Marker assisted separation of resistance genes Rph22 and Rym16^sup Hb^ from an associated yield penalty in a barley: Hordeum bulbosum introgression line

The resistance genes Rph22 and Rym16 ^sup Hb^ transferred into barley from Hordeum bulbosum have been separated from a large yield penalty locus that was present in the original introgression line '182Q20'. The Hordeum bulbosum introgression line '182Q20' possesses resistance to barley leaf rust (Rph22) and Barley mild mosaic virus (Rym16 ^sup Hb^) located on chromosome 2HL. Unfortunately, this line also carries a considerable yield penalty compared with its barley genetic background 'Golden Promise'. Quantitative trait locus (QTL) mapping of the components of yield (total yield, thousand grain weight, hectolitre weight, percentage screenings and screened yield) was performed using 75 recombinant lines derived from the original '182Q20' introgression line. A QTL for the yield penalty was located in the proximal region of the introgressed segment. Marker assisted selection targeting intraspecific recombination events between overlapping H. bulbosum introgression segments was used to develop the lines '372E' and '372H' which feature genetically small introgressions around Rph22. Further yield trials validated the separation of both Rph22 and Rym16 ^sup Hb^ from the proximal yield penalty. These results, combined with molecular markers closely linked to Rph22 and Rym16 ^sup Hb^, make these resistance genes more attractive for barley breeding.