Abstract: In this research, a pot experiment was conducted to test the effects of Funnelliformis mosseae, an arbuscular mycorrhizal (AM) fungus and the rhizobium species Sinorhizobium medicae on the wilt and root rot disease of alfalfa (Medicago sativa) caused by Fusarium oxysporum, to evaluate the biocontrol potential of the two symbiotic microorganisms. The experiment design was a 23 factorial with 8 treatments, involving alfalfa plants with or without inoculation with AM, rhizobium, and the Fusarium pathogen. AM fungi reduced the incidence of wilting and root rot in alfalfa by 80.13% (P<0.05). The interaction of AM fungi and rhizobia promoted the absorption of N and P and the synthesis of chlorophyll in the alfalfa plants. The chlorophyll content (SPAD value), shoot N content, shoot P content and shoot dry weight of AM+rhizobium treatments were, respectively, 61.85%, 26.5 fold, 54.3 fold and 23.4 fold higher than those of the control treatment (P<0.01). AM fungi promoted the formation of alfalfa root nodules, the number of which was on average 111.73% higher than in the control plants. The interaction of AM fungi and rhizobia reduced disease incidence of alfalfa, and significantly improved alfalfa root biochemical indicators. Compared with the control plants, the superoxide dismutase activity, β-1, 3-glucanase activity, the concentration of jasmonic acid and of lignin in alfalfa roots were increased, respectively, by 41.05%, 33.9%, 23.32% and 16.92% (P<0.05), while the concentrations of ABA, NO, H₂O₂ and malondialdehyde were reduced, respectively, by 26.68%, 9.63%, 25.26%, and 24.57%. In conclusion, the synergistic of F. mosseae and S. medicae can effectively reduce the occurrence of wilt and root rot disease caused by F. oxysporum in alfalfa. The two microorganisms have potential to be used as biocontrol agents to reduce alfalfa Fusarium wilt and root rot disease.

Key words: Funnelliformis mosseae, Fusarium oxysporum, alfalfa disease, nutrition, plant hormone, biological control