Screening and characterization of Paenibacillus polymyxa YB-393, a biocontrol agent against wheat crown rot.

To exploit superior microbial strains for the biocontrol of wheat crown rot, we employed high antagonistic activity and strong colonization ability as dual criteria to screen strains from the culture collection of the Agricultural Microbiology Innovation Center of Henan Province. We comprehensively evaluated the candidate strain for both biocontrol efficacy and plant growth-promoting traits, and subsequently identified it through integrated morphological, molecular biological, and genomic analyses. The results showed that Paenibacillus polymyxa YB-393 exhibited the strongest root colonization capacity among all the tested strains in axenic wheat seedlings. It achieved a population density of 1.83×105 CFU·g-1 fresh root after 48 h, displayed potent antagonistic activity against fungal (e.g., Fusarium pseudograminearum) and oomycete (e.g., Phytophthora capsici) pathogens, and also produced β-1,3-glucanase, siderophores, indole-3-acetic acid, as well as possessed phosphate-solubilizing ability. Compared with the water control, seed soaking with YB-393 increased the total fresh weight of wheat seedlings by 58.8% and provided 80.5% control efficacy against crown rot. Genomic analysis revealed that it encompassed five known antimicrobial biosynthesis gene clusters and thirteen uncharacterized secondary metabolite biosynthetic gene clusters, thereby offering promising targets for the discovery of novel biocontrol agents. In summary, Paenibacillus polymyxa YB-393 integrates robust biocontrol activity with plant growth-promoting properties, positioning it as a promising candidate for developing biocontrol agents against wheat crown rot.