短期不同耕作方式对水稻根际土壤细菌群落结构多样性的影响

Effects of short-term different tillage methods on the diversity of bacterial community in rice rhizosphere soils

【目的】研究短期不同耕作方式对水稻根际土壤细菌群落结构多样性的影响,为阐释耕作对稻田土壤微生物多样性的形成机制提供科学依据。【方法】以旋耕、免耕和粉垄3种不同耕作方式下的水稻根际土壤为研究对象,采用Illumina MiSeq高通量测序技术结合土壤理化性质,分析不同耕作方式下水稻根际土壤细菌群落多样性特征及其与土壤理化因子的关系。【结果】旋耕、免耕和粉垄处理文库覆盖率均较高,分别为98.96%、98.93%和99.04%。Alpha多样性分析结果显示,粉垄处理水稻根际土壤细菌群落多样性Shannon指数显著高于免耕处理(P<0.05,下同)。旋耕、免耕和粉垄处理分别获得2747、2734和2813个OTUs,处理间无显著差异(P>0.05)。各样本共检测到细菌类群206个种,隶属于47门48纲85目134科217属。物种群落组成分析表明变形菌门、绿弯菌门、酸杆菌门和硝化螺旋菌门是水稻根际土壤细菌主要优势菌群,共占比69.96%~73.51%;不同耕作处理水稻根际土壤细菌群落结构差异主要表现在菌群的相对丰度上,变形菌门、硝化螺旋菌门、浮霉菌门、放线菌门和绿菌门的相对丰度在3种耕作方式间差异显著。旋耕和免耕处理间OTU水平相似性较高。主成分分析结果显示,第一主成分(PC1)和第二主成分(PC2)菌群结构的差异性贡献率分别为43.15%和23.79%,细菌群落结构表现为粉垄处理受PC1影响明显、旋耕和免耕处理受PC2影响明显。冗余分析结果表明前2个排序轴共解释69.09%细菌群落变化;速效磷、碱解氮和pH是影响细菌群落的重要因子,与变形菌门、硝化螺旋菌门、浮霉菌门、放线菌门和绿菌门的群落分布显著相关。【结论】短期不同耕作方式可在一定程度上改变稻田土壤细菌群落多样性,不同耕作方式间的差异主要体现在细菌群落相对丰度上;土壤速效磷、碱解氮和pH是影响水稻根际土壤细菌群落分布的重要因素。从土壤微生物群落形成角度考虑,粉垄栽培优于旋耕和免耕。

【Objective】In order to provide scientific basis for elucidating the formation mechanisms of soil microbial diversity in paddy soils by tillage,the present experiment was conducted to study the effects of short-term different tillage practices on the diversity of bacterial community in rice rhizosphere soils.【Method】Rice rhizosphere soils under different cultivation modes of rotary tillage,no tillage and Fenlong cultivation were studied by Illumina MiSeq high-throughput sequencing,combined with soil physiochemical traits,to analyze the bacterial diversity characteristics and major microbial communities of rice rhizosphere soils under different cultivation modes,and the correlation between bacterial communities and soil physiochemical traits.【Result】The results of high-throughput sequencing analysis showed that the library coverage of rotary tillage,no tillage and Fenlong cultivation treatments were 98.96%,98.93%and 99.04%,respectively.Alpha diversity analysis showed that the Shannon index of bacterial community diversity of soil rhizosphere in Fenlong cultivation treatment was significantly higher than in no tillage treatment(P<0.05,the same below).The Venn diagram analysis showed that 2747,2734,and 2813 bacterial OTUs were obtained from rotary tillage,no tillage and Fenlong cultivation treatments,respectively,with no significant differences among three treatments.A total of 206 species of bacteria were detected in the samples,belonging to 47 phyla,48 classes,85 orders,134 families,217 genera.The analysis of the species community composition showed that Proteobacteria,Chloroflexi,Acidobacteria and Nitrospirae were the dominant flora of rice rhizosphere soils,totaling about 69.96%-73.51%.The relative abundance of Proteobacteria,Nitrospirae,Planctomycetes,Actinobacteria and Chlorobi were significantly different among three tillage treatments.Cluster analysis showed a high OTU level similarity between rotary tillage and no tillage treatments.Principal component analysis of soil bacterial community at the OTU level showed that the contribution rates of principal component 1(PC1)and principal component 2(PC2)flora structure were 43.15%and 23.79%,respectively,and the bacterial flora structure was influenced by PC1 in the Fenlong cultivation treatment and by PC2 in the rotary tillage and no tillage.Redundancy analysis revealed that the first two ranking axes together explained 69.09%of the variation in the bacterial community.Available phosphorus,alkaline nitrogen and pH value were important factors affecting the bacterial community,which were significantly correlated with the community distribution of Proteobacteria,Nitrospirae,Planctomycetes,Actinobacteria and Chlorobi.【Conclusion】Short-term differences in tillage practices can alter the diversity of bacterial communities in rice paddies to some extents,and the differences between tillage practices are mainly reflected in the relative abundance of bacterial flora.The available phosphorus,alkaline nitrogen and pH of the rhizosphere soils in rice are important factors influencing the distribution of bacterial communities.From the perspective of soil microbial community formation,Fenlong cultivation is preferable to rotary tillage and no tillage.