Gentisaldehyde Suppresses Phytophthora sojae by Combined Damage to Membrane Integrity and Energy Metabolism

Abstract

The soil-borne oomycete Phytophthora sojae causes severe Phytophthora root and stem rot (PRR) in soybean. Rhizosphere metabolites, integral to plant defense, represent an underexplored resource for novel control strategies. A metabolomic comparison of rhizospheres from resistant (Williams82) and susceptible (Williams) soybeans identified gentisaldehyde as a key differential metabolite. In vitro, gentisaldehyde demonstrated broad, concentration-dependent inhibition of P. sojae, suppressing mycelial growth, oospore formation, oospore survival, zoosporangium formation, zoospore encystment, and cyst germination. Integrating physiological and transcriptomic analyses revealed that gentisaldehyde exerts its anti-oomycete activity through a multi-target mechanism, disrupting plasma membrane integrity, inhibiting energy metabolism, and inducing oxidative stress. Importantly, soil application of gentisaldehyde at 0.4 μmol g–1 soil significantly reduced the PRR disease index in natural soil and also provided significant protection in sterilized soil, indicating direct pathogen inhibition. These results suggest that gentisaldehyde plays a role in rhizosphere defense and may be a lead compound for PRR management.