Glycine soja-associated rhizobia: isolation from coastal saline soil and application in soybean

Abstract:

[Objective] To investigate the rhizobial diversity of wild soybean (Glycine soja) in saline soil and screen out the salt-tolerant and plant growth-promoting strains for the cultivation of soybean. [Methods] We used the culture-dependent method to isolate rhizobia from wild soybean growing in coastal saline soil and then evaluated their growth-promoting characteristics and effects on wild soybean and cultivated soybean. [Results] A total of 87 rhizobial strains were isolated from the root and nodule samples of wild soybean, belonging to Sinorhizobium, Rhizobium, and Bradyrhizobium. Next, 24 strains of different species or from different samples were selected as representatives. Among the 24 strains, 16, 6, 16, and 6 strains had the abilities of producing indole-3-acetic acid (IAA), producing 1-amino-cyclopropane-1-carboxylic (ACC) deaminase, dissolving phosphorus, and producing siderophores, respectively. According to the above growth-promoting characteristics, we evaluated the growth-promoting and nodulation effects of 11 strains on wild soybean. The performance of Sinorhizobium americanus DL3 was superior to that of other strains. Finally, pot experiments were carried out to examine the effects of strain DL3 on the salt tolerance of wild soybean and cultivated soybean. Strain DL3 promoted the growth and lowered the level of proline in leaves, thus alleviating the salt stress of wild soybean and cultivated soybean. [Conclusion] Strain DL3 improves the salt tolerance of plants, which has important theoretical and practical significance for soybean cultivation in saline soil.