RESUMEN
In search for SDHIs fungicides, twenty-five novel carboxamides containing a chalcone scaffold were designed, synthesized, and evaluated for antifungal activities against five pathogenic fungi. The results showed that compound 5 k exhibited outstanding antifungal activity against R.â solani with an EC50 value of 0.20â µg/mL, which was much better than that of commercial SDHIs Boscalid (EC50 =0.74â µg/mL). Moreover, compound 5 k also displayed promising antifungal activities against S.â sclerotiorum, B.â cinerea, and A.â alternate (IC50 =2.53-4.06â µg/mL), indicating that 5 k had broad-spectrum antifungal activity. Additionally, inâ vivo antifungal activities results showed that 5 k could significantly inhibit the growth of R.â solani in rice leaves with good protective efficacy (57.78 %) and curative efficacy (58.45 %) at 100â µg/mL, both of which were much better than those of Boscalid, indicating a promising application prospect. Moreover, SEM analysis showed that compound 5 k could remarkably disrupt the typical structure and morphology of R.â solani hyphae. Further SDH enzyme inhibition assay and molecular docking study revealed that lead compound 5 k had a similar mechanism of action as commercial SDHI Boscalid. These results indicated that compound 5 k showed potential as a SDHIs fungicide and deserved further investigation.