Pea‐Saving Partners: <i>Bacillus</i> and <i>Pseudomonas</i> Combat Downy Mildew in Pea Crops

ABSTRACT Downy mildew (DM) is a destructive disease that significantly reduces the yield and quality of important pulses (legumes) and horticultural crops, particularly during humid and cool seasons. This disease is caused by obligate and host‐specific oomycete pathogens. Controlling the pathogen is challenging due to its long‐term spore survival and rapid mutation. Although chemical pesticides have been the most effective method to control DM pathogens, their environmental hazards remain a global concern. Current research is focused on exploring the potential of microbial biological control agents (MBCA), particularly rhizobacteria strains of the genera Bacillus and Pseudomonas , which have shown suppression of plant pathogens. However, to date, no MBCA has been reported to be effective against DM pathogens in pulses. We investigated the effectiveness of Bacillus and Pseudomonas strains as potential biopesticides against the pea downy mildew pathogen Peronospora viciae f. sp. pisi (Pvp). In vitro bioassays showed 100% inhibition of Pvp spore germination compared to the control. In planta antagonism assays further demonstrated significant suppression (&gt; 80%) of Pvp sporulation in pea plants sprayed with strains of Bacillus velezensis or Pseudomonas fluorescens or their filtrates. The drench application also showed significant effects where either a Pseudomonas or cold‐adapted Bacillus strain was used. We observed a synergistic effect for the dual foliar application of the microbes compared to individual application (40%–78% suppression). Molecular biomass analysis supported these findings. Based on these results, we conclude that Bacillus and Pseudomonas MBCAs could be highly effective in combating Pvp infections in the field.