The species of Coleosporium (Pucciniales) on Solidago in North America.

Species of Coleosporium (Pucciniales) are rust fungi that typically alternate between pines and angiosperms. In North America, species of Coleosporium often infect Solidago (goldenrods), although their taxonomy on these hosts is unresolved. Joseph. C. Arthur and George B. Cummins regarded these as a single species, Coleosporium solidaginis (fide Arthur) or C. asterum (fide Cummins), but later inoculation studies demonstrated the presence of more than one species, distinguishable by their aecial hosts. A more recent taxonomic study of Coleosporium found that specimens on Solidago identified as C. asterum in North America were not conspecific with the type, which is from Japan, prompting the present study. Herein, we conducted a systematic study on ca. 60 collections of Coleosporium infecting species of Asteraceae from North America using regions of ribosomal DNA and morphology of teliospores and basidia. Our data indicate at least three species of Coleosporium occur on Solidago in North America, C. solidaginis, C. montanum comb. nov., which is proposed for the taxon that has commonly been identified as C. asterum in North America, and C. delicatulum, all of which can be differentiated by morphology of their basidia. In addition, the challenges of marker selection for molecular barcoding of rust fungi is discussed.