Isolation of wheat-rye 1RS recombinants that break the linkage between the stem rust resistance gene SrR and secalin.

Chromosome 1R of rye is a useful source of genes for disease resistance and enhanced agronomic performance in wheat. One of the most prevalent genes transferred to wheat from rye is the stem rust resistance gene Sr31. The recent emergence and spread of a stem rust pathotype virulent to this gene has refocused efforts to find and utilize alternative sources of resistance. There has been considerable effort to transfer a stem rust resistance gene, SrR, from Imperial rye, believed to be allelic to Sr31, into commercial wheat cultivars. However, the simultaneous transfer of genes at the Sec-1 locus encoding secalin seed storage proteins and their association with quality defects preclude the deployment of SrR in some commercial wheat breeding programs. Previous attempts to induce homoeologous recombination between wheat and rye chromosomes to break the linkage between SrR and Sec-1 whilst retaining the tightly linked major loci for wheat seed storage proteins, Gli-D1 and Glu-D3, and recover good dough quality characteristics, have been unsuccessful. We produced novel tertiary wheat-rye recombinant lines carrying different lengths of rye chromosome arm 1RS by inducing homoeologous recombination between the wheat 1D chromosome and a previously described secondary wheat-rye recombinant, DRA-1. Tertiary recombinant T6-1 (SrR+ Sec-1-) carries the target gene for stem rust resistance from rye and retains Gli-D1 but lacks the secalin locus. The tertiary recombinant T49-7 (SrR- Sec-1+) contains the secalin locus but lacks the stem rust resistance gene. T6-1 is expected to contribute to wheat breeding programs in Australia, whereas T49-7 provides opportunities to investigate whether the presence of secalins is responsible for the previously documented dough quality defects.     

Inheritance of B subunits of glutenin and ω-and γ-gliadins in tetraploid wheats

A double-1RS wheat-rye translocation line lacking all B subunits of glutenin was produced in durum wheat cv ‘Langdon’ for use in backcrosses and testcrosses in the study of the inheritance of low-molecular-weight (LMW) glutenin subunits in tetraploid wheats. The B subunits of glutenin and γ-and ω-gliadin bands present in parents derived from Triticum durum and T. dicoccoides, encoded by Glu-3 and Gli-1 loci, respectively, were found to be inherited mainly as units (blocks), as reported previously. Two rare recombination events between the Glu-A3 and Gli-A1 loci were detected in testcross progeny from ‘Edmore’ x T. dicoccoides landrace 19–27. Several rare recombinants were also detected within the 1BS-controlled B subunits of glutenin blocks, suggesting that there are two separate tightly linked loci (3.07±1.35 cM) within the Glu-B3 ‘locus’. Evidence was also obtained for the presence of an additional locus coding for a B subunit of glutenin in ‘Edmore’ that is loosely linked (20.9±3.18%) with the main Glu-B3 ‘locus’.     

黑麦碱基因（Sec–1）表达缺失的1RS／1BL易位系的鉴定

用改良的Giemsa C－带技术、DNA原位杂交和酸性聚丙烯酰胺凝胶电泳（A-PAGE）对来源于小麦品种绵阳11与不同黑麦自交系远缘杂交获得的高代株系（BC1F7）的染色体结构和醇溶蛋白进行了研究。结果发现,在鉴定的200个株系中,有45个株系经C-带和A-PAGE检测均一致地发现它们含有一对1RS /1BL易位染色体,而一个株系843-1-1,C-带鉴定、原位杂交结果均证明它含有一对1RS/1BL易位染色体,但A-PAGE醇溶蛋白图谱却不具有黑麦1RS染色体臂的黑麦碱特征带,而表达出既不同于黑麦碱又不同于亲本绵阳11的醇溶蛋白带型。这一结果表明,利用不同的黑麦亲本资源,可以获得黑麦碱基因Sec-1表达缺失的新的1RS/1BL易位系。这种新的1RS/1BL易位系缺失了影响小麦品质的黑麦碱蛋白,因此是进一步研究1RS/1BL 易位对小麦品质影响的珍贵材料。研究指出,在利用外源基因的植物育种中,外源种供体材料的遗传多样性是值得重视的基因资源。     

Variation at storage protein loci in winter common wheat cultivars of the central forest-steppe of Ukraine

Genotypes at the gliadin loci Gli-A1, Gli-B1, Gli-D1 and the high-molecular-weight glutenin subunit loci Glu-A1, Glu-B1, Glu-D1 were identified in 77 winter common wheat cultivars developed in the Central Forest Steppe of Ukraine in different periods of time. The highest level of variation was observed at the Gli-A1 locus. Predominant alleles (one or two per locus) were revealed. The comparison of allele frequencies in groups of cultivars developed in different periods of time (before 1996 and in 1996–2007) has demonstrated appearance of new alleles and change of frequencies of existing alleles at the storage protein loci. The high frequency of cultivars with the wheat-rye 1BL/1RS translocation was detected (about 40%). The wheat rye 1AL/1RS translocation was identified in six cultivars developed in the last decade. Four gliadin alleles, Gli-A1w (a marker for the 1AL/1RS translocation), Gli-A1x, Gli-A1y and Gli-B1x, were proposed for cataloging. The article is published in the original.     

Mapping seed storage protein loci Sec-1 and Sec-3 in relation to five chromosomal rearrangements in rye (Secale cereale L.)

Summary Linkage relationships were established between the secalin loci, Sec 1 (40-K gamma and omega secalins, homologous to the wheat gliadins) and Sec 3 (HMW = high-molecular-weight secalins, homologous to the wheat HMW glutenin subunits), and five chromosomal rearrangements involving chromosome 1R of rye (Secale cereale L.). These were: interchanges T273W (1RL/5RS), T306W (1RS/5RL), and T850W (1RS/ 4RL), Robertsonian centromere split Rb1RW and the interchanged Robertsonian split Rb2R/248W. The analysis established the linkage relationships between the secalin loci and the breakpoints of the rearrangements, in addition to the quantitative effects of the rearrangements on the linkage. Sec-1 is located in the satellite at a position at least 2.5 cMorgan from the proximal border of the terminal C-band, and about 30 cMorgan from the nucleolar organizing region (NOR). The locus is also physically closer to the terminal C-band than to the NOR, but not as much as corresponds with the map distances. Similarly, the physical distance between Sec-3 and the centromere is greater than corresponds with the recombination frequency (0%–9%). Although overall recombination in 1RL remains the same, recombination between the centromere and Sec-3 is greatly reduced in the Robertsonian split combined with the interchange. This is not the case with the single Robertsonian split.     

Molecular cytogenetic characterization of a new wheat-rye 1BL•1RS translocation line expressing superior stripe rust resistance and enhanced grain yield

Main conclusion

A new wheat-rye 1BL?1RS translocation line, with the characteristics of superior stripe rust resistance and high thousand-kernel weight and grain number per spike, was developed and identified from progenies of wheat-rye- Psathyrostachys huashanica trigeneric hybrids.

Abstract

The wheat-rye 1BL?1RS translocation line from Petkus rye has contributed substantially to the world wheat production. However, due to extensive growing of cultivars with disease resistance genes from short arm of rye chromosome 1R and coevolution of pathogen virulence and host resistance, these cultivars successively lost resistance to pathogens. In this study, a new wheat-rye line K13-868, derived from the progenies of wheat-rye-Psathyrostachys huashanica trigeneric hybrids, was identified and analyzed using fluorescence in situ hybridization (FISH), genomic in situ hybridization (GISH), acid polyacrylamide gel electrophoresis (A-PAGE), and molecular markers. Cytological studies indicated that the mean chromosome configuration of K13-868 at meiosis was 2n = 42 = 0.14 I + 18.78 II (ring) + 2.15 II (rod). Sequential FISH and GISH results demonstrated that K13-868 was a compensating wheat-rye 1BL?1RS Robertsonian translocation line. Acid PAGE analysis revealed that clear specific bands of rye 1RS were expressed in K13-868. Simple sequence repeat (SSR) and rye 1RS-specific markers ω-sec-p1/ω-sec-p2 and O-SEC5′-A/O-SEC3′-R suggested that the 1BS arm of wheat had been substituted by the 1RS arm of rye. At the seedling and adult growth stage, compared with its recurrent wheat parent SM51 and six other wheat cultivars containing the 1RS arm in southwestern China, K13-868 showed high levels of resistance to stripe rust (Puccinia striiformis f. sp. tritici, Pst) pathogens prevalent in China, which are virulent to Yr10 and Yr24/Yr26. In addition, K13-868 expresses higher thousand-kernel weight and more grain number per spike than these controls in two growing seasons, suggesting that this line may carry yield-related genes of rye. This translocation line, with significant characteristics of resistance to stripe rust and high thousand-kernel weight and grain number per spike, could be utilized as a valuable germplasm for wheat improvement.

     

From the rye Alt3 and Alt4 aluminum tolerance loci to orthologous genes in other cereals

The major limit to plant growth in acid soils is the presence of toxic aluminum (Al) cations, which limit growth by inhibiting root elongation. Aluminum tolerance in rye is controlled by (at least) four independent loci (Alt1, Alt2, Alt3 and Alt4) located on chromosome arms 6RS, 3RS, 4RL and 7RS, respectively. In this work, we analyzed several F₂ populations in which two different Alt loci were segregating. We constructed a map of chromosome 7R, which contains the Alt4 locus and microsatellite and PCR-markers (B1, B4, B11, B26 and BCD1230). These markers were mapped to the S arm of 7R using wheat-rye addition lines. Our results show that all these markers are linked to the Alt4 locus already known to be on 7RS. In addition, the OPS14 ₇₀₅ RAPD marker was linked to the Alt3 locus using bulked segregant analysis. This RAPD marker was transformed into a SCAR (ScOPS14 ₇₀₅ ) and was localized to arm 4RL using wheat-rye addition lines. Finally, this SCAR was linked to the Alt3 locus at a genetic distance of 23.4 cM. In light of the current findings, and taking into account the synteny relationships in cereals, we propose candidate Alt3 and Alt4 orthologues in other cereals.     

Sequence composition and gene content of the short arm of rye (Secale cereale) chromosome 1

Background

The purpose of the study is to elucidate the sequence composition of the short arm of rye chromosome 1 (Secale cereale) with special focus on its gene content, because this portion of the rye genome is an integrated part of several hundreds of bread wheat varieties worldwide.

Methodology/Principal Findings

Multiple Displacement Amplification of 1RS DNA, obtained from flow sorted 1RS chromosomes, using 1RS ditelosomic wheat-rye addition line, and subsequent Roche 454FLX sequencing of this DNA yielded 195,313,589 bp sequence information. This quantity of sequence information resulted in 0.43× sequence coverage of the 1RS chromosome arm, permitting the identification of genes with estimated probability of 95%. A detailed analysis revealed that more than 5% of the 1RS sequence consisted of gene space, identifying at least 3,121 gene loci representing 1,882 different gene functions. Repetitive elements comprised about 72% of the 1RS sequence, Gypsy/Sabrina (13.3%) being the most abundant. More than four thousand simple sequence repeat (SSR) sites mostly located in gene related sequence reads were identified for possible marker development. The existence of chloroplast insertions in 1RS has been verified by identifying chimeric chloroplast-genomic sequence reads. Synteny analysis of 1RS to the full genomes of Oryza sativa and Brachypodium distachyon revealed that about half of the genes of 1RS correspond to the distal end of the short arm of rice chromosome 5 and the proximal region of the long arm of Brachypodium distachyon chromosome 2. Comparison of the gene content of 1RS to 1HS barley chromosome arm revealed high conservation of genes related to chromosome 5 of rice.

Conclusions

The present study revealed the gene content and potential gene functions on this chromosome arm and demonstrated numerous sequence elements like SSRs and gene-related sequences, which can be utilised for future research as well as in breeding of wheat and rye.     

Introgression of Recombinant 1RSWR.1BL Translocation and Rust Resistance Genes in Bread Wheat cv. HD2967 Through Marker-Assisted Selection

Bread wheat (Triticum aestivum L.) is one of the major cereal crops utilized worldwide for bread making. The presence of secalin locus on 1RS leads to the sticky dough and poor bread-making quality of wheat. In the present study, two donor parents, one with distal rye chromatin (1RS44:38) and another with distal wheat chromatin (Pavon MA1) without secalin, and one recipient elite wheat cultivar HD2967 were used. In 1RS44:38, the distal rye region has the Pm8 gene to which the QTL for superior root traits is linked, while in Pavon MA1 with Glu-B3/Gli-B1, the Pm8 gene was found to be absent. This distal rye region having root trait QTL was introgressed into the HD2967 derivatives using marker-assisted backcross selection. The derivatives with distal rye region introgression had higher root biomass, drought resistance, and 6–8% higher yield than the recipient parent cultivar. HD2967 is highly susceptible to yellow rust. Therefore, in the second backcross, the rust-resistant version of HD2967 (Lr57?+?Yr40) was used to introgress rust resistance in the derivatives. Background selection was done using polymorphic wheat anchored SSR markers of A, B, and D genomes of wheat which led to the selection of derivatives with?> 90% background of the recipient cultivar. The significant findings in this study include higher root biomass, improved yield, rust resistance in the derivatives, and retaining the alleles of Glu-B3/Gli-B1 along with Pm8 and the absence of secalin.

     

Production of a new wheat line possessing the 1BL.1RS wheat-rye translocation derived from Korean rye cultivar Paldanghomil

The 1BL.1RS translocations between wheat (Triticum aestivum L.) and rye (Secale cereale L.) are widely used in bread wheat breeding programs, but all modern wheat cultivars with the 1BL.1RS have shown genetic vulnerability due to one rye source – a German cultivar, Petkus. We have developed, a new 1BL.1RS wheat-rye translocation line from the backcross of the F₁ hybrid of wheat cv. Olmil and rye cv. Paldanghomil, both cultivars from Korea. The GISH technique was applied to identify the presence of rye chromatin in 467 BC₁F₆ lines selected from 77 BC₁F₅ lines. Only one line, Yw62–11, showed wheat-rye translocated chromosomes, with a somatic chromosome number of 2n=42. C-banding patterns revealed that the translocated chromosome was 1BL.1RS, showing prominent bands in the terminal and sub-terminal regions of the short arm as well as in the centromeric region and terminal region of the long arm. This new 1BL.1RS translocation line formed 21 bivalents like common wheat at meiotic metaphase I, thereby showing complete homology. Received: 28 February 2001 / Accepted: 17 April 2001     

A Mutant with Expression Deletion of Gene Sec-1 in a 1RS.1BL Line and Its Effect on Production Quality of Wheat

The chromosome arm 1RS of rye (Secale cereal L.) has been used worldwide as a source of genes for agronomic and resistant improvement. However, the 1RS arm in wheat has end-use quality defects that are partially attributable to the presence of ω-secalins, which are encoded by genes at the Sec-1 locus. Various attempts in removing the Sec-1 genes from the 1RS.1BL translocation chromosome have been made. In the present study, two new primary 1RS.1BL translocation lines, T917-26 and T917-15, were developed from a cross between wheat variety “{"type":"entrez-nucleotide","attrs":{"text":"A42912","term_id":"2298361"}}A42912” and Chinese local rye “Weining.” The lines T917-15 and T917-26 carried a pair of intact and homogeneous 1RS.1BL chromosomes. The line T917-26 also harbored an expression deletion of some genes at the Sec-1 locus, which originated from a mutation that occurred simultaneously with wheat-rye chromosome translocations. These results suggest that the accompanying mutations of the evolutionarily significant translocations are remarkable resources for plant improvement. Comparison of translocation lines with its wheat parent showed improvements in the end-use quality parameters, which included protein content (PC), water absorption (WA), sodium dodecyl sulfate sedimentation (SDSS), wet gluten (WG), dry gluten (DG) and dough stickiness (DS), whereas significant reduction in gluten index (GI) and stability time (ST) were observed. These findings indicate that 1RS in wheat has produced a higher amount of protein, although these comprised worse compositions. However, in the T917-26 line that harbored an expression deletion mutation in the Sec-1 genes, the quality parameters were markedly improved relative to its sister line, T917-15, especially for GI and DS (P < 0.05). These results indicated that expression deletion of Sec-1 genes significantly improves the end-use quality of wheat cultivars harboring the 1RS.1BL translocation. Strategies to remove the Sec-1 genes from the 1RS.1BL translocation in wheat improvement are discussed.     

Identification of the 1RS rye chromosomal segment in wheat by RAPD analysis

The introgression of rye DNA into the wheat genome was studied using random decamer and specific primers with the polymerase chain reaction (PCR). DNA from paired near-isolines in Chisholm and Arkan backgrounds differing with respect to the presence of a 1 RS.1 BL translocation was amplified with 120 arbitrary sequence primers. Two of the primers (OPR 19 and OPJ07) amplified rye-specific DNA fragments. The OPR19 primer amplified a 1.35-kb fragment that appeared to be specific to the 1 RS.1 BL translocation, based on its presence only in lines carrying the 1 RS. 1 BL translocation. A fragment of the same size was also amplified in 1 RS.1 AL translocation lines. This 1 RS. 1 BL marker locus was designated Ximc 1. The other primer, OPJ07, amplified a 1.2-kb DNA sequence, that was designated Ximc 2, specific to the wheat-rye translocation in various wheat backgrounds. The sequences of the two marker loci were found to be different from each other. The Ximc 1 locus was a low-copy sequence which was also present in Balboa rye genomic DNA. Through the use of specific primers, the presence of the rye-specific marker was confirmed in hexaploid as well as in tetraploid wheat backgrounds. The use of RAPDs for the study of smaller alien introgressions into wheat is discussed.     

Identification of 1AL/1RS translocation in winter common wheat varieties of Ukrainian selection

Analysis of alcohol-soluble protein (gliadin) patterns of a group of winter common wheat varieties from different breeding centers of Ukraine resulted in identification of six varieties with the rye 1AL/1RS translocation. The line 7086 AR also carries this translocation. The identified 1AL/1RS translocation is similar to that of the variety Amigo in the secalin pattern. The appearance of this translocation in varieties developed in different breeding centers of the forest-steppe of Ukraine indicates its involvement in coadaptive gene associations.     

Linkage mapping of genes for resistance to leaf,stem and stripe rusts and ω-secalins on the short arm of rye chromosome 1R

Summary The genes controlling resistance to three wheat rusts, viz., leaf rust (Lr26), stem rust (Sr31) and stripe or yellow rust (Yr9), and -secalins (Sec1), located on the short arm of rye chromosome 1R, were mapped with respect to each other and the centromere. Analysis of 214 seeds (or families derived from them) from testcrosses between a 1BL.1RS/1R heterozygote and Chinese Spring ditelocentric 1BL showed no recombination between the genes for resistance to the three rusts, suggesting very tight linkage or perhaps a single complex locus conferring resistance to the three rusts. The rust resistance genes were located 5.4 ± 1.7 cM from the Sec1 locus, which in turn was located 26.1 ± 4.3 cM from the centromere; the gene order being centromere — Sec1 — Lr26/Sr31/Yr9 — telomere. In a second test-cross, using a different 1BL.1RS translocation which had only stem rust resistance (SrR), the above gene order was confirmed despite a very large proportion of aneuploids (45.8%) among the progeny. Furthermore, a map distance of 16.0 ± 4.8 cM was estimated for SrR and the telomeric heterochromatin (C-band) on 1RS. These results suggest that a very small segment of 1RS chromatin is required to maintain resistance to all three wheat rusts. It should be possible but difficult to separate the rust resistance genes from the secalin gene(s), which are thought to contribute to dough stickiness of wheat-rye translocation lines carrying 1RS.     

1BL/1RS translocation in durum wheat and its effect on end use quality traits

The gluten proteins document the genotypic identity of a wheat variety, in addition to providing valuable clues about its ancestry and technological properties. In this study, an Indian durum wheat genotype B662 was identified to carry 1BL/1RS translocation and characterized further for its effect on end use quality traits. Comparison of the end use quality traits of B662 with five other durum cultivars without 1BL/1RS, showed decreased gluten content, lower swelling index of glutenins and low MSDS-SV indicating that, B662 with 1BL/1RS is not good for pasta making. In F_2:3 seeds from a durum wheat cross between the 1BL/1RS cultivar B662 and HI8498 without the translocation, the secalin Sec-1 loci segregated in theoretically expected 3:1 proportion and were inherited as a block of the rye chromosome arm. The analysis of F_2:3 harvests for the two most important durum wheat quality tests showed that the presence of 1BL/1RS translocation did not alter the grain protein content values, but was associated with significant reduction of micro SDS-sedimentation volume indicating inferior quality, thus limiting the commercial exploitation of durum wheat genotypes with 1BL/1RS translocation. The cautious use of rye translocation in Indian durum wheat breeding is suggested.     

Chromosome composition of wheat-rye lines and the influence of rye chromosomes on disease resistance and agronomic traits

Identification of the chromosomal composition of common wheat lines with rye chromosomes was carried out using genomic in situ hybridization and 1RS- and 5P-specific PCR markers. It was demonstrated that wheat chromosomes 5A or 5D were substituted by rye chromosome 5R in the wheat-rye lines. It was established that one of the lines with complex disease resistance contained rye chromosome 5R and T1RS.1BL, while another line was found to contain, in addition to T1RS.1BL, a new Robertsonian translocation, T5AS.5RL. Substitution of the wheat chromosome 5A with the dominant Vrn-A1 gene for the Onokhoiskaya rye chromosome 5R led to lengthening of the germination-heading period or to a change in the type of development. A negative influence of T1RS.1BL on SDS sedimentation volume and grain hardness was demonstrated, along with a positive effect of the combination of T1RS.1BL and 5R(5D) substitution on grain protein content. Quantitative traits of the 5R(5A) and 5R(5D) substitution lines were at the level of recipient cultivars. A line with two translocations, T1RS.1BL + T5AS.5Rl, appeared to be more productive as compared to the line carrying T1RS.1BL in combination with the 5R(5D) substitution.     

Mapping of the seed storage protein locus Sec-2 in rye

The segregation of the 75K gamma secalin locus (Sec-2) in combination with five interchanges (reciprocal translocations) and two marker genes was analyzed. The translocations involved chromosome arms 1RL, 1RS, 2RL, 2RS, 4RL, 5RL, 5RS, 6RL and 6RS. The gene loci were both on 2R, but the arm was not known. Although the Sec-2 locus was expected to be on chromosome 2RS, no linkage between Sec-2 and any of the markers was found. This is concluded to be the result of exceptionally frequent recombination between Sec-2 and the break point of one of the translocations, which is the only marker in 2RS.     

Dosage response of rye genes in a wheat background

Summary A series of hexaploid wheat lines containing zero, two or four doses of rye chromosome arm 1RS was used to investigate the response to changes in dosage by the rye genes when in a wheat background. The quantity of protein produced by the secalin protein genes contained on 1RS was directly related to the number of copies of 1RS present in the line. No response could be detected by representative wheat proteins suggesting that the increase in secalin protein observed was due to an increase in mRNA produced when four copies of the secalin gene was present. These results suggest that increasing the dosage of alien genes introgressed into wheat may be a useful tool for enhancing their expression.Mention of a trade name or proprietary product does not constitute a guarantee, warranty or recommendation of the product by the U.S. Department of Agriculture or the University of Missouri and does not imply its approval to the exclusion of other products that may be suitable.Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 11,413     

威岭栽培黑麦抗白粉病特性导入小麦的研究

威岭黑麦(Weiling rye)是一个高抗白粉病(Erysiphe gramininis f．sp．tritici)的中国矮杆栽培黑麦。以Weiling rye作为白粉病抗源,高感白粉病小麦栽培品种My8443为母本,从Weiling rye与小麦My8443远缘杂交的BC_2F_6后代中鉴定出一个新的小麦-黑麦易位系No．147,以实现威岭黑麦白粉病抗性向普通栽培小麦的转移。No．147及其亲本的抗白粉病特性通过苗期和成株期优势生理小种混合接种和室内单生理小种接种鉴定,改良的染色体C-分带和基因组原位杂交技术(GISH。Ge- nomic in situ hybridization)被用于鉴定小麦和黑麦的染色质,酸性聚丙烯酰胺凝胶电泳(APAGE)被用于鉴定黑麦醇溶蛋白1RS特异条带,11个黑麦种属特异性标记SCM(Secale cereale marker)引物被用于扩增分析黑麦特异性简单重复序列(SSR)。研究结果证实No．147是一个新的高抗白粉病的1BL/1RS小麦-黑麦染色体易位系,并对其产生的细胞学机制进行了分析。论文对中国栽培黑麦抗性基因资源的利用和该易位系在小麦遗传育种改良中的利用价值进行了讨论。     

Generation of PCR-based markers for the detection of rye chromatin in a wheat background

Oligonucleotide primers were developed to detect the presence of four rye sequences using a PCR assay. These assays give a rye-specific signal from wheat DNA template which contains various rye chromosomes or chromosome segments. The sequences identified were associated with the nucleolar organiser region, the 5S-Rrna-R1 locus, the telomere, and a widely dispersed, rye-specific repetitive element Ris-1. The primers amplified from the well-established loci Nor-R1 and 5S-Rrna-R1 on rye chromosome arm 1RS, and also located a 5s-Rrna locus on chromosome 3R. The telomere-associated sequence was present on every rye chromosome, and was also present, at a low copy number, in both wheat and barley. These assays will be particularly useful for introgression programmes aimed at reducing the rye content of the 1BL.1RS wheat-rye translocation. When multiplexed, the primers will enable a rapid, simultaneous assay for a number of distinct rye loci, which can be derived from a small portion of mature endosperm tissue.