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Cereal crop yield is greatly affected in many growing areas by abiotic stresses, mainly low temperature and drought. In order to find candidates for the tolerance genes for these stresses, 13 genes encoding for transcription factors and upstream regulators were screened by amplification and SSCP on six parental genotypes of three barley mapping populations (‘Nure’ × ‘Tremois’, ‘Proctor’ × ‘Nudinka’, and ‘Steptoe’ × ‘Morex’), and mapped as newly developed STS, SNP, and SSCP markers. A new consensus function map was then drawn using the three maps above, including 16 regulatory candidate genes (CGs). The positions of barley cold and drought tolerance quantitative trait loci (QTLs) presently described in the literature were added to the consensus map to find positional candidates from among the mapped genes. A cluster of six Hv CBF genes co-mapped with the Fr-H2 cold tolerance QTL, while no QTLs for the same trait were positioned on chromosome 7H, where two putative barley regulators of CBF expression, ICE1 and FRY1, found by homology search, were mapped in this work. These observations suggest that CBF gene(s) themselves, rather than their two regulators, are at present the best candidates for cold tolerance. Four out of 12 drought tolerance QTLs of the consensus map are associated with regulatory CGs, on chromosomes 2H, 5H, and 7H, and two QTLs with effector genes, on chromosomes 5H and 6H. The results obtained could be used to guide MAS applications, allowing introduction into an ideal genotype of favourable alleles of tolerance QTLs. [ABSTRACT FROM AUTHOR]

Leaf stripe, caused by the fungus Pyrenophora graminea Ito et Kuribayashi [anamorph Drechslera graminea (Rabenh. ex. Schlech.) Shoemaker], is an important seed-borne disease of barley (Hordeum vulgare L.). The objective of this study was to verify the reliability of a PCR-based marker (MWG2018) associated with the resistance gene Rdg2a and to assess the leaf stripe resistant phenotype in barley breeding programs. A large number of barley cultivars and accessions were thus evaluated for their reaction to a highly virulent monoconidial isolate (Dg2) of the pathogen and genotyped for the allele of the molecular marker. Several resistant genotypes were identified and four were shown to possess the same allele as the cultivar Thibaut (the resistant parent of the original mapping population in which Rdg2a was identified) at the marker locus. One of them, cv. Rebelle, is being used as a source of leaf stripe resistance in winter barley breeding programs. The allelic composition at the MWG2018 locus was verified in several resistant lines bred from five crosses, in which Rebelle acted directly or indirectly as donor of the resistance. The results showed that the resistant phenotype of the lines was always associated with the resistance allele of the molecular marker, thereby demonstrating its reliability for selecting leaf stripe resistance. The MWG2018 PCR-based marker can therefore be proposed as a tool to assess the resistant phenotype. [ABSTRACT FROM AUTHOR]

Leaf stripe is a seed-borne disease of barley (Hordeum vulgare) caused by Pyrenophora graminea. Little is known about the genetics of resistance to this pathogen. In the present work, QTL analysis was applied on two recombinant inbred line (RIL) populations derived from two- and six-rowed barley genotypes with different levels of partial resistance to barley leaf stripe. Quantitative trait loci for partial resistance were identified using the composite interval mapping (CIM) method of PLABQTL software, using the putative QTL markers as cofactors. In the L94 × 'Vada' mapping population, one QTL for resistance was detected on chromosome 2H; the same location as the leaf-stripe resistance gene Rdg1 mapped earlier in 'Alf', where it confers complete resistance to the pathogen. An additional minor-effect QTL was identified by further analyses in this segregating population on chromosome 7H. In L94 × C123, two QTLs for resistance were mapped, one each on chromosomes 7H and 2H.Key words: QTLs, leaf stripe, Pyrenophora graminea, composite interval mapping, barley.La strie foliaire, causée par le Pyrenophora graminea, est une maladie transmise via les graines chez l'orge et peu de choses sont connues au sujet de la génétique de la résistance à ce pathogène. Dans ce travail, une analyse QTL a été réalisée sur deux populations de lignées recombinantes fixées (RIL) dérivées de croisements entre génotypes d'orge à deux ou six rangs et présentant divers niveaux de résistance partielle à la strie foliaire. Des QTL associés à une résistance partielle ont été identifiés à l'aide de la méthode de cartographie d'intervalles composites (CIM) et du logiciel PLABQTL en prenant les marqueurs QTL putatifs comme cofacteurs. Dans la population de cartographie L94 × 'Vada', un QTL pour la résistance a été détecté sur le chromosome 2H. Il s'agit du même locus où a été précédemment localisé le gène Rdg1 chez 'Alf', un gène qui confère une résistance complète au pathogène. Un autre QTL à effet mineur a été détecté sur le chromosome 7H à la suite d'analyses ultérieures au sein de cette même population. Dans le croisement L94 × C123, deux QTL pour la résistance ont été décelés sur les chromosomes 7H et 2H respectivement.Mots clés : QTL, strie foliaire, Pyrenophora graminea, cartographie d'intervalles composites.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Pyrenophora graminea is a seed-borne pathogen and is the causal agent of the barley leaf stripe disease. Our aim is to study the genetic basis of barley resistance to leaf stripe. A qualitatively acting resistance factor has been identified in the cultivar ‘Vada’ and the partial resistance of the cultivar ‘Proctor’ to a P. graminea isolate has been demonstrated to be dominated by a major quantitative trait locus (QTL), mapped on barley chromosome 1. Map colinearity between the leaf stripe ‘Proctor’ resistance QTLs, ‘Vada’ resistance to leaf stripe, and other disease resistance loci have been investigated in this work using molecular markers. Moreover, since inoculation of barley rootlets by the fungus had been shown to induce the accumulation of several PR (pathogen-related) mRNA families, seven barley PR genes have been mapped as RFLPs, and one assigned to a chromosome arm via ditelosomic analysis to verify possible map associations with resistance QTLs. This work discusses the genetic relationships between the known leaf stripe resistance loci, resistance loci towards other seed-borne pathogens and defence gene loci. [ABSTRACT FROM AUTHOR]