Distinct Defenses Induced in Wheat Against Powdery Mildew by Acetylated and Nonacetylated Oligogalacturonides

Randoux B Renard Merlier D Mulard G Rossard S Duyme F Sanssene J Courtois J Durand R and Reignault P 2010 Distinct defenses induced in wheat against powdery mildew by acetylated and nonacetylated oligogalacturonides Phytopathology 100 1352 1363 In wheat little is known about disease resistance inducers and, more specifically about the biological activities from those derived from endogenous elicitors such as oligogalacturonides (OGAs) Therefore we tested the ability of two fractions of OGAs with polymerization degrees (DPs) of 2-25 to induce resistance to Blumeria graminis f sp tritict and defense responses in wheat One traction was unacetylated (OGAs-Ac) whereas the second one was 30% chemically acetylated (OGAs+Ac) Infection level was reduced to 57 and 58% relative to controls when OGAs Ac and OGAs+Ac respectively were sprayed 48 h before inoculation Activities of various defense related enzymes were then assayed in noninoculated wheat leaves infiltrated with OGAs Oxalate oxidase peroxidase and lipoxygenase were responsive to both OGAs Ac and OGAs+Ac which suggests involvement of reactive oxygen species and oxilipins in OGAs mediated responses in wheat In inoculated leaves both fractions induced a similar increase in H2O2 accumulation at the site of fungal penetration However only OGAs+Ac led to an increase in papilla associated fluorescence and to a reduction of formed fungal haustoria Our work provides the first evidence for elicitation and protection effects of preventive treatments with OGAs in wheat and for new properties of acetylated OGAs