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桑树与土壤的物质交换发生在根际土层,研究不同品种桑树根际土壤的细菌群落,对了解不同品种桑树的根系生理活动差异,确定有利于桑树生长发育的土壤细菌群落生态系统有重要意义.对采集的不同品种桑树根际土壤细菌的16SrDNA部分序列进行PCR,根据扩增产物的变性梯度凝胶电泳(DGGE)图谱计算Shannon-Weaver多样性指数(H)、丰富度(S)和均匀度(E),并结合土壤理化性质,对20个桑品种的桑树根际土壤细菌群落的多样性进行分析.在一定范围内,各桑品种的桑树根际土壤细菌群落多样性指数与含水率和速效钾含量呈负相关,而与pH值及碱解氮、速效磷、有机质和全氮含量呈正相关,说明不同品种桑树根系的生理活动影响到根际土壤的理化性质;不同品种桑树根际土壤中存在共有的细菌,根际土壤细菌16S rDNA扩增产物的DGGE图谱呈现13个优势条带,其中4个条带属于γ-变形菌纲,有4个条带属于拟杆菌门,占条带总数的57.14％,为桑树根际土壤中的优势菌群;20个桑品种的桑树根际土壤样品细菌群落的Shannon-Weaver指数,以实钴11-6最高,桐乡青最低,说明不同品种桑树的根际土壤细菌群落多样性存在差异.综上结果建议生产上选择适合桑品种的栽培土壤并改善土壤质量和施用高效微生物肥料,促进桑树根际土壤优势茵群的形成,从而促进桑树生长.“,”Matter exchange between mulberry tree and soil occurs in the rhizospheric soil layer.To study bacterial community in rhizospheric soil of different mulberry varieties is of great significance for understanding difference of root physiological activity between different mulberry varieties and for determining bacterial community and soil ecosystem beneficial to growth and development of mulberry trees.The 16S rDNA partial sequences of rhizospheric soil bacteria of different mulberry varieties were amplified through PCR and the amplified products were subjected to denaturing gradient gel electrophoresis (DGGE) to calculate the Shannon-Weaver index (H),species richness (S) and evenness (E).Moreover,physicochemical properties of soil were combined to analyze the diversity of rhizospheric soil bacterial community among 20 mulberry varieties.The results indicated that,in certain ranges,the diversity index of rhizospheric soil bacterial community of each mulberry variety was negatively correlated with water content and available potassium content,but positively correlated with pH value,alkaline nitrogen,available phosphorus,organic matter and total nitrogen contents.Thus,root physiological activities of different mulberry varieties had effect on physical and chemical properties of the rhizospheric soil.There were common bacteria in rhizospheric soil of different mulberry varieties.DGGE image of PCR products from 16S rDNAs of mulberry rhizospheric soil displayed 13 dominant bands,among which 4 bands belong to γ-Proteobacteria,and 4 bands belong to Bacteroidetes,both of which accounted for 57.14％ of the total bands and were the dominant bacteria in mulberry rhizospheric soil.Among the 20 mulberry varieties,Shigu 11-6 and Tongxiangqing had the highest and the lowest ShannonWeaver index respectively,indicating that the diversity of rhizospheric soil bacterial community differs with mulberry variety.Based on the above data,it is recommended to choose soil suitable for different mulberry variety,improve soil quality,and apply efficient microbial fertilizer so as to promote formation of dominant rhizospheric soil bacterial community and growth of mulberry trees.