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Survival of Phytophthora infestans in Seeds Extracted from Infected Tomato Fruits. Varoujan G. Vartanian, Graduate research assistant, Department of Plant Pathology, University of California, Riverside 92521; Robert M. Endo, professor, Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 75:375-378. Accepted for publication 8 October 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-375.

Seeds were extracted from healthy and blighted tomatoes collected from three field-grown cultivars, processed as in a commercial operation, and the seeds plated on a selective medium. Phytophthora infestans usually was isolated (avg 91.7%) from discolored, freshly extracted, wet seeds but not from discolored seeds that had been dried in an oven (29.5- 37.5 C) for 6 hr or air-dried for 72 hr following extraction. Fermentation for 24 hr eliminated the fungus from discolored seeds of cultivar 7718 but not from discolored seeds of cultivar Castle 1025 or those of an unidentified cultivar of cherry tomato. Treatment of wet, discolored seeds with either NaOCl (0.5% for 5 min) or 0.12 N HC1 (pH 1.6, for 25 min) significantly reduced the frequency of isolation. In discolored seeds, hyphae were observed on and in the seed coat, in the remnants of the funiculus, and between the endosperm and the seed coat. When freshly extracted, wet or dried discolored seeds were planted in steamed UC soil mix or in field soil in the greenhouse, some of the seedlings emerging from wet seeds were infected (avg 26%), whereas seedlings emerging from dry seeds were healthy. Infected tomato fruits placed in the field on a wet soil surface or plowed under and kept continuously wet by irrigation occasionally gave rise to infected seedlings.