转cry1Ab和epsps基因玉米C0030.3.5对土壤固氮细菌丰度和群落结构的影响

为评估转基因玉米种植对土壤氮周转功能微生物的潜在风险,以转cry1Ab和epsps基因玉米C0030.3.5(TM)及其亲本玉米DBN318(PM)为研究对象,于2015年拔节期、抽雄期、乳熟期、完熟期采集根际土和非根际土进行试验,并采用荧光定量PCR(quantitative real-time PCR,q PCR)和末端限制性片段长度多态性(terminal restriction fragment length polymorphism,TRFLP)技术分析土壤固氮微生物nif H基因丰度和多样性.结果表明,TM和PM根际土和非根际土固氮细菌nif H基因丰度随生长时期整体呈现先升高后降低的变化趋势,无论是根际土还是非根际土,同一生长时期2种玉米nif H基因丰度间差异均不显著.相关分析显示,土壤固氮细菌nif H基因丰度与有机质含量呈极显著正相关.T-RFLP结果表明,所获得的14种TRFs中,43 bp和155 bp片段所代表的固氮细菌为共有优势种群,无论是根际土还是非根际土,同一生长时期各T-RFs的相对丰度在TM和PM间差异同样不显著.土壤固氮细菌的Shannon指数和Evenness指数随生长期整体呈现出先升高后降低的变化趋势,无论是根际土还是非根际土,同一生长时期TM和PM的Shannon指数间及Evenness指数间均无显著差异.主成分分析(principal component analysis,PCA)表明TM和PM土壤固氮细菌群落结构组成无显著差异.冗余分析(redundancy analysis,RDA)显示土壤铵态氮和p H对固氮细菌群落结构组成影响显著.

Effects of Transgenic Maize with cry1Ab and Epsps Genes C0030.3.5 on the Abundance and Community Structure of Soil Nitrogen-fixing Bacteria

In order to evaluate the potential risk of planting transgenic corn on soil nitrogen-fixing microorganisms, in 2015, rhizosphere and non-rhizosphere soil samples were collected at the jointing stage, tassel stage, milky stage, and ripening stage, and the effects of transgenic maize with the cry1Ab and epsps genes on the abundance and diversity of soil nitrogen-fixing bacteria were studied by real-time quantitative PCR and T-RFLP. The results showed that the copy number of the diazotrophic nifH gene in the rhizosphere and non-rhizosphere soil of transgenic maize with the cry1Ab and epsps genes (C0030.3.5) and its parental maize (DBN318) showed a trend where it first increased and then decrease with the growth stages, ranging between 2.99×10⁷ and 7.02×10⁷ copies·g^-1. The abundance of the diazotrophic nifH gene in the rhizosphere soil and non-rhizosphere soil gene showed no significant difference between TM and PM in the same growth stage (P>0.05). The correlation analysis showed that the abundance of the diazotrophic nifH gene was positively correlated with the content of organic matter, but negatively correlated with water content. T-RFLP analysis yielded 14 T-RFs of different lengths, and 43-bp and 155-bp fragments were the dominant population. The community composition of nitrogen-fixing bacteria was the same as that of TM and PM in the rhizosphere soil and non-rhizosphere soil, and there was no significant difference between the TM and PM populations in the same growth period (P>0.05). The Shannon index and Evenness index of the diazotrophic nifH gene showed a trend where they first increased and then decreased with the growth period, and there was no significant difference in the Shannon index and Evenness index in the same growth stage between the rhizosphere and non-rhizosphere soil samples. Principal component analysis(PCA) indicated that the composition of nitrogen-fixing bacteria was not different between TM and PM. Redundancy analysis (RDA) showed that soil ammonium, nitrogen, and pH were significantly correlated with composition of nitrogen-fixing bacteria.