Abstract: Stress tolerance of nodule bacteria(Rhizobium sp.) significantly influences the microorganisms environmental adaptability and nitrogen fixation ability.Thirty-one alfalfa Rhizobium strains isolated from alfalfa nodule bacteria of different areas of Gansu Province were tested on their tolerance to NaCl and pH.Results show that alfalfa Rhizobium strains from the Tianshui area boasted the strongest tolerance to acid,while strains from the Wuwei area showed the strongest tolerance to salinity.Strains from the Dingxi area gave mono-tolerance,while strains from the Gannan area showed multi-tolerance.Among the Gannan strains,12 of strong stress tolerance were selected:WA24 could endure 55 g/L NaCl concentration.DA53、QL31B,and TL47 could multiply in pH3.5 culture medium;and DL67、and GA26 could reproduce in alkaline culture medium of pH12.Four strains boasted double stress-tolerance:QA33B could endure 50 g/L NaCl concentration and alkalinity of pH12 as well;DA42、GL21,and WA32 showed tolerance to acidity of pH 4.0 and alkalinity of pH 12.

Key words: Cold and drought region, Alfalfa, Rhizobium, Stress tolerance, Evaluation

摘要： 对31个分离自甘肃5个不同生态区域的苜蓿根瘤菌株耐酸、耐碱和耐盐能力进行评价研究。结果表明,武威菌株耐盐能力最强,天水菌株耐酸能力最强,定西菌株大多数表现出突出的单一抗性,甘南菌株大多数兼备抗酸、抗碱等多抗能力;筛选出12个抗逆能力较强的菌株,其中W A 24菌株能在55 g/L N aC l盐培养基上生长,DA 53、QL 31B和TL 47菌株能在pH 3.5的酸性培养基上生长,DL 67和GA 26菌株能在pH 12的碱性培养基上生长。QA 33B菌株既能在50 g/L N aC l盐培养基上生长,又能在pH 12的碱性培养基上生长,DA 42、GL 21和W A 32可在pH 4.0~12的环境中生长。

关键词: 寒旱区, 苜蓿, 根瘤菌, 抗逆能力, 评价