Impact of transgenic maize Ruifeng125 on diversity and dy-namics of bacterial community in rhizosphere soil

With the development of commercialized planting of genetically modified crops, their ecological security risks remain a hot topic of public concern. Insect-resistant genetically modified maize Ruifeng125 which expressing a fusion Bt protein (Cry1Ab-Cry2Aj) has obtained the application safety certificate issued by the Chinese government. To determine the effects of Ruifeng125 on the diversity and dynamics of bacterial communities, the accumulation and degradation pattern of the fusion Bt protein in the rhizosphere soil of transgenic maize were detected firstly. Results showed that the contents of Bt protein varied significantly at different developmental stages, but after straw returning to the field, over 97% of Bt proteins has been degraded quickly at the early stages (≤ 10 d) and then they were degraded at a relative slow rate. In addition, the variations of bacterial community diversity in the rhizosphere soil were detected by 16S ribosomal RNA (Rrna) high-throughput sequencing technology. A total of 44 phyla, 435 families and 842 genera were obtained by 16S rRNA sequencing, among which Proteobacteria, Actinobacia, Acidobacter Acidobacterium and Chloroflexi were the dominant taxa. At the same developmental stage, no significant differences in soil bacterial diversity were detected between Ruifeng125 and its non-transgenic control variety. Further analysis revealed that developmental stage, rather than the transgenic event, made the greatest contribution for the changes in soil microbial diversity. This research provides important information for evaluating the impacts of Bt crops on the soil microbiome and establish a theoretical foundation for their environmental safety assessment.