Novel species of Cylindrocarpon (Neonectria) and Campylocarpon gen. nov associated with black foot disease of grapevines (Vitis spp.)

Four Cylindrocarpon or Cylindrocarpon-like taxa isolated from asymptomatic or diseased Vitis vinifera plants in nurseries and vineyards of South Africa, New Zealand, Australia, and France were morphologically and phylogenetically compared with other Neonectrial/Cylindrocarpon taxa. Sequences of the partial nuclear large subunit ribosomal DNA (LSU rDNA), internal transcribed spacers 1 and 2 of the rDNA including the 5.8S rDNA gene (ITS), and partial -tubulin gene introns and exons were used for phylogenetic inference. Neonectria/Cylindrocarpon species clustered in mainly three groups. One monophyletic group consisted of three subclades comprising (i) members of the Neonectria radicicola/Cylindrocarpon destructans complex, which contained strains isolated from grapevines in South Africa, New Zealand, and France; (ii) a Neonectria/Cylindrocarpon species isolated from grapevines in South Africa, Canada (Ontario), Australia (Tasmania), and New Zealand, described here as Cylindrocarpon macrodidymum; and (iii) an assemblage of species closely related to strains identified as Cylindrocarpon cylindroides, the type species of Cylindrocarpon. This monophyletic group excluded two other groups, which comprised (i) members of the Neonectria mammoidea complex, with anamorphs characterised by curved macroconidia, violet or purple pigments in cultures of most of its members, and lack of microconidia and chlamydospores; and (ii) two undescribed Cylindrocarpon-like species, both from grapevines in South Africa. The latter two clades formed a paraphyletic group in LSU rDNA analysis but were supported as a monophyletic group in ITS and -tubulin gene analysis. Strains of the Neonectria radicicola/Cylindrocarpon destructans complex isolated from grapevines matched C. destructans in morphology and DNA sequences. Cylindrocarpon macrodidymum formed micro- and macroconidia, but rarely formed chlamydospores. Its mostly 3-septate macroconidia were more or less straight, minutely widening towards the tip, and had an apical cell slightly bent to one side. Its teleomorph, Neonectria macrodidyma, was obtained in mating experiments, and was characterised by smooth to finely warted ascospores, smooth to finely warted perithecia, and moderately sized angular to subglobose cells in the outer region of the perithecial wall. The other two undescribed Cylindrocarpon-like species mentioned above were characterised by mostly 3-5-septate, curved macroconidia, and by the lack of microconidia. Both species differed from members of the Neonectria mammoidea group by brownish colonies and by brownish hyphal strands formed in the aerial mycelium. For these species a new genus, Campylocarpon gen. nov., is proposed. It comprises the new species Campylocarpon fasciculare and Campylocarpon pseudofasciculare, respectively. Inoculation of 6-mo-old potted grapevine rootstocks (cv. Ramsey) with selected isolates of Cylindrocarpon destructans, Neonectria macrodidyma, Campylocarpon fasciculare, and Campylocarpon pseudofasciculare resulted in a reduced root and shoot mass of inoculated plants and appearance of symptoms typical of black foot disease.