Mechanism Of Trichoderma Viride On Alleviating Continuous Cropping Obstacle In Muskmelon

Muskmelon is a kind of fruit widely planted in the world,and the planting area in China is very large.However,with the increase of planting years,the continuous cropping obstacle of melon gradually appeared.Melon Fusarium wilt is one of the important factors affecting continuous cropping of melon.Trichoderma viride T23 is a biocontrol strain isolated and preserved by the plant immunity Department of Shenyang Agricultural University.It has good effect on alleviating continuous cropping obstacle of melon.In this paper,the effects of T23 on pathogenic Fusarium,melon autotoxic substances,soil environmental substances,soil microbial community structure and melon plants were studied1.Trichoderma viride T23 can effectively reduce the occurrence of melon wilt disease,and the control effect of melon wilt disease can reach 70.32%.After the application of Trichoderma,which could affect the composition of melon root tissue,19 compounds including L-tryptophan,citric acid and itaconic acid in melon root tissue were significantly increased and 33 compounds including benzoic acid,phenylacetic acid and salicylic acid.The decrease of the content of self-toxic substances such as benzoic acid and salicylic acid can effectively alleviate its self-toxic effect on melon plants and reduce the harm to continuous melon.Among the metabolic pathway enrichment,54 metabolic pathways were enriched,among which 22 metabolic pathways were significantly enriched,mainly aminoacyl t RNA biosynthesis,valine,leucine and isoleucine biosynthesis,glucosinolate biosynthesis and arginine and proline metabolism.Most of these metabolic pathways are related to the growth and development of melon and the defense against the invasion of pathogenic bacteria,indicating that after the application of Trichoderma,the metabolic vitality of melon plants can be improved and the related metabolic pathways can be more active.2.After the application of Trichoderma viride T23,it can effectively change the composition of the microbial community structure.In the fungal community,the relative abundance of Penicillium,Trichoderma,bottle,Estaria,thermophilic and mycorrhizae in the Trichoderma treatment group was significantly increased;in the bacterial community,Bacteroidetes,Actinobacteria,Firmicutes and Budomonas were significantly increased.There are more plant probiotics,such as Actinomyces,Bacillus,and Trichoderma.The increase in the relative content of these species can effectively affect the group composition of microorganisms,make the soil microbiological environment more balanced,and avoid the excessive accumulation of a single species.T23 can seize the dominant niche to inhibit the expansion of F.oxysporum,which inhibited 74.40% in limited space.3.The results of the physiochemical properties of the soil show that the Trichoderma viride T23 can effectively improve the soil p H value and improve the soil acidification.The use of Trichoderma can also have an impact on soil metabolites.A total of 48 kinds of soil differential metabolites were identified,mainly including 3-hydroxybenzoic acid,palmitic acid and vegetarian acid.Several active substances are present in these differential metabolites,and 3-oxybenzoic acid and tin can inhibit the growth of the pathogen Fusarium.Among the enriched metabolic pathways,arginine and proline in arginine and proline metabolic pathways are important amino acids in plants,arginine has the functions of immune regulation,hormone secretion and nitrogen storage,proline contributes to plant growth,and can maintain the osmotic balance of plant body and prevent water loss.The pyrimidine metabolic pathway is involved in the formation of pyrimidines,and also in the synthesis of nucleic acids,lipids and sugars,which is closely related to the occurrence of diseases.4.Trichoderma viride T23 can effectively degrade a variety of melon self-toxic substances.With the concentration of solution of 50 mg/L,T23 degraded caffeic acid,cassia bark acid,hydroxybenzoic acid,salicylic acid,benzoic acid and vanillin by over 90%,among which the best degradation effect was cassia bark acid by 99.87%,ferulic acid,2,5-dihydroxybenzoic acid,gallic acid,between 20% and 80%,less than 10%,and the degradation rate of gerillic acid was only 3.58%.Using high degradation rate of several autotoxic substances of Fusarium oxysporum and melon seeds and seedlings,found that cassia bark acid degradation has certain inhibition of pathogen Fusarium,salicylic acid and benzoic acid degradation to promote the melon seed germination and seedling growth,the rest of the degradation of Fusarium and melon seeds and seedlings,did not show obvious inhibition or promotion.