Effects of fungicide application on susceptible pepper cultivar under southern blight stress

• Identification of resistance levels to sclerotium rolfsii in different pepper cultivar. • This work revealed the inhibitory effect of different fungicides on sclerotium rolfsii . • In vivo efficacy of fungicides on susceptible pepper cultivar. Pepper plants are being infected by pepper southern blight, a root disease caused by Sclerotium rolfsii Sacc . However, the resistance of several pepper cultivar and the efficacy of chemical fungicides in controlling root diseases has not yet been well elucidated. This study evaluated the response and mechanisms of different pepper cultivar and fungicides to S. rolfsii . The effects of fungicide application on susceptible cultivar under S. rolfsii stress were assessed through a pot experiment. The results indicated that the Layan 101 (P8) variety exhibited the lowest resistance and Qianjiao 8 (P5) had the highest resistance. The In vitro antifungal activity of hexaconazole and azoxystrobin was superior in protective and curative capacities. Hexaconazole exhibited a consistent response, with the highest protective and curative effects (74.77 % / 32.52 %) observed at 50 μg·mL −1 , which was suboptimal for treatment. In contrast, azoxystrobin displayed a dose-dependent effect, achieving protective solid and therapeutic effects (85.41 % / 82.97 %) at 100 μg·mL −1 . These two fungicides inhibited the growth of pathogenic fungi, promoting the stable growth of pepper roots. In addition, they reduced root reactive oxygen burst and increased root peroxidase (POD and CAT) activity. This study serves as a reference for managing pepper southern blight.