[Effects of planting transgenic Bt + CpTI cotton on rhizosphere denitrifier abundance and diversity].

OBJECTIVE: To evaluate the effect of planting genetically modified cotton on soil denitrifer. METHODS: The impact of transgenic Bt + CpTI cotton (SGK321) and its receptor cotton (SY321) on rhizosphere denitrifier abundance and diversity were investigated by using quantitative PCR (qPCR) and terminal restriction fragment length polymorphism (T-RFLP). We collected rhizosphere soil before cotton planting (Pre) and along with the cotton growth stage (budding, flowering, belling and boll opening). RESULTS: The abundance of denitrifier in both cottons changed significantly across the growth stage, but the variation tendency was different. In the rhizosphere of transgenic cotton, the denitrifier abundance increased from 3.12 x 10(6) copies/g dry soil (Pre) to 2.81 x 10(7) copies/g dry soil (belling). The denitrifier abundance in non-transgenic cotton was significantly affected by the growth stage: increased at budding, decreased at flowering, and then increased at belling. Canonical correspondence analysis and partial canonical correspondence analysis show that the denitrifier diversity was more correlated with pH, concentration of NO3- and budding and flowering. Additionally, cotton genotype was an important factor of influencing the diversity of denitrifier. CONCLUSIONS: This indicates the abundance and diversity were influenced by both the cotton growth stage and the cotton genotype by adjusting the soil pH and concentration of NO3-. Planting of transgenic Bt + CpTI cotton leads an increase in the soil pH, which results in an increase in abundance and diversity of denitrifier.