Studies On The Diversity Of Rhizobial Resource In Xinjiang, China

Rhizobia are able to induce the organogenesis of root nodules on legumeinous plants and reduce atmospheric nitrogen into ammonia. There are a lot of legumes in Xinjiang province, China because of the special topographical condition, geographical environments and weather condition (There are two basins, Zunger and Tarim, between in three montes, Altai, Tianshan, and Kunlun. There is far away from ocean) in this region. This paper investigated the symbiotic resource of rhizobia and legumes in Xinjiang, China, studied the structure of some root nodules by light microscope and transmission electron microscopy, analyzed the phenotypic characteristics and the numerical taxonomy of 36 reference strains and rhizobia isolated from Sophora alopecuroides, from legumes plants growing on Pamirs or in Wuqia county through 118 parameters. 1. There were abundance in the symbiotic resource of rhizobia and legumes in Xinjiang, China. 123 species of 30 genera legumes were collected, among which, all were noduled and 12 species have not been reported for nodulation. 2135 nodule samples were collected and 1976 rhizobia strains were isolated. Water was the limited factor for legumes distributing and the nodule formation. 2. The nodules of Alhagi sparsifolia, Halimodendron halodendron, Sophora alopecuroides were composed of 4 tissues, meristem, cortex, vascular bundle, and center invaded tissue. The center invaded tissue contained uninfected cell and infected cell, the ratio of infected cell were correlation with legumes plant and stage of root nodules. The size, number, shape, distribution and fine structures of the bacteroid were related with the stage of host cell development in root nodules of Alhagi sparsifolia and with the development stage of root nodule of Sophora alopecuroides. Spherical bacteroid were observed in infected host cell in root nodules of Lotus corliculatus, Robinia pseudoacacia, Oxytropis macrobotrys, Orobus luteus, Caragana camilli, Sophora alopecuroides, Swainsonia salsula, Onobrychis viciifolia, Alhagi sparsifolia, Halimodendron halodendron, Vicia angustifolia. Poly-hydroxy butanoic acid (PHB) were observed in bacteroid in root nodules of Lotus corliculatus, Robinia pseudoacacia, Oxytropis macrobotrys, Orobus luteus, Caragana camilli, Sophora alopecuroides, Swainsonia salsula, Alhagi sparsifolia, Halimodendron halodendron. 3. Rhizobia isolated from Sophora alopecuroides, from legumes plants growing on Pamirs or in Wuqia county had some useful characteristics, including utilizing a lot of carbon and nitrogen source, resistance to antibiotics and chemical dye, and endurance to low temperature, salt and alkali. Each of 67 strains of rhizobia isolated from Sophora alopecuroides, 68 strains of rhizobia isolated from legumes plants growing on Pamirs, and 40 strains of rhizobia isolated from legumes plants growing in Wuqia county formed four new clusters defined for at least 84.8%, 86%, and 84.2% similarity. Some strains in new clusters might be new taxa because of the low similarity with reference strains. The central strains of 4 new clusters of rhizobia isolated from Sophora alopecuroides were NWBC15-2, NWTKX10-1, NWYJS1-2, and NWLP11-2. The central strains of 4 new clusters of rhizobia isolated from legumes plants growing on Pamirs were NWHQLP41-2, NWHQLP48-1, NWTX190-2, and NWTX127-2. The central strains of 4 new clusters of rhizobia isolated from legumes plants growing in Wuqia were NWWQ73-2, NWWQ13-1, NWWQ1-2, and NWWQ6-2.