During 2003, 10% of the Hiemalis begonias (Begonia × hiemalis Fotsch) developed wilt symptoms in a commercial greenhouse in Connecticut. Foliage turned a dull green, and stems developed a dark watersoaked discoloration near the soil line and had vascular discoloration. Stems, petioles, and leaves collapsed and became covered with sporodochia of a Fusarium spp. Single conidia were isolated from sporodochia and cultured on carnation leaf agar (CLA) and potato dextrose agar for 10 days. Isolates resembled Fusarium oxysporum, but the profuse sporulation with minimal aerial mycelium and the rare occurrence of polyphialides was consistent with the description of F. foetens (2). A comparison of a partial sequence of the 1-α elongation factor gene showed a 100% match with F. foetens. Inocula from five isolates were grown on CLA, washed from the plate, and adjusted to 106 conidia per ml. Suspension (50 μl) was injected into stems of healthy 6-week-old Hiemalis begonias cv. Barkos (one plant per isolate). Controls received distilled water. After 4 weeks, all inoculated plants turned dark and collapsed, and the same fungus was reisolated from these plants. Control stems remained healthy. An isolate (O-2348) has been deposited at the Fusarium Research Center at Pennsylvania State University, University Park. F. foetens has recently been described in association with a new disease of Hiemalis begonias in Europe (1).
References: (1) R. Schrage, Phytomedizinischen Gesellschaft 33:68, 2003. (2) H.-J. Schroers et al. Mycologia 96:393, 2004.