Taxonomic revision of Bisifusarium (Nectriaceae)

Abstract

Species of Bisifusarium (previously the Fusarium dimerum species complex) have been associated with cheese fermentation and a wide range of opportunistic human infections, but they are generally regarded as saprotrophs. Bisifusarium spp. are also commonly isolated from soils and tissues of plants growing in arid climates. The genus is typically characterized by its distinct pionnotal growth in culture, and typically very short, 0–2(–3)-septate macroconidia, produced in sporodochia or on lateral phialidic hyphal pegs. Only 16 species of Bisifusarium have been described to date, and this study sought to re-evaluate these taxa by examining 116 Bisifusarium isolates from the culture collection of the Westerdijk Fungal Biodiversity Institute in Utrecht, The Netherlands. A multi-gene phylogenetic analysis using partial nucleotide sequences of the translation elongation factor 1-alpha (tef1), partial RNA polymerase II second largest subunit (rpb2), the 5.8S nrDNA with its flanking intergenic spacer regions (ITS), and partial β-tubulin (tub2) genes resolved 25 phylogenetic lineages. Further evaluation of culture and morphological characters, and host-substrates, confirmed eight of these clades as novel taxa that are formally described here. In addition, two putative novel species were identified but not described due to limited available data. We provide the morphological descriptions and photographic illustrations for B. hedylamarriae and B. lovelliae, which were formerly known only from their DNA data. This study significantly increases the number of species in Bisifusarium and provides a crucial foundation for future studies to elucidate the ecology and evolutionary relationships within this expanding genus.