Effects of Bt rice expressing Cry1Ac on ecological functional guilds and community of non-target insects

A 2-year field study was conducted to assess the effects of a Bt-rice line Cr7-1, (Japonica rice cultivar Nakdong) expressing a transgenic Cry1Ac1 gene, which is highly insecticidal against all larval stages of Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae), compared with an isogenic rice line (Japonica rice cultivar Nakdong). We investigated the community structure of insects with a sweep net and suction device in Bt and non-Bt rice fields during the rice growing season in 2007 and 2008 in Chungcheongnam-do, Korea. Two sampling methods, suction and sweeping, were used considering the habitat, behavior, and vertical distribution of insects in this study. A total of 43 families in 10 orders were identified from 64,099 collected insects and classified into four ecological functional guilds: (i) Herbivores; (ii) Predators; (iii) Parasitoids, and (iv) Detritivores, based on their ecosystem service. The temporal patterns of insect family richness, abundance, and Shannon's index were very similar between Bt and non-Bt rice, although significant differences were observed on a few occasions. In ecological functional guilds, abundance of herbivores and predators were significantly different between Bt and non-Bt rice, but there was no consistent trend in the 2 years. Overall, insect community structure, including diversity, abundance, and dominant families, was not significantly different between Bt and non-Bt rice. The results indicated that the transgenic Cry1Ac rice assessed in this study had no adverse effects on the rice insect community structure and ecological functional guilds in rice fields.