Multigene phylogeny and taxonomy of the genus Melanconiella (Diaporthales)

Abstract

Molecular phylogenetic analyses of LSU rDNA demonstrate monophyly of the genus Melanconiella, and its status as a genus distinct from Melanconis is confirmed. Data of macro- and microscopic morphology, pure cultures and phylogenetic analyses of partial SSU-ITS-LSU rDNA, tef1 and rpb2 sequences revealed 13 distinct species of Melanconiella, six of which are described as new (M. chrysodiscosporina, M. chrysomelanconium, M. chrysorientalis, M. echinata, M. elegans, M. meridionalis). Melanconiella hyperopta var. orientalis is described as a new variety. Diaporthe carpinicola, D. ellisii, D. flavovirens, D. hyperopta and D. ostryae are formally combined into Melanconiella. The name Melanconiella chrysostroma is excluded from Melanconiella, as it is an obligate synonym of Wuestneia xanthostroma. The type of Melanconiella is confirmed as M. spodiaea. Several species are lecto- and/or epitypified. A key to all treated species of Melanconiella is provided, and the circumscriptions of the genera Melanconis and Melanconiella are emended. Most Melanconiella species revealed by molecular phylogenetic analyses can be well characterised by a suite of morphological traits including ascospore shape, length and width, colour, absence/presence and shape of appendages and the anamorph. Anamorph-teleomorph connections were confirmed by pure culture and DNA data, revealing the presence of a single melanconium- or discosporina-like anamorph for each species. Colony growth was found to be characteristic of the respective species. Melanconiella is shown to be confined to the host family Betulaceae, and all species are found to be highly host-specific, mostly confined to a single host species. The biodiversity of Melanconiella was determined to be centred on the genus Carpinus with nine species, five of which have been confirmed on C. betulus. Europe appears to be the geographic centre of Melanconiella biodiversity.