Antifungal Activity and Mechanism of Camphor Derivatives against <i>Rhizoctonia solani</i>: A Promising Alternative Antifungal Agent for Rice Sheath Blight

Abstract

Rice sheath blight, caused by the fungus <i>Rhizoctonia solani</i>, poses a significant threat to rice cultivation globally. This study aimed to investigate the potential mechanisms of action of camphor derivatives against <i>R. solani</i>. Compound <b>4o</b> exhibited superior fungicidal activities in vitro (EC₅₀ = 6.16 mg/L), and in vivo curative effects (77.5%) at 500 mg/L were significantly (<i>P</i> < 0.01) higher than the positive control validamycin·bacillus (66.1%). Additionally, compound <b>4o</b> exhibited low cytotoxicity and acute oral toxicity for adult worker honeybees of <i>Apis mellifera</i> L. Mechanistically, compound <b>4o</b> disrupted mycelial morphology and microstructure, increased cell membrane permeability, and inhibited both PDH and SDH enzyme activities. Molecular docking and molecular dynamics analyses indicated a tight interaction of compound <b>4o</b> with PDH and SDH active sites. In summary, compound <b>4o</b> exhibited substantial antifungal efficacy against <i>R. solani</i>, serving as a promising lead compound for further optimization of antifungal agents.