| 452 rhizobium samples were collected from 18 genera and 30 species of legumes according to the investigation in the middle and western areas of Gansu Province,and 328 rhizobium strains were isolated.The results show that the resources of leguminous plants are very scarce,and the growth of rhizobium is related to special ecological condition and topographical features.Especially,drought and high salt concentration are significant factors that limit rhizobium-legume symbiosis.The shape of these nodules is mostly sphericity or stick,and the color is mostly red,sandy beige,brown or yellow.Many kinds of legume have been applied not only to soil and water conservation but also to the improvement of environment in Gansu Province. |