Fungal effector genes involved in the suppression of chitin signaling as novel targets for the control of powdery mildew disease via a nontransgenic RNA interference approach

Chitin is a crucial component of fungal cell walls and an effective elicitor of plant immunity; however, phytopathogenic fungi have developed virulence mechanisms to counteract the activation of this plant defensive response. In this study, the molecular mechanism of chitin-induced suppression through effectors involved in chitin deacetylases (CDAs) and their degradation (EWCAs) was investigated with the idea of developing novel dsRNA-biofungicides to control the cucurbit powdery mildew caused by Podosphaera xanthii. The molecular mechanisms associated with the silencing effect of the PxCDA and PxEWCAs genes were first studied through dsRNA cotyledon infiltration assays, which revealed a ≈80% reduction in fungal biomass and a 50% decrease in gene expression. To assess the impact on powdery mildew disease control, in vitro and in planta assays were carried out in growth chamber and glasshouse experiments, with ≈50% reduction in disease symptoms after 8 days postinoculation (dpi) in leaf discs and 12 dpi in plants' leaves, respectively. This control was extended for 21 days when the dsRNAs were protected on the carbon dot nanocarriers. Additionally, the uptake of the dsRNAs by fungal spores was observed 12 h postapplication via confocal microscopy, and efficient processing of dsRNAs into siRNAs by the melon RNAi machinery was observed 24 h postspraying through sRNA-seq. This study highlights notable advancements in environmentally friendly disease management, and features the technological potential of RNA-based fungicides together with nanotechnology for cucurbit powdery mildew control. © 2025 Society of Chemical Industry.