Pea-Saving Partners: Bacillus and Pseudomonas combat downy mildew in pea crops

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 survival as spores and its rapid mutation. Use of chemical pesticides has been the most effective method to control DM pathogens, but their environmental hazards are a global concern. Current research is focused on exploring the potential of microbial biological control agents (MBCA), particularly rhizobacteria strains of the generaBacillusandPseudomonas, 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 ofBacillusandPseudomonasstrains as potential biopesticides against the pea downy mildew pathogenPeronospora viciaef. sp.pisi(Pvp). In our study,in vitrobioassays showed 100% inhibition ofPvpspore germination compared to the control.In plantaantagonism assays further demonstrated significant suppression (>80%) ofPvpsporulation in pea plants sprayed with strains ofBacillus velezensisorP. fluorescensor their filtrates. The drench application also showed significant effects where either aPseudomonasor cold-adaptedBacillusstrain was used. We observed a synergistic effect for the dual foliar application of the microbes compared to individual application (27.6 to 46.7% suppression). Furthermore, the results from the molecular biomass analysis were consistent with the results of the sporulation assays. This demonstrates the strong interactive and promotive benefits of usingBacillusandPseudomonasas biocontrol agents Based on these results, we conclude that these MBCAs could be effective in combattingPvpinfections in the field.