Hutchinsia alpina (Chamois cress), a plant belonging to the Brassicaceae family, is cultivated as a potted ornamental plant in Italy. In the winter of 2002, leaves and stems of plants grown in pots (14-cm diameter) in commercial farms near Albenga (northern Italy) developed soft and watery tissues covered with whitish mycelium at the soil line. As necrosis progressed, infected plants wilted and died. Dark sclerotia developed on infected tissues. Because of high planting density, the infection spread very rapidly. Sclerotinia sclerotiorum was consistently recovered from infected stem pieces of H. alpina disinfested 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Sclerotia produced on PDA were ellipsoid and measured 1.3 to 9.3 × 1.3 to 4.5 mm (average 3.9 × 2.8 mm) (1). Pathogenicity of three isolates obtained from infected plants grown in a single greenhouse was confirmed by inoculating 90-day-old plants grown in pots (14 cm). Inoculum that consisted of wheat kernels infested with mycelium and sclerotia of each isolate were placed on the soil surface around the base of each of 10 plants. Plants treated with plain wheat kernels served as controls. The inoculation trial was repeated once. All plants were kept at temperatures ranging between 5 and 26°C and watered as needed. Inoculated plants developed symptoms of leaf yellowing, followed by the appearance of white mycelium within 15 days, and eventually wilted while control plants remained symptomless. White mycelium and sclerotia developed on infected tissues, and S. sclerotiorum was reisolated only from inoculated plants. To our knowledge, this is the first report of white mold on Hutchinsia alpina caused by S. sclerotiorum.
Reference: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 1949.