Exploiting barley landraces to reintroduce lost genetic diversity: Resistance to net form net blotch

Centuries of barley (Hordeum vulgare) domestication and selection has resulted in reduced genetic diversity in modern cultivars, limiting breeder's options to select desirable traits. Barley landraces, heirloom varieties, and wild relatives are substantially more variable and can be exploited to reintroduce favorable genes and alleles. Five doubled haploid populations were phenotyped for net form net blotch (NFNB) disease, caused by the pathogen Pyrenophora teres f. teres, at three growth stages. Major, moderate, and minor effect quantitative trait loci (QTLs) associated with NFNB resistance were detected on six of the seven barley chromosomes, with percentage of explained variance (PEV) ranging from less than 10% to over 70%. Previously established major (PEV > 50%) and moderate (PEV 10%–40%) effect QTLs on 3H and 6H were detected against the Australian isolate used, as well as moderate and minor QTLs (PEV < 10%) distributed on 2H, 3H, 4H, and 5H. Differences in effect sizes of individual QTL were apparent between growth stages, tapering up toward heading or down from seedlings, together with growth stage-specific and synergistic QTL. Several of these QTL represent novel sources of resistance that may be combined for durable NFNB resistance.