Origin and evolution of the powdery mildews (Ascomycota,Erysiphales)

Molecular phylogeny suggests a close relationship of Asteraceae to the early evolution of Golovinomyces. The family Asteraceae, with a geographic origin in South America, expanded into the Northern Hemisphere, where it may have been infected by an ancestor of Golovinomyces, thus starting a close host–parasite relationship. Using this event as a calibration point, we designed molecular clocks for powdery mildews using the 28S rDNA D1/D2 and internal transcribed spacer (ITS) regions. According to these clocks, the powdery mildews originated in the Late Cretaceous and the first radiation of the major lineages occurred at the Cretaceous/Paleogene boundary. Ancestral powdery mildews may have first radiated on broad-leaved deciduous trees in the high latitudes of the Northern Hemisphere, and continued further speciation whilst migrating to southward during the world cooling in the Paleogene and Neogene periods. The cradle of four herb infecting genera, viz. Blumeria, Golovinomyces, Leveillula, and Neoërysiphe may be within the area extending from Central/West Asia to the Mediterranean.