Half sib selection for resistance to powdery mildew (Erysiphe graminis DC. f.sp. secalis Marchal) in rye populations

Three rye populations originating from different cultivars were subjected to half sib progeny selection for three cycles to improve their resistance to powdery mildew (Erysiphe graminis DC. f.sp. secalis Marchal). Selection was carried out in the greenhouse (measurement of spore production at the three-leaf stage), in the field (scoring of mildew infections at ear emergence) or at both locations. All selections resulted in significant responses, the level of which varied depending on the genetic base of mildew resistance in the populations. Greenhouse selection was most effective when the frequency of dominant genes could be increased, whereas field selection was less effective. Estimates for heritability in the narrow sense ranged from 0.42-0.94 indicating that mildew resistance can be increased effectively. Inbred lines should be selected in base populations with a high level of quantitative resistance and/or a high frequency of dominant genes. For an effective resistance strategy in hybrid breeding such dominant genes are most valuable, and can be selected in young growth stages. In 'Strain CG' the increase of dominant resistance genes by early selection resulted in a significant improvement of kernel yield.