华北及西北地区岩黄芪根瘤菌的表型及遗传多样性

Phenotypic and genetic diversity of rhizobia isolated from root modules of Hedysarum spp. grown in the northern and northwestern regions of China

选用分离自河北、内蒙古等5省区的岩黄芪根瘤菌30株及17株已知参比菌株,进行了营养利用、抗生素抗性、耐逆性及生理生化反应等12 5项表型性状研究,所得数值分类树状图表明不同宿主及不同地域的岩黄芪根瘤菌的表型多样性。通过对其中部分菌株进行16 S r DNA PCR- RFL P及BOX- PCR指纹图谱分析,聚类结果表明供试岩黄芪根瘤菌具有遗传多样性。

The legume species within the genus Hedysarum are deep-rooted annual or perennial herbs, and they are well distributed in the temperate zones. About 40 species of Hedysarum are native to China and they are potential foliages and are used as resources of herbal medicine. These legumes are pioneers plants, but its geographic distribution may be determined by the existence of proper rhizobia. Aiming at understanding the diversity of rhizobia associated with them, we isolated thirty rhizobial strains from root nodules of Hedysarum spp. grown in the northern and northwestern regions of China and characterized them in this study. The phenotypic characterization of the strains showed that most of the rhizobial strains isolated from Hedysarum spp. had high stress resistance. For instance, all of them grew from pH 5.0 to pH 11.0. Over 80% of these strains grew well in YMA medium at 37℃ and several of them even grew at 4℃ or were resistant to 60℃. Some strains have a tolerance to high concentration of erythromycin or streptomycin (300μg·ml^(-1)) and of NaCl (3%, w/v). The resistance of these strains to the reverse conditions might be the results of their adaptation to the environments because these bacteria were obtained from hosts grown in the soils that are dry, alkaline-saline, and poor in organic materials. Based upon the numerical taxonomy using 125 phenotypic characteristics, the strains isolated from Hedysarum plants were clustered into three phena at the similarity level of 73%, and cluster I could be divided into Sinorhizobium, Agrobacterium and Rhizobium branches.These grouping results were generally confirmed by the 16S rDNA PCR-RFLP and by BOX-PCR fingerprinting. It seems clear that the Hedysarum species grown in the northern and northwestern regions of China nodulate with diverse rhizobia in the genera Mesorhizobium, Rhizobium, and Sinorhizobium.