Effect And Mechanism Of Pythium Oligandrum On Inhibiting Fusarium Graminearum Infection And Promoting Wheat Growth

Pythium oligandrum is an important microbial resource and has been successfully used due to its characteristic of broad spectrum antifungal activity,inducing the plant systemic resistance,plant growth promotion and increasing the yield.It is of practical significance to make full use of the multifunctional biocontrol agent and improve its industrial application potential for the construction of low-carbon green agricultural efficient production mode.In this study,the phytopathogen Fusarium graminearum and its infected host(wheat)were used to systematically study for disease control and growth promotion effects.We also analyzed the biological regulation mechanism of P.oligandrum on soil microbial community.Meanwhile,the sporulation induction and microbial agent development were conducted to overcome the technical obstacles,such as low sporulation and narrow application scenarios in practical application.The main results are as follows:(1)The hyperparasitism of P.oligandrum on F.graminearum was investigated by plate confrontation and viability tests.In vitro antagonism test showed that P.oligandrum can effectively inhibit the mycelia growth,reduce the viability and expression levels associated with DON synthesis,delay the conidia germination and germ tube extension.In vivo assay with wheat seedlings and cherry tomatoes inoculated with conidia suspension showed that,spraying oospore suspension of P.oligandrum significantly reduced the disease incidence and lesion length.The activities of resistance-related enzymes catalase(CAT)and peroxidase(POD)were induced increase.The enzyme related genes,defense related genes CPL1,DWR1,Lap A1,ERF2,Pin2 and disease course related genes PR1 and PR5 were induced up-regulation.(2)P.oligandrum can secrete and produce indole-3-acetic acid(IAA),which can significantly increase wheat substance accumulation,chlorophyll content and root activity,and induce the increase of endogenesis IAA content.Based on the analysis of wheat rhizosphere soil microbial community by high-throughput sequencing technology,we found that P.oligandrum could regulate wheat rhizosphere microbial community structure and significantly reduce the relative abundance of Gibberella,Neocosmospora,Microdochium and other pathogens in soil,and improve the probiotics content such as Skermanella,Pseudarthrobacter and Defluviicoccus.(3)In order to further improve the spore-producing efficiency of P.oligandrum,the inducer composition of spore-producing agent was screened by orthogonal test on the basis of sporulation yield,including 30 mg/L sodium molybdate,150 mg/L ammonium sulfate and 1000 mg/L sodium ferric EDTA in V8 medium.After culture at 20°C for 5 days,the sporulation yield reached 7.04×10~5spores/m L,which was more than 3 times higher than that under normal culture condition.Furthermore,the microbial agent was prepared by biochar loaded with P.oligandrum oospores.The survival rate of oligandrum oospores was 76.44%and 91.48%,respectively,after stored at 25°C and 10°C for 60 d.The treatment of microbial agent could significantly improve the growth of wheat at seedling stage and in the field.The total fresh weight,total dry weight,total chlorophyll content and root activity of wheat at seedling stage were increased by 17.77%,45.00%,33.58%and 141.51%,respectively,which were higher than those treated by biochar or P.oligandrum alone.The aboveground fresh weight,dry weight and heading number of wheat were increased by 35.76%,34.97%and 18.66%,respectively,which were significantly higher than those treated by biochar alone.These findings could be useful in the development of biopesticide for P.oligandrum.