Biocontrol Efficacy of <i>Pseudomonas</i> Consortia Against Botrytis Blight in Petunias

<i>Botrytis cinerea</i>, a fungal pathogen causing Botrytis blight, significantly impacts greenhouse crop management owing to its broad host range and infection capabilities at various growth stages. Traditional control methods, primarily reliant on fungicides, are challenged by environmental concerns and the rise of fungicide-resistant strains. This study investigates the use of beneficial <i>Pseudomonas</i> bacteria as a sustainable alternative. We hypothesized that specific <i>Pseudomonas</i> consortia could provide more effective biocontrol of <i>B. cinerea</i> than individual strains. Our research investigated five <i>Pseudomonas</i> strains (14B11, AP54, 15H3, 94G2, and 89F1) known to reduce Botrytis blight in <i>Petunia × hybrida</i>. Compatibility for bacterial consortia was assessed through biofilm formation and direct bacterial inhibition assays. The biocontrol effects of the bacteria against <i>B. cinerea</i> were investigated in vitro using shared-air-space and dual-culture assays and in planta by inoculating detached petunia flowers. We found that strain 14B11 exhibited the highest biofilm formation, with consortia of 14B11 and 89F1 showing significant enhancement compared with individual cultures, whereas a slight, nonsignificant increase was observed in 14B11 and AP54 consortia. However, strain 14B11 efficacy was inhibited by strain 15H3. Genomic analyses identified antifungal compound-related gene clusters in 14B11 and AP54, contributing to their biocontrol potential. Trials with detached flowers of <i>Petunia × hybrida</i> 'Carpet Red Bright' confirmed significant disease severity reduction with 14B11, AP54, and their consortia. This research highlights strategic <i>Pseudomonas</i> consortia as promising, eco-friendly alternatives to chemical fungicides, promoting sustainable agriculture by enhancing our understanding of how microbial interactions can be used to manage Botrytis blight.