The Discovery of Oxathiapiprolin as a Potential Agent for the Control of Litchi Downy Blight Caused by <i>Peronophythora litchii</i> and the Study of Its Mechanism of Action

Oxathiapiprolin, a novel fungicide targeting oxysterol-binding proteins (OSBP), has proven to be effective against various oomycete diseases, but its effects on pathogens remain underexplored. In this study, we demonstrated that oxathiapiprolin inhibits mycelium growth, sporangium production, zoospore release, and oospore production in <i>Peronophythora litchii</i>, with 50% effective concentrations ranging from 0.000153 to 0.011681 μg mL^-1. Additionally, in vivo tests confirmed its efficacy in controlling litchi downy blight. Our study demonstrated that oxathiapiprolin disrupts cellular ultrastructure and plasma membrane integrity, affects stress sensitivity, inhibits sterol transport, increases autophagy levels, reduces lipid droplet content, and induces lipid metabolism disorders. Gene expression analysis revealed that oxathiapiprolin affects the expression of <i>PlORP1</i> (ORP1 gene of <i>P. litchii</i>), with docking simulations further confirming its interaction with the PlORP1 (ORP1 protein of <i>P. litchii</i>) protein. Ultimately, this cascade of events led to pathogen death. This paper reveals the antioomycete mechanism of oxathiapiprolin against <i>P. litchii</i>.