CONVERSION OF AN RFLP MARKER FOR THE BARLEY STEM RUST RESISTANCE GENE RPG1 TO A SPECIFIC PCR-AMPLIFIABLE POLYMORPHISM

The Rpg1 gene in barley has provided satisfactory levels of stem rust resistance for the last 50 years. The appearance of a new race of stem rust that is virulent to Rpg1 has resulted in efforts to incorporate new stem rust resistance genes into barley. Marker-assisted selection may provide the only means of combining this useful gene with resistance genes for which no virulent races have been identified. Several RFLP markers have been identified as linked to the Rpg1 locus. One of these, ABG704 was converted into a post-amplification restriction polymorphism. To generate a specific PCR-amplifiable polymorphism the sequence of the ABG704 locus from four barley cultivars was determined. Primers were developed that can detect a single-base difference between resistant and susceptible cultivars. The successful conversion of an RFLP marker to an allele-specific PCR-based marker not only demonstrates that this type of conversion is possible for cereals, but also results in an immediately useful marker for application to plant breeding programmes.