Taxonomic status of putative Verticillum alboatrum isolates

Two fungal isolates, formerly classified as Verticillium alboatrum and proposed as forming the basis of a new sub-group (`Group 2') within the species, have been shown to be non-pathogenic to known hosts of V. alboatrum and, on the basis of molecular evidence, to be closely related to Verticillium psalliotae and Verticillium fungicola. We propose that the taxon V. alboatrum be confined to those closely related isolates, usually plant pathogenic and usually producing dark resting mycelium, referred to by other authors as Group 1. The only sub-specific groupings which appear valid (based on pathological and molecular evidence) comprise: (1) host-adapted isolates from lucerne; and (2) all other isolates.