SSR-based genetic linkage analysis of resistance to crown rust (Puccinia coronata f. sp. lolii) in perennial ryegrass (Lolium perenne)

Crown rust (caused by Puccinia coronata f. sp. lolii) is a serious foliar disease of the pasture and turfgrass perennial ryegrass (Lolium perenne). Previous genetic studies have detected both qualitative and quantitative resistance mechanisms, and interpretation of the genetic system is complicated by variation within the sexually reproducing pathogen. Resistant and susceptible parental genotypes of ryegrass were identified using a composite urediniospore population collected from three geographically distinct locations. A two-way pseudo-testcross mapping population was obtained as the F₁ progeny of the pair-cross between ryegrass parental genotypes Vedette₆ and Victorian₉. Both parents showed intermediate resistance against a pathogen population collected in a single geographical zone (Hamilton, Victoria), but in the F₁ population, significant variation for a range of resistance-associated characters was detected. Statistical analysis of phenotypic data suggested a major gene effect, hence bulked segregant analysis with map-assigned simple sequence repeat (SSR) markers was used to scan the genome. A marker showing strong association with resistance was assigned to linkage group (LG) 2 of perennial ryegrass. Analysis of 11 LG2 SSR markers defined an interval between loci xlpssrh03f03 and xlpssrk02e02 as containing the gene or genes (LpPc1) conferring crown rust resistance. Resistance gene determinants were inherited from both parents, with up to 80% of the total phenotypic variation explained by markers segregating from Vedette₆ and up to 26% of the variation explained by markers segregating from Victorian₉. The two contributions together resulted in an additive increase in effect, with fully resistant individuals requiring determinants from both parents. A conserved syntenic relationship was observed with linkage group B of Avena strigosa, which is the location of a cluster of resistance genes to the oat form of crown rust. The implications of this study for marker-assisted selection of disease resistance in perennial ryegrass are discussed.     

Effect of crown rust on regrowth, competitive ability and nutritional quality of perennial and Italian ryegrasses

Infection of susceptible cultivars of perennial (Lolium perenne) and Italian (Lolium multiflorum) ryegrasses with crown rust (Puccinia coronata) reduced yield measured 6 weeks after infection and at two regrowth cuts. In perennial, but not Italian, ryegrass, rust infection of mixed swards of a resistant and a susceptible cultivar reduced the contribution to yield made by the susceptible cultivar and increased that of the resistant cultivar. This effect persisted for three regrowth cuts. The trend in effect on the number of tillers, but not plant height, was similar.
Infection increased leaf protein in susceptible perennial ryegrass but had little effect in Italian ryegrass. In both species, rust reduced water-soluble carbohydrate and the predicted digestibility of susceptible and resistant cultivars, but had no effect on quality of regrowth.     

Characterization and mapping of oat crown rust resistance genes using three assessment methods

ABSTRACT Resistance is the primary means of control for crown rust of oat (Avena sativa L.), caused by Puccinia coronata f. sp. avenae, and better knowledge of the genetics of resistance will enhance resistance breeding. Disease data were generated in the field and greenhouse for parents and recombinant inbred lines of the Ogle/TAM O-301 (OT) oat mapping population using (i) a new quantitative assay that employs quantitative real-time polymerase chain reaction (q-PCR) to estimate fungal growth in the host, (ii) digital image analysis, and (iii) visual ratings. The objectives of this study were to evaluate each assessment method's ability to map a major gene from cv. Ogle and potential quantitative trait loci (QTL) contributed by Ogle and TAM O-301. All three assessment methods identified the major gene in Ogle, which was mapped to linkage group OT6. The resolution produced by q-PCR, however, enabled more precise mapping of the major gene. Quantitative analysis indicated that 64% of the phenotypic variation was accounted for using q-PCR, whereas 41 and 52% were accounted for using visual and digital assessments, respectively. Data generated by q-PCR permitted identification of QTL on linkage groups OT32, accounting for 6% of the phenotypic variation, and OT2, accounting for 4% of the variation. QTL on both OT32 and OT2 were conferred by TAM O-301, one of which (OT2) was indiscernible using data from the visual and digital assessments. The new method of precisely phenotyping crown rust resistance provided a more accurate and thorough means of dissecting resistance in the OT mapping population. Similar methods could be developed and applied to other important cereal rust diseases.     

Quantitative Trait Loci Associated with Seedling Resistance to Isolates of Puccinia coronata in Oat

ABSTRACT In our previous report, quantitative trait loci (QTL) for field adult plant resistance to crown rust were identified in an oat population of 152 F(5:6) recombinant inbred lines from the cross of 'Ogle' (susceptible)/MAM17-5 (resistant). The objectives of the present study were to identify in the same population, the number, genomic location, and effect of QTL and digenic QTL epistasis associated with greenhouse seedling resistance to isolates of Puccinia coronata to determine if the QTL detected are isolate-specific and to compare them with previously detected QTL for field resistance. Reaction type was scored on greenhouse seedlings inoculated with three isolates. Composite interval mapping was conducted to identify genomic regions associated with resistance using a framework map of 272 molecular markers. Two QTL, Pcq1 and Pcq2, were identified for resistance to each of the three isolates. Pcq1, the major QTL controlling field resistance, did not confer detectable greenhouse seedling resistance when present singly; however, Pcq1 did serve as an enhancer of seedling resistance when it was combined with Pcq2. The final model explained 76.5, 77.9, and 79.3% of total phenotypic variation for resistance to isolates MNB248, MNB249, and MNB251, respectively. Race-specificity of quantitative resistance remains to be further examined.     

Development and validation of a quantitative PCR assay method of assessing relative resistance of oat (Avena sativa) to crown rust (Puccinia coronata f. sp. avenae)

Evaluation of oat crown rust resistance is usually based on visual assessment of disease severity or infection types. Visual assessment is subjective, prone to rater bias and requires expert knowledge. PCR-based quantitative assays can overcome challenges associated with visual assessment. New TaqMan primers and probes were designed from Puccinia coronata f. sp. avenae (Pca) sequences. The primer–probe sets were specific to Pca, amplified using as little as 0.5 pg fungal DNA (fDNA) and allowed for scaling to variation in sample total DNA quantity. The quantitative PCR (qPCR) assay was validated using oat recombinant inbred lines (RILs) from the Provena × 94197A1-9-2-2-2-5 cross evaluated under a controlled environment. For comparison with fDNA load, inoculation with the Pca race LCBB provided segregation data on the hypersensitive response, while Pca race LSLG provided data on segregation for reduced pustule number. fDNA content was positively correlated with both pustule number and infection type (IT). Composite interval mapping identified two quantitative trait loci (QTLs) on oat linkage groups Mrg12 and Mrg20 using visual and qPCR assessments (pustule number, IT and fDNA). In this study a qPCR assay method that can be used to assess the relative resistance of oat to crown rust was refined and validated, and single nucleotide polymorphisms (SNPs) closely linked with two QTLs derived from the crown rust resistant line 94197A1-9-2-2-2-5 were identified.     

Virulence associations in oat crown rust

ABSTRACT Isolates of Puccinia coronata obtained from natural populations of Avena sterilis in Israel, winter oat (A. sativa) cultivars in Texas, and spring oat cultivars in the Northern Plains states of Minnesota, North Dakota, and South Dakota were analyzed for significance of pairwise virulence associations. Isolates from all three regions were tested on 25 oat lines with single P. coronata (Pc) genes for crown rust resistance from A. sterilis and one line with a Pc gene from A. sativa. Isolates from Israel were tested also on 11 Iowa backcross lines with undesignated crown rust resistance genes from A. sterilis. Four associated virulence groups were identified from significant positive virulence associations that were consistent across all three regions. Group 38 included virulence to Pc-38, Pc-39, Pc-55, Pc-63, and Pc-71; group 45 included virulence to Pc-45, Pc-46, Pc-48, Pc-52, Pc-54, and Pc-57; group 58 included virulence to Pc-35, Pc-40, Pc-58, and Pc-59; and group 61 included virulence to Pc- 36, Pc-51, Pc-56, Pc-60, and Pc-61. Virulence to Pc-70 showed the strongest association to virulences in group 38 but also showed significant association with virulence to Pc-45, Pc-35, and Pc-58. Virulences in group 61 were consistently negatively associated with virulences in group 38 in each region. In Israel, virulences to five of the Iowa lines showed positive associations to virulences in group 61 and negative associations to virulences in groups 38 and 45. Close similarity of reactions of nearly all isolates to Pc-39, Pc-55, and Pc-71 suggest that these genes may be identical or nearly identical alleles.     

Patterns of Virulence in Natural Populations of Puccinia coronata on Wild Oat in Israel and in Agricultural Populations on Cultivated Oat in the United States

ABSTRACT Crown rust (Puccinia coronata) in indigenous populations of Avena sterilis has been cited as an example of stability of wild pathosystems that consist of natural mixtures of resistance and virulence. This study confirmed that virulence/avirulence polymorphisms in P. coronata on A. sterilis in Israel are highly diverse and that super races do not dominate. Isolates of P. coronata from Israel in 1991 to 1996 were polymorphic for virulence to 35 of 36 differential oat lines with resistance genes from A. sterilis. On average, isolates of P. coronata were more highly virulent to differentials with Pc genes from A. sterilis accessions from Israel than to differentials with Pc genes from other countries. Isolates from Israel also were more virulent on average to 10 additional differentials with Pc genes derived from A. sativa than to differentials with Pc genes from A. sterilis. Frequencies of virulence were usually higher in collections of P. coronata from Israel than in collections from cultivated oat in the United States, even though several of the Pc genes in the differentials have been used extensively in American oat cultivars. Mean virulence complexity of P. coronata from eight regions of Israel was not correlated with the distribution of resistance among collections of A. sterilis from previous surveys in the same areas, probably because pathogen migration between regions within Israel is sufficient to obscure effects of selection locally.     

A Cluster of Major Specific Resistance Genes to Leptosphaeria maculans in Brassica napus

ABSTRACT Two types of genetic resistance to Leptosphaeria maculans usually are distinguished in Brassica napus: qualitative, total resistance expressed at the seedling stage and quantitative, partial resistance expressed at the adult plant stage. The latter is under the control of many genetic factors that have been mapped through quantitative trait loci (QTL) studies using 'Darmor' resistance. The former usually is ascribed to race-specific resistance controlled by single resistance to L. maculans (Rlm) genes. Three B. napus-originating specific Rlm genes (Rlm1, Rlm2, and Rlm4) previously were characterized. Here, we report on the genetic identification of two novel resistance genes, Rlm3 and Rlm7, corresponding to the avirulence genes AvrLm3 and AvrLm7. The identification of a novel L. maculans- B. napus specific interaction allowed the detection of another putative new specific resistance gene, Rlm9. The resistance genes were mapped in two genomic regions on LG10 and LG16 linkage groups. A cluster of five resistance genes (Rlm1, Rlm3, Rlm4, Rlm7, and Rlm9) was strongly suggested on LG10. The relation between all these specific resistance genes and their potential role in adult-plant field resistance is discussed. These two Rlm-carrying regions do not correspond to major QTL for Darmor quantitative resistance.     

Quantitative Trait Loci (QTL) Analysis Reveals Both Broad-Spectrum and Isolate-Specific QTL for Scab Resistance in an Apple Progeny Challenged with Eight Isolates of Venturia inaequalis

ABSTRACT The major scab resistance gene Vf, extensively used in apple breeding programs, was recently overcome by the new races 6 and 7 of the fungal pathogen Venturia inaequalis. New, more durable, scab resistance genes are needed in apple breeding programs. F(1) progeny derived from the cross between partially resistant apple cv. Discovery and apple hybrid 'TN10-8' were inoculated in the greenhouse with eight isolates of V. inaequalis, including isolates able to overcome Vf. One major resistance gene, Vg, and seven quantitative trait loci (QTL) were identified for resistance to these isolates. Three QTL on linkage group (LG)12, LG13, and LG15 were clearly isolate-specific. Another QTL on LG5 was detected with two isolates. Three QTL on LG1, LG2, and LG17 were identified with most isolates tested, but not with every isolate. The QTL on LG2 displayed alleles conferring different specificities. This QTL co-localized with the major scab resistance genes Vr and Vh8, whereas the QTL on LG1 colocalized with Vf. These results contribute to a better understanding of the genetic basis of the V. inaequalis-Malus x domestica interaction.     

Introgression of crown rust (Puccinia coronata) resistance from meadow fescue (Festuca pratensis) into Italian ryegrass (Lolium multiflorum): genetic mapping and identification of associated molecular markers

Crown rust ( Puccinia coronata ) resistance (CRres), which had been introgressed from meadow fescue ( Festuca pratensis ) into the Italian ryegrass ( Lolium multiflorum ) background, was genetically mapped with amplified fragment length polymorphism (AFLP) and sequence tagged site (STS) markers to a terminal segment of chromosome 5. Comparative mapping had previously shown that this region of the Lolium / Festuca genome has a degree of conserved genetic synteny with chromosomes 11 and 12 of rice. Sequences from rice chromosome 12 were used as templates for identifying further STS markers that cosegregated with CRres. The relative genomic positions of molecular markers associated with CRres in L. multiflorum , L. perenne , F. pratensis and oats is discussed, along with their relationships to physical positions on rice chromosomes C11 and C12.     

Microsatellite markers for genes lr34/yr18 and other quantitative trait Loci for leaf rust and stripe rust resistance in bread wheat

ABSTRACT Leaf rust and stripe rust, caused by Puccinia triticina and P. striiformis, respectively, are important diseases of wheat in many countries. In this study we sought to identify molecular markers for adult plant resistance genes that could aid in incorporating such durable resistance into wheat. We used a doubled haploid population from a Japanese cv. Fukuho-komugi x Israeli wheat Oligoculm cross that had segregated for resistance to leaf rust and stripe rust in field trials. Joint and/or single-year analyses by composite interval mapping identified two quantitative trait loci (QTL) that reduced leaf rust severity and up to 11 and 7 QTLs that might have influenced stripe rust severity and infection type, respectively. Four common QTLs reduced stripe rust severity and infection type. Except for a QTL on chromosome 7DS, no common QTL for leaf rust and stripe rust was detected. QTL-7DS derived from 'Fukuho-komugi' had the largest effect on both leaf rust and stripe rust severities, possibly due to linked resistance genes Lr34/Yr18. The microsatellite locus Xgwm295.1, located almost at the peak of the likelihood ratio contours for both leaf and stripe rust severity, was closest to Lr34/Yr18. QTLs located on 1BL for leaf rust severity and 3BS for stripe rust infection type were derived from 'Oligoculm' and considered to be due to genes Lr46 and Yr30, respectively. Most of the remaining QTLs for stripe rust severity or infection type had smaller effects. Our results indicate there is significant diversity for genes that have minor effects on stripe rust resistance, and that successful detection of these QTLs by molecular markers should be helpful both for characterizing wheat genotypes effectively and combining such resistance genes.     

小麦抗条锈病一致性数量性状位点(MQTL)图谱构建

 小麦条锈病是造成小麦减产和品质劣化的最重要病害,定位小麦染色体上一致性条锈病抗性基因/位点/区段是小麦条锈病抗性分子育种的重要基础。本研究对至今分子标记和遗传定位的342个条锈病抗性基因/位点/区段进行数据搜集整理,借助Maccaferr和Andrzej的参考图谱,基于元分析技术进行Meta-QTL(MQTL)检测,共获得194个小麦抗条锈病MQTL,包括74个与严重度(Disease severity, DS)相关,46个与反应型(Infection type, IT)相关、19个与病程曲线下面积相关(Area under disease progress curve, AUDPC)、28个与DS和IT共相关、6个与DS和AUDPC共相关、15个与IT和AUDPC共相关、6个与其他条锈病抗性性状相关。这些抗条锈病一致性QTL定位于小麦21条染色体上,呈非均匀分布,且部分MQTL集中成簇。通过与已发表的正式命名抗条锈病基因比较分析,发现大多数正式命名基因定位于MQTL簇区段,说明这些MQTL簇区段很可能是控制小麦条锈病抗性热点区域。控制小麦抗条锈病一致性QTL遗传图谱的构建为小麦条锈病抗性基因精细定位及抗病育种提供了遗传信息参考依据。     

小麦抗条锈病一致性数量性状位点(MQTL)图谱构建

 小麦条锈病是造成小麦减产和品质劣化的最重要病害,定位小麦染色体上一致性条锈病抗性基因/位点/区段是小麦条锈病抗性分子育种的重要基础。本研究对至今分子标记和遗传定位的342个条锈病抗性基因/位点/区段进行数据搜集整理,借助Maccaferr和Andrzej的参考图谱,基于元分析技术进行Meta-QTL(MQTL)检测,共获得194个小麦抗条锈病MQTL,包括74个与严重度(Disease severity, DS)相关,46个与反应型(Infection type, IT)相关、19个与病程曲线下面积相关(Area under disease progress curve, AUDPC)、28个与DS和IT共相关、6个与DS和AUDPC共相关、15个与IT和AUDPC共相关、6个与其他条锈病抗性性状相关。这些抗条锈病一致性QTL定位于小麦21条染色体上,呈非均匀分布,且部分MQTL集中成簇。通过与已发表的正式命名抗条锈病基因比较分析,发现大多数正式命名基因定位于MQTL簇区段,说明这些MQTL簇区段很可能是控制小麦条锈病抗性热点区域。控制小麦抗条锈病一致性QTL遗传图谱的构建为小麦条锈病抗性基因精细定位及抗病育种提供了遗传信息参考依据。     

Susceptibility in oats to stem rust induced by co-infection with leaf rust

Induction of susceptibility in oats to a normally avirulent pathotype of Puccinia graminis f.sp. avenae was studied in the presence of different pathotypes of P. coronata f.sp. avenae . Induction occurred on seedlings only in the presence of a virulent culture of P. coronata avenae and was not dependent on time or order of inoculation of either pathogen. This phenomenon was restricted to seedlings of lines possessing the Pg-a source of oat stem rust resistance. The specificity of induced susceptibility can be used as a valuable bioassay for screening and identifying Pg-a . Induced susceptibility occurred only at the seedling stage, and apparently provides no obstacle to the use of Pg-a as a source of stem rust resistance in oats.     

Rhamnus lycioides in Tunisia is a new aecial host of oat crown rust

Puccinia coronata was not previously described on Rhamnus spp. in Tunisia. Three sites in the northwest of Tunisia, where Rhamnus is reported to be abundant, were surveyed for the presence of pycnia and aecia of oat crown rust caused by Puccinia coronata f. sp. avenae. Two Rhamnus species (R. lycioides and R. alaternus) were encountered in the sites. Pycnia with viable pycniospores and aecia with viable aeciospores were found on R. lycioides. However, no characteristic structures of crown rust were found on R. alaternus. Aeciospores collected from leaves of R. lycioides were used to inoculate oat plants usually susceptible to oat crown rust. Typical uredinia containing oat crown rust urediniospores appeared on the leaves of these plants. Moreover, the sixteen Pc-gene differential oat lines, used by oat researchers to study the virulence pattern in oat crown rust populations, were artificially inoculated with aeciospores from R. lycioides. These inoculated lines showed resistance/susceptibility similar to the registered resistance level of these lines to crown rust under field conditions in Tunisia. These results indicate that R. lycioides, a common and endemic part of the vegetation in the northwest of Tunisia, is a new aecial host of oat crown rust. The aeciospores produced on this forest plant could constitute the source of the virulence diversity already detected via the Pc-gene line trials.     

Validation of a QTL for resistance to ascochyta blight linked to resistance to fusarium wilt race 5 in chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.)

Ascochyta blight caused by Ascochyta rabiei and fusarium wilt caused by Fusarium oxysporum. f. sp. ciceris are the two most serious diseases of chickpea (Cicer arietinum). Quantitative trait loci (QTL) or genes for ascochyta blight resistance and a cluster of resistance genes for several fusarium wilt races (foc1, foc3, foc4 and foc5) located on LG2 of the chickpea map have been reported independently. In order to validate these results and study the linkage relationship between the loci that confer resistance to blight and wilt, an intraspecific chickpea recombinant inbred lines (RIL) population that segregates for resistance to both diseases was studied. A new LG2 was established using sequence tagged microsatellite sites (STMS) markers selected from other chickpea maps. Resistance to race 5 of F. oxysporum (foc5) was inherited as a single gene and mapped to LG2, flanked by the STMS markers TA110 (6.5 cM apart) and TA59 (8.9 cM apart). A QTL for resistance to ascochyta blight (QTL_AR3) was also detected on LG2 using evaluation data obtained separately in two cropping seasons. This genomic region, where QTL_AR3 is located, was highly saturated with STMS markers. STMS TA194 appeared tightly linked to QTL_AR3 and was flanked by the STMS markers TR58 and TS82 (6.5 cM apart). The genetic distance between foc5 and QTL_AR3 peak was around 24 cM including six markers within this interval. The markers linked to both loci could facilitate the pyramiding of resistance genes for both diseases through MAS.     

Sources and genetics of crown rust resistance in barley

ABSTRACT Crown rust, caused by Puccinia coronata var. hordei, is a new disease threat to barley in the Great Plains region of the United States. Deployment of resistant cultivars is the only economically viable option for the control of this disease. Thus, the objective of this study was to investigate the sources and genetics of crown rust resistance in barley. A geographically diverse sample of barley germ plasm collected around the world (526 accessions total) was evaluated at the seedling stage to P. coronata var. hordei, and only 10 accessions (1.9% of the total) were found resistant. These 10 accessions were also resistant at the adult plant stage in a greenhouse test. Three F(2) populations (Bowman x Hor2596, MR x Hor2596, and MD x Hor2596) were developed to study the inheritance of crown rust resistance in the resistant line Hor2596 (CIho 1243). A close fit to a 3:1 ratio of resistant/susceptible plants was observed in all three populations and is consistent with the segregation of a single resistance gene. F(1) plants from the Bowman x Hor2596 population exhibited slightly higher infection types than the resistant parent, indicating incomplete dominance. The locus symbol Rpc1 and allele symbol Rpc1.a were recommended for the crown rust resistance gene in Hor2596. An attempt was made to associate the Rpc1 locus with one of the seven barley chromosomes by analyzing linkage data with previously mapped morphological markers in crosses with multiple recessive (MR) and multiple dominant (MD) morphological marker stocks. However, no close linkages were detected between Rpc1 and the 20 morphological markers present in the marker stocks. The resistant accessions identified in this study should be useful to breeders for developing barley germ plasm with crown rust resistance.     

Mapping Quantitative Field Resistance Against Apple Scab in a 'Fiesta' x 'Discovery' Progeny

ABSTRACT Breeding of resistant apple cultivars (Malus x domestica) as a disease management strategy relies on the knowledge and understanding of the underlying genetics. The availability of molecular markers and genetic linkage maps enables the detection and the analysis of major resistance genes as well as of quantitative trait loci (QTL) contributing to the resistance of a genotype. Such a genetic linkage map was constructed, based on a segregating population of the cross between apple cvs. Fiesta (syn. Red Pippin) and Discovery. The progeny was observed for 3 years at three different sites in Switzerland and field resistance against apple scab (Venturia inaequalis) was assessed. Only a weak correlation was detected between leaf scab and fruit scab. A QTL analysis was performed, based on the genetic linkage map consisting of 804 molecular markers and covering all 17 chromosomes of apple. With the maximum likelihood-based interval mapping method, eight genomic regions were identified, six conferring resistance against leaf scab and two conferring fruit scab resistance. Although cv. Discovery showed a much stronger resistance against scab in the field, most QTL identified were attributed to the more susceptible parent 'Fiesta'. This indicated a high degree of homozygosity at the scab resistance loci in 'Discovery', preventing their detection in the progeny due to the lack of segregation.     

Molecular mapping of the crown rust resistance gene rpc1 in barley

ABSTRACT Crown rust of barley, caused by Puccinia coronata var. hordei, occurs sporadically and sometimes may cause yield and quality reductions in the Great Plains region of the United States and Canada. The incompletely dominant resistance allele Rpc1 confers resistance to P. coronata in barley. Two generations, F(2) and F(2:3), developed from a cross between the resistant line Hor2596 (CIho 1243) and the susceptible line Bowman (PI 483237), were used in this study. Bulked segregant analysis combined with random amplified polymorphic DNA (RAPD) primers were used to identify molecular markers linked to Rpc1. DNA genotypes produced by 500 RAPD primers, 200 microsatellites (SSRs), and 71 restriction fragment length polymorphism (RFLP) probes were applied to map Rpc1. Of these, 15 RAPD primers identified polymorphisms between resistant and susceptible bulks, and 62 SSR markers and 32 RFLP markers identified polymorphisms between the resistant and susceptible parents. The polymorphic markers were applied to 97 F(2) individuals and F(2:3) families. These markers identified 112 polymorphisms and were used for primary linkage mapping to Rpc1 using Map Manager QT. Two RFLP and five SSR markers spanning the centromere on chromosome 3H and one RAPD marker (OPO08-700) were linked with Rpc1 and, thus, used to construct a 30-centimorgan (cM) linkage map containing the Rpc1 locus. The genetic distance between Rpc1 and the closest marker, RAPD OPO08-700, was 2.5 cM. The linked markers will be useful for incorporating this crown rust resistance gene into barley breeding lines.