Histopathological evidence of concomitant sexual and asexual reproduction of Elsinoe ampelina in grapevine under subtropical climate

Anthracnose caused by Elsinoe ampelina is one of the most serious diseases affecting grapevine production worldwide. Previous studies have described many structural and histochemical changes in grapevine leaves associated with E. ampelina colonization and the presence of ascus-like structures in the lesions. In this paper, we characterized the colonization and reproduction of E. ampelina in grapevine tendrils, stems and berries using light, epifluorescence and scanning electron microscopy. In the early stages of colonization, shape changes and the collapse of epidermal and parenchyma cells were more pronounced in the center of lesions. At this stage, pectic substances accumulated inside the parenchyma cells and hyphae were observed colonizing tissues inter and intracellularly, including tracheary elements. As colonization evolved, lesions enlarged and infected tissues became necrotic and collapsed. Tyloses and conidiogenous cells producing conidia were observed in the tracheary elements. Conidiogenous cells and conidia were also present on the lesion surface. On the same lesions, bitunicate asci containing two-to three-celled ascospores were observed on the surface and throughout the stromatic tissue. Our analyses showed that both sexual and asexual stages of E. ampelina occur from the beginning of the epidemic, which may help to explain the explosive nature of the disease when early stages of grapevine development coincide with rainy seasons.