Identification of QTLs conferring resistance to scald ( Rhynchosporium commune ) in the barley nested association mappin
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RESEARCH ARTICLE
Open Access
Identification of QTLs conferring resistance to scald (Rhynchosporium commune) in the barley nested association mapping population HEB-25 Bianca Büttner1, Vera Draba2, Klaus Pillen2, Günther Schweizer1 and Andreas Maurer2*
Abstract Background: Barley scald, caused by the fungus Rhynchosporium commune, is distributed worldwide to all barley growing areas especially in cool and humid climates. Scald is an economically important leaf disease resulting in yield losses of up to 40%. To breed resistant cultivars the identification of quantitative trait loci (QTLs) conferring resistance to scald is necessary. Introgressing promising resistance alleles of wild barley is a way to broaden the genetic basis of scald resistance in cultivated barley. Here, we apply nested association mapping (NAM) to map resistance QTLs in the barley NAM population HEB-25, comprising 1420 lines in BC1S3 generation, derived from crosses of 25 wild barley accessions with cv. Barke. Results: In scald infection trials in the greenhouse variability of resistance across and within HEB-25 families was found. NAM based on 33,005 informative SNPs resulted in the identification of eight reliable QTLs for resistance against scald with most wild alleles increasing resistance as compared to cv. Barke. Three of them are located in the region of known resistance genes and two in the regions of QTLs, respectively. The most promising wild allele was found at Rrs17 in one specific wild donor. Also, novel QTLs with beneficial wild allele effects on scald resistance were detected. Conclusions: To sum up, wild barley represents a rich resource for scald resistance. As the QTLs were linked to the physical map the identified candidate genes will facilitate cloning of the scald resistance genes. The closely linked flanking molecular markers can be used for marker-assisted selection of the respective resistance genes to integrate them in elite cultivars. Keywords: HEB-25, Hordeum vulgare, Hordeum vulgare ssp. spontaneum, Rrs, Wild barley, Scald resistance, Rhynchosporium commune, Nested association mapping (NAM), Greenhouse trials
Background Rhynchosporium commune, a haploid fungus, is the causal agent of scald or barley leaf blotch, an important foliar disease of barley (Hordeum vulgare ssp. vulgare L.). R. commune has been classified as a hemibiotroph fungus which * Correspondence: [email protected] 2 Martin Luther University Halle-Wittenberg, Institute of Agricultural and Nutritional Sciences, Chair of Plant Breeding, Halle, Germany Full list of author information is available at the end of the article
occurs in all barley growing areas around the world, especially in cool, humid climates [1]. The typical disease symptoms are tan necrotic lesions with dark brown margins, which occur after a latent period [2]. Besides barley the genus Rhynchosporium is able to infect further species, e. g. rye [1] and Lolium species [3]. Scald can cause yield losses of up to 40%, decreases grain quality [2, 4] and is considered a major
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