Structure and abundance of fusarium communities inhabiting the litter of beech forests in central europe

Abstract

Members of the genus Fusarium and related genera are important components of many ecosystems worldwide and are responsible for many plant diseases. However, the structure of beech litter-inhabiting Fusarium communities and their potential role in reducing the natural regeneration of European beech are not well understood. To address this issue, we examined Fusarium communities in the litter of uneven-aged, old-growth beech-dominated forests in the Carpathians (Poland) and in the Alps (Austria), and in a managed beech stand (Poland). The fungi inhabiting beech litter were investigated using beechnuts and pine seedlings as bait. The pathogenicity of the most common species was investigated by inoculating beech germinants. Fusarium spp. were identified based on morphology and DNA sequence comparisons of RPB2 and TEF1-α genes, combined with phylogenetic analyses. Twelve fungal species were identified from 402 isolates, including nine known and three currently undescribed species. The isolates resided in three species complexes within the genus Fusarium. These were the F. oxysporum (one taxon), F. sambucinum (three taxa), and F. tricinctum (six taxa) species complexes. In addition, one isolate was assigned to the genus Neocosmospora, and one isolate could be placed within the genus Fusicolla. The most frequently isolated fungi from beechnuts and beech germinants were F. avenaceum (Fr.) Sacc., F. sporotrichioides Sherb. and Fusarium sp. B. The structure and abundance of species within Fusarium communities varied by beech forest type. The species richness of Fusarium spp. was greatest in old-growth beech-dominated stands, while abundances of Fusarium spp. were higher in managed beech-dominated stands. Pathogenicity tests showed that all four Fusarium species isolated from beechnuts and beech germinants could cause germinants to rot beech, suggesting that these fungi may play a negative role in the natural beech regeneration.