Association mapping of net blotch and spot blotch resistance in a set of Hordeum vulgare accessions originated from the centers of barley diversity

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Net blotch caused by Pyrenophora teres and spot blotch caused by Cochliobolus sativus are two most damaging and widely distributed fungal pathogens of barley. As a result of long-term joint research projects of the Laboratory of Plant Resistance to Diseases of the All-Russian Research Institute of Plant Protection (VIZR) and the Institute for Resistance Research and Stress Tolerance of the Federal Research Center for Cultivated Plants (JKI), 10.000 barley accessions from different genetic centers of barley diversity and commercial cultivars were evaluated for resistance to both P. teres and C. sativus, and as a result about 450 accessions with different levels of resistance were identified. However, up to now very limited or no information on major genes or QTL involved in resistance of these accessions is available. To get this information in such a large number of accessions, genome wide association studies are an efficient tool facilitating the analyses of a much broader diversity than analyses in bi-parental populations.The objectives of the project are (i) to determine the genetic diversity of resistance and identify QTL for resistance to P. teres f. teres, and P. teres f. maculata as well as to C. sativus in a representative barley germplasm collection employing genome wide association studies (GWAS), (ii) to test the stability and transferability of some detected QTL by integrating associated markers in segregating already phenotyped DH-populations, (iii) to saturate these QTL with markers and to link these to the physical and sequence maps of barley towards the identification of candidate genes, (iv) to enhance the use of these QTL in breeding by developing efficient and cheap PCR assays. To achieve this, 450 barley accessions will be phenotyped at the JKI and the VIZR for resistance by inoculation with different isolates of P. teres f. teres, P. teres f. maculata, and C. sativus originated from Russia and Germany to get detailed information on resistance. For genotyping, the Illumina 9k iSelect barley Chip and genotyping by sequencing (GBS) currently under establishment at JKI will be used and population structure will be estimated on two SSRs per chromosome arm. GWAS will be conducted using a mixed linear model approach. Based on these GWAS it is expected that most of the genomic regions of barley encoding resistance to P. teres f. teres, P. teres f. maculata, and C. sativus will be identified. Respective QTL regions will be marker saturated as a first step towards a map based cloning approach. Using this approach detailed information on the genetic diversity of resistance concerning the above mentioned pathogens will be gained and respective markers will facilitate a directed use of this diversity in barley breeding.