Polysaccharides PFP1‐1 Activate Root “Recruitment Signals”: Beneficial Bacteria‐Mediated Rhizoctonia Resistance in Cotton

Cotton damping-off caused by Rhizoctonia solani is the main limiting factor in cotton production, and it is very important to develop effective biological control methods. However, the mechanism by which biostimulants enhance crop disease resistance by recruiting beneficial rhizosphere microorganisms is unclear. Here, we found that after root irrigation of cotton seedlings with PFP1-1, the root soil microbial community structure changed significantly, and the species richness of bacteria and fungi improved. LEfSe analysis confirmed that PFP1-1 could effectively recruit beneficial Bacillus, which was verified by isolation experiments. On this basis, a synthetic microbial community SCII containing the main target Bacillus recruited by PFP1-1 was constructed and configured according to its abundance ratio. Synergistic disease resistance analysis showed that SCII significantly increased the expression levels of resistance genes induced by the jasmonic acid pathway, thereby enhancing the disease resistance of cotton. In addition, chemotaxis experiments confirmed that the PFP1-1 polysaccharide itself and its induced cotton root exudates (such as DL-malic acid and Rosmarinic acid) exhibited significant chemotaxis toward the target Bacillus, indicating the mechanism by which PFP1-1 recruits beneficial bacteria. This study elucidates the protective effect and mechanism of polysaccharide PFP1-1 in cotton, focusing on its ability to recruit beneficial bacteria to enhance crop disease resistance.