Diverse patterns of the tandem repeats organization in rye chromosomes

Although the monomer size, nucleotide sequence, abundance and species distribution of tandemly organized DNA families are well characterized, little is known about the internal structure of tandem arrays, including total arrays size and the pattern of monomers distribution. Using our rye specific probes, pSc200 and pSc250, we addressed these issues for telomere associated rye heterochromatin where these families are very abundant. Fluorescence in situ hybridization (FISH) on meiotic chromosomes revealed a specific mosaic arrangement of domains for each chromosome arm where either pSc200 or pSc250 predominates without any obvious tendency in order and size of domains. DNA of rye-wheat monosomic additions studied by pulse field gel electrophoresis produced a unique overall blot hybridization display for each of the rye chromosomes. The FISH signals on DNA fibres showed multiple monomer arrangement patterns of both repetitive families as well as of the Arabidopsis-type telomere repeat. The majority of the arrays consisted of the monomers of both families in different patterns separated by spacers. The primary structure of some spacer sequences revealed scrambled regions of similarity to various known repetitive elements. This level of complexity in the long-range organization of tandem arrays has not been previously reported for any plant species. The various patterns of internal structure of the tandem arrays are likely to have resulted from evolutionary interplay, array homogenization and the generation of heterogeneity mediated by double-strand breaks and associated repair mechanisms.     

Variation in highly repetitive DNA composition of heterochromatin in rye studied by fluorescence in situ hybridization.

The molecular characterization of heterochromatin in six lines of rye has been performed using fluorescence in situ hybridization (FISH). The highly repetitive rye DNA sequences pSc 119.2, pSc74, and pSc34, and the probes pTa71 and pSc794 containing the 25S-5.8S-18S rDNA (NOR) and the 5S rDNA multigene families, respectively, were used. This allowed the individual identification of all seven rye chromosomes and most chromosome arms in all lines. All varieties showed similar but not identical patterns. A standard in situ hybridization map was constructed following the nomenclature system recommended for C-bands. All FISH sites observed appeared to correspond well with C-band locations, but not all C-banding sites coincided with hybridization sites of the repetitive DNA probes used. Quantitative and qualitative differences between different varieties were found for in situ hybridization response at corresponding sites. Variation between plants and even between homologous chromosomes of the same plant was found in open-pollinated lines. In inbred lines, the in situ pattern of the homologues was practically identical and no variation between plants was detected. The observed quantitative and qualitative differences are consistent with a corresponding variation for C-bands detected both within and between cultivars.     

Diversity and evolution of four dispersed repetitive DNA sequences in the genus Secale

We present the first characterization of 360 sequences in six species of the genus Secale of both cultivated and wild accessions. These include four distinct kinds of dispersed repetitive DNA sequences named pSc20H, pSc119.1, pSaO5(411), and pSaD15(940) belonging to the Revolver family. During the evolution of the genus Secale from wild to cultivated accessions, the pSaO5(411)-like sequences became shorter mainly because of the deletion of a trinucleotide tandem repeating unit, the pSc20H-like sequences displayed apparent homogenization in cultivated rye, and the second intron of Revolver became longer. In addition, the pSc20H-, pSc119.1-, and pSaO5(411)-like sequences cloned from wild rye and cultivated rye could be divided into two large clades. No single case of the four kinds of repetitive elements has been inherited by each Secale accession from a lone ancestor. It is reasonable to consider the vertical transmission of the four repetitive elements during the evolution of the genus Secale. The pSc20H- and pSaO5(411)-like sequences showed evolutionary elimination at specific chromosomal locations from wild species to cultivated species. These cases imply that different repetitive DNA sequences have played different roles in the chromosome development and genomic evolution of rye. The present study adds important information to the investigations dealing with characterization of dispersed repetitive elements in wild and cultivated rye.     

Highly repetitive sequences in B chromosomes of Secale cereale revealed by fluorescence in situ hybridization.

An analysis of the presence and distribution of the rye and wheat repeated sequences in rye B chromosomes was carried out by fluorescent in situ hybridization. Probes used consisted of three highly repetitive sequences from rye (pSc119.2, pSc74, and pSc34) and the multigene families for the 25S-5.8S-18S and 5S rDNA from wheat (pTa71 and pTa794, respectively). pSc74 and pSc119.2 showed hybridization signals in the telomeric regions of rye B chromosomes. The remaining DNA clones did not hybridize to the B chromosomes.     

Heterogeneous organization of a tandem repeat family in subtelomeric heterochromatin of rye

The presence of tandem repeat multicopy families in subtelomeric regions of all chromosomes is a characteristic feature of the rye karyotype, in contrast to the organization of these regions in chromosomes of extensively studied species, such as human, rice, and Arabidopsis. To study the molecular structure of these regions, we analyzed BAC clones from a library constructed from the genetic material of rye chromosome 1 short arm (1RS). Screening of the library detected numerous clones that contained copies of multicopy tandem families of DNA sequences pSc200, pSc250, and pSc119.2. An examination of the molecular organization of tandem arrays of the pSc200 family, which is the most common in the rye genome, showed that the subtelomeric 1RS region includes several such arrays, each of which contains characteristic blocks of multimers of various periodicity. Such pattern of heterogeneous organization of tandem repeat arrays differs from the view of the tandem arrays as monotonous sequence of identical monomers, which was generally accepted in recent past.     

Painting the rye genome with genome-specific sequences

We used rye-specific repetitive DNA sequences in fluorescence in situ hybridization (FISH) to paint the rye genome and to identify rye DNA in a wheat background. A 592 bp fragment from the rye-specific dispersed repetitive family R173 (named UCM600) was cloned and used as a FISH probe. UCM600 is dispersed over the seven rye chromosomes, being absent from the pericentromeric and subtelomeric regions. A similar pattern of distribution was also observed on the rye B chromosomes, but with weaker signals. The FISH hybridization patterns using UCM600 as probe were comparable with those obtained with the genomic in situ hybridization (GISH) procedure. There were, however, sharper signals and less background with FISH. UCM600 was combined with the rye-specific sequences Bilby and pSc200 to obtain a more complete painting. With these probes, the rye chromosomes were labeled with distinctive patterns; thus, allowing the rye cultivar 'Imperial' to be karyotyped. It was also possible to distinguish rye chromosomes in triticale and alien rye chromatin in wheat-rye addition and translocation lines. The distribution of UCM600 was similar in cultivated rye and in the wild Secale species Secale vavilovii Grossh., Secale sylvestre Host, and Secale africanum Stapf. Thus, UCM600 can be used to detect Secale DNA introgressed from wild species in a wheat background.     

Identification and chromosomal organization of two rye genome-specific RAPD products useful as introgression markers in wheat.

Two rye genome-specific random amplified polymorphic DNA (RAPD) markers were identified for detection of rye introgression in wheat. Both markers were amplified in all of the tested materials that contained rye chromatin such as rye, hexaploid triticale, wheat-rye addition lines, and wheat varieties with 1BL.1RS translocation. Two cloned markers, designated pSc10C and pSc20H, were 1012 bp and 1494 bp, respectively. Sequence analysis showed that both pSc10C and pSc20H fragments were related to retrotransposons, ubiquitously distributed in plant genomes. Using fluorescence in situ hybridization (FISH), probe pSc10C was shown to hybridize predominantly to the pericentromeric regions of all rye chromosomes, whereas probe pSc20H was dispersed throughout the rye genome except at telomeric regions and nucleolar organizing regions. The FISH patterns showed that the two markers should be useful to select or track all wheat-rye translocation lines derived from the whole arms of rye chromosomes, as well as to characterize the positions of the translocation breakpoints generated in the proximal and distal regions of rye arms.     

Diversified chromosomal distribution of tandemly repeated sequences revealed evolutionary trends in Secale (Poaceae)

Genomic in situ hybridization (GISH) with Secale cereale cv. ‘Jingzhou rye’ DNA as a probe to chromosomes of hexaploid triticale line Fenzhi-1 revealed that not only were all chromosomes of rye strongly hybridized along the entire chromosome length, but there were also stronger signals in terminal or subtelomeric regions. This pattern of hybridization signals is referred to as GISH banding. After GISH banding, sequential fluorescene in situ hybridizaion (FISH) with tandem repeated sequence pSc200 and pSc250 as probes showed that the chromosomal distribution of pSc200 is highly coincident with the GISH banding pattern, suggesting that GISH banding revealed chromosomal distribution of pSc200 in rye. In addition, FISH using pSc200 and pSc250 as probes to chromosomes of 11 species of the genus Secale and two artificial amphiploids (Triticum aestivum-S. strictum subsp. africanum amphiploid and Aegilops tauschii-S. silvestre amphiploid) showed that (1) the chromosomal distribution of pSc200 and pSc250 differed greatly in Secale species, and the trend towards an increase in pSc200 and pSc250 binding sites from wild species to cultivated rye suggested that pSc200 and pSc250 sequences gradually accumulated during Secale evolution; (2) the chromosomal distribution of pSc200 and pSc250 presented polymorphism on homologous chromosomes, suggesting that the same species has two heterogeneous homologous chromosomes; (3) the intensity and number of hybridization signals varied differently on chromosomes between pSc200 and pSc250, suggesting that each repetitive family evolved independently.     

Comparative analysis of the nucleosomal structure of rye,wheat and their relatives

Analysis of the structure of chromatin in cereal species using micrococcal nuclease (MNase) cleavage showed nucleosomal organization and a ladder with typical nucleosomal spacing of 175–185 bp. Probing with a set of DNA probes localized in the authentic telomeres, subtelomeric regions and bulk chromatin revealed that these chromosomal regions have nucleosomal organization but differ in size of nucleosomes and rate of cleavage between both species and regions. Chromatin from Secale and Dasypyrum cleaved more quickly than that from wheat and barley, perhaps because of their higher content of repetitive sequences with hairpin structures accessible to MNase cleavage. In all species, the telomeric chromatin showed more rapid cleavage kinetics and a shorter nucleosome length (160 bp spacing) than bulk chromatin. Rye telomeric repeat arrays were shortest, ranging from 8 kb to 50 kb while those of wheat ranged from 15 kb up to 175 kb. A gradient of sensitivity to MNase was detected along rye chromosomes. The rye-specific subtelomeric sequences pSc200 and pSc250 have nucleosomes of two lengths, those of the telomeric and of bulk nucleosomes, indicating that the telomeric structure may extended into the chromosomes. More proximal sequences common to rye and wheat, the short tandem-repeat pSc119.2 and rDNA sequence pTa71, showed longer nucleosomal sizes characteristic of bulk chromatin in both species. A strictly defined spacing arrangement (phasing) of nucleosomes was demonstrated along arrays of tandem repeats with different monomer lengths (118, 350 and 550 bp) by combining MNase and restriction enzyme digestion.     

Identification of a repeat sequence of rye DNA in wheat and related species

Polymerase chain reaction (PCR) and enhanced chemiluminescence (ECL) were used to determine the distribution of the rye-specific sequence contained in the pSc119.1 probe among wheat and related species. A specific pair of primers targeting this rye-specific sequence was used. A 745-bp fragment, the predicted size of pSc119.1, was present inSecale cereale, Triticum aestivum, XTriticosecale, Hordeum vulgare, H. bogdanii, andH. parodii. PCR results were verified by hybridizing the rye-specific probe pSc119.1 to dotblots of DNA from the different species used. Strong hybridization signals detected by ECL were consistent with the PCR results. The results demonstrate the effectiveness of PCR and dot-blot ECL in screening plants for defined DNA sequences, and indicate that pSc119.1 has counterparts with strong homology inT. aestivum, H. vulgare, H. bogdanii, andH. parodii.     

Physical mapping of 5S and 18S-25S rDNA and repetitive DNA sequences in Aegilops umbellulata.

An accurate physical map of the location of the 5S and the 18S-5.8S-25S rRNA genes and a repetitive DNA sequence has been produced on Aegilops umbellulata Zhuk., (2n = 2x = 14) chromosomes by in situ hybridization. Chromosome morphology together with the hybridization pattern of pSc119.2, a DNA sequence from rye, allowed identification and discrimination of different chromosomes; pSc119.2 hybridizes with all Ae. umbellulata chromosomes at the telomeres, except for the short arm of chromosome 6U, and shows intercalary sites on the long arms of chromosomes 6U and 7U. The 5S and 18S-25S rDNA have been mapped physically only on the short arms of chromosomes 1U and 5U. On chromosome 1U the order of the genes is 5S rDNA subterminal and 18S-25S rDNA more proximal, while on chromosome 5U the position of the genes is reversed. The relative order of the genes, together with the hybridization pattern of the pSc119.2, is useful in identifying whole chromosomes or chromosome segments from Ae. umbellulata in recombinant or addition lines with wheat. The data help link the physical organization of chromosomes to the genetic map. Other members of the Triticeae vary in the presence and order of the 5S and 18S-25S rDNA sequences on groups 1 and 5, indicating multiple and complex evolutionary rearrangements of the chromosome arms.     

The relationship between two tandem repeat families in rye heterochromatin

A bacterial artificial chromosome (BAC) library constructed from the short arm of rye (Secalecereale L.) chromosome 1R has been screened for clones containing copies of the pSc200 tandem repeat family, most abundant in rye subtelomeric heterochromatin. The molecular organization of the monomer array and adjacent sequences has been studied in BAC-126/C20. Digestion of the array with various restriction endonucleases reveals no higher-order organization. The DNA adjacent to the pSc200 array consists of different repeats, including retrotransposon derivatives and another tandemly repeated family, termed XbaI, with a monomer length of 576 bp, 475 of which show 82% similarity to the long terminal repeat of the known Cereba retrotransposon. Sequencing of the 13 kb long genomic region in BAC-126/C20 revealed a direct junction of the pSc200 and XbaI monomers. The arrays of both families terminate at the same AT-rich sequence CAAAAAT. Another recombination signal is the presence of palindromes in the close proximity to the junction site. The presence of microhomologies promotes the action of proteins involved in double-strand DNA break repair. To our knowledge, it is the first discovery of the direct junction of monomers that are longer than 100 bp and belong to different families of plant tandem repeats.     

黑麦特异重复序列pSc119.1在姊妹T1RS·1BL易位系中的变异

根据公布的黑麦特异重复序列pSc119.1设计特异引物, 分别对两套姊妹T1RS·1BL易位系川农12(CN12)、川农17(CN17)、川农18(CN18)和96Ⅰ176-1、96Ⅰ176-3的基因组DNA进行扩增。从CN12、CN17、CN18的基因组中都能扩增出目的片段, 在96Ⅰ176-1的基因组中, 除目的片段外, 还扩增出了一条非目的片段, 但在96Ⅰ176-3的基因组中没有扩增出产物。Southern blot分析表明, pSc119.1序列并未从96Ⅰ176-3的基因组中消失。将CN12、CN17、CN18的目的片段回收克隆后, 对每个片段各随机挑取10个克隆进行测序, pSc119.1序列在3个品种中都发生了变异, 且在CN18中的变异程度最大。所测的序列多数与原序列达94%和95%的相似性, 在这些序列中, 碱基的改变具有一定的规律, 即多数为转换, 少数为颠换, 且变异碱基和变异位置具有较高的一致性。远缘杂交后代的进化可能是一个持续过程, 姊妹系内的株系之间某些性状存在差异, 这些差异很可能与重复序列的变异有关, 这为后生遗传效应机制的研究提供了有用的材料。     

Rye terminal neocentromeres: characterisation of the underlying DNA and chromatin structure

We have studied rye plants with neocentromeres on the terminal regions of the chromosomes. These neocentromeres only appear in meiosis, they are active together with the normal centromere and move the chromosomal arms polewards from prometaphase to anaphase at both the first and second meiotic divisions. All chromosomes of the normal set may show neocentric activity, but chromosomal arms with terminal heterochromatic blocks, as assessed by C-banding, are significantly more susceptible than those that do not have them. At least three repetitive sequences underlie the neocentromeres: pSc34, pSc74 and pSc200. These sequences are not detectable in B chromosomes, which never showed neocentric activity. Fluorescence in situ hybridisation with these sequences used as probes revealed elongated chromatin extensions on the neocentromeres that have not been observed using other staining techniques. These extensions were never observed in control plants. They suggest a modified chromatin structure, which might be responsible for the interaction with proteins involved in chromosomal movement on the spindle.     

Molecular cytogenetic analysis of radiation-induced wheat-rye terminal and intercalary chromosomal translocations and the detection of rye chromatin specifying resistance to Hessian fly

Radiation-induced wheat-rye chromosome translocation lines resistant to Hessian fly, Mayetiola destructor (say), were analyzed by in situ hybridization using total genomic and highly repetitive rye DNA probes pSc119 and pSc74. In situ hybridization analysis revealed the exact locations of the translocation breakpoints and allowed the estimation of the sizes of the transferred rye segments. T6BS·6BL-6RL and T4BS· 4BL-6RL are terminal translocations with either most of the complete long arm of rye chromosome 6R or only the distal 57% of the 6RL arm attached to the long arms of wheat chromosomes 6B and 4B, respectively. The breakpoint in T6BS·6BL-6RL is located at a fraction length (FL) of 0.11 in the long arm of T6BS 6BL-6RL and at FL 0.46 in the long arm of T4BS·4BL-6RL. Ti4AS·4AL-6RL-4AL is an intercalary translocation with the breakpoint located at FL 0.06 in the long arm of wheat chromosome 4A. The inserted 6RL segment, with the Hessian fly resistance gene, has a size of 0.7 m, and is the smallest and, so far, the first radiation-induced intercalary translocation identified in wheat.by R. Apples     

Inter- and intra-genomic transfer of small chromosomal segments in wheat-rye allopolyploids

Newly synthesized wheat-rye allopolyploids, derived from Triticum aestivum Mianyang11 × S. cereale Kustro, were investigated by sequential fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH) using rye tandem repeat pSc200 and rye genomic DNA as probes, respectively, over the first, second and third allopolyploid generations. FISH signals of pSc200 could be observed at both telomeres/subtelomeres of all 14 chromosomes of the parental rye. In the first allopolyploid generation, there were ten rye chromosomes bearing FISH signals at both telomeres/subtelomeres and four rye chromosomes bearing FISH signals at only one telomere/subtelomere. However, in the second and the third allopolyploid generations, there were 12 rye chromosomes bearing FISH signals at both telomeres/subtelomeres and 2 rye chromosomes bearing FISH signals at only one telomere/subtelomere. Rye telomeric segments were transferred to the centromeric region of wheat chromosomes in some cells and small segments derived from non-telomeric regions of rye chromosome were transferred to the telomeric region of wheat chromosomes in some other cells. These observations indicated that the rye telomeric/subtelomeric region was unstable in newly synthesized wheat-rye allopolyploids and allopolyploidization was accompanied by rapid inter/intra-genomic exchange. The inter-genomic exchange may have occurred in somatic cells.     

Fluorescence in situ hybridization with multiple repeated DNA probes applied to the analysis of wheat-rye chromosome pairing

 Fluorescence in situ hybridization (FISH) with multiple probes has been applied to meiotic chromosome spreads derived from ph1b common wheat x rye hybrid plants. The probes used included pSc74 and pSc 119.2 from rye (the latter also hybridizes on wheat, mainly B genome chromosomes), the Ae. squarrosa pAs1 probe, which hybridizes almost exclusively on D genome chromosomes, and wheat rDNA probes pTa71 and pTa794. Simultaneous and sequential FISH with a two-by-two combination of these probes allowed unequivocal identification of all of the rye (R) and most of the wheat (W) chromosomes, either unpaired or involved in pairing. Thus not only could wheat-wheat and wheat-rye associations be easily discriminated, which was already feasible by the sole use of the rye-specific pSc74 probe, but the individual pairing partners could also be identified. Of the wheat-rye pairing observed, which averaged from about 7% to 11% of the total pairing detected in six hybrid plants of the same cross combination, most involved B genome chromosomes (about 70%), and to a much lesser degree, those of the D (almost 17%) and A (14%) genomes. Rye arms 1RL and 5RL showed the highest pairing frequency (over 30%), followed by 2RL (11%) and 4RL (about 8%), with much lower values for all the other arms. 2RS and 5RS were never observed to pair in the sample analysed. Chromosome arms 1RL, 1RS, 2RL, 3RS, 4RS and 6RS were observed to be exclusively bound to wheat chromosomes of the same homoeologous group. The opposite was true for 4RL (paired with 6BS and 7BS) and 6RL (paired with 7BL). 5RL, on the other hand, paired with 4WL arms or segments of them in more than 80% of the cases and with 5WL in the remaining ones. Additional cases of pairing involving wheat chromosomes belonging to more than one homoeologous group occurred with 3RL, 7RS and 7RL. These results, while adding support to previous evidence about the existence of several translocations in the rye genome relative to that of wheat, show that FISH with multiple probes is an efficient method by which to study fundamental aspects of chromosome behaviour at meiosis, such as interspecific pairing. The type of knowledge attainable from this approach is expected to have a significant impact on both theoretical and applied research concerning wheat and related Triticeae. Received: 21 February 1996 / Accepted: 12 July 1996     

Oligonucleotides replacing the roles of repetitive sequences pAs1, pSc119.2, pTa-535, pTa71, CCS1, and pAWRC.1 for FISH analysis

Hybrids derived from wheat (Triticum aestivum L.) × rye (Secale cereale L.) have been widely studied because of their important roles in wheat cultivar improvement. Repetitive sequences pAs1, pSc119.2, pTa-535, pTa71, CCS1, and pAWRC.1 are usually used as probes in fluorescence in situ hybridization (FISH) analysis of wheat, rye, and hybrids derived from wheat × rye. Usually, some of these repetitive sequences for FISH analysis were needed to be amplified from a bacterial plasmid, extracted from bacterial cells, and labeled by nick translation. Therefore, the conventional procedure of probe preparation using these repetitive sequences is time-consuming and labor-intensive. In this study, some appropriate oligonucleotide probes have been developed which can replace the roles of repetitive sequences pAs1, pSc119.2, pTa-535, pTa71, CCS1, and pAWRC.1 in FISH analysis of wheat, rye, and hybrids derived from wheat × rye. These oligonucleotides can be synthesized easily and cheaply. Therefore, FISH analysis of wheat and hybrids derived from wheat × rye using these oligonucleotide probes becomes easier and more economical.     

Introgression of A- and B-genome of tetraploid triticale chromatin into tetraploid rye

An improvement of rye is one of the mainstream goals of current breeding. Our study is concerned with the introduction of the tetraploid triticale (ABRR) into the 4x rye (RRRR) using classical methods of distant crossing. One hundred fifty BC₁F₉ hybrid plants [(4x rye?×?4x triticales)?×?4x rye] obtained from a backcrossing program were studied. The major aim of this work was to verify the presence of an introgressed A- and B- genome chromatin of triticale in a collection of the 4x rye-tiritcale hybrids and to determine their chromosome compositions. In the present study, karyotypes of the previously reported BC₁F₂s and BC₁F₃s were compared with that of the BC₁F₉ generation as obtained after several subsequent open pollinations. The genomic in situ hybridisation (GISH) allowed us to identify 133 introgression forms in which chromosome numbers ranged between 26 and 32. Using four DNA probes (5S rDNA, 25S rDNA, pSc119.2 and pAs1), the fluorescence in situ hybridisation (FISH) was carried out to facilitate an exact chromosome identification in the hybrid plants. The combination of the multi-colour GISH with the repetitive DNA FISH singled out five types of translocated chromosomes: 2A.2R, 4A.4R, 5A.5R, 5B.5R and 7A.7R among the examined BC₁F₉s. The reported translocation lines could serve as valuable sources of wheat chromatin suitable for further improvements of rye.     

Alterations and Abnormal Mitosis of Wheat Chromosomes Induced by Wheat-Rye Monosomic Addition Lines

Background

Wheat-rye addition lines are an old topic. However, the alterations and abnormal mitotic behaviours of wheat chromosomes caused by wheat-rye monosomic addition lines are seldom reported.

Methodology/Principal Findings

Octoploid triticale was derived from common wheat T. aestivum L. ‘Mianyang11’×rye S. cereale L. ‘Kustro’ and some progeny were obtained by the controlled backcrossing of triticale with ‘Mianyang11’ followed by self-fertilization. Genomic in situ hybridization (GISH) using rye genomic DNA and fluorescence in situ hybridization (FISH) using repetitive sequences pAs1 and pSc119.2 as probes were used to analyze the mitotic chromosomes of these progeny. Strong pSc119.2 FISH signals could be observed at the telomeric regions of 3DS arms in ‘Mianyang11’. However, the pSc119.2 FISH signals were disappeared from the selfed progeny of 4R monosomic addition line and the changed 3D chromosomes could be transmitted to next generation stably. In one of the selfed progeny of 7R monosomic addition line, one 2D chromosome was broken and three 4A chromosomes were observed. In the selfed progeny of 6R monosomic addition line, structural variation and abnormal mitotic behaviour of 3D chromosome were detected. Additionally, 1A and 4B chromosomes were eliminated from some of the progeny of 6R monosomic addition line.

Conclusions/Significance

These results indicated that single rye chromosome added to wheat might cause alterations and abnormal mitotic behaviours of wheat chromosomes and it is possible that the stress caused by single alien chromosome might be one of the factors that induced karyotype alteration of wheat.