稻—稻—油菜轮作土壤细菌群落的特征

Soil bacterial community characteristics of rice-rice-rape crop rotation

为了解南方地区稻—稻—油菜轮作后土壤中细菌群落的变化特征，以长达30年的水稻—水稻—油菜轮作和水稻—水稻连作定点栽培试验土壤为研究对象，采用克隆文库和基因序列分析法，通过细菌16S rDNA基因通用引物对土壤提取DNA进行PCR扩增，然后将扩增片段构建克隆文库对克隆子进行测序分析. 结果显示，2015年7月、10月和2016年4月3次取样中轮作土壤细菌的香农-维纳指数和辛普森指数均高于连作土壤，轮作土壤细菌多样性高于连作. 克隆子序列OTU与GenBank比对结果显示，轮作土壤中常见的变形菌（Proteobacteria）占细菌种类的55%，连作土壤为45%；轮作土壤芽单胞菌（Gemmatimonadetes）占细菌种类的13%，连作土壤为10%；轮作土壤中的酸杆菌（Acidobacteria）、厚壁菌（Firmicutes）和浮霉菌（Planctomycetes）所占细菌比例数小于连作土壤；变形菌和芽单胞菌构成了轮作土壤中的优势菌群，土壤优势菌群的变化对细菌群落结构特征产生影响. 测序结果显示稻—稻—油菜轮作土壤优势菌群中α-变形菌、β-变形菌和γ-变形菌高于稻—稻连作；稻—稻—油菜轮作中发现与绿弯菌（Chloroflexi）序列相似菌类，而稻—稻连作土壤中未发现. 本研究表明微生物群落结构组成与土壤耕作方式相关，稻—稻—油菜轮作增加了细菌群落丰度. （图3 表2 参20）

To investigate the characteristic changes in soil bacterial community under rice-rice-rape rotation in southern China, soil samples from a 30-year crop rotation and continuous cropping system were collected. Clone library and gene sequence analysis were adopted. The PCR amplification was carried out using universal primers of the 16S rDNA gene. The amplified fragments were then used to construct a clone library. The subclones were sequenced and analyzed. The experimental analysis showed that, in July 2015, and October and April 2016, the Shannon Wiener index and richness index of bacteria from the rotation treatment soils were higher than those of the continuous cropping treatment soil. The soil bacterial diversity of the rotation treatment was higher than that of the continuous cropping treatment. The results of BLAST analysis in the GenBank showed that Proteobacteria accounted 55% of total bacteria in the rotation treatment soil, whereas it accounted for 45% of total bacteria in continuous cropping treatment soil. Gemmatimonadetes accounted for 13% of the total bacteria in rotation treatment and 10% in the continuous cropping treatment. The proportion of Acidobacteria, Firmicutes, and Planctomycetes in rotation soil was less than those in the continuous cropping soil. Proteobacteria and Gemmatimonadetes were the dominant flora in soil. The changes in the predominant bacteria affected the diversity of soil bacteria in rotation and continuous cropping. The sequence analysis showed that the dominant bacteria in the soil were Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria, which higher than those in the rice-rice continuous cropping treatment. The sequences similar to Chloroflexi were observed in the rice-rice-rape rotation soils, but not in the continuous cropping soils. The results showed that the soil microbial population is conducted by agricultural tillage, and rice-rice-rape rotation increased the soil bacterial abundance compared with that of the rice-rice continuous treatment.