An endophytic bacterium with biocontrol activity against important wheat pathogens

Fusarium graminearum and Xanthomonas translucens are the causal agents of important diseases in wheat plants worldwide. Seeds carry beneficial microbes known as endophytes that could increase plant growth and have biocontrol activity against pathogens. Therefore, using endophytes could be useful for plant production and they are good alternatives for hazardous synthetic fertilizers or pesticides. In this study, 10 endophytic bacteria were isolated from eight cultivars of wheat surface-sterilized seeds. One isolate based on the result of dual culture assay and its biocontrol activity against mentioned plant pathogens was selected for further evaluation. The isolate was identified as Bacillus subtilis CB2 according to the 16S rRNA and gyrB gene sequencing. Microscopic analysis showed alterations in the fungal hyphal structures. The B. subtilis CB2 could produce protease, amylase, pectinase, cellulase, IAA, ammonia, catalase, and ACC deaminase and could solubilize phosphate. Nevertheless, lipase and chitinase were not produced by the isolate. Spore germination and DON production were reduced when the fungus grew on wheat seeds treated with the B. subtilis CB2. Reduction in percentages of Fusarium head blight infection, Fusarium crown rot severity, and protection rate against bacterial leaf streak were 80.33%, 78.19%, and 64.23%, respectively. Greenhouse trials revealed that the biomass and 1000-grain weight of the treated plants with the Bacillus subtilis CB2 were increased. The crude lipopeptide extract of the isolate inhibited growth of both plant pathogens. LC-MS analyzes showed that the B. subtilis CB2 could produce surfactins and iturins, which are known as antibacterial and antifungal lipopeptides. This is the first report that revealed activity of the seed endophytic B. subtilis in biocontrol of the X. translucens and F. graminearum (crown rot). Formulation of this beneficial bacterium and its application in the field conditions could be an environmentally safe strategy for management of plant diseases.