18S rRNA gene sequences and supraordinal classification of
the Erysiphales
Saenz, G S; Taylor, J W; Gargas, A.
Mycologia, v.86, n.2, (1994): 212-216.
Abstract
The Erysiphales (powdery mildews) exhibit conflicting
morphologies and have been classified as either Pyrenomycetes
or Plectomycetes. The nuclear small subunit ribosomal RNA
gene was sequenced for two isolates of Blumeria graminis
forma speciales hordei in order to help resolve this
classification controversy. A single most parsimonious tree
was obtained grouping the Erysiphales with neither the
Plectomycetes nor the Pyrenomycetes, but rather placing the
powdery mildews in amongst a basal assemblage of apothecial
and pseudothecial fungi. Maximum likelihood tests were
conducted on constraint trees exhibiting three possible
morphological classifications. The results rejected the
placement of the Erysiphales amongst both the Plectomycetes
and Pyrenomycetes but could not reject placement amongst the
Discomycetes; therefore, the powdery mildews are not
Pyrenomycetes nor Plectomycetes. However, higher order
classification of the Erysiphales remains unresolved, since
there is no strong bootstrap support for the Erysiphales
amongst the basal assemblage of apothecial and pseudothecial
fungi.