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Zujun Yang - One of the best experts on this subject based on the ideXlab platform.
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Physical mapping of chromosome 7J and a purple coleoptile gene from Thinopyrum intermedium in the common wheat background.
Planta, 2021Co-Authors: Ahui Zhang, Yan Yin, Lingrong Tang, Peng Zhang, Imtiaz Ahmed Khan, Ian Dundas, Zujun YangAbstract:MAIN CONCLUSION A physical map of Thinopyrum intermedium chromosome 7J was constructed using translocation mapping, and a new seedling purple coleoptile gene was mapped to the bin of FL 0.35-0.63 of 7JS. Thinopyrum intermedium (2n = 6x = 42, JJJsJsStSt), a wild relative of common wheat, harbors numerous beneficial genes for wheat improvement. Previous studies showed that wheat-Th. intermedium partial amphiploid TAF46 and its derived addition line L1 had a purple coleoptile, which was derived from Th. intermedium chromosome 7J. To identify and physically map the purple coleoptile gene, 12 wheat-Th. intermedium 7J translocation lines were analyzed by sequential multicolor fluorescence in situ hybridization (mc-FISH), PCR-based landmark unique gene (PLUG) and intron targeting (IT) markers. A physical map of the 7J chromosome was constructed, consisting of eight chromosomal bins with 89 markers. Seedling evaluation of the coleoptile colors of all tested materials indicated that the purple coleoptile gene was located to the bin with a fraction length (FL) of 0.35-0.63 on chromosome 7JS. Furthermore, based on the syntenic relationships between Th. intermedium and wheat chromosomes, we developed a new chromosome 7J-specific EST-PCR marker from the chromosomal region corresponding to the purple coleoptile gene through the Triticeae multi-omics database. The approach of designing chromosome-specific markers has facilitated fine mapping of the Thinopyrum-specific purple coleoptile gene, and these translocation lines will be valuable for studying the function of the purple coleoptile gene in anthocyanin biosynthesis.
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New ND-FISH-Positive Oligo Probes for Identifying Thinopyrum Chromosomes in Wheat Backgrounds.
International journal of molecular sciences, 2019Co-Authors: Zongxiang Tang, Shuyao Tang, Zujun Yang, Jie LuoAbstract:Thinopyrum has been widely used to improve wheat (Triticum aestivum L.) cultivars. Non-denaturing fluorescence in situ hybridization (ND-FISH) technology using oligonucleotides (oligo) as probes provides a convenient and efficient way to identify alien chromosomes in wheat backgrounds. However, suitable ND-FISH-positive oligo probes for distinguishing Thinopyrum chromosomes from wheat are lacking. Two oligo probes, Oligo-B11 and Oligo-pThp3.93, were designed according to the published Thinopyrum ponticum (Th. ponticum)-specific repetitive sequences. Both Oligo-B11 and Oligo-pThp3.93 can be used for ND-FISH analysis and can replace conventional GISH and FISH to discriminate some chromosomes of Th. elongatum, Th. intermedium, and Th. ponticum in wheat backgrounds. The two oligo probes provide a convenient way for the utilization of Thinopyrum germplasms in future wheat breeding programs.
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Characterization of Chromosomal Rearrangement in New Wheat—Thinopyrum intermedium Addition Lines Carrying Thinopyrum—Specific Grain Hardness Genes
Agronomy, 2019Co-Authors: Hongjin Wang, Tao Lang, Zujun YangAbstract:The wild species, Thinopyrum intermedium. (Genome StStJSJSJJ), serves as a valuable germplasm resource providing novel genes for wheat improvement. In the current study, non-denaturing fluorescence in situ hybridization (ND-FISH) with multiple probes and comparative molecular markers were applied to characterize two wheat-Th. intermedium chromosome additions. Sequential ND-FISH with new labeled Th. intermedium specific oligo-probes were used to precisely determine the chromosomal constitution of Th. intermedium, wheat—Th. intermedium partial amphiploids and addition lines Hy36 and Hy37. The ND-FISH results showed that the added JS-St translocated chromosomes in Hy36 had minor Oligo-5S ribosomal DNA (rDNA) signals at the short arm, while a pair of J-St chromosomes in Hy37 had major Oligo-pTa71 and minor Oligo-5S rDNA signals. The 90K SNP array and PCR-based molecular markers that mapped on wheat linkage group 5 and 3 facilitated the identification of Thinopyrum chromosome introgressions in the addition lines, and confirmed that added chromosomes in Hy36 and Hy37 were 5JSS.3StS and 5JS.3StS, respectively. Complete coding sequences at the paralogous puroindoline-a (Pina) loci from Th. intermedium were cloned and localized on the short arm of chromosome 5JS of Hy36. Line Hy36 showed a reduction in the hardness index, which suggested that Th. intermedium-specific Pina gene sequences may be associated with the softness trait in wheat background. The molecular cytogenetic identification of novel wheat—Th. intermedium derivatives indicated that the frequent chromosome rearrangement occurred in the progenies of wheat-Thinopyrum hybridization. The new wheat-Thinopyrum derived lines may increase the genetic diversity for wheat breeding.
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precise identification of wheat Thinopyrum intermedium translocation chromosomes carrying resistance to wheat stripe rust in line z4 and its derived progenies
Genome, 2018Co-Authors: Tao Lang, Ennian Yang, Qiheng Chen, Zujun YangAbstract:The wheat – Thinopyrum intermedium derived line Z4 has displayed novel and effective stripe rust resistance for over 40 years. This study aimed to precisely identify the chromosome constitution of ...
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introduction of Thinopyrum intermedium ssp trichophorum chromosomes to wheat by trigeneric hybridization involving triticum secale and Thinopyrum genera
Planta, 2017Co-Authors: Jianbo Li, Tao Lang, Bin Li, Zhihui Yu, Hongjin Wang, Guangrong Li, Ennian Yang, Zujun YangAbstract:Fluorescence in situ hybridization and molecular markers have confirmed that several chromosomes from Thinopyrum intermedium ssp. trichophorum have been added to a wheat background, which originated from a cross between a wheat– Thinopyrum partial amphiploid and triticale. The lines displayed blue grains and resistance to wheat stripe rust. Thinopyrum intermedium has been used as a valuable resource for improving the disease resistance and yield potential of wheat. With the aim to transfer novel genetic variation from Th. intermedium species for sustainable wheat breeding, a new trigeneric hybrid was produced by crossing an octoploid wheat–Th. intermedium ssp. trichophorum partial amphiploid with hexaploid triticale. Fluorescence in situ hybridization (FISH) revealed that Thinopyrum chromosomes were transmitted preferably and the number of rye chromosomes tended to decrease gradually in the selfed derivatives of the trigeneric hybrids. Four stable wheat–Th. intermedium chromosome substitution, addition and translocation lines were selected, and a 2JS addition line, two substitution lines of 4JS(4B) and 4J(4B), and a small 4J.4B translocation line were identified by FISH and molecular markers. It was revealed that the gene(s) responsible for blue grains may located on the FL0.60–1.00 of long arm of Th. intermedium-derived 4J chromosome. Disease resistance screenings indicated that chromosomes 4JS and 2JS appear to enhance the resistance to stripe rust in the adult plant stage. The new germplasm with Th. intermedium introgression shows promise for utilization of Thinopyrum chromosome segments in future wheat improvement.
Tao Lang - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Chromosomal Rearrangement in New Wheat—Thinopyrum intermedium Addition Lines Carrying Thinopyrum—Specific Grain Hardness Genes
Agronomy, 2019Co-Authors: Hongjin Wang, Tao Lang, Zujun YangAbstract:The wild species, Thinopyrum intermedium. (Genome StStJSJSJJ), serves as a valuable germplasm resource providing novel genes for wheat improvement. In the current study, non-denaturing fluorescence in situ hybridization (ND-FISH) with multiple probes and comparative molecular markers were applied to characterize two wheat-Th. intermedium chromosome additions. Sequential ND-FISH with new labeled Th. intermedium specific oligo-probes were used to precisely determine the chromosomal constitution of Th. intermedium, wheat—Th. intermedium partial amphiploids and addition lines Hy36 and Hy37. The ND-FISH results showed that the added JS-St translocated chromosomes in Hy36 had minor Oligo-5S ribosomal DNA (rDNA) signals at the short arm, while a pair of J-St chromosomes in Hy37 had major Oligo-pTa71 and minor Oligo-5S rDNA signals. The 90K SNP array and PCR-based molecular markers that mapped on wheat linkage group 5 and 3 facilitated the identification of Thinopyrum chromosome introgressions in the addition lines, and confirmed that added chromosomes in Hy36 and Hy37 were 5JSS.3StS and 5JS.3StS, respectively. Complete coding sequences at the paralogous puroindoline-a (Pina) loci from Th. intermedium were cloned and localized on the short arm of chromosome 5JS of Hy36. Line Hy36 showed a reduction in the hardness index, which suggested that Th. intermedium-specific Pina gene sequences may be associated with the softness trait in wheat background. The molecular cytogenetic identification of novel wheat—Th. intermedium derivatives indicated that the frequent chromosome rearrangement occurred in the progenies of wheat-Thinopyrum hybridization. The new wheat-Thinopyrum derived lines may increase the genetic diversity for wheat breeding.
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precise identification of wheat Thinopyrum intermedium translocation chromosomes carrying resistance to wheat stripe rust in line z4 and its derived progenies
Genome, 2018Co-Authors: Tao Lang, Ennian Yang, Qiheng Chen, Zujun YangAbstract:The wheat – Thinopyrum intermedium derived line Z4 has displayed novel and effective stripe rust resistance for over 40 years. This study aimed to precisely identify the chromosome constitution of ...
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introduction of Thinopyrum intermedium ssp trichophorum chromosomes to wheat by trigeneric hybridization involving triticum secale and Thinopyrum genera
Planta, 2017Co-Authors: Jianbo Li, Tao Lang, Bin Li, Zhihui Yu, Hongjin Wang, Guangrong Li, Ennian Yang, Zujun YangAbstract:Fluorescence in situ hybridization and molecular markers have confirmed that several chromosomes from Thinopyrum intermedium ssp. trichophorum have been added to a wheat background, which originated from a cross between a wheat– Thinopyrum partial amphiploid and triticale. The lines displayed blue grains and resistance to wheat stripe rust. Thinopyrum intermedium has been used as a valuable resource for improving the disease resistance and yield potential of wheat. With the aim to transfer novel genetic variation from Th. intermedium species for sustainable wheat breeding, a new trigeneric hybrid was produced by crossing an octoploid wheat–Th. intermedium ssp. trichophorum partial amphiploid with hexaploid triticale. Fluorescence in situ hybridization (FISH) revealed that Thinopyrum chromosomes were transmitted preferably and the number of rye chromosomes tended to decrease gradually in the selfed derivatives of the trigeneric hybrids. Four stable wheat–Th. intermedium chromosome substitution, addition and translocation lines were selected, and a 2JS addition line, two substitution lines of 4JS(4B) and 4J(4B), and a small 4J.4B translocation line were identified by FISH and molecular markers. It was revealed that the gene(s) responsible for blue grains may located on the FL0.60–1.00 of long arm of Th. intermedium-derived 4J chromosome. Disease resistance screenings indicated that chromosomes 4JS and 2JS appear to enhance the resistance to stripe rust in the adult plant stage. The new germplasm with Th. intermedium introgression shows promise for utilization of Thinopyrum chromosome segments in future wheat improvement.
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New molecular markers and cytogenetic probes enable chromosome identification of wheat-Thinopyrum intermedium introgression lines for improving protein and gluten contents
Planta, 2016Co-Authors: Hongjin Wang, Tao Lang, Ennian Yang, Zujun YangAbstract:Main conclusion New molecular markers were developed for targeting Thinopyrum intermedium 1St#2 chromosome, and novel FISH probe representing the terminal repeats was produced for identification of Thinopyrum chromosomes. Thinopyrum intermedium has been used as a valuable resource for improving the disease resistance and yield potential of wheat. A wheat-Th. intermedium ssp. trichophorum chromosome 1St#2 substitution and translocation has displayed superior grain protein and wet gluten content. With the aim to develop a number of chromosome 1St#2 specific molecular and cytogenetic markers, a high throughput, low-cost specific-locus amplified fragment sequencing (SLAF-seq) technology was used to compare the sequences between a wheat-Thinopyrum 1St#2 (1D) substitution and the related species Pseudoroegneria spicata (St genome, 2n = 14). A total of 5142 polymorphic fragments were analyzed and 359 different SLAF markers for 1St#2 were predicted. Thirty-seven specific molecular markers were validated by PCR from 50 randomly selected SLAFs. Meanwhile, the distribution of transposable elements (TEs) at the family level between wheat and St genomes was compared using the SLAFs. A new oligo-nucleotide probe named Oligo-pSt122 from high SLAF reads was produced for fluorescence in situ hybridization (FISH), and was observed to hybridize to the terminal region of 1St#L and also onto the terminal heterochromatic region of Th. intermedium genomes. The genome-wide markers and repetitive based probe Oligo-pSt122 will be valuable for identifying Thinopyrum chromosome segments in wheat backgrounds.
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Precise identification of two wheat–Thinopyrum intermedium substitutions reveals the compensation and rearrangement between wheat and Thinopyrum chromosomes
Molecular Breeding, 2015Co-Authors: Tao Lang, Gang Dai, Xiao-jin Song, Zujun YangAbstract:Two wheat–Thinopyrum substitution lines X479 and X482 selected from the progenies of wheat “Mianyang26 (MY26)” × wheat–Thinopyrum intermedium ssp. trichophorum partial amphiploid were characterized by seed storage protein electrophoresis, genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and PCR-based molecular markers. Seed storage protein analysis showed that X479 expressed some of Th. intermedium ssp. trichophorum-specific gliadin and glutenin bands. Chromosome counting and GISH probed by Pseudoroegneria spicata genomic DNA indicated that two pairs of Thinopyrum-derived chromosomes (St genome and St–JS translocated chromosomes) substituted for two pairs of wheat chromosomes in both X479 and X482. FISH using pAs1 and pHvG38 as probes showed that chromosomes 1B and 4B, and 4D and 6D were absent in X479 and X482, respectively. Using the newly isolated JS chromosome-specific repetitive sequence pDb12H as a probe, the FISH signals revealed that the translocation of St–JS chromosomes in X479 and X482 occurred in repetitive sequence regions of the short arm. The molecular markers based on wheat–rice colinearity confirmed that the chromosome constitutions of X479 and X482 were 1St (1B) + 4St–4JS (4B) and 4St–JS (4D) + 6St (6D), respectively. The substitution lines were both fully fertile which suggests that the Th. intermedium chromosomes in X479 and X482 substitute well for the corresponding wheat chromosomes. The rust resistance and novel agronomic traits revealed that the substitution lines will be potentially useful for genetic improvement of wheat.
B S Gill - One of the best experts on this subject based on the ideXlab platform.
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homoeologous recombination based transfer and molecular cytogenetic mapping of a wheat streak mosaic virus and triticum mosaic virus resistance gene wsm3 from Thinopyrum intermedium to wheat
Theoretical and Applied Genetics, 2017Co-Authors: Tatiana V Danilova, Guorong Zhang, Wenxuan Liu, Bernd Friebe, B S GillAbstract:Key message Here, we report the production of a wheat–Thinopyrum intermedium recombinant stock conferring resistance to wheat streak mosaic virus and Triticum mosaic virus.
Timothy D. Murray - One of the best experts on this subject based on the ideXlab platform.
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Development of Perennial Wheat Through Hybridization Between Wheat and Wheatgrasses: A Review
Elsevier, 2018Co-Authors: Lei Cui, Timothy D. Murray, Yongkang Ren, Wenze Yan, Qing Guo, Yuqi Niu, Yu SunAbstract:Wheatgrasses (Thinopyrum spp.), which are relatives of wheat (Triticum aestivum L.), have a perennial growth habit and offer resistance to a diversity of biotic and abiotic stresses, making them useful in wheat improvement. Many of these desirable traits from Thinopyrum spp. have been used to develop wheat cultivars by introgression breeding. The perennial growth habit of wheatgrasses inherits as a complex quantitative trait that is controlled by many unknown genes. Previous studies have indicated that Thinopyrum spp. are able to hybridize with wheat and produce viable/stable amphiploids or partial amphiploids. Meanwhile, efforts have been made to develop perennial wheat by domestication of Thinopyrum spp. The most promising perennial wheat–Thinopyrum lines can be used as grain and/or forage crops, which combine the desirable traits of both parents. The wheat–Thinopyrum lines can adapt to diverse agricultural systems. This paper summarizes the development of perennial wheat based on Thinopyrum, and the genetic aspects, breeding methods, and perspectives of wheat–Thinopyrum hybrids. Keywords: Thinopyrum, Wheatgrass, Perennial, Triticum aestivu
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Effective Resources in Wheat and Wheat–Thinopyrum Derivatives for Resistance to Heterodera filipjevi in China
Crop Science, 2012Co-Authors: Lei Cui, Robert L. Conner, Timothy D. Murray, Yu Sun, Xiao-ming Wang, Lijian Wang, Xiu Gao, Shancheng SunAbstract:Cereal cyst nematode (CCN) is becoming one of the important soil-borne pathogens in wheat (Triticum aestivum L.) monocropping or wheat- maize (Zea mays L.)-wheat cropping systems of central China. Heterodera fi lipjevi (Madzhidov, 1981) Stelter, 1984 was recently recognized as a causal agent of CCN in China, but little informa- tion is available on sources of resistance against this nematode species. The present study was initiated to determine the current status of resis- tance in wheat cultivars against H. fi lipjevi and to identify effective resources for improvement of CCN resistance in China. A 3-yr fi eld study of CCN resistance that involved 174 wheat cul- tivars or wheat-Thinopyrum derivatives was conducted in a wheat fi eld in Xuchang, Henan Province, China, where H. fi lipjevi had been present for years. Greenhouse experiments were conducted with representative resistant entries from each group of accessions. None of the 78 wheat cultivars and breeding lines from China was resistant in fi eld tests. Wheat cultivar Madsen from Washington State was most resis- tant among the entries tested both in fi eld and under controlled environment. New sources of resistance to H. fi lipjevi were identifi ed in some wheat-intermediate wheatgrass (Thinopyrum intermedium (Host) Barkworth & D. R. Dewey) and wheat-tall wheatgrass (Thinopyrum ponti- cum (Podp.) Barkworth & D. R. Dewey) partial amphiploids, which will diversify resistance resources in enhancing resistance of wheat against CCN.
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Resistance to soil-borne diseases of wheat: Contributions from the wheatgrasses Thinopyrum intermedium and Th. ponticum
Canadian Journal of Plant Science, 2008Co-Authors: Robert L. Conner, Timothy D. MurrayAbstract:Eyespot, Cephalosporium stripe, and common root rot are soil-borne diseases that damage the stem bases, vascular system, subcrown internodes,and roots of wheat. Resistance in wheat to these diseases is insufficient to prevent significant yield loss when disease is severe. The wheatgrasses Thinopyrum intermedium and Th. ponticum are highly resistant to these diseases. Identification of disease-resistant wheat-Thinopyrum partial amphiploids, chromosome addition, substitution, and translocation lines makes them a valuable source of resistance genes for wheat breeding programs. Single chromosomes or chromosome segments containing resistance genes can be transferred into wheat to produce genetic stocks that afford a better understanding of the genetic control of resistance in wheatgrasses and new genetic resources for wheat improvement. Resistance to eyespot in Th. intermedium and Th. ponticum was associated with the homoeologous group 4 chromosomes, whereas resistance to Cephalosporium stripe was controlled b...
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Resistance to eyespot of wheat, caused by Tapesia yallundae , derived from Thinopyrum intermedium homoeologous group 4 chromosome
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, 2005Co-Authors: M. Arterburn, Stephen S. Jones, Timothy D. MurrayAbstract:Thinopyrum intermedium was identified previously as resistant to Tapesia yallundae, cause of eyespot of wheat. Using GUS-transformed isolates of T. yallundae as inoculum, we determined that wheat lines carrying Th. intermedium chromosome 4Ai#2 or the short arm of chromosome 4Ai#2 were as resistant to the pathogen as the eyespot-resistant wheat- Th. ponticum chromosome substitution line SS767 (PI 611939) and winter wheat cultivar Madsen, which carries gene Pch1 for eyespot resistance. Chromosome 4E from Th. elongatum and chromosome 4J from Th. bessarabicum did not confer resistance to T. yallundae. Genome-specific PCR primers confirmed the presence of Thinopyrum chromatin in these wheat- Thinopyrum lines. Genomic in situ hybridization using an St genomic probe from Pseudoroegneria strigosa demonstrated that chromosome 4Ai#2 belongs to the Js genome of Thinopyrum. The eyespot resistance in the wheat- Th. intermedium lines is thus controlled by the short arm of this Js chromosome. This is the first report of resistance to T. yallundae controlled by a Js genome chromosome of Th. intermedium.
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A New Source of Resistance to Tapesia yallundae Associated with a Homoeologous Group 4 Chromosome in Thinopyrum ponticum
Phytopathology, 2004Co-Authors: M. Arterburn, S. S. Jones, Timothy D. MurrayAbstract:Li, H. J., Arterburn, M., Jones, S. S., and Murray, T. D. 2004. A new source of resistance to Tapesia yallundae associated with a homoeologous group 4 chromosome in Thinopyrum ponticum. Phytopathology 94:932937. Wheat (Thinopyrum ponticum line SS767; PI 611939) with 42 chromosomes previously was identified as a new source of eyespot resistance. Individual plants of SS767 were tested for reaction to Tapesia yallundae, the major pathogen of eyespot in the Pacific Northwest region of the United States. Resistance of this line was similar to the resistant winter wheat cv. Madsen (carrying gene Pch1 for eyespot resistance). Polymerase chain reaction analysis with primers specific for the J or E genomes revealed that SS767 contains Thinopyrum chromatin. Cytological and Cbanding analyses demonstrated that SS767 is a chromosome substitution line in which wheat chromosome 4D is replaced by a homoeologous group 4 chromosome of Thinopyrum ponticum. Genomic in situ hybridization using St genomic DNA from Pseudoroegneria strigosa as a probe, which can differentiate chromosomes from different genomes of Thinopyrum, indicated that this chromosome belongs to the J genome. Molecular analysis of an F2 population segregating for chromosome 4J and resistance to eyespot confirmed that eyespot resistance in line SS767 is associated with chromosome 4J of Thinopyrum ponticum. This is the first report of genetic control of resistance to eyespot derived from Thinopyrum ponticum. This source of resistance provides a new opportunity to improve wheat resistance to eyespot by adding to the diversity of resistance sources available. Additional keywords: blue kernel color, Pseudocercosporella.
P J Larkin - One of the best experts on this subject based on the ideXlab platform.
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the pontin series of recombinant alien translocations in bread wheat single translocations integrating combinations of bdv2 lr19 and sr25 disease resistance genes from Thinopyrum intermedium and th ponticum
Theoretical and Applied Genetics, 2013Co-Authors: L Ayalanavarrete, A A Mechanicos, J M Gibson, Davinder Singh, H S Bariana, J Fletcher, S Shorter, P J LarkinAbstract:Two bread wheat lines each with a translocation on chromosome 7DL from either Thinopyrum intermedium (TC5 and TC14) or Thinopyrum ponticum (T4m), were hybridized in a ph1b mutant background to enhance recombination between the two translocated chromosomal segments. The frequency of recombinants was high in lines derived from the larger and similar-sized translocations (TC5/T4m), but much lower when derived from different-sized translocations (TC14/T4m). Recombinant translocations contained combinations of resistance genes Bdv2, Lr19 and Sr25 conferring resistance to Barley yellow dwarf virus (BYDV), leaf rust and stem rust, respectively. Their genetic composition was identified using bioassays and molecular markers specific for the two progenitor Thinopyrum species. This set of 7DL Th. ponticum/intermedium recombinant translocations was termed the Pontin series. In addition to Thinopyrum markers, the size of the translocation was estimated with the aid of wheat markers mapped on each of the 7DL deletion bins. Bioassays for BYDV, leaf rust and stem rust were performed under greenhouse and field conditions. Once separated from ph1b background, the Pontin recombinant translocations were stable and showed normal inheritance in successive backcrosses. The reported Pontin translocations integrate important resistance genes in a single linkage block which will allow simultaneous selection of disease resistance. Combinations of Bdv2 + Lr19 or Lr19 + Sr25 in both long and short translocations, are available to date. The smaller Pontins, comprising only 20 % of the distal portion of 7DL, will be most attractive to breeders.
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Varying chromosome composition of 56-chromosome wheat × Thinopyrum intermedium partial amphiploids
Genome, 1993Co-Authors: P. M. Banks, R. R.-c. Wang, P J LarkinAbstract:Thinopyrum intermedium (2n = 42) is a source of many potentially useful genes for wheat improvement. Many partial amphiploids have been produced between Th. intermedium and Triticum aestivum that are fertile and stable. These partial amphiploids all have 56 chromosomes, including seven pairs of chromosomes from Th. intermedium. To explore the genomic composition of these lines, meiotic analysis was conducted on 32 hybrid combinations between eight different partial amphiploids. All but two of the chosen parents were distinguishable on the basis of perenniality, head morphology, and reactions to leaf, stripe, and stem rusts and to barley yellow dwarf virus. Chromosome pairing in the hybrids clearly indicated that all but two of the partial amphiploids differed in their composition of Thinopyrum chromosomes. The differences varied from one to five chromosomes. This confirms molecular evidence that the extra genome of the octoploid partial amphiploids is a variable synthetic genome combining chromosomes of t...