title: Host surface properties affect prepenetration processes in the barley powdery mildew fungus.
abstract: The initial contact between Blumeria graminis f.sp. hordei and its host barley (Hordeum vulgare) takes place on epicuticular waxes at the surfaces of aerial plant organs. Here, the extent to which chemical composition, crystal structure and hydrophobicity of cuticular waxes affect fungal prepenetration processes was explored. The leaf surface properties of barley eceriferum (cer) wax mutants were characterized in detail. Barley leaves and artificial surfaces were used to investigate the early events of fungal infection. Even after epicuticular waxes had been stripped away, cer mutant leaf surfaces did not affect fungal prepenetration properties. Removal of total leaf cuticular waxes, however, resulted in a 20% reduction in conidial germination and differentiation. Two major components of barley leaf wax, hexacosanol and hexacosanal, differed considerably in their ability to effectively trigger conidial differentiation on glass surfaces. While hexacosanol, attaining a maximum hydrophobicity with contact angles of no more than 80 degrees, proved to be noninductive, hexacosanal significantly stimulated differentiation in c. 50% of B. graminis conidia, but only at contact angles > 80 degrees. These results, together with an observed inductive effect of highly hydrophobic, wax-free artificial surfaces, provide new insights into the interplay of physical and chemical surface cues involved in triggering prepenetration processes in B. graminis.
authors.affiliation: Universität Würzburg, Julius-von-Sachs-Institut für Biowissenschaften, D-97082 Würzburg, Germany.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Zabka
authors.affiliation: Universität Würzburg, Julius-von-Sachs-Institut für Biowissenschaften, D-97082 Würzburg, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Stangl
authors.affiliation: Universität Würzburg, Institut für Organische Chemie, D-97074 Würzburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Bringmann
authors.affiliation: Universität Würzburg, Julius-von-Sachs-Institut für Biowissenschaften, D-97082 Würzburg, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Vogg
authors.affiliation: Universität Würzburg, Julius-von-Sachs-Institut für Biowissenschaften, D-97082 Würzburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Riederer
authors.affiliation: Universität Würzburg, Julius-von-Sachs-Institut für Biowissenschaften, D-97082 Würzburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hildebrandt
mesh_terms: D001203:Ascomycota / Q000502:physiology*; D001467:Hordeum / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000382:microbiology*; D019441:Plant Epidermis / Q000378:metabolism; D018515:Plant Leaves / Q000382:microbiology*; D014885:Waxes
chemical_list: D014885:Waxes