Effect of Cuticular Wax Layers of Green and Red Pepper Fruits on Infection by Colletotrichum gloeosporioides

Colletotrichum gloeosporioides isolate KG13 caused necrotic, sunken anthracnose symptoms on unwounded, wax-removed, and wounded green pepper fruits and on wounded red fruits 7 days after inoculation. Hypersensitive reactions with small brownish discolorations, on some occasions, were found on unwounded red fruits. The isolate produced whitish symptoms with brown margins, but not the typical anthracnose on red fruits wax-removed by chloroform treatment. Generally, wax-removed red fruits, but not green ones, produced larger lesions and more conidia than untreated controls. Wounded pepper fruits had larger lesions than those with other treatments. More germinated conidia, appressoria, and infection hyphae were found on wax-removed fruits than on controls; however, differences between green and red fruits were not found. Cuticular wax layers of fruits were dissolved partially by chloroform and the outer epidermal cells were disrupted slightly. Anthracnose development was negatively related with fruit developmental stage. Well-developed fruits had more cuticular wax than less developed fruits. These results suggest that the cuticular wax layers of pepper fruits may play a significant role in fruit infection by C. gloeosporioides isolate KG13, and mainly determine the incompatibility of red fruits to the isolate. Biochemical differences may also play a role.