Molecular cytogenetic characterization of Aegilops biuncialis and its use for the identification of 5 derived wheat-Aegilops biuncialis disomic addition lines.

The aim of the experiments was to produce and identify different Triticum aestivum-Aegilops biuncialis disomic addition lines. To facilitate the exact identification of the Ae. biuncialis chromosomes in these Triticum aestivum-Ae. biuncialis disomic additions, it was necessary to analyze the fluorescence in situ hybridization (FISH) pattern of Ae. biuncialis (2n = 4x = 28, U(b)U(b)M(b)M(b)), comparing it with the diploid progenitors (Aegilops umbellulata, 2n = 2x = 14, UU and Aegilops comosa, 2n = 2x = 14, MM). To identify the Ae. biuncialis chromosomes, FISH was carried out using 2 DNA clones (pSc119.2 and pAs1) on Ae. biuncialis and its 2 diploid progenitor species. Differences in the hybridization patterns of all chromosomes were observed among the 4 Ae. umbellulata accessions, the 4 Ae. comosa accessions, and the 3 Ae. biuncialis accessions analyzed. The hybridization pattern of the M genome was more variable than that of the U genome. Five different wheat-Ae. biuncialis addition lines were produced from the wheat-Ae. biuncialis amphiploids produced earlier in Martonvásár. The 2M, 3M, 7M, 3U, and 5U chromosome pairs were identified with FISH using 3 repetitive DNA clones (pSc119.2, pAs1, and pTa71) in the disomic chromosome additions produced. Genomic in situ hybridization (GISH) was used to differentiate the Ae. biuncialis chromosomes from wheat, but no chromosome rearrangements between wheat and Ae. biuncialis were detected in the addition lines.     

Molecular cytogenetic analysis of Aegilops cylindrica host.

The genomic constitution of Aegilops cylindrica Host (2n = 4x = 28, DcDcCcCc) was analyzed by C-banding, genomic in situ hybridization (GISH), and fluorescence in situ hybridization (FISH) using the DNA clones pSc119, pAs1, pTa71, and pTA794. The C-banding patterns of the Dc- and Cc-genome chromosomes of Ae. cylindrica are similar to those of D-and C-genome chromosomes of the diploid progenitor species Ae. tauschii Coss. and Ae. caudata L., respectively. These similarities permitted the genome allocation and identification of the homoeologous relationships of the Ae. cylindrica chromosomes. FISH analysis detected one major 18S-5.8S-25S rDNA locus in the short arm of chromosome 1Cc. Minor 18S-5.8S-25S rDNA loci were mapped in the short arms of 5Dc and 5Cc. 5S rDNA loci were identified in the short arm of chromosomes 1Cc, 5Dc, 5Cc, and 1Dc. GISH analysis detected intergenomic translocation in three of the five Ae. cylindrica accessions. The breakpoints in all translocations were non-centromeric with similar-sized segment exchanges.     

Evaluation of phylogenetic relationships between five polyploid Aegilops L. species of the U-genome cluster by means of chromosomal analysis

Four tetraploid (Aegilops ovata, Ae. biuncialis, Ae. columnaris, and Ae. triaristata) and one hexaploid (Ae. recta) species of the U-genome cluster were studied using C-banding technique. All species displayed broad C-banding polymorphism and high frequency of chromosomal rearrangements. Chromosomal rearrangements were represented by paracentric inversions and intragenomic and intergenomic translocations. We found that the processes of intraspecific divergence of Ae. ovata, Ae. biuncialis, and Ae. columnaris were probably associated with introgression of genetic material from other species. The results obtained confirmed that tetraploid species Ae. ovata and Ae. biuncialis occurred as a result of hybridization of a diploid Ae. umbellulata with Ae. comosa and Ae. heldreichii, respectively. The dissimilarity of the C-banding patterns of several chromosomes of these tetraploid species and their ancestral diploid forms indicated that chromosomal aberrations might have taken place during their speciation. Significant differences of karyotype structure, total amount and distribution of C-heterochromatin found between Ae. columnaris and Ae. triaristata, on the one hand, and Ae. ovata and Ae. biuncialis, on the other, evidenced in favor of different origin of these groups of species. In turn, similarity of the C-banding patterns of Ae. columnaris and Ae. triaristata chromosomes suggested that they were derived from a common ancestor. A diploid species Ae. umbellulata was the U-genome donor of Ae. columnaris and Ae. triaristata; however, the donor of the second genome of these species was not determined. We assumed that these tetraploid species occurred as a result of introgressive hybridization. Similarity of the C-banding patterns of chromosomes of Ae. recta and its parental species Ae. triaristata and Ae. uniaristata indicated that the formation of the hexaploid form was not associated with large modifications of the parental genomes.     

Cytogenetic comparison of N-genome Aegilops L. species

Differential C-banding and in situ hybridization were employed in a cytogenetic comparison of thee N-genome Aegilops species: diploid Ae. uniaristata, tetraploid Ae. ventricosa, and hexaploid Ae. recta. The formation of Ae. recta was shown to involve only minor functional modifications of the parental genomes, while intraspecific divergence was accompanied by large genome rearrangements, namely, translocations involving the total chromosome arms of all of the three genomes. The formation of tetraploid Ae. ventricosa involved substantial structural chromosome rearrangements, including a partial deletion of the short arm of chromosome 5D, including the nucleolus-organizing region; a redistribution of C bands on chromosomes of the D and N genomes along with a reduction of the heterochromatin content; and a considerable decrease in the hybridization intensity of the pAs1 repeat. Chromosomes of the Ae. ventricosa D genome were more similar to chromosomes of the Ae. crassa D1 genome than to Ae. tauschii chromosomes.     

New 18S·26S ribosomal RNA gene loci: chromosomal landmarks for the evolution of polyploid wheats

Three new 18S·26S rRNA gene loci were identified in common wheat by sequential N-banding and in situ hybridization (ISH) analysis. Locus Nor-A7 is located at the terminal area of the long arm of 5A in both diploid and polyploid wheats. Locus Nor-B6 is located in N-band 1BL2.5 of the long arm of chromosome 1B in Triticum turgidum and Triticum aestivum. ISH sites, similar to Nor-B6, were also detected on the long arms of chromosomes 1G in Triticum timopheevii and 1S in Aegilops speltoides, but their locations on the chromosomes were different from that of Nor-B6, indicating possible chromosome rearrangements in 1GL and 1BL during evolution. The third new locus, Nor-D8, was only found on the short arm of chromosome 3D in the common wheat Wichita. The loss of rRNA gene locus Nor-A3 and gain of repetitive DNA sequence pSc119 on the terminal part of 5AS suggest a structural modification of 5AS. Comparative studies of the location of the 18S·26S rRNA gene loci in polyploid wheats and putative A and B (G) genome progenitor species support the idea that: (1) Triticum monococcum subsp. urartu is the donor of both the A and A^t genome of polyploid wheats. (2) Ae. speltoides is closer to the B and G genome of polyploid wheats than Aegilops longissima and is the most probable progenitor of these two genomes.     

Characterization of chromosome-specific S-SAP markers and their use in studying genetic diversity in Aegilops species.

The short interspersed nuclear element (SINE), Au, was used to develop sequence-specific amplified polymorphism (S-SAP) markers for U- and M-genome chromosomes. The markers were localized using Triticum aestivum (wheat)-- Aegilops geniculata and wheat-- Aegilops biuncialis disomic chromosome addition lines. Thirty-seven markers distributed over 6 U and 6 M chromosomes were produced. A genetic diversity study carried out on 37 accessions from Ae. biuncialis, Ae. comosa, Ae. geniculata, and Ae. umbellulata suggested that Ae. biuncialis have arisen from its diploid ancestors more recently than Ae. geniculata. Several earlier studies indicated that the M genomes in polyploid Aegilops species had accumulated substantial rearrangements, whereas the U genomes remained essentially unmodified. However, this cannot be attributed to the preferential insertion of retroelements into the M genome chromosomes. Fourteen markers from a total of 8 chromosomes were sequenced; 3 markers were similar to known plant genes, 1 was derived from a long terminal repeat (LTR) retrotransposon, and 10 markers did not match to any known DNA sequences, suggesting that they were located in the highly variable intergenic regions.     

山羊草属核型分析及其与小麦属的进化关系

作者研究了山羊草属(Aegilops)中的新疆节节麦(Ae.squarrosa)、拟斯卑尔脱山羊草(Ae.speltoides)、沙融山羊草(Ae.sharonensis)、尾状山羊草(Ae.caudata)、卵圆山羊草(Ae.ovata)、偏凸山车草(Ae.ventricosa),钩状山羊草(Ae.triuncialis)、三芒山羊草(Me.triaristata)、欧山羊草(Ae.biuncialis)、柱穗山羊草(Ae.cylindrica)、可兹山羊草(Ae.kotschyi)和肥厚山羊草(Ae.crassa)的核型和部分材料的Giemsa N-带,结果表明山羊草属的C组核型为:4sm+3st;D组核型为:6m+1sm;S组的核型为:6m+1sm;M组的核型为:4m+1sm+2t。在四倍体、六倍体中,各染色体组保持着相对稳定。山羊草属S、D染色体组的核型与带型表明它们是小麦B、D染色体组的可能供体,C、M染色体组的一部分染色体带型亦与小麦B组带型相似。     

Comparative FISH mapping of two highly repetitive DNA sequences in Hordeum chilense (Roem. et Schult.)

Hordeum chilense Roem. et Schult. (2n = 14) is an autogamous wild barley from Chile and Argentina included in the section Anisolepis Nevski. This species shows interesting agronomic traits that can be incorporated into crop plant species. Hordeum chilense has been successfully crossed with species of the genus Aegilops. Among the amphiploids obtained, the hexaploid tritordeum (2n = 6x = 42, AABBHchHch) is outstanding and shows good agronomic characteristics, suggesting its potential either as a new crop or as a bridge species to introgress interesting traits into cultivated cereals. The aim of the present work was to study the hybridization patterns of the two repetitive DNA probes pAs1 and pSc119.2 to evaluate their utility for the identification of H. chilense chromosomes. Fourteen lines of H. chilense were analyzed with fluorescent in situ hybridization using probes pSc119.2 and pAs1. The probe pAs1 was more widely dispersed than pSc119.2 over the H. chilense (Hch) genome. We found 89 different signals for pAs1, distributed evenly over the whole genome, and 10 for pSc119.2, located mainly over the telomeric regions. Five distinct hybridization signals were found for pAs1 and four distinct signals for pSc119.2. These signals allow the identification of different H. chilense lines. For example, centromeric signals for pAs1 on the short arms of chromosomes 1 and 7 identify line H46, and a telomeric signal for pSc119.2 on the short arm of chromosome 2 identifies line H1. A high degree of polymorphism in the hybridization patterns was found, confirming the extensive variability present in H. chilense. This work provides tools for the identification of H. chilense chromosomes in different genetic backgrounds.     

Genome differentiation in Aegilops. 3. Evolution of the D-genome cluster

 Six polyploid Aegilops species containing the D genome were studied by C-banding and fluorescence in situ hybridization (FISH) using clones pTa71 (18S-5.8S-26S rDNA), pTa794 (5S rDNA), and pAs1 (non-coding repetitive DNA sequence) as probes. The C-banding and pAs1-FISH patterns of Ae. cylindrica chromosomes were identical to those of the parental species. However, inactivation of the NOR on chromosome 5D with a simultaneous decrease in the size of the pTa71-FISH site was observed. The N^v and D^v genomes of Ae. ventricosa were somewhat modified as compared with the N genome of Ae. uniaristata and the D genome of Ae. tauschii. Modifications included minor changes in the C-banding and pAs1-FISH patterns, complete deletion of the NOR on chromosome 5D^v, and the loss of several minor 18S-5.8S-26S rDNA loci on N^v genome chromosomes. According to C-banding and FISH analyses, the D^cr1 genome of Ae. crassa is more similar to the D^v genome of Ae. ventricosa than to the D genome of Ae. tauschii. Mapping of the 18S-5.8S-26S rDNA and 5S rDNA loci by multicolor FISH suggests that the second (X^cr) genome of tetraploid Ae. crassa is a derivative of the S genome (section Emarginata of the Sitopsis group). Both genomes of Ae. crassa were significantly modified as the result of chromosomal rearrangements and redistribution of highly repetitive DNA sequences. Hexaploid Ae. crassa and Ae. vavilovii arose from the hybridization of chromosomal type N of tetraploid Ae. crassa with Ae. tauschii and Ae. searsii, respectively. Chromosomal type T1 of tetraploid Ae. crassa and Ae. umbellulata were the ancestral forms of Ae. juvenalis. The high level of genome modification in Ae. juvenalis indicates that it is the oldest hexaploid species in this group. The occurrence of hexaploid Ae. crassa was accompanied by a species-specific translocation between chromosomes 4D^cr1 and 7X^cr. No chromosome changes relative to the parental species were detected in Ae. vavilovii, however, its intraspecific diversity was accompanied by a translocation between chromosomes 3X^cr and 3D^cr1. Received July 24, 2001 Accepted October 1, 2001     

Phylogenetic reconstruction of Aegilops section Sitopsis and the evolution of tandem repeats in the diploids and derived wheat polyploids.

The evolution of 2 tandemly repeated sequences Spelt1 and Spelt52 was studied in Triticum species representing 2 evolutionary lineages of wheat and in Aegilops sect. Sitopsis, putative donors of their B/G genomes. Using fluorescence in situ hybridization we observed considerable polymorphisms in the hybridization patterns of Spelt1 and Spelt52 repeats between and within Triticum and Aegilops species. Between 2 and 28 subtelomeric sites of Spelt1 probe were detected in Ae. speltoidies, depending on accession. From 8 to 12 Spelt1 subtelomeric sites were observed in species of Timopheevi group (GAt genome), whereas the number of signals in emmer/aestivum accessions was significantly less (from 0 to 6). Hybridization patterns of Spelt52 in Ae. speltoides, Ae. longissima, and Ae. sharonensis were species specific. Subtelomeric sites of Spelt52 repeat were detected only in T. araraticum (T. timopheevii), and their number and chromosomal location varied between accessions. Superimposing copy number data onto our phylogenetic scheme constructed from RAPD data suggests 2 major independent amplifications of Spelt52 and 1 of Spelt1 repeats in Aegilops divergence. It is likely that the Spelt1 amplification took place in the ancient Ae. speltoides before the divergence of polyploid wheats. The Spelt52 repeat was probably amplified in the lineage of Ae. speltoides prior to divergence of the allopolyploid T. timopheevii but after the divergence of T. durum. In a separate amplification event, Spelt52 copy number expanded in the common ancestor of Ae. longissima and Ae. sharonensis.     

BAC libraries of Triticum urartu, Aegilops speltoides and Ae. tauschii, the diploid ancestors of polyploid wheat

Triticum urartu, Aegilops speltoides and Ae. tauschii are respectively the immediate diploid sources, or their closest relatives, of the A, B and D genomes of polyploid wheats. Here we report the construction and characterization of arrayed large-insert libraries in a bacterial artificial chromosome (BAC) vector, one for each of these diploid species. The libraries are equivalent to 3.7, 5.4 and 4.1 of the T. urartu, Ae. speltoides, Ae. tauschii genomes, respectively. The predicted levels of genome coverage were confirmed by library hybridization with single-copy genes. The libraries were used to estimate the proportion of known repeated nucleotide sequences and gene content in each genome by BAC-end sequencing. Repeated sequence families previously detected in Triticeae accounted for 57, 61 and 57% of the T. urartu, Ae. speltoides and Ae. tauschii genomes, and coding regions accounted for 5.8, 4.5 and 4.8%, respectively.     

Transferability of wheat microsatellites to diploid Aegilops species and determination of chromosomal localizations of microsatellites in the S genome.

Overall, 253 genomic wheat (Triticum aestivum) microsatellite markers were studied for their transferability to the diploid species Aegilops speltoides, Aegilops longissima, and Aegilops searsii, representing the S genome. In total, 88% of all the analyzed primer pairs of markers derived from the B genome of hexaploid wheat amplified DNA fragments in the genomes of the studied species. The transferability of simple sequence repeat (SSR) markers of the T. aestivum A and D genomes totaled 74%. Triticum aestivum-Ae. speltoides, T. aestivum-Ae. longissima, and T. aestivum-Ae. searsii chromosome addition lines allowed us to determine the chromosomal localizations of 103 microsatellite markers in the Aegilops genomes. The majority of them were localized to homoeologous chromosomes in the genome of Aegilops. Several instances of nonhomoeologous localization of T. aestivum SSR markers in the Aegilops genome were considered to be either amplification of other loci or putative translocations. The results of microsatellite analysis were used to study phylogenetic relationships among the 3 species of the Sitopsis section (Ae. speltoides, Ae. longissima, and Ae. searsii) and T. aestivum. The dendrogram obtained generally reflects the current views on phylogenetic relationships among these species.     

山羊草属异源多倍体植物基因组进化的ＲＡＰＤ分析

和２４个随机引物对山羊草属（Ａegilops L.)异源多倍体物种对其祖先二倍体物进行ＲＡＰＤ分析,对扩增出的３１３条带进行聚类分析发现,含Ｄ基因组的多倍体与二倍体祖先Ａe.squarrosa(DD)在聚类图上聚为一支;除Ａe.juvenalis(DDMMUU)聚到上一支外,含Ｕ基因组的多倍 与二倍体祖先Ae.umbellulata(ＵＵ）在聚类图上聚为另一支;多倍体与其他二倍体均不聚在一起,表明多倍体分别与Ａe.squarrosa(DD)、Ae.umbellulata(UU)具有较近的亲缘关系,这说明多倍体开之后,Ｄ和Ｕ基因组变化较小,而其他基因组则发生了较大的变化。     

Genetic Diversity of the Cytoplasm in Triticum and Aegilops. VIII. Fraction I Protein of 39 Cytoplasms

The electrophoretic characteristics of the cytoplasmically controlled large subunit of the Fraction I protein of 36 alloplasmic and three euplasmic control lines are reported. These lines, representing the cytoplasms of 32 Triticum and Aegilops species, had either H- or L-type large subunits in their Fraction I protein; the diploid Triticum and most Aegilops species, including Ae. bicornis and Ae. sharonensis, had the L-type subunits; whereas, all the polyploid Triticum species (emmer, timopheevi, common wheats), Ae. speltoides, Ae. aucheri, and Ae. longissima had H-type subunits. Therefore, section Sitopsis of Aegilops exhibits interspecific heterogeneity. The H-type is believed to have originated in the Sitopsis section from an L-type subunit because of the prevalence of the latter among the diploid species.     

RAPD markers linked to the nuclear gene from Triticum timopheevii that confers compatibility with Aegilops squarrosa cytoplasm on alloplasmic durum wheat.

Alien cytoplasms cause a wide range of phenotypic alterations in the nucleus-cytoplasm (NC) hybrids in the Triticeae. Nuclear genomes of timopheevii wheat (Triticum timopheevii and Triticum araraticum) are fully compatible with the cytoplasm of Aegilops squarrosa, while those of a majority of emmer or durum wheat cultivars and more than half the wild emmer wheats are incompatible, and a maternal 1D chromosome is required to restore seed viability and male fertility in the NC hybrids. A euploid NC hybrid of Triticum durum cv. Langdon with Ae. squarrosa cytoplasm produced by introgressing the NC compatibility (Ncc) gene from T. timopheevii was used to identify random amplified polymorphic DNA (RAPD) markers linked to it. After a survey of 200 random decamer primers, four markers were selected, all of which were completely linked in 64 individuals of a SB8 mapping population. One marker was derived from a single locus, while three others were from interspersed repetitive sequences. Also, the hybrid chromosomes and those of the parental T. durum had identical C-banding patterns. RAPD-PCR analysis of 65 accessions from wild and cultivated tetraploid wheat species showed the exclusive presence of the markers in timopheevii wheat. In conclusion, the chromosomal region flanking Ncc of T. timopheevii is highly conserved in the genome of this group of tetraploid wheats.     

Isolation and characterization of S genome specific sequences from Aegilops sect. sitopsis species.

Three S genome specific sequences were isolated from Aegilops sect. sitopsis species using different experimental approaches. Two clones, UTV86 and UTV39, were isolated from a partial genomic library obtained from DNA of Aegilops sharonensis, whereas a third clone, UTV5, was isolated from Aegilops speltoides. The three clones were characterized by sequencing, analysis of methylation, and sequence organization and abundance in some Aegilops and Triticum species. The clones UTV39 and UTV5 belong to the same family of tandem repeated sequences and showed high homology with a sequence already present in nucleotide databases. The UTV86 clone from Ae. sharonensis corresponded to an interspersed low frequency repeated sequence and did not show any significant homology with reported sequences. Southern hybridization experiments, using the cloned sequences as probes, detected polymorphism in the restriction patterns of all the five Aegilops species in section sitopsis. Aegilops speltoides showed the most divergent hybridization pattern. A close relationship was detected between the S genome of Ae. speltoides and the G genome of the wild Triticum timopheevii. In situ hybridization revealed a telomeric and (or) subtelomeric location of the sequences UTV39 and UTV5.     

Characterization of Hordeum chilense chromosomes by C-banding and in situ hybridization using highly repeated DNA probes.

C-banding patterns of Hordeum chilense and of Triticum aestivum 'Chinese Spring' - H. chilense disomic addition lines were analyzed and compared with in situ hybridization patterns using a biotin-labeled highly repetitive Triticum tauschii DNA sequence, pAs1, and a wheat 18S-26S rDNA probe. All seven H. chilense chromosomes pairs and the added H. chilense chromosomes present in the addition lines were identified by their characteristic C-banding pattern. Chromosome morphology and banding patterns were similar to those of the corresponding chromosomes present in the parent H. chilense accession. A C-banded karyotype of the added H. chilense chromosomes was constructed and chromosome lengths, arm ratios, and relative length, as compared with chromosome 3B, were determined. The probe pAs1 was found to hybridize to specific areas on telomeres and interstitial sites along the chromosomes, allowing the identification of all seven pairs of the H. chilense chromosomes. Comparison of the patterns of distribution of the hybridization sites of clone pAs1 in the T. tauschii and H. chilense chromosomes was carried out by in situ hybridization on somatic metaphase chromosomes of the HchHchDD amphiploid. In situ hybridization using the 18S-26S rDNA probe confirmed that the H. chilense chromosomes 5Hch and 6Hch were carrying nucleolus organizer regions. The results are discussed on the basis of phylogenetic relationships between D and Hch genomes.     

Recurrent deletions of puroindoline genes at the grain hardness locus in four independent lineages of polyploid wheat

Polyploidy is known to induce numerous genetic and epigenetic changes but little is known about their physiological bases. In wheat, grain texture is mainly determined by the Hardness (Ha) locus consisting of genes Puroindoline a (Pina) and b (Pinb). These genes are conserved in diploid progenitors but were deleted from the A and B genomes of tetraploid Triticum turgidum (AB). We now report the recurrent deletions of Pina-Pinb in other lineages of polyploid wheat. We analyzed the Ha haplotype structure in 90 diploid and 300 polyploid accessions of Triticum and Aegilops spp. Pin genes were conserved in all diploid species and deletion haplotypes were detected in all polyploid Triticum and most of the polyploid Aegilops spp. Two Pina-Pinb deletion haplotypes were found in hexaploid wheat (Triticum aestivum; ABD). Pina and Pinb were eliminated from the G genome, but maintained in the A genome of tetraploid Triticum timopheevii (AG). Subsequently, Pina and Pinb were deleted from the A genome but retained in the A(m) genome of hexaploid Triticum zhukovskyi (A(m)AG). Comparison of deletion breakpoints demonstrated that the Pina-Pinb deletion occurred independently and recurrently in the four polyploid wheat species. The implications of Pina-Pinb deletions for polyploid-driven evolution of gene and genome and its possible physiological significance are discussed.     

Evaluation of Phylogenetic Relationships between Five Polyploid Aegilops L. Species of the U-Genome Cluster by Means of Chromosome Analysis

Four tetraploid (Aegilops ovata, Ae. biuncialis, Ae. columnaris, and Ae. triaristata) and one hexaploid (Ae. recta) species of the U-genome cluster were studied using C-banding technique. All species displayed broad C-banding polymorphism and high frequency of chromosomal rearrangements. Chromosomal rearrangements were represented by paracentric inversions and intragenomic and intergenomic translocations. We found that the processes of intraspecific divergence of Ae. ovata, Ae. biuncialis,and Ae. columnaris were probably associated with introgression of genetic material from other species. The results obtained confirmed that tetraploid species Ae. ovata and Ae. biuncialis occurred as a result of hybridization of a diploidAe. umbellulata with Ae. comosa and Ae. heldreichii, respectively. The dissimilarity of the C-banding patterns of several chromosomes of these tetraploid species and their ancestral diploid forms indicated that chromosomal aberrations might have taken place during their speciation. Significant differences of karyotype structure, total amount and distribution of C-heterochromatin found between Ae. columnarisand Ae. triaristata, on the one hand, and Ae. ovata and Ae. biuncialis, on the other, evidenced in favor of different origin of these groups of species. In turn, similarity of the C-banding patterns of Ae. columnaris and Ae. triaristata chromosomes suggested that they were derived from a common ancestor. A diploid species Ae. umbellulata was the U-genome donor of Ae. columnaris and Ae. triaristata;however, the donor of the second genome of these species was not determined. We assumed that these tetraploid species occurred as a result of introgressive hybridization. Similarity of the C-banding patterns of chromosomes of Ae. recta and its parental species Ae. triaristata and Ae. uniaristata indicated that the formation of the hexaploid form was not associated with large modifications of the parental genomes.     

Quantification of genetic relationships among A genomes of wheats.

The genetic relationships of A genomes of Triticum urartu (Au) and Triticum monococcum (Am) in polyploid wheats are explored and quantified by AFLP fingerprinting. Forty-one accessions of A-genome diploid wheats, 3 of AG-genome wheats, 19 of AB-genome wheats, 15 of ABD-genome wheats, and 1 of the D-genome donor Ae. tauschii have been analysed. Based on 7 AFLP primer combinations, 423 bands were identified as potentially A genome specific. The bands were reduced to 239 by eliminating those present in autoradiograms of Ae. tauschii, bands interpreted as common to all wheat genomes. Neighbour-joining analysis separates T. urartu from T. monococcum. Triticum urartu has the closest relationship to polyploid wheats. Triticum turgidum subsp. dicoccum and T. turgidum subsp. durum lines are included in tightly linked clusters. The hexaploid spelts occupy positions in the phylogenetic tree intermediate between bread wheats and T. turgidum. The AG-genome accessions cluster in a position quite distant from both diploid and other polyploid wheats. The estimates of similarity between A genomes of diploid and polyploid wheats indicate that, compared with Am, Au has around 20% higher similarity to the genomes of polyploid wheats. Triticum timo pheevii AG genome is molecularly equidistant from those of Au and Am wheats.