Monitoring changes in the actinobacterial field communities present in the rhizosphere soil of a transgenic cotton producing Cry1Ab/Ac proteins

Transgenic cotton GK 12 producing Cry1Ab/Ac proteins can effectively control lepidopteran pests in agriculture. However, there are concerns that GK 12 has unintended side-effects on actinobacterial communities in the soil. Actinobacterial communities in the rhizosphere soil of cottons were analyzed by real-time PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE) at different growth stages in three annual replications under field conditions. Population sizes and community structures of Actinobacteria were markedly affected by natural variations in years, growth stages and cultivars. No significant differences were found in population sizes (excepting at budding in 2009), community structures, and Shannon indices of Actinobacteria (excepting at budding in 2010) between the GK 12 and its non-transgenic parent Simian 3, although there were differences between the GK 12 and the conventional cotton DP 5415. Phylogenetic analysis of DGGE band sequences indicated that Cellulosimicrobium sp. and Rhodococcus sp. only occurred in the GK 12 and the Simian 3. The dominant Actinobacteria did not differ between the GK 12 and the Simian 3. In conclusion, the overall impacts of the GK 12 on actinobacterial communities in the rhizosphere soil, based on qPCR and DGGE, were not significant during three continuous years in northern China.