Molecular Characterization of BYDV Resistance Gene Ryd4Hb Introgressed from Hordeum bulbosum into Barley

Barley yellow dwarf virus (BYDV) causes high yield losses worldwide. Thereby aphids play an important role as virus vectors. Yield losses caused by BYDV may be reduced using virus-tolerance genes from the primary genepool of barley. Additionally, complete resistance to the virus has been introgressed from the secondary genepool via interspecific crosses with the tetraploid wild species Hordeum bulbosum. Previous studies indicate that this resistance was introgressed to barley chromosome 3HL and is governed by a dominant gene, Ryd4^Hb. In the present study, a BC₂F₄ mapping population consisting of 140 individuals was used to establish a molecular-marker map for Ryd4^Hb. For marker development three strategies are applied: (I) Using the orthology to the model genome of Oryza sativa, (II) Massive Analysis of cDNA Ends (MACE), and (III) RNASeq.  The approaches provide a potential of approximately 200 markers for the 3HL introgression. So far, 25 markers were mapped on 3HL including 10 MACE markers. Three MACE markers are located with a distance of 0.1 to 0.5 cM to Ryd4^Hb and are of potential use for marker-assisted breeding programs.