Defense against chitin-containing fungal pathogens. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Localized to infected area. By infection with Cercospora beticola. O-glycosylated on hydroxyprolines; contains xylose. Belongs to the glycosyl hydrolase 19 family. Chitinase class I subfamily.