DNA polymorphisms among near-isogenic lines for powdery-mildew-resistant genes in barley detected by primers targeting resistance-gene analogs

Barley powdery mildew, caused by Erysiphe graminis f. sp. hordei, is a disease of economic importance in Europe and many other parts of the world. Genetic resistance is one of the most effective means to control this disease. The use of molecular markers closely linked to powdery-mildew-resistant genes would facilitate barley improvement. In this study, primers were synthesized based on the resistance-gene analogs primers used in genomic studies of maize, rice, barley, wheat, and potato. These primers were then used to detect DNA polymorphism in 15 near-isogenic lines (NILs) derived from 'Pallas', each carrying a different gene for resistance to E. graminis f. sp. hordei. We identified nine resistance-gene analogs putatively linked to the powdery-mildew-resistant genes Mla3, Mlp, and Mlg carried by the 'Pallas' NILs P2, P19, and P21, respectively. These molecular markers are potentially valuable tools for barley breeders to stack genes conferring resistance to powdery mildew. The three NILs will be individually crossed with a common susceptible barley cultivar to determine the linkage between the targeted resistance genes and the newly identified molecular markers.