Occurrence of Colletotrichum acutatum, Causal Organism of Strawberry Anthracnose in Southwestern Spain

Abstract

A wilting disease of strawberry (Fragaria × ananassa Duchesne ‘Oso Grande’) was observed in production fields in Huelva, southwestern Andalucía, Spain. Crowns of wilted plants developed a reddish brown, firm rot. Longitudinal sections of roots of diseased plants showed a black coloration of the cortex. Symptons also included blighting of flowers due to floral infection and rotting of green and ripening fruits. On the fruit, the round, firm sunken lesions were covered with masses of salmon-colored spores. Lesions on the leaves were round, ranged in diameter from 5 to 10 mm, and were light brown with purple edges. Infected tissues were surface disinfected in 20% sodium hypoclorite, blotted dry, and plated on water agar. Dishes were incubated at 25°C; hyphal tips made of fungi growing from lesions were transferred to potato dextrose agar (PDA) and incubated under cool-white fluorescent light at 25°C. One fungus was isolated consistently from lesions on different tissues. It was identified as Colletotrichum acutatum by morphological characteristics (2) and enzyme-linked immunosorbent assay (1). On PDA, the mycelium of the fungus was white to gray and covered with salmon spore masses. Colony diameters on PDA averaged 45 mm after 7 days at 25°C. Hyaline, aseptate conidia were cylindrical, fusiform, and intermediate in shape and averaged 12.8 × 4.2 μm in size. The fungus produced setae on infected fruit. Inoculations of strawberry cvs. Oso Grande and Chandler with conidial suspensions (106 conidia per ml) of C. acutatum produced lesions on the fruit, petioles, and crowns, and caused wilt. The pathogen was reisolated from lesions on the inoculated plants. This is the first report of C. acutatum causing strawberry anthracnose in Huelva. References: (1) T. A. Cooke et al. EPPO Bulletin 25:57, 1995. (2) B. C. Sutton. The Coelomycetes. CMI, Kew, England, 1980.