The pre-penetration and infection processes of Colletotrichum guaranicola on resistant and susceptible clones of Paullinia cupana var. sorbilis were studied by light microscopy. The percentage of germination of conidia on young leaves was higher than on old leaves, although no difference was found between resistant and susceptible clones. Quantitative differences were observed in the appressorium formation on susceptible and resistant leaf surfaces. More appressoria were found on susceptible than on resistant leaves 24 h after inoculation. The morphology of pre-penetration and infection structures was similar for both clones: direct penetration, with infection hyphae and vesicles present in the epidermal cells; development of primary and secondary hyphae; inter and intracellular colonization of the parenchyma. However, events such as parenchyma colonization and onset of leaf symptoms took 48-hours longer to unfold in resistant leaves than in susceptible leaves.
