Impact of Bt-transgenic rice (SHK601) on soil ecosystems in the rhizosphere during crop development

In contrast to other transgenic Bacillus thuringiensis (Bt) crops (e.g. Bt maize and cotton), risk assessments of Bt rice on soil ecosystem are few. To assess the influence of Bt rice on rhizosphere soil ecosystems, soil samples from Bt, non-Bt and controls were taken at seedling, tillering, booting, heading and maturing stages. The activities of dehydrogenases, invertase, phenol oxidases, acid phosphatases, ureases and proteases showed no significant differences between Bt and non-Bt rice. A Biolog system was used to evaluate the effect of Bt rice on functional diversity of microbial communities. Although there were differences in carbon substrate utilization between Bt and non-Bt rice at seedling, tillering and heading stages, these differences were transient and not persistent. Denaturing gradient gel electrophoresis (DGGE) fingerprint patterns showed that Bt rice had little effect on the dominant rhizosphere bacterial, fungal and actinobacterial communities. The richness and consistency of microbial communities according to carbon substrate utilizations and DGGE band patterns did not differ significantly between Bt and non-Bt rice, and were close to that of control soil. There was no evidence to indicate apparent effects of Bt rice on soil enzyme activities, microbial community composition and functional diversity in this study.