Reassessment of Phomopsis species on grapevines
Ten species of Phomopsis have previously been identified from grapevines. Of these, P. viticola, the causal agent of Phomopsis cane and leaf spot, and P vitimegaspora, the causal agent of swelling arm of grapevines, have been confirmed as severe pathogens of this host. Earlier taxonomic treatments of Phomopsis species chiefly distinguished taxa based on host specificity, cultural characteristics and morphology. More recent studies have indicated, however, that these characteristics can no longer be used to distinguish species of Phomopsis due to the wide host ranges of some species, and the morphological plasticity of others. Using morphology, DNA sequences (ITS-1, 5.8S, ITS-2) and pathogenicity data, 15 Phomopsis spp. were distinguished from grapevines in the present study. Diaporthe helianthi, a known pathogen of sunflowers, is for the first time reported from grapevines. A further six, presently unknown species of Phomopsis, are also distinguished from grapevines. A phylogenetic analysis of ITS data generated in this study distinguished three clades containing isolates previously identified as D. perjuncta. Based on type studies, the name D. viticola can be applied to collections from Portugal and Germany. A new species, D. australafricana, is proposed for South African and Australian isolates formerly treated as D. perjuncta or D. viticola. A description for D. perjuncta is provided based on newly designated lectotype and epitype specimens. D. perjuncta is distinguished from D. viticola and D. australafricana based on morphology and DNA phylogeny. Artificial inoculations of green grapevine shoots indicated that, of the species tested, P. amygdali, a known pathogen of peaches in the USA, and P. viticola were the most virulent. © Australasian Plant Pathology Society 2005.