Synergistic Interactions Between Salt-tolerant Rhizobia and Arbuscular Mycorrhizal Fungi on Salinity Tolerance of Sesbania cannabina Plants

Legumes can host rhizobia and mycorrhizal fungi, and this triple symbiosis might be exploited to improve saline soil fertility. Therefore, a greater understanding of the interaction of rhizobia and arbuscular mycorrhizal fungus during legume growth in saline soil is required. We investigated the efficiency of salt tolerance conferred by rhizobia in mycorrhizal Sesbania cannabina. Greenhouse experiments were conducted in which S. cannabina plants inoculated with Glomus mosseae BGC NM03D (GM), and two rhizobia strains Agrobacterium pusense YIC4105 (4105) and Neorhizobium huautlense YIC4083 (4083), were exposed to 100 and 200 mM NaCl. Under 200 mM NaCl stress, plants inoculated with 4105, rather than 4083, showed significant increases in shoot and root dry mass compared with non-inoculated plants. Simultaneously, a significant increase over GM-inoculated plants in mycorrhizal colonization and dependency was recorded for 4105 + GM-inoculated plants compared with 4083 + GM-inoculated plants. In addition, under NaCl stress, significant increases in the number and mass of nodules, nitrogenase activity, and leghemoglobin content of nodules occurred in 4105 + GM-inoculated plants compared with 4083 + GM-inoculated plants. Furthermore, the activities of antioxidant enzymes in rhizobia-inoculated plants were significantly higher in the GM + 4105 group than the 4083 + GM group. The malondialdehyde content of plants from the 4105 + GM group was significantly lower than in the 4083 + GM group. Thus, the results revealed a synergistic relationship among the 4105 and GM in alleviating salt stress in S. cannabina. Salt-tolerant rhizobia might improve the salinity tolerance of S. cannabina by enhancing the antioxidant system