Synergistic antifungal activity of citral combined with its acylthiourea derivative against Rhizoctonia solani and its underlying mechanisms

Rhizoctonia solani is a significant soil-borne plant pathogenic fungus. Its sclerotial structure confers strong environmental adaptability and persistent infectivity, posing a serious threat to the production of numerous crops. Citral, a plant-derived monoterpene aldehyde, exhibits antifungal activity; however, its antifungal potency is limited. In this study, citral was combined with its acylthiourea derivatives, leading to the screening and construction of an efficient synergistic antifungal system, CE4. CE4 significantly inhibits mycelial growth of R. solani and reduces its capacity for sclerotia formation, with an EC 50 value of 10.97 mg/L. Further research has revealed that CE4 disrupts the surface structure of hyphae, significantly increases cell membrane permeability, and reduces ergosterol content, thereby disrupting cellular membrane homeostasis. Meanwhile, CE4 induces the accumulation of ROS and lipid peroxidation products, significantly disrupts the antioxidant enzyme system, and inhibits the activity of key enzymes in energy metabolism, thereby reducing ATP levels. Cytotoxicity evaluation demonstrated that CE4 did not significantly increase cytotoxicity toward mammalian cells at the effective antifungal concentration. The above results indicate that CE4 effectively inhibits the growth of R. solani through the synergistic disruption of cell membrane homeostasis, induction of oxidative stress, and interference with energy metabolism. The results of this study provide a novel theoretical and experimental foundation for the synergistic application of plant-derived antifungal agents.