Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/2/2008
Publication Date: 9/2/2008
Citation: Schroers, H., Lamprecht, S.C., O Donnell, K., Kammeyer, P.L., Johnson, S., Sutton, D.A., Rinaldi, M.G., Summerbell, R.C. 2008. Morphological and molecular variation among species of the Fusarium dimerum species group. Meeting Abstract. Interpretive Summary:
Technical Abstract: The name Fusarium dimerum has been used in the past for saprotrophic fungi and opportunistic human pathogens with up to 3-septate but mostly 0- or 1-septate Fusarium-like conidia. On the basis of narrowly defined morphological characters, the varieties Pusillum, Nectrioides and Violaceum were distinguished but phylogenetic analysis on the basis of sequences of 4 loci indicate that the morphospecies Fusarium dimerum comprises more than 10 phylogenetic species. When formed on the agar surface, septate conidia are produced in these species only sparsely and swell and become vacuolated quickly. Therefore, they cannot be used for refined morphological characterizations. On surfaces of carnation leaf pieces placed on synthetic nutrient-poor agar, most species of the Fusarium dimerum group form well-developed sporodochia with consistently shaped macroconidia and with a uniform number of septa, with the help of which some of the phylogenetic species can be morphologically segregated. Six of these species form predominantly 2-septate conidia or immature conidia, where the single septum is placed asymmetrically. By way of contrast, several other species form sporodochial conidia with a single, more or less medial septum. Among the species with 2-septate septa, one is characterized by almost annulate conidia, while conidia of the other species can either be more strongly curved distally than proximally or lunate. Similarly, conidia in species with 1-septate spores can either be almost straight but with bent and pointed ends or lunate. The morphological and molecular variation among the phylogenetic species of the Fusarium dimerum species group so far recognized is illustrated.