Impact of transgenic Cry1Ac + CpTI cotton on diversity and dynamics of rhizosphere bacterial community of different root environments.

The objective of this study was to characterize the diversity and dynamics of rhizosphere bacterial community, especially the response of dominant and rare bacterial taxa to the cultivation of Bt cotton for different root environments at different growth stages. qPCR analyses indicated that bacterial abundances of the taproots and lateral root rhizospheres of the Bt cotton SGK321 were significantly different at seedling and bolling stages. But no significant differences were detected between the same root zones from Bt and the conventional cotton varieties. Total bacterial genera had similar pattern with dominant genera in abundance, and with rare genera in richness to the changes of bacterial community, respectively. Although the rhizosphere bacterial diversity of the three cotton varieties changed in taproot and lateral root, no significant differences were detected in the same root environments between Bt and conventional cotton. Moreover, Soil pH was more correlated with variations in the bacterial community composition than Bt proteins. In conclusion, these results revealed no indication that rhizosphere bacterial community of Bt cotton had different response to increased Bt protein regarding the same root environment. In particular, dominant and rare bacterial taxa showed the variation in diversity and community composition in different root microhabitats.