Frequency of Powdery Mildew Resistances in Spring Barley Cultivars in Czech Variety Trials

In 2006-2010, resistance to the powdery mildew pathogen was studied in 277 spring barley cultivars. They were represented by 54 cultivars in Czech official variety trials, of which 42 were foreign, and 223 cultivars in variety trials conducted by domestic breeding companies in that period. Sixty-eight domestic cultivars (28.8%) exhibited heterogeneity in the examined trait, i.e. they were composed of lines with different resistances to powdery mildew. Thirteen known resistances were identified (Ab, Ar, HH, La, Ly, Mlo, Ri, Ro, Ru, Sp, St, Tu2 and We). The most frequent resistance was Mlo detected in 160 homogeneous cultivars (= 76.6%). The newly described resistance Ro was found in 13 cultivars. Frequency of other resistances was low (maximally 2.4%). Unknown resistances were found in 16 cultivars, in five of which they were effective to all used pathotypes of the pathogen. Research on cultivars possessing unknown resistances and registered heterogeneous cultivars continues.