High resolution mapping and identification of candidate genes for the BaMMV/BaYMV-resistance gene rym13 and Ryd3 involved in BYDV-tolerance of barley

Barley yellow mosaic disease, caused by Barley mild mosaic virus (BaMMV} and Barley yellow mosaic virus (BaYMV}, and barley yellow dwarf, caused by Barley yellow dwarf virus (BYDV}, are important diseases of barley causing high yield losses. As BaMMV and BaYMV are transmitted by the soil-borne plasmodiophorid Polymyxa graminis and BYDV by aphids, the only environmently sound way to prevent these yield losses is breeding for resistant/tolerant cultivars.In this thesis, high resolution mapping and candidate gene analysis for the BaMMV/BaYMV resistance gene rym13 and the BYDV tolerance conferring gene Ryd3 was conducted. For rym13, a high resolution mapping population based on 5,191 F plants was established and marker saturation was conducted by mapping the flanking markers to published genomic resources of barley. Using these genomic resources in combination with next-generation- sequencing-techniques led to a fast saturation of the resistance harbouring interval and identification of candidate genes. Analysing phenotypic and genotypic data revealed an independent inheritance of the BaMMV and BaYMV resistance in the cultivar ´Taihoku A´. Two candidate genes for rym13, co-segregating with BaMMV resistance in an independent population, were identified.Regarding Ryd3, the former mapping population established by Lüpken et al. (2014) was extended to 7,427 F plants. After mapping the co-segregating markers to the published reference genome of barley, the interval related to tolerance was shortened to 104.14 mio bp. This interval harbours a number of candidate genes. For further investigations to unravel the mechanism of tolerance, a TILLING population was established in the course of this thesis.This study lays the foundation for subsequent isolation and validation of rym13 and Ryd3.