新疆苦豆子根瘤菌的数值分类研究

苦豆子(Sophora alopecuroides)对于干旱荒漠地区的畜牧业发展有着非常重要的意义，其生长特性与根瘤菌有密切关系。我们对分离自新疆苦豆子根瘤的67株根瘤菌及36个模式菌株进行了118项表型性状的测定，包括唯一碳源利用、唯一氮源利用、对抗生素和染料的抗性、耐盐性、初始pH值生长范围、生长温度范围及石蕊牛奶反应、氧化酶、过氧化氢酶和脲酶。对测定结果用聚类分析方法进行了分析，获得数值分类树状图。结果表明：新疆苦豆子根瘤菌在碳氮源利用、抗生素敏感性以及对染料的抗性程度等方面存在着差异。新疆苦豆子根瘤菌能耐受低温，并具有较强的耐盐、碱能力，所有供试菌株均能在初始pH值为9－12的YMA培养基上生长，92.5％的菌株能耐受3.0％的NaCl，91.0％的菌株能耐受4.0％的NaCl，有18株菌甚至能耐受5.0％和6.0％的NaCl。聚类结果表明， 在84.8%的相似性水平上，67个供试菌株构成了4个新的表观群，第Ⅰ、Ⅱ、Ⅲ、Ⅳ类群分别有21、7、4、3个菌株，中心菌株分别为NWBC152、NWTKX101、NWYJS12、NWLP112。此外，数值分类结果还表明，苦豆子根瘤菌与模式菌株的相似性较低，它们所形成的4个独立群可能有新种出现。

Numerical taxonomy of rhizobia isolated from the nodules of Sophora alopecuroides from Xinjiang

We collected the nodules of Sophora alopecuroides from a number of locations in Xinjiang, China. From these nodules, we isolated 67 previously unknown strains of rhizobia. We analyzed the phenotypic characteristics and the numerical taxonomy of these rhizobia and 36 reference strains through 118 parameters. The results showed that the strains differed in some characteristics, including carbon and nitrogen source, resistance to antibiotics and chemical dye, and endurance to salt and alkali. All unknown strains were tolerant to low temperature, and grew in YMA medium with an initial pH from 9 to 12. Up to 92.5% of the strains were able to grow on YMA medium containing 3.0% NaCl, and more than 91.0% were able to grow on YMA medium containing 4.0% NaCl. Eighteen strains were able to tolerate NaCl concentrations as high as 5%-6% in the growth medium. The unknown strains formed four new clusters defined by at least 84.8% similarity. Cluster I had 21 strains and NWBC152 was the central strain. Cluster II had 7 strains and NWTKX101 was the central strain. Cluster III had 4 strains and NWYJS12 was the central strain. Cluster IV had 3 strains and NWLP112 was the central strain. In addition, the numerical taxonomic analysis indicates that some strains in the new clusters could be new taxa.