Selection of Spring Barley Varieties for Exploiting Quantitative Resistance for Powdery Mildew Control

Barley (Hordeum vulgare L.) is an important cereal, and powdery mildew caused by Blumeria hordei is a major disease of this crop. The most appropriate way to protect barley from the disease is to grow resistant varieties, and a method to achieve this is to exploit quantitative minor genes that confer sufficiently effective and long-lasting resistance. However, when searching for quantitative resistance, broken major genes can also play a role and might affect the infection of evaluated varieties, especially on small plots in experimental fields. Therefore, our present research focused on identifying accessions without major resistance genes. We tested 2804 genebank accessions of spring barley originating from 70 countries using nine isolates of the pathogen known to have a very wide spectrum of avirulence. In 143 accessions, no major resistance gene was found, and 304 accessions carried major genes Mla8 or MlCh, which cannot affect their resistance in the field because of the absence of corresponding avirulent pathotypes. These 447 accessions can therefore be preferably used to reveal and exploit targeted minor genes.