Sources of seedling and adult plant resistance to Puccinia striiformis f.sp. tritici in European wheats

One-hundred-and-forty-one wheat cultivars were tested at the seedling stage using up to 16 yellow rust isolates of diverse origin. Sixty-five resistance spectra were observed, including 20 spectra defined by differential cultivars with specific genes for resistance to Puccinia striiformis f.sp. tritici . Yr1 , Yr2 , Yr3 , Yr4 , Yr6 , Yr9 , Yr15 , Yr17 , Yr25 , Yr32 , and several additional sources of resistance were recognized. The resistance spectra were often conferred by Yr -genes and resistance factors with an unresolved genetic basis. All cultivars carried resistance and 27 had resistance for which no fully compatible isolate was detected. Yr15 was detected in four cultivars, a resistance from wild Emmer not previously reported in commercial wheat. There was no indication of Yr5 , Yr7 , Yr8 , Yr10 and Yr24 in any cultivar. Most cultivars were also investigated in field nurseries using up to nine isolates of Danish origin. Fifty-six cultivars displayed high or very high levels of resistance to any isolate in the field, and 18 of these showed full compatibility at the seedling stage to at least one isolate, i.e. revealing components of adult plant resistance.