Screening Of Trichoderma For Biocontrol Of Sunflower Sclerotinia Sclerotiorum And Study Of Its Disease Control Mechanis

The experiment was conducted from May to August 2021 in the modern greenhouse of Trichoderma Research Group,Institute of Plant Protection,Chinese Academy of Agricultural Sciences.The sunflower variety Fengkuza 1 was used as test material,and five isolates of Sclerotinia sclerotiorum（Lib.）de were screened by plate confrontation culture Bary)had better antagonistic effect against Trichoderma strains,and its control effect was verified by in vitro leaf method.Potted plants were used to set different experimental treatments,i.e.CK1（Sunflower sclerotinia sclerotii was used for root irrigation alone without Trichoderma suspensions）CK2（the root was irrigated with sterile water alone without the application of sunflower sclerotinia sclerotiformis and Trichoderma trichoderma suspension）T1（100 m L of Trichoderma suspensions were mixed with soil 5 days before sowing+100m L of Trichoderma suspensions were irrigated with roots 2 days before inoculation with sclerotinia sclerotii）T2(5 days before sowing with 200m L pin^-1Trichoderma suspensions mixed with soil)T3(200 m L pin^-1Trichoderma suspensions were used for root irrigation 2d before inoculation with sclerotinia sclerotii),and the morphological indicators of sunflower seedlings,substance accumulation indicators and physiological indicators were determined Through transcriptome and metabolomics analysis,the physiological effect of Trichoderma on the growth and development of sunflower was studied,and the prevention mechanism of Trichoderma on sunflower sclerotinia sclerotinia was determined,providing technical support for the future research and development and promotion of Trichoderma agent.The test results are as follows:1.Five Trichoderma strains with good antagonistic effect against Sunflower sclerotinia were screened by plate confrontation culture method,which were 838,573,752,940,respectively 758,the control efficiency of 5 Trichoderma against Sclerotinia was all 82.13%by in vitro method.The antagonistic bacterium 838 was preliminarily identified as T.afroharzianum,and the antagonistic bacterium 573,940,758 was preliminarily identified as T.asperellum,antagonistic bacterium 752 was preliminarily identified as T.harzianum.2.All the 5 strains screened out could inhibit the growth of sclerotia formation and sclerotia germination,and reduce the virulence and oxalic acid content of T.harzianum 838 had the best effect on the growth of sclerotia,sclerotia formation and sclerotia germination,and the inhibition rates of the virulence and oxalic acid content of SCLerotia were 100.00%,92.50%,17.50%,92.58%,92.09%respectively.3.At 35 d after inoculation,T.afroharzianum 838 had the best effect on T1 treatment.Under T1 treatment,sunflower seedlings were tall and stem thick The whole plant fresh weight and root shoot ratio were 58.82%higher than those of CK1,respectively.Soluble sugar soluble protein proline and chlorophyll content increased by 179.91%132.10%98.68%129.27%compared with CK1,MDA content membrane permeability decreased by 49.44%61.43%compared with CK1,respectively.The content of peroxidase,catalase,superoxide dismutase,phenylalanine ammonia lyase,ascorbate,peroxidase and polyphenol oxidase increased by64.35%35.62%40.20%50.02%43.39%30.89%,respectively.4.The three different application methods of T.afroharzianum 838 showed significant indigenous inhibitory effects on sunflower sclerotinia in pot experiments.Among them,T1treatment had the best control effect,reaching 98.58%.5.Transcriptome analysis was performed on the leaves of T.afroharzianum 838 and sunflower treated with Sclerotinia sclerotiorum.The results showed that T.afroharzianum 838competed with Sclerotinia sclerotiorum for nutrients and energy,regulated the down-regulation of plant photosynthesis-related pathways,and reduced the nutrients and energy obtained by Sclerotinia sclerotiorum in host plants.Through the signal transduction mechanism,genes regulate the expression of disease resistance-related proteins,enzymes and transcription factors,and down-regulate the expression of genes related to ribosome,amino acid and protein synthesis to reduce the survival rate of Sclerotinia sclerotiorum.At the same time,regulation of resistance-related metabolic pathways up-regulated expression to resist the invasion of Sclerotinia sclerotiorum and plant self-healing stability.6.Metabonomics analysis was performed on the leaves of T.afroharzianum 838 and sunflower treated with Sclerotinia sclerotiorum.The results showed that T.afroharzianum 838could inhibit some substances promoting Sclerotinia sclerotiorum parasitism in plants and produce stress-related substances by affecting the metabolic pathways such as TCA cycle,oxidative phosphorylation and amino acid metabolism of Sclerotinia sclerotiorum,so as to inhibit Sclerotinia sclerotiorum.To sum up,T.afroharzianum 838 treated susceptible plants,down regulated the expression by regulating the metabolic pathway of photosynthesis,and reduced the uptake of nutrients and energy by Sclerotinia sclerotiorum to host plants.The signal transduction mechanism is used to regulate the expression of disease resistance related proteins,enzymes and transcription factors,so as to down regulate the gene expression related to the synthesis of ribosomes,amino acids and proteins,so as to reduce the survival rate of Sclerotinia sclerotiorum.At the same time,Trichoderma regulates the down-regulated expression of metabolic pathways related to disease resistance to resist the invasion of Sclerotinia sclerotiorum.