E. D. Badaeva

Intraspecific karyotype divergence inTriticum araraticum (Poaceae)

Karyotypes of 185 accessions ofTriticum araraticumJakubz. (2n = 28 = 4x = AtAtGG) from Iraq, Iran, Turkey, and Transcaucasia were analyzed using C-banding technique. All accessions showed a certain degree of C-banding polymorphism and further karyotypic diversity was generated by structural rearrangements, mainly translocations. Eighty-one accessions had the normal karyotype similar to that ofT. timopheevii (cultivation), i.e., they showed C-banding polymorphism but no chromosomal rearrangements based on the resolving power of the C-banding technique. One-hundred four accessions showed 34 karyotypic variants, 31 had reciprocal translocations with the breakpoints in the centromeric regions of chromosomes. Three showed reciprocal translocations with the breakpoints in intercalary regions of chromosomes. A paracentric inversion for 7At chromosome was observed in some accessions. The rearranged karyotypes differed from the normal by one translocation in 21 variants, by two in 9 variants, by three in 1 variant, and by four in 2 variants of karyotypes. Translocations occurred more frequenty in the chromosomes of G-genome than of At-genome. Individual chromosomes differed in the frequencies of their involvement in translocations. Each geographical region contained a unique spectrum of translocations. Karyotypic diversity was the highest in Iraq followed by Transcaucasia and Turkey. Iran showed little karyotypic variation. Based on karyotypic analysis, Iraq should be considered as a centre of origin and primary centre of diversity ofT. araraticum.

Genome differentiation in Aegilops. 4. Evolution of the U-genome cluster

Abstract.Phylogenetic relationships of polyploid Aegilops species sharing the U-genome were investigated by analyzing heterochromatin banding patterns of their somatic metaphase chromosomes as revealed by C-banding and fluorescence in situ hybridization (FISH) with the heterochromatin-limited repetitive DNA probes pSc119, pAs1, as well as the distribution of NOR and 5S DNA loci revealed by pTa71 (18S-26S rDNA), and pTa794 (5S rDNA) probes. Seven tetraploid (Ae. triuncialis, Ae. peregrina, Ae. kotschyi, Ae. geniculata, Ae. biuncialis, Ae. columnaris, and 4x Ae. neglecta) and one hexaploid (6x Ae. neglecta) Aegilops species of the U-genome cluster were studied. The Ut and Ct chromosomes of 4x Ae. triuncialis (UtCt) were similar to the diploid donors Ae. umbellulata (U) and Ae. caudata (C). However, the size of the NOR locus on chromosome 5Ut was reduced. Karyotypic analyses confirmed that 4x Ae. peregrina (SpUp) was derived from a hybridization of the diploid species Ae. umbellulata with Ae. longissima, whereas Ae. umbellulata and Ae. sharonensis (or an immediate precursor) were the diploid progenitor species of Ae. kotschyi (SkUk). In both 4x species, the NORs on S-genome chromosomes were inactivated and were accompanied with a decrease or loss of rDNA sequences. Karyotypes of the tetraploid species, Ae. geniculata (UgMg) and Ae. biuncialis (UbMb) differed from each other and from the putative diploid progenitors Ae. umbellulata and Ae. comosa indicating that various types of chromosomal alterations occurred during speciation. Inactivation of major NORs on the M-genome chromosomes, redistribution of 5S rDNA sites, and loss of some minor 18S-26S rDNA loci were observed in Ae. geniculata and Ae. biuncialis. Significant differences in the total amount and distribution of heterochromatin, the number and location of 5S and 18S-26S rDNA loci observed between Ae. columnaris (UcXc)/4x Ae. neglecta (UnXn) and Ae. geniculata/Ae. biuncialis indicate that these species have different origins. Similarities in C-banding and FISH patterns of most Ae. columnaris and 4x Ae. neglecta chromosomes suggest that they were probably derived from a common ancestor, whereas distinct differences of three chromosome pairs may indicate that the divergence of these species was probably associated with chromosomal rearrangements and/or introgressive hybridization. Ae. umbellulata contributed the U genome, however, the source of their second genomes remains unknown. The formation of 6x Ae. neglecta (UnXnNn) was not associated with large modifications of the parental genomes.

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

Abstract. 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 Nv and Dv 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 5Dv, and the loss of several minor 18S-5.8S-26S rDNA loci on Nv genome chromosomes. According to C-banding and FISH analyses, the Dcr1 genome of Ae. crassa is more similar to the Dv 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 (Xcr) 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 4Dcr1 and 7Xcr. No chromosome changes relative to the parental species were detected in Ae. vavilovii, however, its intraspecific diversity was accompanied by a translocation between chromosomes 3Xcr and 3Dcr1.

FRIZZY PANICLE Drives Supernumerary Spikelets in Bread Wheat

Wheat transcription factors located on chromosome group 2 drive the yield-related production of supernumerary spikelets. Bread wheat (Triticum aestivum) inflorescences, or spikes, are characteristically unbranched and normally bear one spikelet per rachis node. Wheat mutants on which supernumerary spikelets (SSs) develop are particularly useful resources for work towards understanding the genetic mechanisms underlying wheat inflorescence architecture and, ultimately, yield components. Here, we report the characterization of genetically unrelated mutants leading to the identification of the wheat FRIZZY PANICLE (FZP) gene, encoding a member of the APETALA2/Ethylene Response Factor transcription factor family, which drives the SS trait in bread wheat. Structural and functional characterization of the three wheat FZP homoeologous genes (WFZP) revealed that coding mutations of WFZP-D cause the SS phenotype, with the most severe effect when WFZP-D lesions are combined with a frameshift mutation in WFZP-A. We provide WFZP-based resources that may be useful for genetic manipulations with the aim of improving bread wheat yield by increasing grain number.

Cytogenetic analysis of forms produced by crossing hexaploid triticale with common wheat

SummaryHexaploid triticales were crossed with common wheats, and the resultant froms were selected for either triticale (AD 213/5-80) or common wheat (lines 381/80, 391/80, 393/80). The cytogenetic analysis showed that all forms differ in their chromosome composition. Triticale AD 213/5-80 and wheat line 381/80 were stable forms with 2n = 6x = 42. Lines 391/80 and 393/80 were cytologically unstable. In triticale AD 213/5-80, a 2R (2D) chromosome substitution was found. Each of the three wheat lines had a chromosome formed by the translocation of the short arm of IR into the long arm of the IB chromosome. In line 381/80, this chromosome seems to be inherited from the ‘Kavkaz’ wheat variety. In lines 391/80 and 393/80, this chromosome apparently formed de novo since the parent forms did not have it. The karyotype of line 381/80 was found to contain rye chromosomes 4R/7R, 5R and 7R/4R. About 15% of the cells in line 391/80 contained an isochromosome for the 5R short arm and also a chromosome which arose from the translocation of the long arms of the 5D and 5R chromosomes. About one-third of the cells in the common wheat line 393/80 contained the 5R chromosome. This chromosome was normal or rearranged. Practical applications of the C-banding technique in the breeding of triticale is discussed.

Molecular Cytogenetic Analysis of Tetraploid and Hexaploid Aegilops Crassa

The distribution of highly repetitive DNA sequences on chromosomes of tetraploid and hexaploid cytotypes of Aegilops crassa (Dcr1Xcr and Dcr1XcrDcr2 genomes) was studied using C-banding and in situ hybridization analyses with the pSc119, pAs1 and pTa794 DNA clones. In total, 14 tetraploid and five hexaploid accessions were examined. All chromosomes can be identified by their C-banding and ISH pattern with the pAs1 DNA clone. Only a few pSc119 hybridization sites were observed in the telomeric regions of several chromosomes. We found a high level of C-banding polymorphism and only minor variations in labeling patterns. The position of C-bands generally coincided with the location of the pAs1 sequence. Three 5S rDNA loci were detected in tetraploid Ae. crassa, whereas five pTa794 ISH sites were observed in 6x Ae. crassa. All the hexaploid accessions differed from the tetraploids by a reciprocal non-centromeric translocation involving chromosomes A and N. Three additional translocations were detected in the accessions analyzed. The Dcr1 genome of 4x Ae. crassa is highly modified compared with the D genome of the progenitor species Ae. tauschii. Because of the large amount of chromosomal rearrangements, the origin of the Xcr genome remains unknown. The second Dcr2 genome of 6x Ae. crassa is different from the Dcr1 genome but is similar to the D-genome chromosomes of Ae. tauschii, indicating that no additional large rearrangements occurred at the hexaploid level.

Genetic and epigenetic changes of rDNA in a synthetic allotetraploid, Aegilops sharonensis × Ae. umbellulata

The synthetic allotetraploid Aegilops sharonensis x Ae. umbellulata (genomic formula S(sh)U) was used to study inheritance and expression of 45S rDNA during early stages of allopolyploid formation. Using silver staining, we revealed suppression of the NORs (nucleolar organizing regions) from the S(sh) genome in response to polyploidization. Most allopolyploid plants of the S(2)-S(4) generations retained the chromosomal location of 45S rDNA typical for the parental species, except for two S(3) plants in which a deletion of the rDNA locus on one of the homologous 6S(sh) chromosomes was revealed. In addition, we found a decrease in NOR signal intensity on both 6S(sh) chromosomes in a portion of the S(3) and S(4) allopolyploid plants. As Southern hybridization showed, the allopolyploid plants demonstrated additive inheritance of parental rDNA units together with contraction of copy number of some rDNA families inherited from Ae. sharonensis. Also, we identified a new variant of amplified rDNA unit with MspAI1 restriction sites characteristic of Ae. umbellulata. These genetic alterations in the allopolyploid were associated with comparative hypomethylation of the promoter region within the Ae. umbellulata-derived rDNA units. The fast uniparental elimination of rDNA observed in the synthetic allopolyploid agrees well with patterns observed previously in natural wheat allotetraploids.

Standard karyotypes ofAegilops uniaristata, Ae. mutica, Ae. comosa subspeciescomosa andheldreichii (Poaceae)

C-banding patterns and polymorphisms were analyzed in several accessions of the diploidAegilops speciesAe. uniaristata, Ae. mutica, andAe. comosa subsp.comosa and subsp.heldreichii, and standard karyotypes of these species were established. Variation in C-band size and location was observed between different accessions, but did not prevent chromosome identification. One accession ofAe. uniaristata was homozygous for whole-arm translocations involving chromosomes 1N and 5N. The homoeologous relationships of these chromosomes were established by comparison of chromosome morphologies and C-banding patterns to other diploidAegilops species with known chromosome homoeology. In addition, in situ hybridization analysis with a 5S rDNA probe was used to identify homoeologous groups 1 and 5 chromosomes. The present analysis permitted the assignment of allAe. mutica, comosa subsp.comosa, andAe. comosa subsp.heldreichii chromosomes, and three of the sevenAe. uniaristata chromosomes according to their homoeologous groups. The data presented will be useful analyzing genome differentiation in polyploidAegilops species.

[A comparative cytogenetic study of the tetraploid oat species with the A and C genomes: Avena insularis, A. magna, and A. murphyi].

C-banding of chromosomes and in situ hybridization with the probes pTa71 and pTa794 were used for a comparative cytogenetic study of the three tetraploid oat species with the A and C genomes: Avena insularis, A. magna, and A. murphyi. These species were similar in the structure and C-banding patterns of several chromosomes as well as in the location of the loci 5S rRNA genes and major NOR sites; however, they differed in the number and localization of minor 45S rDNA loci as well as in the morphology and distribution of heterochromatin in some chromosomes. According to the data obtained, A. insularis is closer to A. magna, whereas A. murphyi is somewhat separated from these two species. Presumably, all the three studied species originated from the same tetraploid ancestor, and their divergence is connected with various species-specific chromosome rearrangements. The evolution of A. murphyi is likely to have occurred independently of the other two species.

Intraspecific chromosomal polymorphism of Triticum araraticum (Poaceae) detected by C-banding technique

DifferentTriticum araraticum lines were studied by C-banding method. The intraspecific divergence ofT. araraticum was shown to be caused mainly by large chromosomal rearrangements. Two main chromosomal types were distinguished among the studied lines: (1) a karyotype similar to that ofT. timopheevii and (2) different one. The first type includes some lines ofT. araraticum subspp.kurdistanicum andararaticum; the second comprises most lines ofT. araraticum subsp.araraticum. The lines of the first type can give fertile F1 hybrids withT. timopheevii.