Dynamics in Kanamycin-Resistant Bacterial Population and Detection of npt II Gene Flow in the Rhizosphere of Insect-Resistant Transgenic Cotton

【Objective】 The dynamics in kanamycin-resistant bacterial population were studied and the flow of npt II in the rhizosphere of insect-resistant transgenic cotton was monitored. 【Method】 Insect-resistant transgenic cotton GK12, GK19, 33B, and SGK321, and corresponding receptor cotton 33, Shiyuan 321 and Simian No.3 cotton were sampled at different growing stages. Dynamics and diversity among kanamycin-resistant bacterial populations in the rhizosphere were analyzed with the conventional culture methods. In addition, the flow of npt II was monitored by germ PCR, and the unique primer was designed from the sequence of npt II, the CK was pBI121 plasmids. 【Result】 The population of kanamycin-resistant bacteria in cotton rhizosphere decreased along with the cotton growth. Significant difference was found among the same cotton cultivar at different sample times, but little difference was found between insect-resistant transgenic cotton and corresponding receptor cotton at the same time. Simpson diversity index, Shannon-Wiener diversity index and Pielou’s evenness index were calculated, and the results showed that the diversity index of kanamycin-resistant bacterial population in rhizosphere of conventional cotton was larger than that of insect-resistant transgenic cotton. The monitoring result by PCR amplication showed that positive PCR products of 18 strains were found from 21 kanamycin-resistant strains, no sequences had 100% similarity with the known nptⅡ gene sequence. 【Conclusion】 It was suggested that little differences were found among the total rhizospheric population of kanamycin-resistant bacteria between insect-resistant transgenic cotton lines and their receptor cotton cultivars, the diversity index of rhizospheric kanamycin-resistant bacteria population of receptor cotton cultivar is larger than the corresponding insect-resistant transgenic cotton line, and is more even and stable. No gene flow of nptⅡ in insect-resistant transgenic cottons into the rhizosphere bacteria was detected.