Synthesis, antifungal activity and action mechanism of novel citral amide derivatives against Rhizoctonia solani

Abstract BACKGROUND Rice sheath blight caused by Rhizoctonia solani is a severe threat to the yield and quality of rice. Due to the unscientific abuse of common fungicides causing resistance and environmental issues, the development of new fungicides is necessary. In this study, we used citral as the lead compound, designed and synthesized a series of novel citral amide derivatives, and evaluated their antifungal activity and mode of action against R. solani . RESULT Bioassay results indicated that antifungal activities of most citral amide derivatives against R. solani were significantly improved compared to citral, with EC 50 values ranging from 9.50–27.12 mg/L. Among them, compound d21 containing the N‐(Pyridin‐4‐yl)carboxamide group exhibited in vitro and in vivo fungicidal activities, with curative effects at 500 mg/L as effectively as the commercial fungicide validamycin·bacillus. Furthermore, d21 prolonged lag phase of the growth curve of R. solani , reduced the amount of growth, and inhibited sclerotium germination and formation. Mechanistically, d21 deformed the mycelia, increased cell membrane permeability, and inhibited the activities of antioxidant and TCA‐related enzymes. Metabolome analysis showed the abundance of some energy‐related metabolites within R. solani increased, and simultaneously the antifungal substances secreted by itself reduced. Transcriptome analysis showed that most genes encoding ABC transporters and peroxisomes upregulated after the treatment of d21, and cell membrane destruction. CONCLUSION This study indicates that novel citral amide derivatives possess antifungal activity against R. solani and are expected to develop an alternative option for chemical control of rice sheath blight. This article is protected by copyright. All rights reserved.