Detection and validation of novel QTL for shoot and root traits in barley (Hordeum vulgare L.)

Shoot and root attributes are essential for plant performance in agriculture. Here, we report detection and validation of quantitative trait loci (QTL) for shoot and root traits in 301 BC2DH lines achieved by crossing cultivar Scarlett and wild barley accession ISR42-8. Phenotypic evaluations were made for six traits across 3 years under control and drought conditions. QTL analysis was performed using 371 DNA markers genotyped by different protocols, such as sequence repeats, diversity array technology as well as gene-specific markers. Marker by trait analysis revealed 33 QTL of which 15 and 18 QTL showed trait-improving effects of the exotic and elite alleles, respectively. Two major QTL for plant height (PH) were found on chromosome 2H (QPh.S42.2H) and 3H (QPh.S42.3H.b). The strongest QTL QSdw.S42.5H for increasing shoot dry weight was associated with an exotic allele on chromosome 5H. QTL QTkw.S42.1H underlie a novel exotic allele that improved thousand kernel weight. Seven QTL were associated with root dry weight of which at four loci introgression of exotic alleles enhanced traits values. The strongest QTL QRdw.S42.7H was linked to a gene-specific marker VrnH3 on chromosome 7H. At QRl.S42.5H, the exotic allele accounted for a 9 % increase in root length. In addition, 18 epistatic interactions were linked to PH, shoot and root dry weights. QTL validation was performed with 53 introgression lines (ILs) carrying ISR42-8 introgressions in the Scarlett background. Nine novel QTL alleles of exotic origin were validated in the isogenic background. These QTL-bearing ILs provide valuable genetic resources for plant breeding and positional cloning of the underlying genes.