,Yunhe Li
The area planted with insect-resistant genetically engineered crops expressing Bacillus thuringiensis (Bt) genes has greatly increased in many areas of the world. Given the nearby presence of non-Bt crops (including those planted as refuges) and non-crop habitats, pests targeted by the Bt trait have a choice between Bt and non-Bt crops or weeds, and their host preference may greatly affect insect management and management of pest resistance to Bt proteins. In this study, we examined the oviposition preference of the target pest of Bt rice, Chilo suppressalis, for Bt versus non-Bt rice plants as influenced by previous damage caused by C. suppressalis larvae. The results showed that C. suppressalis females had no oviposition preference for undamaged Bt or non-Bt plants but were repelled by conspecific-damaged plants whether Bt or non-Bt. Consequently, C. suppressalis egg masses were more numerous on Bt plants than on neighbouring non-Bt plants both in greenhouse and in field experiments due to the significantly greater caterpillar damage on non-Bt plants. We also found evidence of poorer performance of C. suppressalis larvae on conspecific-damaged rice plants when compared with undamaged plants. GC-MS analyses showed that larval damage induced the release of volatiles that repelled mated C. suppressalis females in wind tunnel experiments. These findings suggest that Bt rice could act as a dead-end trap crop for C. suppressalis and thereby protect adjacent non-Bt rice plants. The results also indicate that the oviposition behaviour of target pest females should be considered in the development of Bt resistance management strategies.
危险品化学品经营许可证（带存储）