江汉平原及其周边地区花生根瘤菌的遗传多样性

Genetic diversity of peanut rhizobia isolated from Jianghan Plain and the adjacent area

采用 RAPD分析技术和 1 6S- 2 3S r RNA间隔区段 (IGS) RFLP分析 ,分别对分离自江汉平原及其周缘地区的花生根瘤菌进行了遗传多样性和系统发育研究。结果表明 ,全部供试菌株分别在 48%和 50 %的相似性水平分为 I、II两群。供试花生根瘤菌与参比菌株 B. japonicum和 B. elkanii聚在群 I,参比菌株Rhizobium Sinorhizobium、Mesorhizobium和 Agrobacterium聚在群 。供试花生根瘤菌的遗传多样性及其在系统发育中的地位主要受地域因素的影响 ,来自江汉平原中心地带天门和潜江的菌株在 76%以上的相似性水平上聚在一起。处于周边地带的武汉和荆州 ,由于其特定的地理因素的影响 ,菌株的多样性更为丰富 ,部分菌株在分类上与其它地域的菌株相互融合 ,并在较高的相似水平存在一定摆动性。来自外缘随州的菌株 ,表现了明显的地理分隔作用 ,其在系统演化中的地位相对独立。总体上从平原腹地到外缘地区 ,根瘤菌地理分隔作用逐渐明显 ,在平原外缘的交接地带 ,根瘤菌的多样性最为丰富。

Genetic diversity of rhizobia from peanut on Jiangh an Plain and adjacent area was studied by the methods of Randomly Amplified Poly morphic DNA (RAPD) and 16S-23S rRNA Intergenic Spacer (IGS) PCR RFLP. The resul ts showed that all strains were divided into 2 groups at the similarity 48% or 5 0% respectively. Peanut rhizobia and representatives of B.japonicum and B. elkanii were clustered into group I and the reference strains of Rhizobium, Sinorhizobium, Mesorhizobium and Agrobacterium were clustered into group Ⅱ, which means that all peanut rhizobia belong to the genus of Bradyrhizobium . Peanut rhizobia showed some genetic diversity and were subdivided into four subgroups, A, B, C and D, at the similarity of 65% and 70% by RAPD and IGS PCR R FLP measures respectively. Strains isolated from Tianmen and Qianjiang, central area of Jianghan Plain, showed high homology and less divergence. They were clus tered into the largest cluster, subgroup A, by both measures. Some strains from Wuhan were also in subgroup A. Strains from the margin of the plain, Wuhan and J ingzhou, showed more abundant genetic diversity and were clustered into subgroup B and C by RAPD analysis or C and B by IGS PCR RFLP. Strains from an area adjac ent to the plain, Suizhou, showing geographical isolation in systematic developm ent and molecular evolution, were clustered into subgroup D independently by bot h measures. Reference strains of B. japonicum and B. elkanii were cluste red into subgroup E; together with subgroups A, B, C and D, they form group I, w hich means peanut rhizobia are phylogenetically adjacent to B. japonicum and B. elkanii. Thus the genetic diversity of the strains from the plain and the adjacent area was mainly determined by geographical factors. Strains from the center of the plain have high similarity and little divergence, but strains from the marginal area have the highest genetic diversity and the strains from the adjacent area s how geographical isolation and phylogenetic independence.