Resistance to Rhynchosporium secalis in the winter barley cultivar Vulcan

The six-rowed winter barley cultivar Vulcan was found to be highly resistant to Rhynchosporium secalis in the field, although this resistance was not apparent in routine screening tests of barley genotypes carried out at the seedling stage. More precise seedling tests, using graded inoculum levels to derive dose-response curves, showed that cv. Vulcan had an ED₅₀ which was 4.8 times that of the susceptible, two-rowed cv. Maris Otter, and 4.1 times that of cv. Maris Puma. The inheritance of resistance was investigated at the adult plant stage in a cross with cv. Maris Otter. Although a clear-cut segregation of the F₃ progeny into resistant, segregating and susceptible phenotypes was not observed, the genetic variance of the F₃ family means was compatible with the hypothesis of monogenic control of resistance. Resistance was inherited independently of the factor for six-rowed head type.     

The inheritance of resistance to Rhynchosporium secalis in some European spring barley cultivars

The inheritance of partial resistance to Rhynchosporium secalis, which appears to be race non-specific, was studied in a diverse range of European spring barley cultivars. Data from the F₂ generation of a 6 × 6 diallel cross and the F₃ generation of three crosses selected from this diallel set suggested that resistance was complex in inheritance, the results being incompatible with any hypothesis involving less than four genes. The F₂ studies indicated that both dominant and recessive genes were active in conferring resistance, and that there were significant additive gene effects. Transgressive segregation occurred in all cross combinations in the F₃ material. Consequently the alleles conferring resistance were not completely concentrated in the most resistant cultivar studied (cv. Proctor). Heritability estimates obtained from F₂ and F₃ material suggested that field selection was of limited reliability, even when spreader drills were incorporated amongst the segregates. Single-plant selection (in F₂) was considered to be of little value, and the results of F_a head-row tests would require confirmation by replicated tests in subsequent generations.     

Molecular Analysis of Rhynchosporium secalis Population Collected from Barley Cultivars having Different Resistance Specificities

Molecular analysis was performed to detect genetic diversity in 106 Rhynchosporium secalis isolates collected from different regions of Canada using random amplified polymorphic DNA (RAPD) markers. The isolates collected from barley cultivars having different resistance specificity to R. secalis and grown in geographically distinct regions, exhibited reproducible variation for 2–3 polymorphic PCR products per decamer primer. Analysis of 1960 RAPD markers data obtained with five primers formed 5 groups with different genetic similarity. High genetic variation was observed in R. secalis isolates obtained from resistant and susceptible cultivars of barley. Isolates collected from susceptible cultivars showed a tendency to group together, whereas isolates from resistant cultivars were divergent. R. secalis isolates infecting different barley cultivars released as resistant to the barley scald formed a specific group with UPGMA, even though all these isolates were collected from the same epidemiological region. Analysis of 15 isolates collected from one resistant cultivar Duke formed three clusters with low bootstrap values indicating high genetic diversity among the isolates present on a single host cultivar.     

RFLP mapping of the Ha 2 cereal cyst nematode resistance gene in barley

 The cereal cyst nematode (CCN), Heterodera avenae Woll., is an economically damaging pest of barley in many of the world’s cereal-growing areas. The development of CCN-resistant cultivars may be accelerated through the use of molecular markers. A number of resistance genes against the pest are well known; one of them, the single dominant Ha 2 resistance gene, has been shown to be effective against the Australian pathotype and maps to chromosome 2 of barley. Segregation analysis identified two restriction fragment length polymorphism (RFLP) markers flanking the resistance gene in two doubled-haploid populations of barley. AWBMA 21 and MWG 694 mapped 4.1 and 6.1 cM respectively from the Ha 2 locus in the Chebec×Harrington cross and 4.0 and 9.2 cM respectively in the Clipper×Sahara cross. Analysis of a further seven sources of CCN resistance in the form of near-isogenic lines (NILs) indicates that all available sources of resistance to the Australian pathotype of CCN in barley represent the Ha 2 locus. Received: 5 December 1996 / Accepted: 20 December 1996     

Components of partial resistance of barley to Rhynchosporium secalis: use of seedling tests to predict field resistance

Components of partial resistance [disease incidence (DI), infection frequency (IF), latent period (LP), spores per lesion (SPL)] were assessed on glasshouse-grown barley seedlings following inoculation with spore suspensions of Rhynchosporium secalis at growth stage 12 (Zadoks, Chang & Konzak, 1974). Four experiments were carried out at different times during 1988. Three spring barley cultivars [two from Cyprus (cvs Kantara and Athenais) and one from the UK (cv. Triumph)] were used in the first three experiments. In the fourth experiment eight additional UK cultivars with NIAB resistance ratings ranging from 3 to 9 were used. Two races of R. secalis were used in the first three experiments and three in the fourth. The three cultivars, Kantara, Athenais and Triumph, were examined in all four experiments and significant differences detected for virtually all components of partial resistance in each. Differences, however, were often small and ranking of cultivars varied in different experiments. The greater susceptibility of cv. Kantara compared to cv. Athenais, observed under field conditions in Cyprus, would not be anticipated from the small differences in components of partial resistance observed in these experiments, but, for these cultivars, the possibility of a marked genotype x environment interaction cannot be discounted. Mean values for the components of partial resistance differed in the four experiments. LP was correlated with mean glasshouse temperature from inoculation to the onset of sporulation but differences in IF and SPL were not correlated with temperature. For these components, light quality and/or duration appeared to be more important. Overall, there were no differences between races but significant race X cultivar interactions were observed in two experiments. In the fourth experiment, examining 11 cultivars, there were significant differences between cultivars for all components of partial resistance. IF and LP were correlated but neither of these components was correlated with SPL indicating independent control of this latter component. Both IF and LP were correlated with field performance (NIAB ratings) but there was no correlation with SPL. However, combining IF with mean values of SPL restricted to the 5 days following the end of the LP, produced the best correlation (r= 0.92) with NIAB ratings. Problems of assessing components of partial resistance and possible means of improving assessments are discussed.     

RFLP mapping in barely of a dominant gene conferring resistance to scald (Rhynchosporium secalis)

A progeny consisting of 52 anther-derived doubled haploid barley lines from a F₁ between the winter cultivars Igri (susceptible) and Triton (resistant) was tested for resistance to Rhynchosporium secalis. A dominant gene was detected and tagged by a series of cosegregating RFLP markers located in the proximal portion of the long arm of chromosome 3, close to the centromere. One of the cosegregating RFLP markers, cMWG680, was converted into a codominant sequence tagged site marker. Polymerase chain reaction analysis with this marker of a series of accessions carrying known resistance genes provided evidence that scald resistance in cv Triton is due to the presence of the Rh gene.     

Analysis of molecular diversity,population structure and linkage disequilibrium in a worldwide survey of cultivated barley germplasm (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.)

Background

The goal of our study was a systematic survey of the molecular diversity in barley genetic resources. To this end 953 cultivated barley accessions originating from all inhabited continents except Australia were genotyped with 48 SSR markers. Molecular diversity was evaluated with routine statistics (allelic richness, gene diversity, allele frequency, heterozygosity and unique alleles), Principal Coordinate Analysis (PCoA), and analysis of genome-wide linkage disequilibrium.

Results

A genotyping database for 953 cultivated barley accessions profiled with 48 SSR markers was established. The PCoA revealed structuring of the barley population with regard to (i) geographical regions and (ii) agronomic traits. Geographic origin contributed most to the observed molecular diversity. Genome-wide linkage disequilibrium (LD) was estimated as squared correlation of allele frequencies (r²). The values of LD for barley were comparable to other plant species (conifers, poplar, maize). The pattern of intrachromosomal LD with distances between the genomic loci ranging from 1 to 150 cM revealed that in barley LD extended up to distances as long as 50 cM with r² > 0.05, or up to 10 cM with r² > 0.2. Few loci mapping to different chromosomes showed significant LD with r² > 0.05. The number of loci in significant LD as well as the pattern of LD were clearly dependent on the population structure. The LD in the homogenous group of 207 European 2-rowed spring barleys compared to the highly structured worldwide barley population was increased in the number of loci pairs with r² > 0.05 and had higher values of r², although the percentage of intrachromosomal loci pairs in significant LD based on P < 0.001 was 100% in the whole set of varieties, but only 45% in the subgroup of European 2-rowed spring barleys. The value of LD also varied depending on the polymorphism of the loci selected for genotyping. The 17 most polymorphic loci (PIC > 0.80) provided higher LD values as compared to 19 low polymorphic loci (PIC < 0.73) in both structured (all accessions) and non-structured (European 2-rowed spring varieties) barley populations.

Conclusion

A global population of cultivated barley accessions was highly structured. Clustering highlighted the accessions with the same geographic origin, as well as accessions possessing similar agronomic characters. LD in barley extended up to 50 cM, and was strongly dependent on the population structure. The data on LD were summarized as a genome-wide LD map for barley.

     

Cytoplasmic male sterility in barley

Summary The associations between seedling reactions to three fungal pathogens (Puccinia hordei, Pyrenophora teres, and Rhynchosporium secalis) or between adult plant reaction to Rh. secalis and the male fertility restoration ability of msml cytoplasm were studied in about 100 accessions of Hordeum spontaneum. Significant differences in the severity of infection between classes of restoration ability were observed with two cultures of P. hordei (751 and 7,649) and with Rh. secalis on adult plants in the field. The cultures 7,432, 751 and 7,649 of P. hordei showed significant positive correlations between infection severity and restoration percentage. The culture 7,620 of P. hordei displayed a significant negative correlation. Rh. secalis (cultures 492A and 531 combined) on seedlings and the natural field infection in the 1978 season showed significant positive correlations. The accession class with the partial restoration ability of 0.1 to 5.0% of the four arbitrary classes (0.0, 0.1–5.0, 5.1–55.0, and 90.1–100%), displayed the lowest mean severity of infection in six of the eleven tests. Some frequently appearing races of these pathogens may operate as selective agents in the maintenance of restoration ability in the original spontaneum populations.     

Compatibility of Erysiphe graminis Hybrids f. sp. secalis X f. sp. Tritici with Wheat Lines Involving Resistance Genes from Rye

Compatibility of hybrid cultures Erysiphe graminis ff. sp. secalis (SI) ×tritici (t2) was tested in the laboratory with wheat cultivars involving different resistance genes and with two rye cultivars. Segregation was observed on wheat without resistance gene and with resistance genes Pm1, Pm3b and Pm3c compatible with t2, but not on wheat with resistance gene Pm2, Pm 3a, Pm 4a and Pm 5 incompatible with t2, nor on rye. It was obvious that S1 involves avirulence genes to Pm1, Pm2, Pm 3a, pm 3b, Pm 3c, Pm 4a, Pm 5. Segregation was found on wheat cultivars involving rye resistance genes Pm 7 (Transfed) and Pm 8 (Kavkaz), but cv. Transec (Pm7) was incompatible with all cultures used, because Transec involves another gene for resistance. The results indicate that hybridization between formae speciales secalis and tritici of the fungus can be a source of fungus compatibility with wheat with rye resistance, even in field conditions.     

Fine mapping,physical mapping and development of diagnostic markers for the <Emphasis Type="Italic">Rrs2</Emphasis> scald resistance gene in barley

The Rrs2 gene confers resistance to the fungal pathogen Rhynchosporium secalis which causes leaf scald, a major barley disease. The Rrs2 gene was fine mapped to an interval of 0.08 cM between markers 693M6_6 and P1D23R on the distal end of barley chromosome 7HS using an Atlas (resistant) × Steffi (susceptible) mapping population of 9,179 F₂-plants. The establishment of a physical map of the Rrs2 locus led to the discovery that Rrs2 is located in an area of suppressed recombination within this mapping population. The analysis of 58 barley genotypes revealed a large linkage block at the Rrs2 locus extending over several hundred kb which is present only in Rrs2 carrying cultivars. Due to the lack of recombination in the mapping population and the presence of a Rrs2-specific linkage block, we assume a local chromosomal rearrangement (alien introgression or inversion) in Rrs2 carrying varieties. The variety analysis led to the discovery of eight SNPs which were diagnostic for the Rrs2 phenotype. Based on these SNPs diagnostic molecular markers (CAPS and pyrosequencing markers) were developed which are highly useful for marker-assisted selection in resistance gene pyramiding programmes for Rhynchosporium secalis resistance in barley.     

Differential Reactions Between the Genus Brassica and Aggressive Single Spore Isolates of Leptosphaeria maculans

Based on sirodesmin production and pathogenicity tests with Brassica cotyledons, strains of Leptosphaeria maculans were classified as aggressive (pathotype group A), or non-aggressive (pathotype group NA). NA strains caused no differential reactions. However, the pathotype group A could be divided into 5 sub-groups. AO isolates caused non-sporulating lesions with dark margins while Al isolates sporulated on cotyledons of most Brassica hosts tested. Only the cv. Erfurter Zwerg (B. oleracea var. botrytis) reacted resistant against AO and Al strains. A2 isolates caused resistance reactions on cotyledons of the cvs. Quinta (B. napus var. oleifera) and Runde (B. rapa var. rapa). A3 and A4 isolates were not detectable in our material. Isolates of these pathotype groups, supplied by Dr. P. H. Williams, Madison, USA, caused differential reactions on the oilseed rape cvs. Glacier, Quinta and Jet Neuf. In glasshouse and field experiments strains of pathotype groups Al, A2 and NA were tested on true leaves and hypocotyls of different oilseed rape cultivars. The low aggressiveness of NA isolates was evident under all experimental conditions. A2 strains caused resistance reactions not only on cotyledons but also on true leaves and hypocotyls of Quinta. Moreover, compared with Al, pathotype group A2 was more aggressive on hypocotyls of Jet Neuf. The resistance of this cultivar against Al isolates was clearly visible on hypocotyls and true leaves but not on cotyledons.     

Construction of a YAC library from barley cultivar Franka and identification of YAC-derived markers linked to the Rh2 gene conferring resistance to scald (Rhynchosporium secalis).

The Rh2 resistance gene of barley (Hordeum vulgare) confers resistance against the scald pathogen (Rhynchosporium secalis). A high-resolution genetic map of the Rh2 region on chromosome I (7H) was established by the use of molecular markers. Tightly linked markers from this region were used to screen existing and a newly constructed yeast artificial chromosome (YAC) library of barley cv. Franka composed of 45,000 clones representing approximately two genome equivalents. Corresponding YAC clones were identified for most markers, indicating that the combined YAC library has good representation of the barley genome. The contiguous sets of YAC clones with the most tightly linked molecular markers represent entry points for map-based cloning of this resistance gene.     

Resistance to <Emphasis Type="Italic">Rhynchosporium commune</Emphasis> in a collection of European spring barley germplasm

Key message

Association analyses of resistance to Rhynchosporium commune in a collection of European spring barley germplasm detected 17 significant resistance quantitative trait loci. The most significant association was confirmed as Rrs1.

Abstract

Rhynchosporium commune is a fungal pathogen of barley which causes a highly destructive and economically important disease known as rhynchosporium. Genome-wide association mapping was used to investigate the genetic control of host resistance to R. commune in a collection of predominantly European spring barley accessions. Multi-year disease nursery field trials revealed 8 significant resistance quantitative trait loci (QTL), whilst a separate association mapping analysis using historical data from UK national and recommended list trials identified 9 significant associations. The most significant association identified in both current and historical data sources, collocated with the known position of the major resistance gene Rrs1. Seedling assays with R. commune single-spore isolates expressing the corresponding avirulence protein NIP1 confirmed that this locus is Rrs1. These results highlight the significant and continuing contribution of Rrs1 to host resistance in current elite spring barley germplasm. Varietal height was shown to be negatively correlated with disease severity, and a resistance QTL was identified that co-localised with the semi-dwarfing gene sdw1, previously shown to contribute to disease escape. The remaining QTL represent novel resistances that are present within European spring barley accessions. Associated markers to Rrs1 and other resistance loci, identified in this study, represent a set of tools that can be exploited by breeders for the sustainable deployment of varietal resistance in new cultivars.

     

The gene conferring susceptibility to spot blotch caused by <Emphasis Type="Italic">Cochliobolus sativus</Emphasis> is located at the <Emphasis Type="Italic">Mla</Emphasis> locus in barley cultivar Bowman

Key message

We identified, fine mapped, and physically anchored a dominant spot blotch susceptibility gene Scs6 to a 125 kb genomic region containing the Mla locus on barley chromosome 1H.

Abstract

Spot blotch caused by Cochliobolus sativus is an important disease of barley, but the molecular mechanisms underlying resistance and susceptibility to the disease are not well understood. In this study, we identified and mapped a gene conferring susceptibility to spot blotch caused by the pathotype 2 isolate (ND90Pr) of C. sativus in barley cultivar Bowman. Genetic analysis of F₁ and F₂ progeny as well as F₃ families from a cross between Bowman and ND 5883 indicated that a single dominant gene (designated as Scs6) conferred spot blotch susceptibility in Bowman. Using a doubled haploid (DH) population derived from a cross between Calicuchima-sib (resistant) and Bowman-BC (susceptible), we confirmed that Scs6, contributed by Bowman-BC, was localized at the same locus as the previously identified spot blotch resistance allele Rcs6, which was contributed by Calicuchima-sib and mapped on the short arm of chromosome 1H. Using a genome-wide putative linear gene index of barley (Genome Zipper), 13 cleaved amplified polymorphism markers were developed from 11 flcDNA and two EST sequences and mapped to the Scs6/Rcs6 region on a linkage map constructed with the DH population. Further fine mapping with markers developed from barley genome sequences and F₂ recombinants derived from Bowman?×?ND 5883 and Bowman?×?ND B112 crosses delimited Scs6 in a 125 kb genomic interval harboring the Mla locus on the reference genome of barley cv. Morex. This study provides a foundational step for further cloning of Scs6 using a map-based approach.

     

The Nir1 locus in barley is tightly linked to the nitrite reductase apoprotein gene Nii

pBNiR1, a cDNA clone encoding part of the barley nitrite reductase apoprotein, was isolated from a barley (cv. Maris Mink) leaf cDNA library using the 1.85 kb insert of the maize nitrite reductase cDNA clone pCIB808 as a heterologous probe. The cDNA insert of pBNiR1 is 503 by in length. The nucleotide coding sequence could be aligned with the 3′ end of other higher plant nitrite reductase apoprotein cDNA sequences but diverges in the 3′ untranslated region. The whole-plant barley mutant STA3999, previously isolated from the cultivar Tweed, accumulates nitrite after nitrate treatment in the light, has very much lowered levels of nitrite reductase activity and lacks detectable nitrite reductase cross-reacting material due to a recessive mutation in a single nuclear gene which we have designated Nir1. STA3999 has the characteristics expected of a nitrite reductase apoprotein gene mutant. Here we have used pB-NiR1 in RFLP analysis to determine whether the mutation carried by STA3999 is linked to the nitrite reductase apoprotein gene locus Nii. An RFLP was identified between the wild-type barley cultivars Tweed (major hybridising band of 11.5 kb) and Golden Promise (major hybridising band of 7.5 kb) when DraI-digested DNA was probed with the insert from the partial barley nitrite reductase cDNA clone, pBNiR1. DraI-digested DNA from the mutant STA3999 also exhibited a major hybridising band of 11.5 kb after hybridisation with the insert from pBNiR1. F₁ progeny derived from the cross between the cultivar Golden Promise and the homozygous nir1 mutant STA3999 were heterozygous for these bands as anticipated. Co-segregation of the Tweed RFLP band of 11.5 kb and the mutant phenotype (leaf nitrite accumulation after nitrate treatment/loss of detectable nitrite reductase cross-reacting material at M_r 63000) was scored in an F₂ population of 312 plants derived from the cross between the cultivar Golden Promise and the homozygous mutant STA3999. The Tweed RFLP band of 11.5 kb and the mutant phenotype showed strict co-segregation (in approximately one quarter (84) of the 312 F₂ plants examined). Only those F₂ individuals heterozygous for the RFLP pattern gave rise to F₃ progeny which segregated for the mutant phenotype. We conclude that the nir1locus and the nitrite reductase apoprotein gene Nii are very tightly linked.     

RFLP mapping of BaYMV resistance gene rym3 in barley (Hordeum vulgare)

The rym3 (formerly designated ym3) gene conferring resistance to barley yellow mosaic virus (BaYMV) is effective against all strains of the virus but up to now has not been mapped to any chromosome. We performed a linkage analysis, using DNA extracted from individually harvested mature leaves of 153 F₂ plants derived from a cross between BaYMV-resistant cv ’Ishuku Shirazu’ carrying rym3 and susceptible cv ’Ko A’. Additionally, the F₃ lines derived from F₂ plants were grown in the BaYMV-infested field and examined for their reaction to BaYMV. Our results indicated that rym3 is located on the short arm of chromosome 5H and flanked by RFLP markers MWG28and ABG705A at distances of 7.2 and 11.7 cM, respectively. The chromosomal configuration estimated by DNA markers around rym3 and the utilization of these molecular markers for pyramiding with the BaYMV resistance genes in barley breeding programs are discussed. Received: 24 August 1998 / Accepted: 30 January 1999<@head-com-p1a.lf>Communicated by F. Salamini     

Molecular evidence for recent founder populations and human-mediated migration in the barley scald pathogen Rhynchosporium secalis

Rhynchosporium secalis is an important pathogen of barley globally. Fourteen polymorphic microsatellites were analyzed for 1664 R. secalis isolates sampled from 37 field populations to infer their demographic history. The results falsified the hypothesis that R. secalis co-evolved with its barley host in the Middle East. Populations from Scandinavia had significantly higher allelic diversities, the greatest number of private alleles and the highest genotypic diversities. All but three of the analyzed populations had an excess of gene diversity compared to the number of alleles, consistent with a recent population bottleneck. The remaining populations had a gene diversity deficit consistent with a population expansion following a recent population bottleneck in the last ±100 years. A coalescent analysis revealed that the effective population sizes based on θ, of the analyzed populations were small relative to their ancestral population sizes, indicating that only a fraction of the diversity present in the ancestral populations was transmitted into current populations. These findings are consistent with the hypothesis that the pathogen population on barley experienced a selection bottleneck imposed by the host and/or are founder populations. The mean estimate of migration rates was 2.2 (avg 90% confidence interval = 1.3–3.1). Major migration routes were identified among populations separated by long distances, eg between South Africa and Australia, as well as among North Africa, the Middle East and California, suggesting contemporary exchange of infected barley seed. In contrast with earlier findings, most populations exhibited significant gametic disequilibrium, probably as a result of genetic drift. We conclude that the majority of R. secalis populations have experienced human-mediated migration that led to numerous and relatively recent founder events around the world.     

Localization of quantitative trait loci (QTL) for agronomic important characters by the use of a RFLP map in barley (Hordeum vulgare L.)

Two hundred and fifty doubled haploid lines were studied from a cross between two 2-row winter barley varieties. The lines were evaluated for several characters in a field experiment for 3 years on two locations with two replications. From a total of 431 RFLP probes 50 were found to be polymorphic and subsequently used to construct a linkage map. Quantitative trait loci (QTLs) were determined and localized for resistance against Rhynchosporium secalis and Erysiphe graminis, for lodging, stalk breaking and ear breaking tendency, for the physical state before harvest, plant height, heading date, several kernel parameters and kernel yield. The heritability of the traits ranged from 0.56 to 0.89. For each trait except for kernel thickness, QTLs have been localized that explain 5–52% of the genetic variance. Transgressive segregation occurred for all of the traits studied.     

The distribution of pathotypes of the cereal cyst-eelworm Heterodera avenae in England and Wales

Two pathotypes of the cereal cyst-eelworm (Heterodera avenae), occurred commonly in England and Wales and a third pathotype was apparently present in low numbers in a few areas. Pathotype 1, which can breed on most cultivars of wheat, barley and oats, but not on Drost barley nor barley cultivars containing the gene for resistance from barley No. 191, was most common in the south west of England. Pathotype 2, which can breed on most cereals, including Drost barley but not No. 191, was common throughout England and Wales and mixtures of these pathotypes occurred in many places. Pathotype 3, which can breed on barley No. 191 and probably on Drost and most cultivars of cereals, was rare and was found only in low numbers together with either or both Pathotypes 1 and 2. In the initial tests it was present or suspected in only nine fields (6%), but when these soils were retested in more detail the following year, Pathotype 3 was confirmed at only one site.     

Genetic and molecular analyses of resistance to a variant of Puccinia striiformis in barley

Seedlings of 62 Australian barley cultivars and two exotic barley genotypes were assessed for resistance to a variant of Puccinia striiformis, referred to as “Barley Grass Stripe Rust” (BGYR), first detected in Australia in 1998, which is capable of infecting wild Hordeum species and some genotypes of cultivated barley. Fifty-three out of 62 cultivated barley cultivars tested were resistant to the pathogen. Genetic analyses of seedling resistance to BGYR in six Australian barley cultivars and one Algerian barley landrace indicated that they carried either one or two major resistance genes to the pathogen. A single recessive seedling resistance gene, rpsSa3771, identified in Sahara 3771, was located on the long arm of chromosome 1 (7 H), flanked by the restriction fragment length polymorphism (RFLP) markers Xwg420 and Xcdo347 at genetic distances of 12.8 and 21.9 cM, respectively. Mapping resistance to BGYR at adult plant growth stages using the doubled haploid (DH) population Clipper × Sahara 3771 identified two major quantitative trait loci (QTL), one on the long arm of chromosome 3 (3 H) and the second on the long arm of chromosome 1 (7 H), accounting for 26 % and 18 % of the total phenotypic variation, respectively. The QTL located on chromosome 7HL corresponded to seedling resistance gene rpsSa3771 and the second QTL was concluded to correspond to a single APR gene, designated rpsCl, contributed by cultivar Clipper.