First Report of Anthracnose Caused by Colletotrichum acutatum on Strawberry in the Czech Republic.

Abstract

Colletotrichum acutatum J. H. Simmond is the causal agent of anthracnose rot and strawberry blackspot. This pathogen is listed by the EPPO as a regulated (formerly quarantined) organism for all European countries and is widely distributed throughout Europe (e.g., the United Kingdom, France, and Germany) (2). In the autumn of 2005, typical symptoms of anthracnose caused by C. acutatum (circular, dark, and sunken spots on fruit, dark, sunken lesions on petioles, and withering of the leaf, buds, and flowers) were repeatedly observed on field-grown strawberry plants in the Mělník Region of central Bohemia and Břeclav Region in southern Moravia, Czech Republic. Strawberry fruits and petioles showing typical symptoms were surface sterilized (30 s in 70% ethanol, 1 min in 10% NaOCl, and 15 s in 70% ethanol), rinsed in sterile water, dissected under aseptic conditions, and plated on 2% malt extract agar or placed in wet chambers and incubated at room temperature (18 to 20°C) for 10 days. All isolated strains were independently identified by morphological characteristics, plate-trapped antigen enzyme-linked immunosorbent assay (PTA-ELISA) (1), and PCR with the C. acutatum-specific primers ITS4 and CaInt2 (3). Morphological studies of C. acutatum were carried out on potato dextrose agar (4). The colonies were white, cream, grayish, or rose-orange before sporulation and the colony reverse was cream to orange with brown spots. The mycelial growth rate was 7.5 mm per day at 25°C. The conidia were one-celled, hyaline, cylindrical, 11.3 to 19.7 × 3.6 to 5.5 μm, and the majority of conidia were pointed at either or both ends. The appresoria were brown, globose to ellipsoidal, 5.0 to 7.5 × 5.0 to 6.2 μm, and the sclerotia were absent. Ten strawberry plants with green fruits of each cultivar Elsanta and Kama were sprayed with 500 ml of suspension of C. acutatum conidia (104 conidia per ml). This test was carried out in the glasshouse under quarantine conditions at 20 to 25°C. C. acutatum caused withering of the flowers or dark brown spots on green fruits on five plants of cv. Elsanta and on four plants of cv. Kama after a 6-week incubation period. Isolation and identification of the pathogen from the diseased tissues were done as described above. C. acutatum was reisolated from three fruits, four leaf blades, and four petioles from five plants of cv. Elsanta and four fruits, four leaf blades, and two petioles from four plants of cv. Kama. The fungus was not reisolated from the control strawberry plants. In three cases, the pathogen was detected in the crown of plants of cv. Elsanta by PCR and ELISA.