ABSTRACT
Trichoderma species are asexual, saprophytic –lamentous fungi with teleomorphs belonging to the genus Hypocrea (Ascomycota, Pyrenomycetes, Hypocreales, Hypocreaceae). Comprehensive historical overviews about the developments in the taxonomy of the genus Trichoderma were presented by Druzhinina et al.1,2 The genus was introduced by Persoon in 1794 for a green fungus growing on fallen branches and other substrates.3 Bisby4 suggested that the genus Trichoderma consisted of a single species, T. viride. Until 1969, most species were referred to as either T. viride or T. koningii, depending upon whether they produced globose or oval conidia, respectively. In 1969, Rifai5 revised the taxonomy of the genus Trichoderma and described nine “species aggregates” based on the types of branching systems of the conidiophores, the character of phialospores, the phialide disposition, and conidial morphology. In the 1980s and early 1990s, Bissett6-9 dissected several of Rifai’s aggregate species into several de–ned taxa and proposed an infrageneric classi–cation of Trichoderma, which divides the genus into sections Trichoderma, Pachybasium, Saturnisporum, Longibrachiatum, and Hypocreanum. The
introduction of sequence-based molecular methods10 and multigene phylogenic approaches11 as well as the application of the genealogical concordance phylogenetic species recognition (GCPSR) concept12 enabled the revision of the morphology-based taxonomy in Trichoderma and the identi–cation of new species. The number of described and con-–rmed, phylogenetically different Trichoderma species has already reached 100.2
Macroscopically, Trichoderma species can be generally characterized by rapidly growing, initially smooth and translucent or watery white colonies, later becoming ¼occose, with distinct tufts of conidiophores that frequently form concentric ringlike zones, gradually changing their color from whitish green to light olive green at maturity. Microscopically, conidia occur in balls at the apexes of ¼ask-shaped phialides that arise at angles from the conidiophores. The identi–cation of Trichoderma strains at the species level by morphological examinations is problematic. In order to aid the fast and reliable identi–cation of isolates, the online resources TrichOkey, a DNA-barcode system based on de–ned nucleotide sequence differences in the ITS1 and ITS2 region,13,14 and TrichoBLAST, a multiloci database of phylogenetic markers for Trichoderma and Hypocrea powered by sequence diagnosis and similarity search tools15 have been developed.
