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Etiology

Etiology and Histology of Alternaria Rot of Persimmon Fruits. D. Prusky, Division of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, Israel; R. Ben-Arie(2), and S. Guelfat-Reich(3). (2)(3)Division of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, Israel. Phytopathology 71:1124-1128. Accepted for publication 9 February 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1124.

The causal organism of the black spot disease of persimmon fruits, Diospyros kaki has been identified as Alternaria alternata. Conidia of the fungus, pathogenic to the fruit, were found in the orchard on necrotic leaf spots. Germinating conidia were seen to penetrate the fruit cuticle directly. Following infection in the orchard, the hyphae developed intercellularly and produced tiny, dark, quiescent infections, which renewed development during postharvest fruit ripening. Latent infections increased in number throughout the growth period of the fruit. Infection via wounds also occurred in the orchard, resulting in the development of large lesions during storage. Even though germination of conidia at 0 C was only slightly delayed, the development of new infections during prolonged storage at this temperature was limited. This was probably due to the low incidence of infection by A. alternaria at 0 C. Black spot development was also very slow at this storage temperature. High relative humidity significantly increased the rate of symptom development and the disease incidence.