Blumeria graminis

Blumeria graminis (commonly called barley powdery mildew or corn mildew) is a fungus that causes powdery mildew on grasses, including cereals. It is the only species in the genus Blumeria. It has also been called Erysiphe graminis and (by its anamorph) Oidium monilioides or Oidium tritici. Previously B. graminis was included within the genus Erysiphe, but molecular studies have placed it into a clade of its own. In 1975, it was moved to the new monospecific genus Blumeria. Blumeria differs from Erysiphe in its digitate haustoria and in details of the conidial wall. Blumeria is also considered to be phylogenetically distinct from Erisiphe as it solely infects the true grasses of Poaceae. Eight special forms or formae speciales (ff.spp.) of B. graminis have been distinguished, each of which is parasitic on a particular genus or pareticular genera of grasses. Those that infect crop plants are B. g. f.sp. , which causes powdery mildew of wheat and infects other grasses in the genera Triticum and Aegilops, f.sp. on barley, f.sp. on oats and f.sp. on rye. Other formae speciales are pathogenic on wild grasses, including on grasses in the genera Agropyron and Elymus, on Bromus spp., on Poa spp. and on Lolium spp. (ryegrass). The mycelium can cover the plant surface almost completely, especially the upper sides of leaves. Ascocarp is dark brown, globose with filamentous appendages, asci oblong. Ascospores hyaline, ellipsoid, 20–30 x 10–13 μm in size. Anamorph produces on hyaline conidiophores catenate conidia of oblong to cylindrical shape, not including fibrosin bodies, 32–44 x 12–15 μm in size. Haustoria are palmate. B. graminis is unique among the Erysiphales by having conidia with a primary germ tube and finger-shaped ("digitate") appressoria. The genus name of Blumeria is in honour of Samuel Blumer (b. 1895), a Swiss botanist (Mycology), Phytopathology, from the University of Bern (Universität Bern). The genus was circumscribed by Golovin ex Speer in Sydowia Vol.27 on page 2 in 1975. B.