Strain Mesorhizobium sp. CCNWGX035: A Stress-Tolerant Isolate from Glycyrrhiza glabra Displaying a Wide Host Range of Nodulation

Thirty-nine rhizobial isolates were isolated from the root nodules of Glycyrrhiza uralensis and Glycyrrhiza glabra, growing in the arid and semiarid regions of northwestern China, to test their taxonomic position and stress tolerance and to select one promising putative inoculant strain for further studies. On the basis of 113 physiological and biochemical characteristics, the isolates were clustered into three groups. One isolate CCNWGX035 was found to have high tolerance to NaCl, pH, and temperature. By sequencing the 16S rDNA, isolate CCNWGX035 was placed in genus Mesorhizobium. Nodulation tests demonstrated that the isolate not only formed nitrogen-fixing nodules on its original host plant Glycyrrhiza glabra, but also on Sophora viciifolia, Lotus corniculatus, Trifolium repens, Melilotus suaveolens, and Sophora alopecuroides. On the basis of sequence analysis of the nodA gene, isolate CCNWGX035 was closely related to strains of the genus Mesorhizobium, exhibiting some novel characteristics of root nodule bacteria.