Study On The Characteristics Of Fungal Communities And Antibacterial Effects Of Rosa Roxburghii Leaf Spot Disease Plants During Fruiting Perio

Leaf spot disease is a generic term for leaf spot diseases of plants caused by a variety of pathogens,which can cause extensive yield reduction or even crop failure.Plants and microbiomes together form holobiont,often as the basic unit of ecology and evolution.Plant microbiome can promote plant growth by improving nutrient acquisition or producing hormone stimulation,enhance plant stress resistance by inducing plant systemic resistance,or inhibiting the growth of pathogens,which is closely related to the growth and health of host.Traditionally,the study of plant leaf spot disease is mainly focused on the isolation,identification and disease resistance of pathogens,but the study of microbiome which plays an important role in the health of Rosa roxburghii has not been reported.Therefore,based on culturable methods and high-throughput sequencing,this study analyzed the community characteristics and ecological guilds of microbial in the rhizosphere,phyllosphere and root of healthy and diseased R.roxburghii from the Tianfu R.roxburghii Industrial Park in Panzhou city,Guizhou province,and explore the potential source of pathogens by building a occurrence network.Meanwhile,the pathogenic fungi of R.roxburghii leaf spot disease were identified and further screened for broad-spectrum and efficient antagonistic fungi.It aims to elucidate the response of microbiome to plant diseases and improve the biological control of R.roxburghii leaf spot disease from the perspective of microbial ecology,providing biological resources and theoretical basis,which helps to further clarify the soil-plant-microbial interactions and deepen our understanding of holobiont.The results were as follows.(1)There are differences in the composition of fungal communities in different parts of healthy and diseased R.roxburghii.Pestalotiopsis was the dominant genus of cultured phyllosphere epiphytic fungi in both healthy and diseased R.roxburghii,but their relative abundance is different,that is,LDS 32.26% LHS 11.49%.The dominant genera of endophytic fungi were Alternaria,LDE 63.16% and LHE 33.33%,respectively.Penicillium was the dominant genus of epiphytic and endophytic fungi under different health conditions,with the relative abundance of RDS 86.86%,RHS 72.31%,RDE 20.69% and RHE52.17%,respectively.The dominant genus of culturable rhizosphere fungi were also Penicillium,and the relative abundance were RSD 72.45% and RSH 87.34%,respectively.The results of high-throughput sequencing showed that the dominant genera of phyllosphere fungi of healthy and diseased plants was Unspecified＿Pleosporales,with relative abundance of LH 15.91% and LD 14.83%,respectively.Unspecified＿Helotiales was the dominant genera of root fungi,with the relative abundance of RH17.85% and RD 45.47%,respectively.Mortierella(33.34%)was the dominant genus of rhizosphere fungi,accounting for 33.34% in RSD and 32.36% in RSH.In addition,there were differences in core mycobiota between healthy and diseased R.roxburghii.In the co-occurrence network of healthy R.roxburghii,the core mycobiota were Fusarium,Unspecified＿Sordariomycetes,Unspecified＿Nectriaceae and Exophiala.In the co-occurrence network of diseased plants,Unspecified＿Nectriaceae,Unspecified＿Hypocreales,Unspecified＿Ascomycota,Exophiala and Unspecified＿Sordarialeswere the core mycobiota.(2)The ecological guilds differed between healthy and diseased plants according to an FUNGuild analysis.The results of cultured experiments and high-throughput sequencing showed that the proportion of plant pathogens and related groups in different parts of diseased plants was higher than that of healthy plants,and the distribution of plant pathogenic fungi was the most widely distributed in healthy epiphytic fungi LDS.In addition,the high-throughput sequencing results also showed that Lichenized-Undefined Saprotroph were higher in the phyllosphere(LH),root(RH),and rhizosphere(RSH)of the healthy R.roxburghii,exceeding those of the diseased R.roxburghii by 2.34% in the phyllosphere(LD),0.44% in the root(RD),and 1.54% in the rhizosphere(RSD),respectively.(2)In addition,the co-occurrence network and ecological guilds analysis based on the combination of the identification of leaf spot pathogenic fungi and the annotation of potential plant pathogenic fungi showed that the potential leaf spot pathogenic fungi distributed in all parts of R.roxburghii and were mainly from the diseased phyllosphere.(3)α diversity analysis showed that the fungal diversity index of healthy plants was higher than that of diseased plants.Principal coordinate analysis(Principal coordinate analysis,PCo A)and ANOSIM results showed that there were significant differences in fungal communities in phyllosphere and rhizosphere between healthy and diseased samples,but there was no significant difference in root fungal community structure between healthy and diseased samples.Overall,the fungal diversity in different parts of healthy plants was higher than that of diseased plants.(4)Three strains of pathogenic fungi were identified to cause R.roxburghii leaf spot disease,and one antagonistic strain was screened.In this study,3 strains of fungi with pathogenic effects on the leaves of R.roxburghii were screened out by pathogenicity detection,and the leaf lesions showed obvious browning and irregular spots,and the spots spread from the inoculum to the leaf margin and vein.The phylogenetic trees of the three pathogenic fungi were constructed,and the R.roxburghii leaf spot pathogens were identified as Pestalotiopsis microspora,Neofusicoccum parvum and Alternaria alternata,respectively.In addition,in the study,three pathogenic strains were used as indicator fungi,and a strain of Trichoderma Koningiopsis was screened through plate confrontation experiment,which had broad-spectrum antagonistic effect on R.roxburghii leaf spot pathogenic fungi,with inhibition rate of 76%,87% and 91%,respectively,and the antagonism coefficient was Ⅰ-Ⅱ grade.Through further study,it was found that the antagonistic mechanism of Trichoderma Koningiopsis against Pestalotiopsis microspora,Neofusicoccum parvum and Alternaria alternata was to inhibit the growth of plant pathogens through competition and hyperparasitism.