Application of molecular markers in breeding for resistance to the Barley yellow mosaic virus complex

Barley yellow mosaic virus disease - caused by barley mild mosaic virus (Ba MMV), barley yellow mosaic virus (BaYMV) and BaYMV-2 - has to be considered as one of the most important diseases of winter barley in Europe. Due to t ransmission by the soil-borne fungus Polymyxa graminis, chemical measures a gainst the disease are neither efficient nor economic. Therefore, breeding for resistance to this disease is of special importance. By segregation ana lysis followed by the application of molecular techniques, like RFLPs, RAPD s, SSRs and AFLPs, different resistance genes have been integrated into the RFLP-map of barley barley and PCR-based markers have been developed for th ese genes (ym4, ym5, ym3, ym11). These markers are useful tools in barley b reeding today as they can be used in marker-based selection procedures, mar ker-assisted backcrossing programmes and in order to combine different resi stance genes in one genotype ('pyramiding'), thereby facilitating efficient breeding of resistant lines.