LAUSR

AIMS Potato late blight, caused by the Phytophthora infestans, is one of the most devastating diseases impacting potato yield. This study investigates the potential role and mechanism of Paenibacillus polymyxa YF and Bacillus amyloliquefaciens HT as biocontrol agents against potato late blight. METHODS AND RESULTS In vitro antagonism assays showed both strains effectively inhibited mycelial growth of P. infestans. In sporangia germination tests, either strain reduced germination by over 80% at 50% concentration. Enzymatic and biochemical assays revealed they secreted multiple extracellular enzymes and produced siderophores and IAA-like compounds. Strain YF exhibited significantly stronger inhibition and robust potato root/stem colonization in preliminary screens, so it was selected for subsequent in planta studies. In excised tissue and potted plant experiments, strain YF-treated groups had significantly lower disease severity indices and higher biomass than controls. Biochemical assays also showed YF inoculation significantly increased the activity of four resistance enzymes compared to controls. CONCLUSIONS Overall, this study's findings provide a theoretical foundation for leveraging strain YF and strain HT as potential biocontrol agents, with strain YF showing particularly high promise due to its efficacy in disease suppression and bolstering plant growth and resistance mechanisms.