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First Report of Anthracnose Fruit Rot of Strawberry Caused by Colletotrichum acutatum in China

In 2004, fruits showing dark and sunken necrotic lesions were observed on strawberries (Fragaria × ananassa Duch. cv. Mei No. 3) in a field in Shanghai, China. All isolates obtained from the infected fruits easily produced orange spore masses and developed orange colonies with orange reverse colony color; none formed setae or the ascigerous stage in culture or on the host. The conidia were hyaline, straight and fusiform, 8 to 16 × 2.5 to 4 μm, and produced melanized, ellipsoid, ball- or pear-shaped appressoria at the end of germ tubes. These isolates were similar to those described for Colletotrichum acutatum J. H. Simmonds. To confirm pathogenicity of the isolate, inoculum suspension with 4 × 10⁶ conidia/ml was sprayed onto 10 fruiting strawberry plants until runoff. The inoculated plants were maintained at 25°C and 100% relative humidity in a growth chamber with a 12-h period of fluorescent light daily. Plants inoculated with sterilized water were controls. After 3 days, dark brown lesions appeared in the leaves, petioles, and fruits of all inoculated plants. The symptoms were similar to those observed on the strawberry fruit from which the isolate was originally isolated. The pathogen was consistently reisolated from the symptomatic fruit. No symptoms were observed on the control plants. To our knowledge, this is the first report of C. acutatum as the casual agent of anthracnose fruit rot of strawberry in China.