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First Report of Sclerotinia minor as a Pathogen of Cauliflower In California. S. T. Koike, University of California Cooperative Extension, Salinas 93901. T. G. Gonzales, and M. Vidauri, University of California Cooperative Extension, Salinas 93901; and K. V. Subbarao, Department of Plant Pathology, University of California, Davis and located at U.S. Agricultural Research Station, Salinas. Plant Dis. 78:1216. Accepted for publication 10 October 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1216C.

In the Salinas Valley, aerial parts of cauliflower (Brassica oleracea L. var. botrytis L.) are susceptible to Sclerotinia sclerotiorum (Lib.) de Bary. Recently, however, commercially produced cauliflower plants had Scle-rotinia-like symptoms at the base of the plants. Symptoms consisted of a soft, watery rot at the crown and upper tap root. Diseased tissue turned brown, and plants wilted and collapsed. White mycelia and black sclerotia of Sclerotinia minor Jagger developed on the outer surfaces of affected areas. In advanced stages of the disease, stems became hollow with sclerotia impregnated in them. Koch's postulates were conducted using inoculum that was produced on sterilized potato pieces incubated at 25 C (1). Five-week-old cauliflower plants (cv. White Rock) were potted into sterilized sand amended with sclerotia (35 sclerotia/100 cm3 of soil) and into sterilized, noninfested sand. Plants were incubated in a greenhouse at 23-25 C. After 4 wk, inoculated plants showed identical symptoms and 5. minor was recovered from diseased tissue. Uninoculated plants were asymptomatic. In addition, 4-week-old lettuce [Lactuca sativa L.) seedlings, inoculated with the cauliflower isolate, developed similar symptoms; S. minor was recovered from these diseased lettuce plants. This is the first report of S. minor causing a disease of cauliflower. Cauliflower is commonly planted in rotation with lettuce and may possibly influence soil inoculum levels and subsequent lettuce drop incidence.

Reference: (1) C. L. Patterson and R. G. Grogan. Plant Dis. 72:1046, 1988.