Identification And Mechanism Of Antifungal Substances In Maize Root Exudates Against Fusarium Spp.

Root exudates are organic substances released by plant roots into the rhizosphere environment,which can induce interaction between plants and rhizosphere microbiota.When plants are subjected to specific environmental stresses,they usually change the content and composition of their root exudates to resist external invasions,and some substances in root exudates are closely related to plant disease resistance.As a native fax disease,corn stem rot seriously threatens maize production,and the fungal pathogen that causes the disease is mainly Fusarium spp.,so the search for effective bacteriostatic substances can provide potential new substances for the control of maize diseases.In the early stage of the study,LC-MS combined technology and non-targeted metabolomics were used to analyze the root exudates of Fusarium spp.infested maize and uninfected maize root exudates.In this project,the bacteriostatic activities of the above differential components were further analyzed,and the substances with antifungal effect were identified by the mycelial growth rate measurement.Subsequently,the effects of root exudate components on Fusarium spp.conidia and their hyphae and spore reactive oxygen species,cell activity,cell morphology and pathogenicity were further elucidated to further elucidate the antifungal mechanism of root exudate components on Fusarium spp..The main findings are:1.The differential metabolic components were screened by the hyphal growth rate determination method,and four components with bacteriostatic activity were identified;Then,in order to further understand the antifungal effect of the four components,a concentration gradient was set to calculate the growth rate of mycelium under the treatment of different components.The results showed that Niflunic acid could significantly inhibit the growth of hyphae compared with other bacteriostatic components,and its bacteriostatic ability was the strongest,and it also had a strong inhibitory effect at a low concentration of 50 μg/mL,with an inhibition rate of 38%.2.Through the spore yield and spore germination experiments,it was confirmed that the four components could inhibit the formation of Fusarium spp.spores,among which Niflunic acid had the best inhibition effect,and 50 μg/mL Niflunic acid treatment could still significantly inhibit Fusarium spp.spore production,with an inhibition rate of up to71%.In addition,4-methyl-3-nitrobenzoic acid and vanillin acetate can delay the germination of spores,while niflunic acid can inhibit the germination of spores,with an inhibition rate of 23%.3.The reactive oxygen fluorescent probe was used to detect the accumulation of reactive oxygen species in Fusarium spp.acetate,and it was found that the hyphae treated with vanillin acetate accumulated a large amount of reactive oxygen species;The spores treated with niflunic acid and 4-methyl-3-nitrobenzoic acid accumulated a large amount of reactive oxygen species.4.The cell activity was investigated by FDA and PI double staining.The results showed that the mycelia and conidia treated with nifluronic acid and4-methyl-3-nitrobenzoic acid produced red light,indicating that these two substances caused cell death of Fusarium spp.mycelia and spores.5.By observing the morphological changes of Fusarium mycelia and spores after treatment,it was found that 4-methyl-3-nitrobenzoic acid could cause spores to shrink and mycelia to produce holes.Nifluronic acid can cause spore to shrink or even rupture,and the surface of mycelium appears dense fold.Vanillin acetate can cause spore swelling and even rupture,making mycelium thin and wide.Then,the influence of component treatment on the relative conductivity of Fusarium spp.solution was further studied to explore the influence of components on the permeability of cell membrane of Fusarium spp.solution.The experimental results showed that the relative conductivity of Fusarium spp.solution did not change much after the component treatment.6.The pathogenicity of Fusarium spp.was determined by pot experiment in the laboratory.It was found that the four components of 50 μg/mL and 100 μg/mL could significantly inhibit the elongation of the disease spot.Vanillin acetate and nifulinic acid had the shortest disease spot length compared with the control group and other components,and had significant differences with other components.These results indicated that these two components had the greatest influence on Fusarium spp.pathogenicity.