Study Of Trichoderma Asperellum Against Cucumber Fusarium Wilt On Soil Microecosystem

Trichoderma is a kind of filamentous fungi widely used in biological control of plant diseases.Fusarium oxysporum f.sp.cucumerinum Owen(FOC)is the most common and serious soil borne fungal disease in cucumber cultivation.A Trichoderma asperellum(TA5)strain with good control effect against cucumber Fusarium wilt was screened in our previous studies.In order to further study the mechanism of TA5 on disease prevention and growth promotion,the effects of interaction between TA5 and FOC on enzyme activities,microbial communities of cucumber rhizosphere soils and root metabolites of cucumber were studied by pot experiment,so as to clarify the effects of interaction among cucumber root,TA5 and FOC on soil microecology.It has a guiding significance to analyze the disease prevention mechanism of chlamydospores of Trichoderma,ensure the safe production of cucumber,and provide guidance for exploring the use of biocontrol bacteria to control plant soil borne diseases.The main results are as follows:1.The Colonization dynamics of conidia,chlamydospores of T.asperellum(TA5)in natural soil with different humidity were determined.The results showed that the colony forming unit(CFU)detection rate of conidia and chlamydospores in soil was positively correlated with soil water addition,and the correlation coefficient(R~2)was conidia(0.9704)>chlamydospores(0.8585).The survival ability of chlamydospores in soils with different water additions was significantly higher than that of conidia.The CFU of chlamydospores,conidia were 84.9%,9.7%respectively after 15 months in soil with 20%water addition,indicating that chlamydospores survived longer in natural soil and had strong tolerance to soil environment.2.The activities of sucrase,catalase,cellulase and phosphatase in cucumber rhizosphere soils were measured after application of T.asperellum TA5 and FOC.The results showed that the above enzyme activities in cucumber rhizosphere soils increased along with the growth of cucumber.Treatment with TA5 and FOC respectively could rapidly increase the above enzyme activities,and simultaneous application of TA5 and FOC could further improve the enzyme activities,which indicated that the application of exogenous fungi could improve the material transformation abilities,fertilities and biological activities of cucumber rhizosphere soils,which was conducive to the nutrient absorption of plants.The abundance of carbohydrate active enzyme genes in cucumber rhizosphere soil treated with TA5 and/or FOC was higher than those of control according to the metagenome sequencing,which verified that application of exogenous fungi was beneficial to the transformation and absorption of soil nutrients.However,the effects of a large number of pathogenic fungi on the absorption of soil nutrients of plants need to be further studied.3.The effects of T.asperellum TA5 and FOC on cucumber rhizosphere soil microbial communities were detected by metagenome sequencing.The results showed that T.asperellum TA5 increased the abundance of Sphingomonas,Arenimonas and Povalibacter,but decreased the abundance of Pseudoribacter and Niatella.FOC increased the abundance of Methylbium,Methyliversitilis and Pandoraea.Simultaneous application of T.asperellum TA5 and FOC could improve the abundance of Pseudomonas sp.AOB-7,Actinobacteria Bacteria,Acidimicrobia bacterium.The effects of the above groups on plant growth and disease resistance need to be further studied.4.Metabonomics analysis showed that T.asperellum TA5 can stimulate energy metabolism pathway,and regulated the resistance factors of cucumber roots,and the interaction of T.asperellum TA5 and FOC had significant effects on starch and sucrose metabolism pathway andα-linolenic acid pathway of cucumber roots.