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

Abstract

Strawberry (Fragaria × ananassa) is the most important small fruit crop in Denmark. The quarantine pathogen Colletotrichum acutatum was detected for the first time in June 2000 in Denmark in a production field on the island of Falster. Strawberry plants of cv. Kimberly showed typical symptoms of anthracnose fruit rot. On mature fruits, brown-to-black lesions with spore masses that were orange to salmon in color were observed. Mummified berries were also observed. The fungus was isolated and identified on the basis of morphological characteristics, and identification was confirmed using enzyme-linked immunosorbent assay at the Central Science Laboratory, York, U.K. Species-specific polymerase chain reaction with the C. acutatum-specific primer pairs acut1/col2 (1) and CaInt2/ITS4 (3) also supported the identification. Additionally, the internal transcribed spacer regions, ITS1 and ITS2, of the ribosomal DNA were sequenced in both directions (GenBank Accession No. AY818361). Homology searches with this sequence using BLAST also confirmed the identity. Colonies grown on potato dextrose agar developed white-to-grey aerial mycelium with salmon-colored spore masses, and were beige to black on the reverse side. Conidia were 11.3 (7.3 to 16.6) μm × 3.9 (2.5 to 5.2) μm, hyaline, cylindrical with at least one pointed end, and aseptate. Mycelial growth rate was 8.4 mm per day at 25°C which is similar to earlier reports (2). Spray-inoculated (106 conidia per ml) strawberry fruits cv. Elsanta developed brown, sunken, irregular lesions with salmon-colored acervuli after 2 to 5 days at 25°C. Koch's postulates were fulfilled since the reisolated fungus from these lesions developed the same morphological characteristics as described above. To our knowledge, this is the first report of C. acutatum in Denmark. References: (1) P. V. Martinez-Culebras et al. J. Phytopathol. 151:135, 2003. (2) B. J. Smith et al. Plant Dis. 74:69, 1990. (3) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996.