Objective In order to further analyze the biodiversity of indigenous rhizobia from soybean nodules in Xinjiang, screen razobia with nodulation cabability, and explore matching relationship between different rhizobia strains and different soybean varieties, provide rhizobia strains for the development of fertilizer agents suitable for soybean nodulation and nitrogen-fixing.
Methods The culturable and culture-free methods were used to analyze the biodiversity of rhizobia in soybean nodules, and the pot method was used to screen the rhizobia capable of nodulation and the matching relationship.
Results The culture-free method analysis showed that the dominant genus of rhizobia in soybean nodules was Sinorhizobium. 187 bacterial strains were isolated from soybean nodule samples with the culturable method. The main genus of isolated rhizobia were Sinorhizobium, Rhizobium and Mesorhizobium. Three salt-tolerant rhizobia strains were screened for their matching relationship with 11 different soybean varieties. The results showed that Sinorhizobium fredii TRM33501 had significant nodulation ability on soybean varieties from the highest to the lowest as in order Xiangfeng 6, Huadou 22, Jiadou 2, and Shenzhou 3. Mesorhizobium mediterraneum TRM33510 had significant nodulation ability on Zhonghuang 13, Huadou 14, Jiadou No. 6, and Qihuang 34, respectively. The most suitable soybean varieties for Rhizobium marinum subsp. marinum TRM33661 were Yundou No. 1, Ruidou No. 1, and Hedou No. 3, respectively. In addition, mixed inoculation of one soybean variety with two or three species of rhizobia did not increase the number of nodules.
Conclusion The resources of indigenous rhizobia strains from soybean nodules in Xinjiang were relatively limited, mainly species from Sinorhizobium, Rhizobium and Mesorhizobium.The indigenous characteristics of rhizobia from the soybean nodules in Xinjiang was ralated to the salt-tolerance of rhizobia. There were significant differences in the ability of nodulating for different rhizobia strains to different soybean varieties. Although there was no strict one-to-one correspondence between soybean varieties and rhizobia species, there was a clear preference for different soybean varieties in recruiting and selecting rhizobia species, suggesting the importance of "bacteria-bean" matching relationship in the procedure of developing fertilizer for soybean nodulation and nitrogen-fixing.
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