Distribution of Nonstructural Variation along Three Chromosome Arms between Wheat Cultivars Chinese Spring and Cheyenne

Metaphase I (MI) pairing of wheat homologous chromosomes is usually reduced in hybrids between cultivars relative to the parental inbred lines. Previous work suggested that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The present work investigated the distribution of this variation along three selected chromosome arms between cultivars Chinese Spring and Cheyenne. Chinese Spring ditelosomics 3Aq, 6Ap and 6Bp were crossed with disomic substitutions of Cheyenne chromosomes 3A, 6A and 6B in Chinese Spring, respectively. The resulting F₁ plants, called substituted monotelodisomics, were crossed with the respective Chinese Spring monosomics, producing potentially "recombinant" substituted monosomics. When these "recombinant" chromosomes were combined with the parental Chinese Spring telosomes, marked reductions in mean telosome-pairing frequency were found compared with the corresponding Chinese Spring monotelodisomics. The mean pairing frequencies of the "recombinant" chromosomes showed a continuous distribution between those of the substituted and Chinese Spring monotelodisomics. The results suggest that the nonstructural variation that reduces MI pairing between chromosomes of different wheat cultivars is not localized in a specific site but distributed along each chromosome arm. Little variation was found among monotelodisomics for either the number of ring bivalents per cell or the number of univalents other than those constituting the heteromorphic pair. This implies that the reductions in MI pairing between the Cheyenne and Chinese Spring chromosomes are caused by something residing within these specific chromosomes that does not affect the pairing of the remaining Chinese Spring chromosomes in the same cell. Furthermore, the absence of parental types among the "recombinant"-substituted monotelodisomics suggests that the sequences involved in the variation studied here are capable of converting heterohomologous chromosomes to something intermediate in nature in the span of only a single generation.     

中国春双端二体中端体的配对研究

21个中国春双端二体与中国春品种杂交,观察了杂种F_1减数分裂中期Ⅰ端体与相应染色体的配对。结果表明:14个组合的中期Ⅰ具有1个异形三价体的PMC的百分数超过90%;有3个组合(6A、5B和6D)分别为89.87%、83.56%和85.71%;2个组合(4A和1B)低于80%。在4A、1B和5B的3个组合中,具有1个异形二价体和1个单价端体的PMC超过15%。在4A、1B和4D的组合中,还有一定频率的PMC具有2个单价端体。用21个组合中端体配对频率计算的二价体频率与中国春品种中期Ⅰ构型频率基本一致。这些结果表明,染色体臂作为端体时和它作为双臂染色体的一部分时,是以同样的方便程度配对的。     

Distribution of Nonstructural Variation between Wheat Cultivars along Chromosome Arm 6Bp: Evidence from the Linkage Map and Physical Map of the Arm

Metaphase I (MI) pairing of homologous chromosomes in wheat intercultivar hybrids (heterohomologous chromosomes) is usually reduced relative to that within the inbred parental cultivars (euhomologous chromosomes). It was proposed elsewhere that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The distribution of this polymorphism along chromosome arm 6Bp (=6BS) of cultivars Chinese Spring and Cheyenne was investigated. A population of potentially recombinant chromosomes derived from crossing over between telosome 6Bp of Chinese Spring and Cheyenne chromosome 6B was developed in the isogenic background of Chinese Spring. The approximate length of the Chinese Spring segment present in each of these chromosomes was assessed by determining for each chromosome the interval in which crossing over occurred (utilizing the rRNA gene region, a distal C-band and the gliadin gene region as markers). The MI pairing frequencies of these chromosomes (only the complete chromosomes were used) with the normal Chinese Spring telosome 6Bp were determined. These were directly proportional to the length of the euhomologous segment. The longer the incorporated euhomologous segment the better was the MI pairing. This provided evidence that the heterohomologous chromosomes are differentiated from each other in numerous sites distributed throughout the arm.—The comparison of the physical map of arm 6Bp with the linkage map showed a remarkable distortion of the linkage map; no crossing over was detected in the proximal 68% of the arm. A population of 49 recombinant chromosomes was assayed for recombination within the rRNA gene region, but none was detected. No new length variants of the nontranscribed spacer separating the 18S and 26S rRNA genes were detected either.     

Chromosome and nucleotide sequence differentiation in genomes of polyploid Triticum species

Summary The nature of genome change during polyploid evolution was studied by analysing selected species within the tribe Triticeae. The levels of genome changes examined included structural alterations (translocations, inversions), heterochromatinization, and nucleotide sequence change in the rDNA regions. These analyses provided data for evaluating models of genome evolution in polyploids in the genus Triticum, postulated on the basis of chromosome pairing at metaphase I in interspecies hybrids.The significance of structural chromosome alterations with respect to reduced MI chromosome pairing in interspecific hybrids was assayed by determining the incidence of heterozygosity for translocations and paracentric inversions in the A and B genomes of T. timopheevii ssp. araraticum (referred to as T. araraticum) represented by two lines, 1760 and 2541, and T. aestivum cv. Chinese Spring. Line 1760 differed from Chinese Spring by translocations in chromosomes 1A, 3A, 4A, 6A, 7A, 3B, 4B, 7B and possibly 2B. Line 2541 differed from Chinese Spring by translocations in chromosomes 3A, 6A, 6B and possibly 2B. Line 1760 also differed from Chinese Spring by paracentric inversions in arms 1AL and 4AL whereas line 2541 differed by inversions in 1BL and 4AL (not all chromosomes arms were assayed). The incidence of structural changes in the A and B genomes did not coincide with the more extensive differentiation of the B genomes relative to the A genomes as reflected by chromosome pairing studies.To assay changing degrees of heterochromatinization among species of the genus Triticum, all the diploid and polyploid species were C-banded. No general agreement was observed between the amount of heterochromatin and the ability of the respective chromosomes to pair with chromosomes of the ancestral species. Marked changes in the amount of heterochromatin were found to have occurred during the evolution of some of the polyploids.The analysis of the rDNA region provided evidence for rapid fixation of new repeated sequences at two levels, namely, among the 130 bp repeated sequences of the spacer and at the level of the repeated arrays of the 9 kb rDNA units. These occurred both within a given rDNA region and between rDNA regions on nonhomologous chromosomes. The levels of change in the rDNA regions provided good precedent for expecting extensive nucleotide sequence changes associated with differentiation of Triticum genomes and these processes are argued to be the principal cause of genome differentiation as revealed by chromosome pairing studies.     

用中国春双端二体分析西藏小麦的染色体构成

用普通小麦“中国春”双端二体系列(double ditelosomics)作母本分别与西藏小麦杂交,对全套21个F_1的PMC在MI进行端体配对分析。在(“中国春”双端二体7B×西藏小麦)F_1中,含有(t′,t1″)构型的PMC占观察总数的87.3％,7BS常不参与配对,显示出有较大差异。“中国春”3A、7A、2D—7D等8条染色体的两臂可以分别同时与西藏小麦对应染色体配成异型三价体(tt1′′′)的PMC频率达80.0—95.5％,表明西藏小麦与“中国春”之间这8条染色体差异很小。在涉及其余12条染色体的组合中,出现(tt1′′′)、(t′t1″)和(t′,t′)构型的PMC分别占观察细胞总数的42.3—77.6％、21.9—55.5％和0—8.0％,表明它们之间仅某个染色体臂间有轻度变异或分化。从总体来看,西藏小麦与“中国春”之间除7BS有较大差异外在染色体构成上基本相似。     

Meiotic pairing in hybrids between tetraploid Triticale and related species: new elements concerning the chromosome constitution of tetraploid Triticale

Summary Two F5 strains of tetraploid triticale (2n= 4x=28), obtained from 6x triticaleX2 rye progenies, were crossed with diploid and tetraploid rye, some durum and bread wheats, and various 8x and 6x triticale lines. Meiosis in the different hybrid combinations was studied. The results showed that the haploid complement of these triticales consists of seven chromosomes from rye and seven chromosomes from wheat. High frequencies of PMCs showing trivalents were observed in hybrids involving the reference genotypes of wheat and triticale. These findings proved that several chromosomes from the wheat component have chromosome segments coming from two parental wheat chromosomes. The origin of these heterogeneous chromosomes probably lies in homoeologous pairing occurring at meiosis in the 6x triticaleX2x rye hybrids from which 4x triticale lines were isolated. A comparison among different hybrids combinations indicated that the involvement of D-genome chromosomes in homoeologous pairing is quite limited. In contrast, meiotic patterns in 4x triticale X 2x rye hybrids showed a quite high pairing frequency between some R chromosomes and their A and B homoeologues.     

Somatic karyotype,heterochromatin distribution,and nature of chromosome differentiation in common wheat,Triticum aestivum L. em Thell

Heterochromatin distribution and structural differentiation of somatic chromosomes of five common wheat cultivars — Chinese Spring, Wichita, Cheyenne, Timstein, and Hope — were studied by an acetocarmine/N-banding technique. Detailed morphological observations on acetocarmine stained somatic chromosomes of Chinese Spring were made on all A genome chromosomes (except 1A), all B genome chromosomes, and chromosomes 1D, 2D, and 7D. N-banding patterns of chromosomes 2A, 3A, 5A, 6A, 1D, 2D, and 7D were described for the first time. Substitution lines of 21 individual chromosomes each of Cheyenne, Timstein, and Hope in Chinese Spring were analyzed by N-banding. A high frequency of N-band polymorphism was observed, especially for most of the B genome chromosomes. Chromosomes 3A, 5A, 2D, and 7D showed a constant banding pattern. Three cases of doubtful substitutions, Hope 2A, 2B, and Timstein 7A, and several cases of incomplete and chromosomally modified substitutions were observed. The reduced level of chromosome pairing that is often observed in intercultivar hybrids of wheat may be due to heterochromatic differentiation, genic and structural heterozygosity, or hybrid dysgenesis.     

Latent Nonstructural Differentiation among Homologous Chromosomes at the Diploid Level: Chromosome 6B of AEGILOPS LONGISSIMA

Previous work has shown that chromosome pairing at metaphase I (MI) of wheat homologous chromosomes from different inbred lines (heterohomologous chromosomes) is reduced relative to that between homologous chromosomes within an inbred line (euhomologous chromosomes). In order to determine if a potential for this phenomenon exists in diploid species closely related to the wheat B genome, MI chromosome pairing was investigated between euhomologous and heterohomologous 6B^e (=6S^e) chromosomes, each from a different population of Aegilops longissima Schweinf. et Muschl. (2n = 2x = 14) substituted for chromosome 6B of Chinese Spring wheat (Triticum aestivum L., 2n = 6x = 42). Euhomologous and heterohomologous monotelodisomics, i.e., plants with one complete chromosome 6B^e and a telosome of either 6B^ep or 6B^eq, were constructed in the isogenic background of Chinese Spring. Pairing at MI of the Ae. longissima chromosomes was reduced in heterohomologous monotelodisomics compared to that in the corresponding euhomologous monotelodisomics. The remaining 20 pairs of Chinese Spring chromosomes paired equally well in the euhomologous and heterohomologous monotelodisomics. Thus, the cause of the reduced pairing must reside specifically in the Ae. longissima heterohomologues. In the hybrids between the Ae. longissima lines that contributed the substituted chromosomes, pairing between the heterohomologous chromosomes was normal and did not differ from that of the euhomologous chromosomes. These data provide evidence that a potential for reduced pairing between the heterohomologues is present in the diploid species, but is expressed only in the polyploid wheat genetic background. The reduction in heterohomologous chromosome pairing was greater in the p arm than in the q arm, exactly as in chromosome 6B of wheat. It is concluded that the reduced pairing between Ae. longissima heterohomologues has little to do with constitutive heterochromatin. The value of chromosome pairing as an unequivocal means of determining the origin of genomes in polyploid plants is questioned.     

Chromosomal location of powdery mildew resistance genes and cytogenetic analysis of meiosis in common wheat cultivar Meri

Common wheat cv. Meri was crossed to a set of 21 Chinese Spring monosomic lines to characterize resistance to powdery mildew and to determine the chromosomal location of the gene(s). Monosomic F1 plants were allowed to self-pollinate and to produce F2 seeds. Seedlings of F2 and F3 plants and their parents were inoculated with isolates Ns 2 and 9 of Erysiphe graminis f. sp. tritici. Analysis of obtained data revealed that one major dominant gene conferring resistance is located on chromosome 1B of cv. Meri. The new gene is designated by symbol Pm28. On the basis of the trivalent configuration frequency (without univalent) at the 1st metaphase of meiosis it was found that two reciprocal translocations involving chromosomes 2A/5A and 5B/5D differentiate cv. Meri from cv. Chinese Spring. In the F1 monosomic hybrids, genes causing a decrease in pairing are found on chromosomes 4D and 6D, and genes enhancing pairing--on chromosomes 3A and 7B.     

小麦-黑麦代换系5A/5R与6A/6R杂交诱导同祖染色体配对与易位的研究

利用两个小麦-黑麦异源双代换系DS 5A/5R与DS 6A/6R杂交,探讨同祖染色体配对的可能性与创制小麦黑麦异源易位系.在方法上对杂种F1的减数分裂行为进行研究,观察5R与5A、6R与6A配对频率,探讨同祖染色体配对规律.实验结果看到杂交F1减数分裂中有22.91%的花粉母细胞有小麦染色体(ABD组)与黑麦染色体(R组)发生同祖配对.在F2及以后世代,通过染色体C分带、原位杂交检测,选择小麦-黑麦易位系.在F2代的45株中检测到9株有易位,易位频率为20%,是目前小麦-黑麦染色体易位频率最高的.染色体易位有的来源于同祖配对的交换,有的来源于单价体错分裂或断裂的重建.     

应用原位杂交技术对小麦—黑麦代换系间杂交的细胞遗传研究

应用原位杂交技术结合染色体组型分析方法,对两个小麦-黑麦异源双代换系5R/5A和6R/6A杂交后代的遗传进行了研究,探讨同祖染色体配对的可能性并获得小麦-黑麦易位系。实验中对杂种F1代植株减数分裂各时期的花粉母细胞染色体行为进行分析,结果发现有22.91%的花粉母细胞中黑麦染色体与小麦染色体发生同祖配对。F2代通过C-分带、原位杂交鉴定,在45株中检测到9株易位,易位频率为20%,是目前报道易位频率最高的。染色体易位有的来源于同祖配对交换,有的来源于单价体错分裂或断裂的重建。     

phlb基因诱导小麦ABD染色体组部分同源染色体配对的研究

通过花药培养首次获得了“中国春”phlb突变体单倍体,同时也获得了“中国春”单倍体。对其细胞学观察表明,前者花粉母细胞减数分裂中期Ⅰ每个细胞染色体交叉为5.08个,后者为1.30个。证明了phlb基因在单倍体状态下具有强的诱导ABD染色体组部分同源染色体间的配对作用。     

Cytogenetic studies on two F1 hybrids of autotetraploid rice varieties showing extremely high level of heterosis

Mechanisms of two F1 hybrids (D46A × DTP-4 and D46A × Dminghui63) of autotetraploid rice (2n = 4x = 48) showing extremely high pollen fertility 87.40% and 85.97%, respectively, seed set 82.00% and 79.00%, respectively and extremely high level of heterosis were analyzed cytologically. The chromosome pairing of D46A × DTP-4 and D46A × Dminghui63 was normal at metaphase I(MI), and had almost no I or III, with an average of 0.020I +14.36 II 6.44rod+7.91ring) +0.01III + 4.80 IV + 0.01VIII and 0.06 I + 17.67 II (11.01rod + 6.67ring)] + 0.06 III +3.10IV+0.01VI, respectively. The most frequent chromosome configurations were 10II+7IV and 12II+bIV. The bivalent frequency was less frequent in hybrids than that in restoring parents, and the same results were gained from univalents, trivalent and multivalents. However, the quadrivalent frequency was significantly higher in hybrids than that in restoring parents at MI. The other meiotic phases progressed normally, except for low percentages of PMCs with lagging chromosomes at AI and low percentages of PMCs with micronuclei at telophaseI (TI) and telophaseII (TII). PMCs with lagging chromosomes at AI and PMCs with micronuclei at TI and TII showed negative correlation between pollen fertility and seed set. Above 90% of the PMCs could form normal microspores, which resulted in the production of viable pollen grains, abnormal microspores were observed including penta-fission and hexa-fission. Based on these results we suggest that the two F1 hybrids had better behaviors of chromosome pairing and genetic stability than autotetraploid rice and other autotetraploid plants ever studied.     

Development of Triticum aestivum-Leymus racemosus translocation lines using gametocidal chromosomes

Maan[1] and Endo[2] et al. first reported that some chromosomes from Ae. longgissima, Ae. sharonensis and Ae. triuncialis showed preferential transmission when introduced into wheat background. The mechanism for this phenomenon rests with the fact that contrary to the normal fertility of gametes with these chromosomes, chromosome structural aberrations occur seriously in the gametes without these chromosomes, causing less compatibility in selective fertilization and resulting in semi-sterilit…     

普通小麦与鹅观草属间杂种F1及BC1的分子细胞遗传学、育性和赤霉病抗性研究

通过胚拯救, 成功获得鹅观草Roegneria kamoji (2n=6x=42, SSHHYY)和普通小麦中国春Triticum aesti-vum (2n=6x=42, AABBDD)的正反交属间杂种F1, 并对这些杂种F1及其BC1的形态学、减数分裂配对行为、育性和赤霉病抗性进行研究。结果表明, (鹅观草×中国春)F1和(中国春×鹅观草)F1的形态介于双亲之间。杂种F1花粉母细胞减数分裂中期I染色体构型分别为40.33I + 0.78II + 0.03III和40.40I + 0.79II 。杂种F1高度雄性不育, 用中国春花粉与其回交可获得BC1代种子。(鹅观草×中国春) F1×中国春BC1植株的染色体数目主要分布在55~63之间, 单价体较多, 植株高度不育; (中国春×鹅观草)F1×中国春BC₁植株染色体数目也主要分布在55~63之间, 但其中部分植株拥有整套小麦染色体且能正常配对、分离, 可形成部分可育花粉粒, 能收到少量自交结实种子。在 (鹅观草×中国春)F1中有1株穗型趋向中国春, 其染色体数目为2n=63, 经染色体分子原位杂交(GISH)检测, 含有42条小麦染色体和21条鹅观草染色体。该杂种F1在减数分裂中期I平均每个花粉母细胞有26.40I+18.30II, 但植株高度雄性不育, 用中国春花粉回交能收到BC₁种子。(鹅观草×中国春) F₁ (2n=63)×中国春BC₁的染色体数目主要分布在40~59之间, 其中的外源染色体已经逐渐减少, 虽然该BC₁的穗型已接近中国春, 但仍然高度不育。赤霉病抗性鉴定结果显示, 所有杂种F1及大部分BC₁对赤霉病均表现出较好的抗性。     

Comparison of homoeologous chromosome pairing between hybrids of wheat genotypes Chinese Spring ph1b and Kaixian-luohanmai with rye

The ph-like genes in the Chinese common wheat landrace Kaixian-luohanmai (KL) induce homoeologous pairing in hybrids with alien species. In the present study, meiotic phenotypic differences on homoeologous chromosome pairing at metaphase I between hybrids of wheat genotypes Chinese Spring ph1b (CSph1b) and KL with rye were studied by genomic in situ hybridization (GISH). The frequency of wheat-wheat associations was higher in CSph1b×rye than in KL×rye. However, frequencies of wheat-rye and rye-rye associations were higher in KL×rye than in CSph1b×rye. These differences may be the result of different mechanisms of control between the ph-like gene(s) controlling homoeologous chromosome pairing in KL and CSph1b. Wheat-wheat associations were much more frequent than wheat-rye pairing in both hybriods. This may be caused by lower overall affinity, or homoeology, between wheat and rye chromosomes than between wheat chromosomes.     

Development and characterization of wheat- Leymus racemosus translocation lines with resistance to Fusarium Head Blight

Wheat scab (Fusarium Head Blight, FHB) is a destructive disease in the warm and humid wheat-growing areas of the world. Finding diverse sources of FHB resistance is critical for genetic diversity of resistance for wheat breeding programs. Leymus racemosus is a wild perennial relative of wheat and is highly resistant to FHB. Three wheat- L. racemosus disomic addition (DA) lines DA5Lr#1, DA7Lr#1 and DALr.7 resistant to FHB were used to develop wheat- L.racemosus translocation lines through irradiation and gametocidal gene-induced chromosome breakage. A total of nine wheat-alien translocation lines with wheat scab resistance were identified by chromosome C-banding, GISH, telosomic pairing and RFLP analyses. In line NAU614, the long arm of 5Lr#1 was translocated to wheat chromosome 6B. Four lines, NAU601, NAU615, NAU617, and NAU635, had a part of the short arm of 7Lr#1 transferred to different wheat chromosomes. Four other lines, NAU611, NAU634, NAU633, and NAU618, contained translocations involving Leymus chromosome Lr.7 and different wheat chromosomes. The resistance level of the translocation lines with a single alien chromosome segment was higher than the susceptible wheat parent Chinese Spring but lower than the alien resistant parent L. racemosus. At least three resistance genes in L. racemosus were identified. One was located on chromosome Lr.7, and two could be assigned to the long arm of 5Lr#1 and the short arm of 7Lr#1.     

萝卜与甘蓝属间杂种基因组原位杂交分析

用基因组原位杂交方法（Genomic in situ hybridization, 简称GISH）研究了萝卜( Raphanus sativus,2n=18,RR)和甘蓝（Brassica oleracea , 2n=18, CC）属间杂种F1减数分裂过程。结果表明杂种体细胞染色体组成为RC,2n=18,但花粉母细胞有三种不同类型：1. RC,2n=18, 终变期染色体平均配对构型为14.87Ⅰ+1.20Ⅱ+0.04Ⅲ+0.06Ⅳ, 染色体配对主要发生在萝卜和甘蓝染色体之间, 后期Ⅰ9条萝卜染色体主要以5/4和6/3的分离比移向两极, 所形成配子的染色体数目和组成均不平衡,配子败育; 2. RRCC,4n=36, 终变期染色体形成18个二价体,后期Ⅰ染色体均衡分离,形成RC不减数配子;3. RRCC缺体,4n=30－34, 少数萝卜染色体丢失,形成的配子具有全套的甘蓝染色体和部分萝卜染色体。     

普通小麦与鹅观草属间杂种F1及BC1的分子细胞遗传学、育性和赤霉病抗性研究

通过胚拯救, 成功获得鹅观草Roegneria kamoji (2n=6x=42, SSHHYY)和普通小麦中国春Triticum aesti-vum (2n=6x=42, AABBDD)的正反交属间杂种F1, 并对这些杂种F1及其BC1的形态学、减数分裂配对行为、育性和赤霉病抗性进行研究。结果表明, (鹅观草×中国春)F1和(中国春×鹅观草)F1的形态介于双亲之间。杂种F1花粉母细胞减数分裂中期I染色体构型分别为40.33I + 0.78II + 0.03III和40.40I + 0.79II 。杂种F1高度雄性不育, 用中国春花粉与其回交可获得BC1代种子。(鹅观草×中国春) F1×中国春BC1植株的染色体数目主要分布在55~63之间, 单价体较多, 植株高度不育; (中国春×鹅观草)F1×中国春BC₁植株染色体数目也主要分布在55~63之间, 但其中部分植株拥有整套小麦染色体且能正常配对、分离, 可形成部分可育花粉粒, 能收到少量自交结实种子。在 (鹅观草×中国春)F1中有1株穗型趋向中国春, 其染色体数目为2n=63, 经染色体分子原位杂交(GISH)检测, 含有42条小麦染色体和21条鹅观草染色体。该杂种F1在减数分裂中期I平均每个花粉母细胞有26.40I+18.30II, 但植株高度雄性不育, 用中国春花粉回交能收到BC₁种子。(鹅观草×中国春) F₁ (2n=63)×中国春BC₁的染色体数目主要分布在40~59之间, 其中的外源染色体已经逐渐减少, 虽然该BC₁的穗型已接近中国春, 但仍然高度不育。赤霉病抗性鉴定结果显示, 所有杂种F1及大部分BC₁对赤霉病均表现出较好的抗性。     

Chromosomal assignment and deletion mapping of barley EST markers

From about 10000 PCR-based EST markers of barley we chose 1421 EST markers that were demonstrated to be amplified differently by PCR between wheat (Triticum aestivum cv. Chinese Spring) and barley (Hordeum vulgare cv. Betzes). We assigned them to the seven barley chromosomes (1H to 7H) by PCR analysis using a set of wheat-barley chromosome addition lines. We successfully assigned 701 (49.3%) EST markers to the barley chromosomes: 75 to 1H, 127 to 2H, 119 to 3H, 94 to 4H, 108 to 5H, 81 to 6H and 97 to 7H. By using a set of Betzes barley telosomic addition lines of Chinese Spring, we could successfully determine the chromosome-arm (S or L) location of at least 90% of the EST markers assigned to each barley chromosome. We conducted a trial mapping using 90 EST markers assigned to 7HS (49) or 7HL (41) and 19 wheat lines carrying 7H structural changes. More EST markers were found in the distal region than in the proximal region.