慢生根瘤菌交叉结瘤及其系统发育关系的研究

选用包括6株花往根瘤菌Bradyrhizobium sp.(Arachis)]在内的13株慢生根瘤菌，进行了6种豆科植物结瘤试验及共系统发育分析。研究结果表明，慢生根瘤菌与试验的豆科宿主植物间普遍存在交叉结瘤，还发现有些菌株在原宿主外的豆科植物根部形成类根瘤的现象。16S rDNA和23S rDNA的PCR－RFLP分析揭示出这些菌株rDNA基因的差异性，不同宿主来源的慢生根瘤菌株可以同属一个rDNA类型，而从同一宿主中分离的根瘤菌菌株可分属多种不同的rDNA类型，研究结果表明，采用rDNA PCR-RFLP等遗传背景分析的手段，可能筛选出广谱的根瘤菌力株，表4参8。

CROSS-NODULATION TEST FOR BRADYRHIZOBIAL STRAINS AND THEIR PHYLOGENY ANALYSIS BASED ON 16S- AND 23S- rDNA PCR-RFLP

Thirteen bradyrhizobial strains, including 6 strains of Bradyrhizobium sp.(Arachis) and 7 other bradyrhizobia, were chosen to perform cross-nodulation experiments with 6 leguminous species. The results showed that cross-nodulation existed frequently between bradyrhizobia and their hosts, and para-nodules (pseudo-nodules) were found in some tests. PCR-RFLP analyses of 16S rDNA and 23S rDNA were performed after the chromosome digested with 9 restriction enzymes. 5 and 8 distinct restriction patterns of the 16S rDNA and 23S DNA were produced for the strains, respectively, which indicated that bradyrhizobia were genetically diverse. Some strains isolated from different hosts may belong to the same restriction patterns of the rDNA. On the other hand, some strains from the same host may show different restriction patterns of rDNA. The results suggested that effective strains could be screened for nodulating on several legume hosts by method of rDNA analyses. Tab 4, Ref 8