Hiemalis begonias Fotsch (Begonia × hiemalis), a member of the family Begoniaceae, is a commercially important potted flowering plant in Europe and North America. In the spring of 2010, stunted growth and dull green leaves of H. begonias were observed in a commercial greenhouse in southern Ontario, Canada. Symptoms began with dull green foliage, followed by wilted leaves, then the stem base became water soaked with vascular discoloration, and finally, large macroconidial masses of a fungus developed on the collapsed stems and veins. A fungus was consistently isolated from the leaves, stems, and roots of symptomatic plants. Single conidia were isolated from sporodochia and cultured on potato dextrose agar (PDA) and oatmeal agar (OA) for 7 days. Isolates exhibited strong pungent odors on PDA and OA and a brownish orange colony on OA and a light orange colony on PDA. Masses of light orange and hemispherical-shaped conidia and stromata formed on OA. Conidiophores formed from aerial mycelium producing ellipsoidal microconidia without septation. Sporodochia formed on agar surface producing three-septate, slightly curved macroconidia. The cultural and conidial characteristics of the isolates were similar to those of Fusarium foetens Schroers (4). Partial translation elongation factor 1-α (TEF) gene was amplified and sequenced with primers ef1 and ef2. A comparison of a partial sequence has been deposited in GenBank (Accession No. HM748968) and showed a 100% match with F. foetens (2). Inoculations with F. foetens isolates were performed by injecting a 100-μl suspension of 1 × 106 conidia/ml into stems of five healthy plants near the ground or soaking the soil of five healthy 6-week-old H. begonias cv. Golden Edith with 50 ml of suspension. Control plants were similarly injected with sterile water or sown in sterile soil. After 4 weeks, all inoculated plants developed dark, wilting leaves and collapsed stems and veins similar to those observed in the commercial greenhouse. F. foetens was reisolated from diseased plants, and identification was reconfirmed by conidial characteristics and TEF 1-α sequence. Control plants were healthy and symptom free. F. foetens has recently been described in association with a new disease of H. begonias in Europe (3) and the United States (1). F. foetens can cause major economic losses to farmers and marketers of H. begonias in Europe and the United States. To our knowledge, this is the first report of F. foetens causing wilt disease of H. begonias in Canada.
References: (1) W.-H. Elmer et al. Plant Dis. 88:1287, 2004. (2) D.-M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) R. Schrage. Phytomed. Ges. 33:68, 2003. (4) H.-J. Schroers et al. Mycologia 96:393, 2004.
