Development of a marker within the candidate Un8 true loose smut resistance gene for use in barley breeding

Breeding for resistance to true loose smut infection caused by the pathogen (Ustilago nuda (Jens.) Rostr.) is an economical and environmentally safe way to limit the effect of this pathogen on barley. However, screening for resistance using natural infection can lead to inconsistent results and artificial inoculation is labour intensive, and can fail, leading to erroneous phenotyping. Marker assisted selection of genes conferring disease resistance can increase the efficiency of breeding programs. A candidate gene for Un8 resistance was used to develop a genetic marker which was tested on a recombinant inbred line (RIL) population derived from the resistant CDC Freedom and the susceptible Samson varieties. The RIL population (98 lines) was phenotyped for resistance to true loose smut by artificial inoculation and genotyped with the newly developed marker. The genotyping results obtained with the marker developed in this study were mostly consistent with true loose smut resistance determined by artificial inoculation. The markers was also tested in additional barley cultivars and breeding material. Repeated analysis of inconsistent results is required to confirm or revise these results, as well as further investigation of the candidate gene to confirm its role in barley true loose smut resistance is being planned.