紫云英根瘤分离菌株质粒多样性的研究

PLASMID DIVERSITY OF THE ISOLATES FROM ASTRAGALUS SINICUS L. IN SOUTHERN CHINA

从广东、广西、湖南、湖北、江西、浙江、江苏７省紫云英（ＡｓｔｒａｇａｌｕｓｓｉｎｉｃｕｓＬ．）主要分布区４６个采集点的紫云英根瘤中分离到１０１个菌株．检测发现有１６种不同质粒类型，所含质粒１～４个不等，含两个质粒的菌株占绝大部分，质粒Ｍｒ为３６×１０６～３６４×１０６．用克隆Ｍ．ｈｕａｋｕｉ７６５３Ｒ的ｎｏｄＤＢＣ４．２ｋｂ片段为探针（α３２ｐｄＣＴＰ）进行的分子杂交结果表明，所有这些菌株均含有共生质粒，通常为第一大质粒，但Ｃ、Ｌ、Ｍ、Ｎ和Ｏ型为第二大质粒，共生质粒Ｍｒ在１３１×１０６～３６４×１０６之间．比较质粒类型与１６Ｓ２３ＳｒＤＮＡＩＧＳ（ｐＨｒ，ｐ２３ＳＲ０１）ＰＣＲＲＦＬＰ分析结果表明，ＩＧＳ类型不同，即使在同一植株分离所得的根瘤其质粒类型常不同，但在同一植株上分离菌株的质粒类型相同，则其ＩＧＳ常表现相同．

strains were isolated from Astragalus sinicus L. at 46 sites in southern China, including the provinces Guangdong, Guangxi, Hunan, Hubei, Zhejiang, Jiangshu and Jiangxi. Through plasmid profile analyses 16 plasmid types were found. They contain 1～4 plasmids, which range in size between 36×10 6～364×10 6 ( M r). All the strains carry a symbiotic plasmid (131×10 6～364×10 6 in size)that was determined by the hybridization with nod DBC probe. Usually,the symbiotic plasmid is the largest and C,L,M,N and O plasmid types are the second largest. On the other hand, the plasmid types were compared with the results of 16S 23S rDNA IGS PCR RFLP as chromosomal background. They are not closely related. Different IGS types of strains usually carry different types of plasmids even though they come from the same plant. But the plasmid type of rhizobia is resulted from the reaction between the chromosomal background and the living surrounding (eg.symbiosis) of rhizobia.