Identification of QTL for agronomic traits in a backcross involving a barley landrace

The basis of this study is the finding that some Spanish barley landraces perform better than modern cultivars at low production sites. The best of these lines are being introduced through backcrosses in the national Spanish barley breeding program. The objectives of this study are to identify favorable QTLs for interesting agronomic traits contributed by the landrace SBCC073 and to characterize shoot, root and physiological traits of a group of landraces and cultivars, under control and drought conditions. In order to achieve these objectives, a population of 100 BC1F5 lines, was derived from the cross between the elite cultivar (Orria), with high productivity, and the Spanish landrace SBCC073, which was the best at low production trials, and used for QTL detection. The population was evaluated in field trials for three years (2011, 2013, and 2014) in Zaragoza. In parallel, the parents of the population, together with the elite cultivar Scarlett, were evaluated under control and stress conditions in a long-term standard greenhouse experiment carried out in Zaragoza (Spain). Another experiment, focusing primarily on short-term growth (1 month) of the root system was conducted in a high-throughput phenotyping platform (GROWSCREEN-Rhizo) in Forchungszentrum, Jülich (Germany) using six barley genotypes including the above mentioned genotypes. SBCC073 displayed higher values of physiological traits like relative water content and chlorophyll levels (SPAD readings) than Orria and Scarlett under drought. However, there were no major differences in growth of the aerial part among genotypes. In the short term experiment, landraces in general presented higher growth vigor of shoot and root than cultivars, particularly under control conditions. SBCC073 showed higher root dry weight than any other genotype. The population was genotyped with a DArTseq® genotyping-by-sequencing assay. A genetic linkage map was developed using markers of flowering time genes and 1227 SNPs of good quality. The genetic map resulted in 11 linkage groups, covering a total distance of 871.1 cM, with 4 complete chromosomes (1H, 3H, 4H and 5H) and three fragmented ones (2H, 6H and 7H). Five QTL for grain yield were detected on 2H.1, 4H, 5H and 6H.2. SBCC073 alleles contributed to increase yield in three of them. A region, at the end of chromosome 5H, contains favorable alleles for early vigor, higher grain yield and earlier flowering, all derived from SBCC073. Orria alleles contributed to increase grain yield and simultaneously to reduce plant height on the same region of 6H.2, and to increase thousand kernel weight on chromosomes 3H and 5H. The value of landrace SBCC073 as contributor of valuable traits for breeding has been confirmed, and a strategy to introduce its favorable alleles in breeding through MAS is proposed