Inhibition Mechanism And Application Of FHB By A Pseudomonas W55

Fusarium head blight(FHB),caused by FHB species complex with Fusarium graminearum as the dominant species,is a major fungal disease that harms wheat yield and quality in China.This disease not only reduces wheat yield,but also produces DON toxin during infection,which accumulates in diseased grains and wheat products,is harmful to human and animal health.Due to the lack of resistant varieties,chemical pesticides have always been the most common way to control FHB.However,longterm use of chemical pesticides alone also leads a series of problems such as resistance of pathogens.As an effective supplement to chemical pesticides,biological control gained more attention in recent years.To reveal the interaction mechanism between microorganisms and search for new beneficial microbes will provide a new strategy for controlling the occurrence of FHB.When inoculated in the field,there were healthy spikelets on diseased wheat occasionally.The spikelets are green compared to the blighted and white ones around them,so they are called “green spikelets”.We speculated that there might be endophytic bacteria in “green spikelets”,which could reduce the occurrence of FHB by inhibiting the growth and infection of pathogens.Based on this hypothesis,the endophytic bacteria in “green spikelets” were analyzed by microbiome sequencing.Compared with the diseased spikelets,the bacteria were significantly enriched in Pseudomonadaceae,Xanthomonadales and Enterobacteriales.An endophytic strain W55,which can effectively inhibit FHB,was screened by coleoptile infection,and identified as Pseudomonas sp.by 16 S sequencing.The metabolites of W55 were found that did not inhibit the diseases,which was different from the common biocontrol bacteria.The further results showed that W55 affected the extension of infected mycelia in wheat cob.RNA-seq analysis showed that W55 changed the expression of genes specifically expressed in the infection stage,this may be an important reason for the reduction of F.graminearum virulence.In order to explore the main mechanism,we sequenced and assembled the whole genome of W55,and knocked out the secretion system type 6(T6SS)and secretion system type 3(T3SS)respectively.The results showed that the two mutants could not effectively inhibit the infection.These results suggest that these two secretion systems may play a key role in inhibiting the infection of F.graminearum.In order to identify functional proteins secreted by these two secretion systems,the secreted protein gene HCP of T6 SS was knocked out,but no mutants were obtained.The candidate secreted proteins will be further knocked out and explored their functions.This study is expected to lay a foundation for elucidating the interaction mechanism of W55-F.graminearum and wheat,and provide new resources and new ideas for the prevention and control of FHB.