First Report of Colletotrichum gloeosporioides on Cyclamen persicum in Florida

Between March and April of 1996, an estimated 20% of the Cyclamen persicum Mill. grown in Florida were infected with Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. Symptoms included extensive lesions on flowers, stems, and leaves. Acervuli containing masses of spores and dark setae were observed within lesions. The most severe damage was observed on the cultivar Red Delight. Infected tissues were dipped into 0.26% sodium hypochlorite for 5 s, blotted dry, embedded in water agar, and incubated at 27 ± 1°C. Hyphal tips that grew from lesions were transferred to potato dextrose agar (PDA) and incubated under cool-white fluorescent lights. Developing colonies were gray and contained masses of orange conidia. Conidia were straight with rounded or bulbous ends and averaged 16.8 (SD 5.2) × 2.25 (SD 0.54) μm. Three isolates were selected to complete Koch's postulates. Conidia of each isolate were obtained from 3-day-old PDA cultures, and suspended in sterile, distilled water (SDW) to 10⁴ conidia/ml. These suspensions were sprayed till runoff with hand sprayers onto C. persicum plants. Plants were incubated in plastic bags for 24 h at 27°C, then placed in a glasshouse. Within 3 days, lesions had developed on flowers; within 7 days, they were visible on stems and leaves. Lesion diameter varied from 2 to 5 mm; however, lesions soon coalesced, causing leaf, stem, and flower death. The fungus was reisolated from acervuli that developed on the flowers, stems, and leaves, following previously outlined procedures. Inoculation tests were repeated once. Symptoms did not appear on controls sprayed with SDW nor was the teleomorph stage of the pathogen observed.