Validation for root‐related quantitative trait locus effects of wild origin in the cultivated background of barley (Hordeum vulgare L.)

With 4 figures and 2 tables ABSTRACT: Extensive root system plays a major role in plant’s ability to tolerate water deficit conditions. Recently, quantitative trait locus (QTL) effects of wild origin associated with natural variation of root parameters were detected on the distal arm of chromosome 5H using 301 BC2DH lines of a cross between spring barley cultivar ‘Scarlett’ and the wild barley accession ISR42‐8. Here, we report the validation of these QTL effects in the near isogenic background of ‘Scarlett’ by using introgression lines (ILs; S42IL‐126 and S42IL‐176) of the targeted region. S42IL‐126 encompasses a single wild introgression on chromosome 5H, reaching out from 145.57 to 200.12 cM, whereas S42IL‐176 harbours a major introgression on chromosome 5H from 154.37 to 234.98 cM along with three minor introgressions on chromosomes 1H, 2H and 3H. S42IL‐126, S42IL‐176, ‘Scarlett’ and ISR42‐8 were evaluated for the root‐related traits; root dry weight (RDW), root volume (RV), root length and the associated traits; shoot dry weight and change in tiller number during drought stress (ΔTIL). The phenotypic evaluations revealed contrasting root systems in both parents where ISR42‐8 inherited highly extensive fibrous roots with respect to ‘Scarlett’. Both ‘Scarlett’ and S42IL‐126 developed smaller roots and showed no variation in root parameters, indicating that the wild introgression present in S42IL‐126 does not contain QTL alleles for the above‐mentioned root traits. On the contrary, S42IL‐176 revealed remarkable trait increases in RDW, RV and ΔTIL, which are similar to the donor parent ‘ISR42‐8’. The trait increases in S42IL‐176 are presumably due to the presence of exotic alleles at the QTLs QRDW.S42IL‐1, QRV.S42IL‐1 and QΔTIL.S42IL‐1. The comparison of phenotypic data and overlapping introgressions between S42IL‐126 and S42IL‐176 suggests that these QTLs reside on chromosome 5H in the interval between 200.12 and 234.98 cM. On the basis of the magnitude of QRDW.S42IL‐1, QRV.S42IL‐1 and QΔTIL.S42IL‐1, it is likely that these QTL effects are also linked to extra introgressions of S42IL‐176 present on chromosomes 1H where a QTL effect for RDW was also detected previously at the corresponding region of the wild introgression. In future, a follow‐up study with segregating offspring which are derived from S42IL‐176 will help to ultimately quantify and map the identified QTLs. On the basis of our QTL study, S42IL‐176 can be used for positional cloning of the underlying genes as well as to improve the root parameters of cultivated varieties.