Soil Biochemical Priming by a Bacillus – Pseudomonas Consortium Underpins Synergistic Suppression of Phytophthora infestans and Enhances Potato Resistance to Late Blight
Abstract
Potato late blight, caused by Phytophthora infestans , remains the most economically destructive disease of potato worldwide, yet the durability of chemical control is increasingly eroded by fungicide resistance and regulatory restriction. This study demonstrates that a rationally designed Bacillus – Pseudomonas consortium (BDR) suppresses P. infestans through complementary direct and indirect biological activities. The combined cell‐free supernatant of Bacillus amyloliquefaciens BaC21 and Pseudomonas sp. DS17R yielded a fractional inhibitory concentration index of 0.484, indicating formal synergy with fourfold minimum inhibitory concentration reduction for each strain. Mechanistically, BDR triggered premature zoospore encystment (81.9%), inhibited sporangiogenesis (87.6%) and induced progressive membrane lysis. Reverse transcription‐quantitative PCR revealed coordinate transcriptional suppression of core virulence genes ( inpA , avrBlb1 , Pi02860 ) to 12.8%–23.0% of control levels. In silico docking predicted that iturin A, surfactin and phenazine‐type metabolites interact with conserved AVR3a/PexRD2 interfaces and V‐ATPase, supporting the observed antivirulence and membrane‐lytic phenotypes. Under greenhouse conditions, BDR reduced disease severity by 80.5% (area under the disease progress curve), matching the disease control exhibited by the fungicide Ridomil Gold. Field validation confirmed 73.3% disease reduction and a 72% yield increase (23.7 t ha −1 ), alongside elevated marketable tuber proportion (86.4%). Soil microcosm analyses showed consortium‐specific enhancement of urease and dehydrogenase activities, ammonium‐nitrogen mobilization, and microbial biomass carbon accumulation, confirming biochemical priming of the rhizosphere. These findings provide evidence for three complementary biological activities—synergistic antibiosis, suppression of selected pathogen virulence‐associated genes, and soil biochemical priming—that offers a transferable framework for microbial consortium engineering in sustainable potato production.