A revision of Verticillium sect. Prostrata - I. Phylogenetic studies usingITS sequences

The anamorph genus Verticillium is extremely heterogeneous, comprising memb ers of the Phyllachorales and Hypocreales, among the latter particularly th e Clavicipitaceae. In view of vast biological differences (plant pathogens vs. parasites of fungi, insects, nematodes, and rotifers, which are often v aluable in biological control), a subdivision into more natural entities is needed. A representative selection of strains available at CABI Bioscience and Centraalbureau voor Schimmelcultures was examined morphologically, and sequences of the ITS regions of nrDNA were analysed phylogenetically. Four clades are sharply delimited: Clade A comprises the type species of the ge nus,V. luteo-album, and members of Verticillium sect. Nigrescentia, which a ll have consistently erect conidiophores and are probably affiliated with t he Phyllachorales. The large clade B contains species with white fluffy col onies lacking any resting structures, the most important members are the ag gregates of V. lecanii with cylindrical and V. psalliotae with falcate coni dia. Thus both entomogenous and fungicolous taxa are comprised in this clad e. Cordyceps militaris belongs to this clade as do Aphanocladium aranearum and A. dimorphum; the latter taxon merges strains with exclusively short, e vanescent 'aphanophialides' with those showing typical aculeate phialides. On the other hand, the type species of the genus Aphanocladium, A. album, i s just distantly related to this clade. Teleomorphs of V. lecanii and 'Ceph alosporium' lanosoniveum belong to Torrubiella, a genus that is scarcely di stinct from Cordyceps. Clade C comprises a few taxa around V. bulanoides, e ndoparasites of nematodes with balanoid to conoid and distally adhesive con idia. Clade D comprises mainly parasites of nematode eggs or cysts, which i n the typical case produce dictyochlamydospores. These taxa were previously classified in the separate genus Diheterospora. A subclade contains the pa rasites of bdelloid rotifers classified in Rotiferophthora. The necessary n omenclatural conclusions will be drawn in a subsequent paper, when addition al DNA portions have been sequenced.