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

Abstract

Symptoms typical of anthracnose fruit rot; sunken, dark brown lesions on maturing fruits, were found in a commercial field of strawberry (Fragaria × ananassa) cv. Cal Giant in Yangyang County, Korea in May 2007. Masses of conidia were produced in acervuli in the center of lesions. The fungus was isolated on potato dextrose agar (PDA). Colonies grown on PDA were pale to mouse gray and became dark green to black in reverse. Conidia were formed in orange-to-salmon pink masses in the center of the culture. The average size of conidia on PDA was 15.2 × 4.6 μm, and they were hyaline, straight, cylindrical, with pointed ends, and aseptate (1). The fungus did not form an ascigerous stage in culture. Mycelial growth rate was 7.5 mm per day at 25°C on PDA. The identity of two isolates was confirmed as Colletotrichum acutatum J.H. Simmonds by PCR amplification using species-specific primers TBCA and TB5 (2), resulting in a characteristic 330-bp band on agarose gel. Morphological characters were in accordance with previous reports on C. acutatum. A pathogenicity test was conducted with five healthy plants of cvs. Cal Giant, Maehyang, Seolhyang, Kumhyang, Akihime, and Redpearl. After fruits and flowers were sprayed with a conidia suspension (105 conidia per ml), the plants were maintained at 10 to 25°C and 100% relative humidity in a greenhouse. As a control, five healthy plants were sprayed with sterile distilled water and incubated under the same conditions. Dark brown, water-soaked spots appeared on mature fruits of all cultivars after 5 days, and lesions on green fruits appeared on individual achenes. Flowers developed dark lesions, dried out, and died. No symptoms were found on the control plants. After the pathogen was reisolated from fruits and flowers lesions, the morphological characters developed in culture as described above. To our knowledge, this is the first report of C. acutatum causing strawberry anthracnose in Korea.