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Cytology and Histology

Histopathology of Ripe Rot Caused by Colletotrichum gloeosporioides on Muscadine Grape. M. E. Daykin, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; R. D. Milholland, professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Phytopathology 74:1339-1341. Accepted for publication 8 June 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1339.

In a histological study of ripe rot on attached fruit of muscadine grape (Vitis rotundifolia), the susceptible cultivar, Carlos, and the resistant cultivar, Pride, responded similarly to the early stages of infection by Colletotrichum gloeosporioides. Conidia germinated and produced appressoria, and hyphae penetrated the cuticle within 1 wk after inoculation on green or ripening fruit. Further fungal growth ceased until the fruit ripened. Plant responses to the penetration hyphae varied from a slightly darker staining reaction in protoplasm adjacent to the hyphae, to a necrosis of the epidermal cells below the hyphae. The necrotic reaction in Carlos often was accompanied by hyperplasia in the subepidermal cells. When Carlos fruit ripened, C. gloeosporioides colonized the pericarp inter- and intracellularly and produced acervuli, but fungal growth was not resumed in ripe fruit of the resistant cultivar, Pride.