Molecular phylogeny of dogwood anthracnose fungus (Discula destructiva) and the Diaporthales

Dogwood anthracnose, caused by Discula destructiva Redlin (1991), is a dise ase of several native dogwood species in North America. A teleomorph has no t been found since the first reports of this disease in the 1970s, although the conidial state suggested a relationship to diaporthalean species. Phyl ogenetic analyses based on nuclear small subunit rDNA sequences of 47 perit hecial ascomycetes placed D. destructiva into the Diaporthales with high bo otstrap support. A phylogeny of 20 diaporthalean species based on large sub unit rDNA inferred three major clades in the Diaporthales. Discula destruct iva and four other Discula species formed a clade with Plagiostoma euphorbi ae, Gnomonia padicola, G. setacea, Pleuroceras pleurostylum, Linospora capr eae, Amphiporthe castanea, Apioplagiostoma aceriferum, Melanconis marginali s, and Apiosporopsis carpinea. Its sister group included Cryphonectria para sitica, Cryptodiaporthe corni, Endothia eugeniae, Valsa ambiens subspecies leucostomoides, and Apiognomonia supraseptata. Diaporthe phaseolorum formed a distinct basal branch. A primer pair (RPB2-P2F and RPB2-P3R) was develop ed to amplify a part of the gene encoding the second largest subunit of RNA polymerase II (RPB2) based on published pyrenomycete sequences. The RPB2 p hylogeny supported the close relationship of D. destructiva and the diaport halean species. Characters of pigmentation and anamorph agree with the phyl ogeny to some extent and emphasize the importance of anamorphs and pigmenta tion in the taxonomy of the Diaporthales. Family concepts based on perithec ium position, ascus persistence, and ascospore morphology were rejected, an d a new phylogenetic classification is needed.