Antifungal and eliciting properties of chitosan against Ceratocystis fimbriata in sweet potato

•Chitosan inhibited the cell growth and led to the cell necrosis of C. fimbriata.•Chitosan altered the chitin deposition and fatty acid composition of C. fimbriata.•Chitosan effectively controlled the C. fimbriata development in sweet potato TRs.•The PAL and SOD activity were enhanced, while the MDA production was decreased.•Chitosan exhibited the dual effects to control C. fimbriata in sweet potato.