Abstract: Alfalfa is a perennial legume with high forage yield and quality that plays an important role in eco-environment improvement and cropping rotations. However, land salinization seriously inhibits the normal growth and development of alfalfa. Arbuscular mycorrhizal fungi (AMF) and rhizobia (R) are common symbiotic soil microorganisms. They can coexist with legumes such as alfalfa, and form a symbiotic system comprising AMF-alfalfa-R. In this study, we inoculated alfalfa with Glomus mosseae and Sinorhizobium meliloti, and compared the alkali resistance of plants with inoculum combinations. It was found that without alkali stress, the growth of G. mosseae-inoculated plants or R-inoculated plants was higher than that of non-inoculated (NI) ones. Important differences included higher chlorophyll content, relatively longer root length, higher plant height, and increased branch number. With alkali stress treatment, the growth of each group was inhibited in different ways, but the inoculated groups again showed higher alkali tolerance than NI. Compared with NI, the malondialdehyde content and relative conductivity remained at a low level in the NI group. The relative water content of the cells was higher, as were the activities of superoxide dismutase, peroxidase and catalase. Based on these results, single inoculation and mixed inoculation can both improve the osmotic adjustment ability and antioxidant capacity of alfalfa, and reduce damage to the cell membrane, but the results of mixed inoculation is even better.

Key words: AMF, rhizobia, alfalfa, alkali tolerance, Glomus mosseae