Measurements were taken of Bt protein expressed in the leaves of transgenic cotton (Gos- sypium hirsutum) transformed with a synthesized Bt (Bacillus thuringiensis) cry1A gene and its persistent level in larval bodies and faeces of a non-targeted insect pest, beet armyworm (Spodoptera exigua). We performed enzyme linked immunosorbent assays (ELISA) and bioassays using neonate larvae of cot- ton bollworm (Helicoverpa armigera) to detect the insecticidal activity of residual Bt protein at the sec- ond trophic level. The results showed that Bt protein content in functional leaves was different at various developmental stages and was different among plants at the same stage. Even though Bt protein concentration in the larval bodies and faeces de- creased 97.5%―99% compared to that found in cotton leaves subsequently fed to beet armyworm larvae, it still had a lethal effect on neonate cotton bollworm larvae. Therefore, Bt protein present at the second trophic level had insecticidal activity. This result is important in understanding and predicting the effect of transgenic plants on nontarget organisms.
SHI HongZHANG LifuHUA BaozhenMI XiangchengWEI WeiZHANG YongjunMA Keping
Transgenic insect-resistant cotton is being increasingly planted in Xinjiang cotton-planting regions, where geographical climate conditions and species composition of pests and natural enemies are greatly unique in China. Limited studies have been conducted on the ecological impacts of transgenic insect-resistant cotton, especially for transgenic double genes (Bt+CpTI) cotton, in this region. In this study, the potential effects of transgenic Bt+CpTI cotton on the seasonal abundance of non-target pests and predators were assessed from 2009 to 2011 in Korla, Xinjiang. The results showed that species composition and seasonal abundance of 5 groups of pests and 5 groups of predators were not significantly different between transgenic Bt+CpTI cotton and non-transgenic cotton every year. It suggests that transgenic Bt+CpTI cotton per se does not affect the population dynamics of non-target pests and predators on this crop in Xinjiang.
