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Etiology

Pathogenicity of Alternaria alternata on Potato in Israel. S. Droby, Division of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel, and Department of Plant Pathology, The Hebrew University of Jerusalem, Faculty of Agriculture, P.O. Box 12, Rehovot 76100, Israel; A. Dinoor(2), D. Prusky(3), and Rivka Barkai-Golan(4). (2)(3)(4)Division of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel, and Department of Plant Pathology, The Hebrew University of Jerusalem, Faculty of Agriculture, P.O. Box 12, Rehovot 76100, Israel. Phytopathology 74:537-542. Accepted for publication 1 January 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-537.

A fungal pathogen responsible for brown spots on the underside of potato leaves in Israel was identified as Alternaria alternata. The fungus infected the leaf by direct penetration and via stomata. Young plants, at the 10- 12 leaf stage, were less susceptible than adult plants; a differential susceptibility of the leaves was observed in which the middle leaves of the plant showed the highest disease incidence at any given growth stage. Susceptibility varied also according to the cultivar and the rate of sprinkler irrigation. Under field conditions, 28% foliar disease incidence significantly reduced tuber yield (18%). Fungicidal sprays with maneb, imazalil, or iprodione reduced the severity of disease significantly. The evidence indicated that A. alternata is a new pathogen of the potato crop in Israel.