|De Gruyter, J|
Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2003
Publication Date: 2/1/2004
Citation: Schroers, H., Baayen, R.P., Meffert, J.P., De Gruyter, J., Hooftman, M., O Donnell, K. 2004. Fusarium foetens, a new species pathogenic to Elatior begonia (begonia x hiemalis) hybrids and the sister taxon of the Fusarium oxysporum species complex. Mycologia. 96(2):393-406. Interpretive Summary: We used molecular, morphological and pathogenicity data to characterize strains of a filamentous mold that were isolated from a vascular wilt of begonia in several nurseries. The molecular and morphological data revealed that the begonia pathogen represents a new species of Fusarium that is closely related to other wilt pathogens within the Fusarium oxysporum species complex. Pathogenicity studies demonstrated that several begonia cultivars are highly susceptible to the new species which was called Fusarium foetens because cultures of this fungus exhibit a noxious odor. Inoculated plants developed signs of a vascular wilt within 4 weeks and most of them died within 8 weeks. Morphological characters and molecular tests are described that allow for the rapid identification of this economically important pathogen.
Technical Abstract: A new disease was recently discovered in Elatior hybrid begonia (Begonia x hiemalis) nurseries in The Netherlands. Diseased plants showed a combination of basal rot, vein yellowing and wilting. A species of Fusarium was consistently isolated from the discolored veins of leaves and stems. This species differed morphologically from F. begoniae, a known agent of begonia flower, leaf and stem blight. Unusually large masses of macroconidia formed by the pathogen covered the base of collapsing begonias. The Fusarium species resembled members of the F. oxysporum species complex in producing short monophialides on the aerial mycelium and abundant chlamydospores. Other phenotypic characters such as occasional polyphialides, presence of relatively long monophialides intermingled with the short monophialides formed on the aerial mycelium, distinct sporodochial conidiomata, and distinct pungent colony odor distinguished it from the F. oxysporum species complex. Phylogenetic analyses of partial sequences of the mitochondrial small subunit of the ribosomal DNA (mtSSU rDNA), nuclear translation elongation factor 1a (EF-1a) and ß-tubulin gene exons and introns indicate that the Fusarium species represents a sister group of the F. oxysporum species complex. Begonia x hiemalis cultivars Bazan, Bellona, and Netja Dark proved to be highly susceptible to the new species. Inoculated plants developed tracheomycosis within 4 wk and most of them died within 8 wk. The new taxon was not pathogenic to Euphorbia pulcherrima, Impatiens walleriana, and Saintpaulia ionantha that are commonly grown in nurseries along with B. x hiemalis. Inoculated plants of Cyclamen persicum did not develop the disease but had discolored vessels from which the inoculated fungus was isolated. Given that the newly discovered begonia pathogen is distinct in pathogenicity, morphology, and phylogeny from other fusaria, it is described here as a new species, Fusarium foetens Schroers, O'Donnell, Baayen et Hooftman.