Characterization of a Novel Chitinase from Sweet Potato and Its Fungicidal Effect against Ceratocystis fimbriata.

Black rot, caused by Ceratocystis fimbriata, is a destructive disease of sweet potatoes (Ipomoea batatas). In this study, a novel chitinase (IbChiA) was screened from sweet potatoes, which showed a remarkably higher expression level in resistant varieties than in susceptible ones after inoculation with C. fimbriata. Sequence analysis indicated that IbChiA belongs to family 19 class II extracellular chitinase with a MW of 26.3 kDa and pI of 5.96. Recombinant IbChiA, produced by Pichia pastoris, displayed antifungal activity and stability. IbChiA could restrain the mycelium extension of C. fimbriata. FDA/PI double staining combined with transmission electron microscopy observation revealed the remarkable fungicidal effect of IbChiA on the conidia of C. fimbriata. The disease symptoms on the surface of slices and tuberous roots of sweet potatoes were significantly reduced after treatment with IbChiA. These results indicated that IbChiA could be used as a potential biofungicide to replace chemical fungicides.