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Disease Note.

A New Race (Race 4) of Spinach Downy Mildew in Italy. G. Lorenzini, University of Pisa, Sezione Patologia Vegetale, Dipartimento CDSL, 56100 Pisa, Italy. C. Nali, University of Pisa, Sezione Patologia Vegetale, Dipartimento CDSL, 56100 Pisa, Italy. Plant Dis. 78:208. Accepted for publication 10 September 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0208A.

In the fall of 1992, spinach (Spinacia oleracea L.) cultivars grown for the frozen food industry in the province of Foggia (Apulia region of southern Italy) showed severe symptoms associated with infection by the downy mildew fungus Peronospora farinosa (Fr.) Fr. f. sp. spinaciae By-ford, in spile of their reported resistance to races 1, 2, and 3 of this parasite. Only plants of cv. Bolero were not infected. Leaves of diseased plants had typical spots or large irregular yellow-green chlorotic areas, and dense bluish gray sporulation was frequently present on the abaxial leaf surface. Overhead irrigations and dew episodes were frequent in the crop production area. Applications of commercial formulations of metalaxyl and protective fungicides such as copper oxychloride and chlorothalonil were ineffective. Epiphytotics progressed very rapidly, and many fields were lost to the disease. Spores from infected leaves were collected by wet-brushing with chilled distilled water. Inoculations were performed under controlled conditions on the following cultivars: Viroflay (susceptible to races 1, 2, and 3), Nores (resistant to races 1 and 2), Califlay (resistant to races 1 and 3), and Polka and Lina (both resistant to races 1, 2, and 3); all were susceptible to our isolates. We attribute this recent epiphytotic to race 4, which was recently described in the United States (1). The origin of this new race in Europe is not known, but since the pathogen can be Seedborne (2), we speculate that it may have been introduced with commercial seed imports

References: (1) L. P. Brandenberger et al. Plant Dis. 75:630, 1991. (2) T. Inaba et al. Plan! Dis. 67:1139, 1983.