1 ANALYSIS OF POWDERY MILDEW RESISTANCE IN THE SPANISH BARLEY CORE COLLECTION C. Silvar 1,4 , K. Flath 2 , D. Kopahnke 3 , M.P. Gracia 1 , J.M. Lasa 1 , A.M. Casas 1 , E. Igartua 1 , and F. Ordon 3 1 Department of Genetics and Plant Production, Aula Dei Experimental Station, CSIC, E-50080 Zaragoza, Spain. 2 Institute for Plant Protection in Field Crops and Grassland, Julius Kühn-Institute, D-14532 Kleinmachnow, Germany. 3 Institute for Resistance Research and Stress Tolerance, Julius Kühn-Institute, D-06484 Quedlinburg, Germany. 4 Corresponding author: silvar@eead.csic.es