Isolation and identification of endophytic fungi of Vicia villosa var. and their biocontrol against banana wilt and growth promotion potentials

【Objective】The purpose of the study was to screen endophytic fungi with biocontrol and growth promotion potentials against banana wilt, and to provide reference basis and potential strains for the biological control of banana wilt. 【Method】Using Fusarium oxysporum f. sp. cubense tropical race 4(Foc TR4) as the target fungus and endophytic fungi isolated and purified from the roots of Vicia villosa var. as the test strains, the plate standoff method was used to evaluate the plate inhibitory effect of the endophytic fungi on Foc TR4. Combining morphology and molecular biology to determine the taxonomic status of the antagonist fungi, the effects of the antagonist fungi on the morphology of Foc TR4mycelium were observed by scanning electron microscopy. The ability of the antagonist fungi to detoxify inorganic phosphorus, fix nitrogen and produce iron carriers was detected by plate phosphorus solubilizing circle method, plate nitrogen fixing circle method and CAS plate method. The biocontrol effect on banana wilt and growth promotion effects of the antagonist fungi on banana were verified by poted test. 【Result】Eight strains of antagonistic fungi were isolated and purified from the roots of V. villosa var., among which strains 201, 204 and 401 had the best inhibitory effect, and were identified by morphology and molecular biology as Chaetomium cochliodes, Penicillium simplicissimum, and Talaromyces oumaeannae. Plate confrontation showed that strain 201 showed the highest in vitro inhibition on Foc TR4 at 74.39%, followed by strain 401 at 71.00% and strain 204 at 69.83%. Scanning electron microscopy results showed that all three strains of antagonistic fungi were able to inhibit mycelial growth of Foc TR4 and lead to mycelial deformity, cross-linking and deformation, as well as increase in spore number aggregation, obvious swelling of mycelium, shortening of internodes, increase in branching, roughness of mycelium, expansion of tips, vesicularity and breakage. Strains 204 and 401 also possessed a certain potential to promote the growth of mycelium on the functional plate, with the capacity of solubilizing inorganic phosphorus, nitrogen fixation and iron carrier production. The potted results showed that all the three antagonistic fungal strains 201, 204 and 401 had strong inhibitory activity against Foc TR4 and showed good control effects against banana wilt with 90.625%, 65.623% and 96.876% on bulbs and 90.745%, 90.743% and 90.750% on leaves, respectively.Meanwhile, all the three strains of the antagonistic fungi were able to reduce the inhibitory effect of Foc TR4 on the growth of banana within a certain range, thus promoting the growth of banana plants. 【Conclusion】The three strains of antagonistic fungi 201, 204 and 401 isolated from the roots of V. villosa var. have good antagonistic effects on banana wilt, can inhibit the virulence of banana wilt and promote the growth of banana plants, and have good potentials of biocontrol and growth promotion.