Control Effects And Mechanism Of AM Fungus And Trichoderma On Two Leaf Spot Diseases Of Vicia Villosa

Leaf spot diseases caused by Stemphylium vesicarium and Alternaria alternata are important diseases affecting smooth vetch（Vicia villosa）,and there is a lack of effective control techniques for these diseases at present.Arbuscular mycorrhizal（AM）fungi are the most widespread fungi that form symbioses with plants in nature,and they can improve the absorption of water and nutrients by plants,promote plant growth,and enhance disease resistance of plants.Trichoderma is mainly distributed in plant rhizosphere soil,especially near the root surface and outermost root cells of plants,and it is an important biocontrol agent for many crop diseases.In view of the role of AM fungi and Trichoderma in the control of plant diseases,this study used V.villosa as plant material to explore the physiological and RNA-Seq mechanisms of the effects of AM fungi and Trichoderma on two leaf spot diseases of smooth vetch through greenhouse experiments.The main results were as follows:（1）Sieverdingia tortuosa and T.longibrachiatum can promote root growth and nutrient uptake of V.villosa.Single inoculation with S.vesicarium and T.longibrachiatum and mixed inoculation increased the root biomass of V.villosa by28.79%,28.47% and 88.38%（P < 0.05）.Inoculation with S.tortuosa and T.longibrachiatum significantly increased the N content in the stems and leaves of V.villosa by 87.09%（P<0.05）.Trichoderma longibrachiatum increased soil neutral phosphatase activity by 15.9%（P < 0.05）.Inoculation with S.tortuosa and T.longibrachiatum significantly increased the N content in the leaves and stems of V.villosa by 5% and 3%,respectively（P < 0.05）.Sieverdingia tortuosa increased the P content in the roots of V.villosa by 42.12%（P<0.05）.Simultaneous inoculation with S.tortuosa and T.longibrachiatum had superior effects,as the root P content of V.villosa inoculated with both species was 45.59% higher than that inoculated with S.tortuosa alone.AM fungi increased the total K content in the stems and leaves of V.villosa by9.15%,and under inoculation with T.longibrachiatum,the K content in the roots of V.villosa was 1.41 times higher than that of the control treatment（P<0.05）.Trichoderma longibrachiatum increased the soil neutral phosphatase activity by 15.9% compared with the control（P < 0.05）.（2）The shoot biomass of V.villosa infected with S.vesicarium and A.alternata significantly decreased by 24.56% and 14.79%,respectively（P < 0.05）.The net photosynthetic rate of V.villosa decreased by 27.75–38.78% after A.alternata infection.AM fungus S.vesicarium and T.longibrachiatum effectively reduced the incidence of S.vesicarium and A.alternata leaf spot by 14.72–33.38% and 26.86–40.14%,respectively.Single inoculation with S.vesicarium and T.longibrachiatum and mixed inoculation with both species increased the net photosynthetic rate of V.villosa infected with S.vesicarium by 49.03%,47.54%,and 87.66%（P<0.05）,respectively,and decreased the malondialdehyde content of V.villosa infected with S.vesicarium by27.43%,24.25%,and 45.92%（P < 0.05）,respectively.（3）The hormone content and enzymatic activity of V.villosa were regulated by S.tortuosa and T.longibrachiatum in response to infection by S.vesicarium and A.alternata.Inoculation with S.tortuosa or T.longibrachiatum alone increased the chitinase activity of healthy plants by 9.45% and 8.35%,respectively（P<0.05）.Inoculation with T.longibrachiatum significantly increased the SA content of V.villosa infected with S.vesicarium by 15.64%.Sieverdingia tortuosa and mixed inoculation with S.tortuosa and T.longibrachiatum increased the phenylalanine ammonia lyase activity in S.vesicarium-infected plants by 44.07% and 69.29%,respectively（P < 0.05）.Inoculation with S.tortuosa or T.longibrachiatum alone or simultaneously each significantly increased the SA content of V.villosa infected with A.alternata by 20.48%,16.7%,and 28.99%（P<0.05）,respectively,and significantly increased PAL activity by105.15%,52.66%,and 90.86%（P<0.05）.（4）RNA-Seq suggested there are similar mechanisms of the V.villosa response to infection with S.vesicarium and A.alternata.Differentially expressed genes of V.villosa were enriched for Gene Ontology（GO）terms such as nitric oxide biosynthesis process,cell wall biogenesis,and cell wall organization after infection by S.vesicarium and A.alternata.Expression of genes in the Kyoto Encyclopedia of Genes and Genomes pathway of photosynthesis was decreased in the plants inoculated with S.tortuosa or T.longibrachiatum as well.Differential expression of genes with GO terms such as phenylpropane biosynthesis process,negative regulation of translation in response to stress,regulation of response to reactive oxygen species,defense response to other organisms,response to biological stimuli,and defense response was significantly enriched in the plants inoculated with S.tortuosa and T.longibrachiatum in response to infection by S.vesicarium and A.alternata.