Rye Chromosome Research Articles

Chromosome aberrations induced by zebularine in triticale.

Chromosome engineering is an important approach for generating wheat germplasm. Efficient development of chromosome aberrations will facilitate the introgression and application of alien genes in wheat. In this study, zebularine, a DNA methylation transferase inhibitor, was successfully used to induce chromosome aberrations in the octoploid triticale cultivar Jinghui#1. Dry seeds were soaked in zebularine solutions (250, 500, and 750 μmol/L) for 24 h, and the 500 μmol/L treatment was tested in three additional treatment times, i.e., 12, 36, and 48 h. All treatments induced aberrations involving wheat and rye chromosomes. Of the 920 cells observed in 67 M1 plants, 340 (37.0%) carried 817 aberrations with an average of 0.89 aberrations per cell (range: 0-12). The aberrations included probable deletions, telosomes and acentric fragments (49.0%), large segmental translocations (28.9%), small segmental translocations (17.1%), intercalary translocations (2.6%), long chromosomes that could carry more than one centromere (2.0%), and ring chromosomes (0.5%). Of 510 M2 plants analyzed, 110 (21.6%) were found to carry stable aberrations. Such aberrations included 79 with varied rye chromosome numbers, 7 with wheat and rye chromosome translocations, 15 with possible rye telosomes/deletions, and 9 with complex aberrations involving variation in rye chromosome number and wheat-rye translocations. These indicated that aberrations induced by zebularine can be steadily transmitted, suggesting that zebularine is a new efficient agent for chromosome manipulation.

The expansion of heterochromatin blocks in rye reflects the co-amplification of tandem repeats and adjacent transposable elements.

BackgroundA prominent and distinctive feature of the rye (Secale cereale) chromosomes is the presence of massive blocks of subtelomeric heterochromatin, the size of which is correlated with the copy number of tandem arrays. The rapidity with which these regions have formed over the period of speciation remains unexplained.ResultsUsing a BAC library created from the short arm telosome of rye chromosome 1R we uncovered numerous arrays of the pSc200 and pSc250 tandem repeat families which are concentrated in subtelomeric heterochromatin and identified the adjacent DNA sequences. The arrays show significant heterogeneity in monomer organization. 454 reads were used to gain a representation of the expansion of these tandem repeats across the whole rye genome. The presence of multiple, relatively short monomer arrays, coupled with the mainly star-like topology of the monomer phylogenetic trees, was taken as indicative of a rapid expansion of the pSc200 and pSc250 arrays. The evolution of subtelomeric heterochromatin appears to have included a significant contribution of illegitimate recombination. The composition of transposable elements (TEs) within the regions flanking the pSc200 and pSc250 arrays differed markedly from that in the genome a whole. Solo-LTRs were strongly enriched, suggestive of a history of active ectopic exchange. Several DNA motifs were over-represented within the LTR sequences.ConclusionThe large blocks of subtelomeric heterochromatin have arisen from the combined activity of TEs and the expansion of the tandem repeats. The expansion was likely based on a highly complex network of recombination mechanisms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2667-5) contains supplementary material, which is available to authorized users.

Cytogenetic Behavior of Trigeneric Hybrid Progeny Involving Wheat, Rye and Psathyrostachys huashanica

Trigeneric hybrids are commonly used as bridges to transfer genes from some wild species to cultivated wheat and to measure the genomic interaction between donor species. We previously reported that trigeneric germplasms were produced by crossing wheat-Psathyrostachys huashanica amphiploids (PHW-SA, 2n = 8x = 56, AABBDDNsNs) with hexaploid triticale (Zhongsi 828, 2n = 6x = 42, AABBRR). In the present study, chromosome pairing behavior and the genome constitution of the F₄ progenies of wheat-rye-P. huashanica trigeneric hybrids were studied. Cytological analysis showed that the chromosome number of F₄ progenies ranged from 39 to 46, and 57.5% of them had 42 chromosomes. The mean meiotic configuration of F₄ lines was 1.71 univalents, 20.26 bivalents, 0.04 trivalents, and 0.001 quadrivalents per pollen mother cell. Among the lines with 2n = 42, the average pairing configuration was 1.21 univalents, 16.22 ring bivalents, 4.16 rod bivalents, and 0.01 trivalents. This result indicated that these lines were cytologically stable. Other lines with 2n = 39, 40, 41, 43, 44, 45, and 46, bearing a high number of univalents or multivalents, showed abnormal meiotic behavior. Genomic in situ hybridization (GISH) revealed that all F₄ lines had 11-14 rye chromosomes, but no P. huashanica chromosomes. The complete set of 14 rye chromosomes was found in 19 lines. At meiosis, GISH detected 1-6 univalents with hybridization signals of rye in 13 lines. Bivalents with fluorescence signals were identified in each line, ranging from 3 to 7. A quadrivalent with hybridization signals was observed in only 1 line, K13-714-8. Lagging chromosomes, chromosome bridges, micronuclei, and chromosome fragments hybridizing with the probe were not discovered in any of the lines. These results inferred that the behavior of rye chromosomes was normal during meiosis. In addition, 21 lines of 2n = 42 (91.3%) with 12 or 14 rye chromosomes, always contained 6 or 7 bivalents bearing fluorescence signals. This suggested that the rye chromosomes exhibiting complete pairing in these lines were cytologically stable during meiosis and may therefore be considered as new hexaploid triticales. Thus, these lines might be potential materials for further hexaploid triticale improvement.

Use of the synthetic Oligo-pTa535 and Oligo-pAs1 probes for identification of Hordeum chilense-origin chromosomes in hexaploid tritordeum

The synthetic oligonucleotide probes Oligo-pTa535 and Oligo-pAs1 were previously developed by other authors based on the repetitive sequences of clones pTa535 and pAs1 available in GenBank, and have been used as probes in fluorescence in situ hybridization (FISH) experiments allowing the identification of wheat and rye chromosomes. Their suitability as nondenaturing fluorescence in situ hybridization (ND-FISH) probes turned the hybridization procedure less time consuming, easier and more affordable. Contrastingly to conventional FISH, ND-FISH does not require DNA denaturing, preserving the chromosomal morphology and being adequate for successive hybridizations on the same chromosome spread. In this study, we hybridized, for the first time, the Oligo-pTa535 and Oligo-pAs1 probes on mitotic chromosomes of hexaploid tritordeum using ND-FISH. Tritordeum (HchHchAABB) is the synthetic amphiploid resultant from crosses between wild barley (HchHch) and cultivated durum wheat (AABB). Both Oligo-pTa535 and Oligo-pAs1 hybridized on all H. chilense-origin chromosomes of tritordeum, allowing their identification and the construction of an ideogram based on their hybridization patterns and on the physical location of the 45S ribosomal DNA (rDNA) loci detected by pTa71. We are confident that this ideogram will be further useful for the identification of H. chilense-origin chromosomes in other tritordeum lines or allopolyploids involving the Hch-genome.

The application of GBS markers for extending the dense genetic map of rye (Secale cereale L.) and the localization of the Rfc1 gene restoring male fertility in plants with the C source of sterility-inducing cytoplasm.

Genotyping by sequencing (GBS) is an efficient method of genotyping in numerous plant species. One of the crucial steps toward the application of GBS markers in crop improvement is anchoring them on particular chromosomes. In rye (Secale cereale L.), chromosomal localization of GBS markers has not yet been reported. In this paper, the application of GBS markers generated by the DArTseq platform for extending the high-density map of rye is presented. Additionally, their application is used for the localization of the Rfc1 gene that restores male fertility in plants with the C source of sterility-inducing cytoplasm. The total number of markers anchored on the current version of the map is 19,081, of which 18,132 were obtained from the DArTseq platform. Numerous markers co-segregated within the studied mapping population, so, finally, only 3397 unique positions were located on the map of all seven rye chromosomes. The total length of the map is 1593 cM and the average distance between markers is 0.47 cM. In spite of the resolution of the map being not very high, it should be a useful tool for further studies of the Secale cereale genome because of the presence on this map of numerous GBS markers anchored for the first time on rye chromosomes. The Rfc1 gene was located on high-density maps of the long arm of the 4R chromosome obtained for two mapping populations. Genetic maps were composed of DArT, DArTseq, and PCR-based markers. Consistent mapping results were obtained and DArTs tightly linked to the Rfc1 gene were successfully applied for the development of six new PCR-based markers useful in marker-assisted selection.Electronic supplementary materialThe online version of this article (doi:10.1007/s13353-016-0347-4) contains supplementary material, which is available to authorized users.

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

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. 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.

A new 2DS·2RL Robertsonian translocation transfers stem rust resistance gene Sr59 into wheat.

A new stem rust resistance gene Sr59 from Secale cereale was introgressed into wheat as a 2DS·2RL Robertsonian translocation. Emerging new races of the wheat stem rust pathogen (Puccinia graminis f. sp. tritici), from Africa threaten global wheat (Triticum aestivum L.) production. To broaden the resistance spectrum of wheat to these widely virulent African races, additional resistance genes must be identified from all possible gene pools. From the screening of a collection of wheat-rye (Secale cereale L.) chromosome substitution lines developed at the Swedish University of Agricultural Sciences, we described the line 'SLU238' 2R (2D) as possessing resistance to many races of P. graminis f. sp. tritici, including the widely virulent race TTKSK (isolate synonym Ug99) from Africa. The breakage-fusion mechanism of univalent chromosomes was used to produce a new Robertsonian translocation: T2DS·2RL. Molecular marker analysis and stem rust seedling assays at multiple generations confirmed that the stem rust resistance from 'SLU238' is present on the rye chromosome arm 2RL. Line TA5094 (#101) was derived from 'SLU238' and was found to be homozygous for the T2DS·2RL translocation. The stem rust resistance gene on chromosome 2RL arm was designated as Sr59. Although introgressions of rye chromosome arms into wheat have most often been facilitated by irradiation, this study highlights the utility of the breakage-fusion mechanism for rye chromatin introgression. Sr59 provides an additional asset for wheat improvement to mitigate yield losses caused by stem rust.

Identification and Physical Mapping of New PCR-Based Markers Specific for the Long Arm of Rye (Secale cereale L.) Chromosome 6

To effectively use elite genes on the long arm of rye chromosome 6 (the 6RL arm) in wheat breeding programs, precise and fast identification of 6RL chromatin in wheat backgrounds is necessary. PCR-based 6RL-specific markers can facilitate the detection of elite genes on 6RL in wheat breeding. However, only a limited number of 6RL-specific markers have been developed. In the present study, 300 new PCR-based 6RL-specific markers were identified using specific length amplified fragment sequencing (SLAF-seq) technology, and were further physically mapped to four regions on the 6RL arm using 6R and 6RL deletion lines. Interestingly, 127 of the 300 markers were physically localized to a region from the site between 2.3 and 2.5 to the telomere, the same region where the powdery mildew resistance gene was mapped. In addition, 95 of the 300 markers exhibit polymorphisms, which can be used to investigate the diversity of rye 6RL arms. The markers developed in this study can be used to identify given segments of 6RL in wheat backgrounds and accelerate the utilization of elite genes on 6RL in wheat breeding.

Molecular cytogenetic identification of a wheat-rye 1R addition line with multiple spikelets and resistance to powdery mildew.

Alien addition lines are important for transferring useful genes from alien species into common wheat. Rye is an important and valuable gene resource for improving wheat disease resistance, yield, and environment adaptation. A new wheat-rye addition line, N9436B, was developed from the progeny of the cross of common wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) cultivar Shaanmai 611 and rye (Secale cereal L., 2n = 2x = 14, RR) accession Austrian rye. We characterized this new line by cytology, genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), molecular markers, and disease resistance screening. N9436B was stable in morphology and cytology, with a chromosome composition of 2n = 42 + 2t = 22II. GISH investigations showed that this line contained two rye chromosomes. GISH, FISH, and molecular maker identification suggested that the introduced R chromosome and the missing wheat chromosome arms were 1R chromosome and 2DL chromosome arm, respectively. N9436B exhibited 30-37 spikelets per spike and a high level of resistance to powdery mildew (Blumeria graminis f. sp. tritici, Bgt) isolate E09 at the seedling stage. N9436B was cytologically stable, had the trait of multiple spikelets, and was resistant to powdery mildew; this line should thus be useful in wheat improvement.

Cloning of the ω-secalin gene family in a wheat 1BL/1RS translocation line using BAC clone sequencing

Background: Wheat 1BL/1RS translocation lines are planted around the world for their disease resistance and high yield. Most of them are poor in bread making, which is partially caused by ω-secalins that are encoded by the ω-secalin gene family, which is located on the short arm of rye chromosome 1R (1RS). However, information on the structure and evolution of the ω-secalin gene family is still limited. Results: We first generated a physical map of the ω-secalin gene family covering 195 kb of the Sec- 1 locus based on sequencing three bacterial artificial chromosome (BAC) clones of the 1BL/1RS translocation wheat cultivar Shimai 15. A BAC contig was constructed spanning 168 kb of the Sec -1 locus on 1RS. Twelve ω-secalin genes were arranged in a head-to-tail fashion, separated by 8.2-21.6 kb spacers on the contig, whereas six other ω-secalin genes were arranged head-to-tail, separated by 8.2-8.4 kb of spacers on clone BAC125. The 18 ω-secalin genes can be classified into six types among which eight ω-secalin genes were expressed during seed development. The ω-secalin genes with the 1,074-bp open reading frame (ORF) represented the main population. Except for two pseudogenes, the N-terminal of the ω-secalin gene was conserved, whereas variations in the C-terminal led to a change in ORF length. The spacers can be sorted into two classes. Class-1 spacers contained conserved and non-conservative sequences. Conclusion: The ω-secalin gene family consisted of at least 18 members in the 1BL/1RS translocation line cv. Shimai 15. Eight ω-secalin genes were expressed during seed development. Eighteen members may originate from a progenitor with a 1,074-bp ORF. The spacers differed in length and sequence conservation.

Chromatin Ring Formation at Plant Centromeres.

We observed the formation of chromatin ring structures at centromeres of somatic rye and Arabidopsis chromosomes. To test whether this behavior is present also in other plant species and tissues we analyzed Arabidopsis, rye, wheat, Aegilops and barley centromeres during cell divisions and in interphase nuclei by immunostaining and FISH. Furthermore, structured illumination microscopy (super-resolution) was applied to investigate the ultrastructure of centromere chromatin beyond the classical refraction limit of light. It became obvious, that a ring formation at centromeres may appear during mitosis, meiosis and in interphase nuclei in all species analyzed. However, varying centromere structures, as ring formations or globular organized chromatin fibers, were identified in different tissues of one and the same species. In addition, we found that a chromatin ring formation may also be caused by subtelomeric repeats in barley. Thus, we conclude that the formation of chromatin rings may appear in different plant species and tissues, but that it is not specific for centromere function. Based on our findings we established a model describing the ultrastructure of plant centromeres and discuss it in comparison to previous models proposed for animals and plants.

Development of new PCR-based markers specific for chromosome arms of rye (Secale cereale L.).

PCR-based rye (Secale cereale L.) chromosome-specific markers can contribute to the effective utilization of elite genes of rye in wheat (Triticum aestivum L.) breeding programs. In the present study, 578 new PCR-based rye-specific markers have been developed by using specific length amplified fragment sequencing (SLAF-seq) technology, and 76 markers displayed different polymorphism among rye Kustro, Imperial, and King II. A total of 427 and 387 markers were, respectively, located on individual chromosomes and chromosome arms of Kustro by using a set of wheat-rye monosomic addition lines and 13 monotelosomic addition lines, which were derived from T. aestivum L. 'Mianyang11' × S. cereale L. 'Kustro'. In addition, two sets of wheat-rye disomic addition lines, which were derived from T. aestivum L. var. Chinese Spring × S. cereale L. var. Imperial and T. aestivum L. 'Holdfast' × S. cereale L. var. King II, were used to test the chromosomal specificity of the 427 markers. The chromosomal locations of 281 markers were consistent among the three sets of wheat-rye addition lines. The markers developed in this study can be used to identify a given segment of rye chromosomes in wheat background and accelerate the utilization of elite genes on rye chromosomes in wheat breeding programs.

RNA interference targeting rye secalins alters flour protein composition in a wheat variety carrying a 1BL.1RS translocation

Wheat varieties carrying chromosome translocations from rye are part of the international wheat breeding pool despite being associated with defects in dough processing quality. One cause proposed for the quality defects of wheat carrying 1BL.1RS translocations is the presence of the secalins encoded by the Sec1 locus on the short arm of rye chromosome 1. In this report, we decrease the levels of these and related wheat proteins by RNA interference (RNAi). A plasmid designed to down-regulate secalin was introduced by biolistics into ‘Bobwhite’, which carries a 1BL.1RS translocation. Flour proteins of two independent transformants were analyzed in detail by 2-dimensional gel electrophoresis and tandem mass spectrometry. Compared to the parent, the transformants exhibited up to 5.5-fold decreases in the levels of individual secalins, up to 7-fold decreases in the closely related omega gliadins, and lesser decreases in many gamma gliadins, low-molecular-weight (LMW)-glutenins, and farinins. Increased levels were found for nearly all identified alpha gliadins, triticins, and y-type high-molecular-weight (HMW)-glutenins. Flour from the transgenic lines exhibited changes in dough mixing behavior in the 2-g mixograph, including longer development times and greater tolerance to mixing. We conclude that changes in protein composition engineered by this RNAi construct improved dough handling characteristics.

Genetic and epigenetic alterations induced by different levels of rye genome integration in wheat recipient.

The narrow genetic variation present in common wheat (Triticum aestivum) varieties has greatly restricted the improvement of crop yield in modern breeding systems. Alien addition lines have proven to be an effective means to broaden the genetic diversity of common wheat. Wheat-rye addition lines, which are the direct bridge materials for wheat improvement, have been wildly used to produce new wheat cultivars carrying alien rye germplasm. In this study, we investigated the genetic and epigenetic alterations in two sets of wheat-rye disomic addition lines (1R-7R) and the corresponding triticales. We used expressed sequence tag-simple sequence repeat, amplified fragment length polymorphism, and methylation-sensitive amplification polymorphism analyses to analyze the effects of the introduction of alien chromosomes (either the entire genome or sub-genome) to wheat genetic background. We found obvious and diversiform variations in the genomic primary structure, as well as alterations in the extent and pattern of the genomic DNA methylation of the recipient. Meanwhile, these results also showed that introduction of different rye chromosomes could induce different genetic and epigenetic alterations in its recipient, and the genetic background of the parents is an important factor for genomic and epigenetic variation induced by alien chromosome addition.

Distribution of Wheat-Rye Translocation Line T1BL·1RS in Wheat and Its Association with Fusarium Head Blight Resistance

The short arm of 1R chromosome (1RS) of rye carries resistant genes to stripe rust, leaf rust, stem rust, powdery mil- dew and aphids. To understand if 1RS also mediates resistance to wheat Fusarium head blight (FHB), we genotyped a panel of 192 wheat accessions from diverse geographic regions and a population of recombinant inbred lines (RIL) consisting of 184 lines developed from the cross of Ning 7840 and Chokwang by 1RS-specific molecular marker Xscm9 and evaluated FHB severities in three consecutive seasons in greenhouses using single floret inoculation method. The results demonstrated that 22 of 192 acces- sions carried a T1BL1RS translocation, and the mean FHB severity (PSS) of varieties carrying T1BL1RS translocation was sig- nificantly lower than that of lines without the translocation across the three experiments (P < 0.05), indicating 1RS may have a positive effect on reducing FHB severity. 1RS-specific marker Xscm9 and Genome in situ hybridization (GISH) showed Ning 7840 carries T1BL1RS translocation. In the population of RILs, irrespective of Fhb1 locus, the mean PSS of lines with T1BL1RS translocation was significantly lower than that of those lines without T1BL1RS. The effects of Fhb1 and 1RS on FHB resistance were additive and the interactions between them were not significant (P = 0.48). The results of this study suggested that 1RS of rye most likely carries the genes resistant to FHB.

Correlation between Fusarium head blight severity and DON content in triticale as revealed by phenotypic and molecular data

AbstractFusarium head blight (FHB) in triticale (× Triticosecale Wittmack) results in yield losses and mycotoxin contamination, for example, by deoxynivalenol (DON). This study aimed to analyse the correlation between FHB severity and DON content in a DH population of 146 entries across environments. Additionally, Fusarium damaged kernel (FDK) rating, heading stage and plant height were recorded. Highly significant (P &lt; 0.001) genotypic variances were found throughout, but also significant (P &lt; 0.001) genotype–environment interaction variances occurred. Correlation between FHB severity and heading stage or plant height was low (r = 0.144 and r = −0.153, P &lt; 0.10). A prediction of DON content from FHB severity or FDK rating is not possible caused by low correlations (r = 0.315 and 0.572, respectively, P &lt; 0.001). A common quantitative trait locus (QTL) for all FHB‐related traits was found on wheat chromosome 2A being of minor importance for FHB severity, but of high importance for DON content and FDK rating. Another QTL on rye chromosome 5R was more important for FHB severity. In conclusion, DON content has to be measured in triticale after selection for FHB severity to gain for healthy and mycotoxin‐reduced feed.

Cytological and morphological characterization of rye-wheat derivatives for important agronomic traits

Ninety two derivatives derived from rye-wheat crosses were analyzed for their rye chromosome/chromatin constitution using molecular cytogenetic tools FISH and GISH, to detect targeted rye chromatin introgression with minimum linkage drag. Of the 92 recombinants lines analyzed, 17 exhibited one pair of rye chromosome substituting different chromosomes of A, B, and D genomes, 10 lines showed substitution and translocations at the same time and 55 lines had 1BL.1RS translocations. Four lines that had more than 10 chromosomes from rye were alike triticale, whereas remaining six lines exhibited no rye chromatin/chromosome. These lines were evaluated for different agronomic traits such as days to maturity, type of spike, colour of spike, compactness of spike etc. for ascertaining correlation between rye chromatin with morphological traits.

The wheat Sr50 gene reveals rich diversity at a cereal disease resistance locus.

We identify the wheat stem rust resistance gene Sr50 (using physical mapping, mutation and complementation) as homologous to barley Mla, encoding a coiled-coil nucleotide-binding leucine-rich repeat (CC-NB-LRR) protein. We show that Sr50 confers a unique resistance specificity different from Sr31 and other genes on rye chromosome 1RS, and is effective against the broadly virulent Ug99 race lineage. Extensive haplotype diversity at the rye Sr50 locus holds promise for mining effective resistance genes.

Multiple structural aberrations and physical mapping of rye chromosome 2R introgressed into wheat

Multiple structural aberrations produced by chromosome breakage and reunion not only provide new germplasm for enriching genetic diversity but are also helpful for physical mapping of alien chromosomes introgressed into wheat. In this study, mass structural aberrations of rye chromosome 2R were induced by means of spontaneous breakage and reunion, gametocidal chromosome action and irradiation. A total of 88 chromosome 2R aberrations were identified in 65 plants. From the self-pollinated progenies of plants carrying these aberrations, 19 stable lines with different segments of chromosome 2R which included seven whole arm, six small segmental and three large segmental translocations, one deletion and two ditelosomic additions, were subsequently identified and characterized using cytogenetic and molecular markers. Based on these lines, 88 markers specific for chromosome 2R were physically mapped to 13 different blocks of 2R with three in arm 2RS and 10 in arm 2RL. The powdery mildew resistance gene PmJZHM2RL was located to a region corresponding to the block 2RL-7. A total of eighteen 2R-specific EST markers were located in the same block where ten were derived from genes that were up-regulated during powdery mildew infection. Potential use of these stable aberrations and the colinearity of chromosome 2R with corresponding chromosomes in the other model monocot species were discussed.

Oligonucleotide Probes for ND-FISH Analysis to Identify Rye and Wheat Chromosomes.

Genomic in situ hybridization (GISH) has been widely used to detect rye (Secale cereale L.) chromosomes in wheat (Triticum aestivum L.) introgression lines. The routine procedure of GISH using genomic DNA of rye as a probe is time-consuming and labor-intensive because of the preparation and labeling of genomic DNA of rye and denaturing of chromosomes and probes. In this study, new oligonucleotide probes Oligo-1162, Oligo-pSc200 and Oligo-pSc250 were developed. The three new probes can be used for non-denaturing fluorescence in situ hybridization (ND-FISH) assays and replace genomic DNA of rye as a probe to discriminate rye chromosomes in wheat backgrounds. In addition, previously developed oligonucleotide probes Oligo-pSc119.2-1, Oligo-pSc119.2-2, Oligo-pTa535-1, Oligo-pTa535-2, Oligo-pTa71-2, Oligo-pAWRC.1 and Oligo-CCS1 can also be used for ND-FISH of wheat and rye. These probes have provided an easier, faster and more cost-effective method for the FISH analysis of wheat and hybrids derived from wheat × rye.