Diploid endosperm formation in Tulipa spp. and identification of a 1:1 maternal-to-paternal genome ratio in endosperms of T. gesneriana L.

Most Liliaceae plants have the tetrasporic Fritillaria-type embryo sac and normally form diploid embryos and pentaploid endosperms derived from a 4:1 maternal-to-paternal genome ratio (4m:1p) after double fertilization. Here we characterize embryo sac and endosperm formation in Tulipa spp. of Liliaceae. Chromosome analysis using seeds derived from 2x × 2x crosses of Tulipa gesneriana (2n = 2x = 24) identified diploid chromosome number in the endosperm. Similarly, flow cytometric analysis confirmed diploid endosperm formation in T. gesneriana, T. fosteriana (2n = 2x = 24) and T. greigii (2n = 2x = 24). To further study the possible mechanism of diploid endosperm formation, we made interploidy crosses of triploid (2n = 3x = 36) × diploid in which aneuploid seeds with various chromosome numbers (2n = 25–36) were produced. Again, flow cytometric analysis confirmed the same ploidy level in both embryos and endosperms at all aneuploidy levels, suggesting that only a single haploid polar nucleus contributes to endosperm formation at fertilization. Histological observation further confirmed the physical separation of two polar nuclei by a large vacuole in the Fritillaria-type embryo sac of T. gesneriana that appeared to prevent the fusion of the two polar nuclei that originated at the micropylar and chalazal ends before fertilization. Taken together, these results indicate that diploid endosperms (1m:1p) are normally formed in Tulipa spp. by fusion of the micropylar polar nucleus (n) and a spermatid (n) but not by normal triple fusion. We also show that tulip endosperm partially overcomes the triploid block mechanism that occurs in interploidy crosses. Based on these observations, the possible role of triple nuclear fusion in double fertilization is discussed.     

Holcus azoricus M. Seq. & Castrov. (Poaceae), a new species from the Azores Islands

A new species of Holcus L. (Poaceae), endemic to the Azores archipelago (Portugal), is described. The vegetative and reproductive structures were studied. The diagnostic characters were compared with those of closely related species. New chromosome counts in Holcus azoricus M. Seq. & Castrov. (2 n  = 35) and H. rigidus Hochst. (2 n  = 28) are included. A possible hybrid origin is hypothesized; the potential parents are H. lanatus L. and H. rigidus .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 259–267.     

The fate of ribosomal RNA genes in spontaneous polyploid dogrose hybrids [Rosa L. sect. Caninae (DC.) Ser.] exhibiting non‐symmetrical meiosis

Dogroses represent an exceptional system for studying the effects of genome doubling and hybridization: their asymmetrical meiosis enables recombination in bi‐parentally inherited chromosomes but prevents it in maternally inherited ones. We employed fluorescent in situ hybridization, genome skimming, amplicon sequencing of genomic and cDNA as well as conventional cloning of nuclear ribosomal DNA in two phylogenetically distinct pentaploid (2n = 5x = 35) species, Rosa canina and Rosa inodora, and their naturally occurring reciprocal hybrids, Rosa dumalis (5x) and Rosa agrestis (5x, 6x). Both progenitor species differed in composition, meiotic behaviour and expression of rDNA loci: R. canina (five 18S and 5–8 5S loci) was dominated by the Canina ribotypes, but R. inodora (four 18S loci and 7–8 5S loci) by the Rubiginosa ribotype. The co‐localized 5S/18S loci occurred on either bivalent‐forming (R. canina) or univalent‐forming (R. inodora) chromosomes. Ribosomal DNA loci were additively inherited; however, the Canina ribotypes were dominantly expressed, even in genotypes with relatively low copy number of these genes. Moreover, we observed rDNA homogenization towards the paternally transmitted Canina ribotype in 6x R. agrestis. The here‐observed variation in arrangement and composition of rDNA types between R. canina and R. inodora suggests the involvement of different genomes in bivalent formation. This results supports the hypothesis that the asymmetrical meiosis arose at least twice by independent ancient hybridization events.     

Photosynthetic and genetic differentiation in sun and shade populations of Holcus mollis L.

Three Holcus mollis L. populations, one with 2n = 28 chromosomes living in a forest and two with 2n = 35 chromosomes, the first living in a forest, the second in open land, are compared for photosynthesis.Simultaneous measurements of oxygen and carbon dioxide, either in high light, low light, or dark experiments indicate that the 2n = 28 chromosomes population is photosynthetically well adapted to shade, while 2n = 35 chromosomes forest population, is not.The 2n = 35 chromosomes plants growing in the forest does not automatically acquire the photosynthetic character of a shade plant, the genome must show an evolution for this. In our study, only the plants with 2n = 28 chromosomes demonstrated the shade adaptation.     

Hypericum maculatum CRANTZ subsp.Maculatum XH. perforatum L. (Hypericaceae): Corroboration of natural hybridization by secondary metabolite analysis

The presence of various flavonoids, naphthodianthrones and phloroglucinol derivatives was studied in the natural pentaploid hybridH. maculatum Crantz subsp.maculatum × H. perforatum L. The hybrid taxon was shown to have secondary metabolites in common with both putative parents thus confirming its parentage. Morphological and nomenclatural questions are briefly discussed.     

Assessment of intergenomic recombination through GISH analysis of F1, BC1 and BC2 progenies of Tulipa gesneriana and T. fosteriana

Using 23 F1 hybrids, 14 BC1 and 32 BC2 progenies, the genome composition of Darwin hybrid tulips was analysed through genomic in situ hybridisation (GISH) of somatic chromosomes. All plants were diploids (2n = 2x = 24) with the exception of one tetraploid BC1 (2n = 4x = 48) and one aneuploid BC2 (2n = 2x + 1 = 25) hybrid. Morphometric analysis in F1 hybrids revealed a difference in the total length of chromosomes representing genomes of T. gesneriana and T. fosteriana, where the percentage of each genome equaled 55.18 ± 0.8 and 44.92 ± 0.6% respectively. GISH distinguished chromosomes from both parent genomes although there was a lack of consistent chromosome labelling in some cases. In both T. gesneriana and T. fosteriana chromosomes some segments of heterochromatin in the telomeric and intercalary regions exhibited a higher intensity of fluorescence. In situ hybridisation with 5S rDNA and 45S rDNA probes to metaphase chromosomes of F1 hybrids showed that these regions are rich in rDNA. A notable feature was that, despite genome differences, there was a considerable amount of intergenomic recombination between the parental chromosomes of the two species as estimated in both BC1 and BC2 offspring. The number of recombinant chromosomes ranged from 3 to 8 in BC1 and from 1 to 7 in BC2 progenies. All recombinant chromosomes possessed mostly a single recombinant segment derived from either a single crossover event or in a few cases double crossover events. This explains the fact that, unlike the situation in most F1 hybrids of other plant species, certain genotypes of Darwin hybrid tulips behave like normal diploid plants producing haploid gametes and give rise to mostly diploid sporophytes.     

THE VARIABILITY OF NUCLEAR DNA AND ITS IMPLICATIONS FOR POLYPLOIDY IN WHITE ASH (FRAXINUS AMERICANA L.: OLEACEAE)

Cytophotometric studies of both mature and embryonic tissues of white ash (Fraxinus americana L.) revealed considerable variability of nuclear DNA content in this dioecious polyploid species (2n = 46, 92, 138). Triploid and pentaploid embryos may be produced, and mature individuals of these odd ploidy levels, in turn, may occur in natural populations. Polyploidy may have originated in this species through the union of unreduced gametes.     

Cytology of a pentaploid hybrid and genome analysis in Solanum nigrum L.

Cytology of a pentaploid hybrid (2n=60) produced by crossing an autotetraploid (2n=48) of a diploid race of Solanum nigrum L. as seed parent with the naturally occurring hexaploid S. nigrum (2n=72) was studied which showed approximately 24_II+12_I. Chromosome pairing in the gametic complement of the hexaploid was deduced to be 12_II+12_I and on this basis it is concluded that the natural hexaploid is an autoallohexaploid, which has three sets (genomes) of 12 chromosomes each, two of which are to a large extent homologous to each other. Theoretically the genomic formula can be tentatively written as AAAABB. Since the natural hexaploid does not show any quadrivalents between the four homologous A genomes, chromosome pairing appears to be restricted to bivalent formation by a special genetic mechanism. The probability that S. nigrum could be an autohexaploid, parallelling Pheleum pratense, has been discussed.     

Cytogeography of Cenchrus ciliaris (Poaceae) in Tunisia

Belonging to the genus Cenchrus with 16–22 species, Cenchrus ciliaris L. (syn. Pennisetum ciliare (L.) Link, buffelgrass) is a perennial, common in warmer regions of both hemispheres, growing as a C4 grass in a wide range of habitats. In the present study we determined chromosome number and nuclear DNA content (2C DNA) for 28 natural populations collected from northern to southern Tunisia. Three ploidy levels were found: one tetraploid population (2n?=?4x?=?36), three pentaploid (2n?=?5x?=?45), and 24 hexaploid populations (2n?=?6x?=?54). The hexaploid chromosome number has already been reported for Tunisian populations of C. ciliaris but tetraploid and pentaploid (2n?=?45) are new for this area. The tetraploid population was found in the semi-arid north; pentaploids were mostly on the northern side of the arid region, while the hexaploids were located mainly in the arid southern Tunisian and Saharan region. 2C DNA values, assessed using flow cytometry, correlated with chromosome counts. Nuclear DNA content ranged from 2C?=?3.03 to 4.61 pg, revealing three ploidy levels corresponding to 4x, 5x, 6x, and mean 2C DNA amounts were of 3.03, 3.7 and 4.48 pg, respectively. Each cytotype produced viable pollen. Flow cytometric seed screening neither proved nor disproved apomixis. The most frequent hexaploid populations seem best adapted to arid conditions in southern Tunisia. The monoploid value, 1Cx, was constant. The existence of pentaploid cytotype suggests hybridization ability between tetraploids and hexaploids. It appears that polyploidization is the major evolutionary mechanism in the speciation of C. ciliaris.     

Individual vs. population plastic responses to elevated CO2, nutrient availability, and heterogeneity: a microcosm experiment with co-occurring species

We conducted an experiment to evaluate the plastic phenotypic responses of individuals, growing under intra-specific competition, and populations of three co-occurring grassland species (Lolium perenne, Plantago lanceolata, and Holcus lanatus) to joint variations in atmospheric CO₂ partial pressure (P _CO2; 37.5 vs. 70 Pa), nutrient availability (NA; 40 vs. 120 mg N added as organic material), and the spatial pattern of nutrient supply (SH; homogeneous vs. heterogeneous nutrient supply). At both the population and individual levels, the aboveground biomass of the three species significantly increased when the nutrients were heterogeneously supplied. Significant two- (SH × NA) and three-term (P _CO2 × NA × SH) interactions determined the response of traits measured on populations (aboveground biomass and below: aboveground biomass ratio, BAR) and individuals (aboveground biomass and specific leaf area). The combination of a high SH and NA elicited the highest plasticity of aboveground biomass in populations and individuals of the three species evaluated, and of BAR in Holcus. Soil heterogeneity and elevated P _CO2 elicited the highest plasticity in the SLA of Plantago and Lolium individuals. Our results show that populations, and not only individuals, respond to soil heterogeneity in a plastic way, and that plastic responses to elevated P _CO2 are complex since they vary across traits and species, and are influenced by the availability of nutrients and by their spatial distribution. They also emphasize the importance of soil heterogeneity as a modulator of plant responses to global change drivers. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Responsible Editor: Angela Hodge     

Effect of rye Secale cereale L. chromosomes 1R and 3R on polyembryony expression in hybrid combinations between ( Hordeum L.)-Triticum aestivum L. alloplasmic recombinant lines and wheat-rye substitution lines T. aestivum L.- S. cereale L.

The effect of rye chromosomes on polyembryony was studied for reciprocal hybrid combinations between (Hordeum vulgare L.)-Triticum aestivum L. alloplasmic recombinant lines and five wheat T. aestivum L. (cultivar Saratovskaya 29)-rye Secale cereale L. (cultivar Onokhosikaya) substitution lines: 1R(1D), 2R(2D), 3R(3B), 5R(5A), and 6R(6A), and for direct hybrid combinations between the [H. marinum ssp. gussoneanum (H. geniculatum All.)]-T. aestivum alloplasmic recombinant line and the wheat-rye substitution lines 1R(1A), 1R(1D), and 3R(3B). Chromosomes 1R and 3R of rye cultivar Onokhoiskaya proved to affect the expression of polyembryony in the hybrid combinations that involved the alloplasmic recombinant lines of common wheat as maternal genotypes. Based on this finding, polyembryony was regarded as a phenotypic expression of nuclear-cytoplasmic interactions where an important role is played by rye chromosomes 1R and 3R and the H. vulgare cytoplasm. Consideration is given to the association between the effect of rye chromosomes 1R and 3R on polyembryony in the [(Hordeum)-T. aestivum × wheat-rye substitution lines] hybrid combinations and their stimulating effect on the development on androgenic embryoids in isolated anther cultures of the wheat-rye substitution lines. Original Russian Text ? L.A. Pershina, T.S. Rakovtseva, L.I. Belova, E.P. Devyatkina, O.G. Silkova, L.A. Kravisova, A.I. Shchapova, 2007, published in Genetika, 2007, Vol. 43, No. 7, pp. 955–962.     

Introgression into the allotetraploid coffee ( Coffea arabica L.): segregation and recombination of the C. canephora genome in the tetraploid interspecific hybrid ( C. arabicax C. canephora)

Transfer of desired characters from the diploid relative species such as Coffea canephora into the cultivated allotetraploid coffee species (Coffea arabica L.) is essential to the continued improvement of varieties. Behaviour of the C. canephora genome and its interaction with the C. arabica genome were investigated in tetraploid interspecific hybrids (C. arabica×C. canephora 4x) resulting from a cross between an accession of C. arabica and a tetraploid plant of C. canephora obtained following colchicine treatment. Segregation and co-segregation of restriction fragment length polymorphism (RFLP) and microsatellite loci-markers were studied in two BC₁ populations. These two populations of 28 and 45 individuals, respectively, resulted from the backcross of two tetraploid F₁ plants to C. arabica. The presence in BC₁ plants of specific C. canephora markers was scored for 24 loci (11 RFLP and 13 microsatellites) distributed on at least 7 of the 11 linkage groups identified in C. canephora. At almost all loci analysed, the segregation of C. canephora alleles transmitted by the (C. arabica×C. canephora 4x) hybrids conformed to the expected ratio assuming random chromosome segregation and the absence of selection. The recombination fractions of C. canephora chromosome segments were estimated for seven marker intervals, and compared with the recombination fractions previously observed in C. canephora for the equivalent marker intervals. The recombination frequencies estimated in both plant materials were rather similar, suggesting that recombination in the (C. arabica×C. canephora 4x) hybrid is not significantly restricted by the genetic differentiation between chromosomes belonging to the different genomes. The hybrid (C. arabica×C. canephora 4x) therefore appeared particularly favourable to intergenomic recombination events and gene introgressions. Received: 26 March 2001 / Accepted: 29 June 2001     

Transfer of clover cyst nematode resistance from Trifolium nigrescens Viv. to T. repens L. by interspecific hybridisation

 Resistance to clover cyst nematode (Heterodera trifolii) has been successfully transferred from Trifolium nigrescens to T. repens by interspecific hybridisation. A sterile triploid hybrid (H-6909-5, 2n=3x=24) was initially produced with the aid of embryo culture. The hybrid was chromosome-doubled from axillary meristems by an in vitro colchicine method. Three chromosome-doubled plants were obtained, and these showed a marked increase in pollen stainability from 10% in 3x H-6909-5 to an average of 89% (range 88–91%) in 6x H-6909-5. T. nigrescens was a source of clover cyst nematode resistance. A mean of 23 (range 0–150) cysts per plant was recorded for T. nigrescens in comparison to a mean of 150 (range 50–240) cysts per plant for T. repens. The 3x and 6x interspecific hybrids were shown to be as resistant as the most resistant. T. nigrescens genotype and were significantly lower in cyst number per gram of root dry weight than the susceptible T. nigrescens and T. repens genotypes. Received: 11 July 1997 / Accepted: 15 July 1997     

The extent and position of homoeologous recombination in a distant hybrid of Alstroemeria: a molecular cytogenetic assessment of first generation backcross progenies

To estimate the extent and position of homoeologous recombination during meiosis in an interspecific hybrid between two distantly related Alstroemeria species, the chromosome constitution of six first generation backcross (BC₁) plants was analysed using sequential fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH) analysis. Four different probes were used for the FISH analysis: two species-specific and two rDNA probes. The six BC₁ plants were obtained from crosses between the hybrid A. aurea×A. inodora with its parent A. inodora. GISH clearly identified all chromosomes of both parental genomes as well as recombinant chromosomes. The sequential GISH and FISH analysis enabled the accurate identification of all individual chromosomes in the BC₁ plants, resulting in the construction of detailed karyotypes of the plants. The identification of the recombinant chromosomes provided evidence which chromosomes of the two species are homoeologous. Two of the BC₁ plants were aneuploid (2n=2x+1=17) and four triploid (2n=3x=24), indicating that both n and 2n gametes were functional in the F₁ hybrid. Using GISH, it was possible to estimate homeologous recombination in two different types of gametes in the F₁ hyrid. The positions of the crossover points ranged from highly proximal to distal and the maximum number of crossover points per chromosome arm was three. Compared with the aneuploid plants, the triploid plants (which received 2n gametes) clearly possessed fewer crossovers per chromosome, indicating reduced chromosome pairing/recombination prior to the formation of the 2n gametes. Besides homeologous recombination, evidence was found for the presence of structural rearrangements (inversion and translocation) between the chromosomes of the parental species. The presence of the ancient translocation was confirmed through FISH analysis of mitotic and meiotic chromosomes. Received: 7 October 1998; in revised form: 4 December 1998 / Accepted: 10 December 1998     

Chromosome investigations in annual Medicago species (Fabaceae) with emphasis on the origin of the polyploid Medicago rugosa and M. scutellata

Chromosome number variations play an important role in the genus Medicago. In addition to polyploidy there are cases of dysploidy as evidenced by two basic numbers, x = 8 and x = 7, the latter limited to five annual species having 2n = 14. Annuals are diploid with the exception of Medicago scutellata and Medicago rugosa which have 2n = 30 and are considered the result of crosses between the 2n = 16 and 2n = 14 species. However, this hypothesis has never been tested. This study was carried out to investigate the 2n = 14 and 2n = 30 karyotypes and verify the allopolyploid origin of M. scutellata and M. rugosa. Fluorescence in situ hybridization (FISH) of rDNA probes and genomic in situ hybridization (GISH) were performed. FISH showed that all five diploids with 2n = 14 have one pair of 45S and one pair of 5S rDNA sites. M. scutellata displayed four sites of 45S and four sites of 5S rDNA, while in M. rugosa only one pair of each of these sites was found. GISH did not produce signals useful to identify the presumed progenitors with 14 chromosomes. This result suggests alternative evolutionary pathways, such as the formation of tetraploids (2n = 32) and subsequent dysploidy events leading to the chromosome number reduction.     

Cytogenetic characterization and nuclear DNA content of three North African endemic Centaurea species

Three endemic Centaurea species from North Africa are investigated for the first time by chromomycin fluorochrome banding for GC-rich DNA distribution, fluorescence in situ hybridization for physical mapping of rRNA genes, and flow cytometry for genome-size assessment. Investigated species belong to three different sections and possess three basic chromosome numbers: C. tougourensis subsp. tougourensis 2n = 4x = 36 (x = 9), C. musimonum 2n = 2x = 20 (x = 10), and C. maroccana 2n = 2x = 24 (x = 12). The number and distribution of chromomycin positive bands (CMA⁺) and 18S-5.8S-26S (35S) rDNA loci were different among investigated species and ranged from 6 to 80 chromomycin bands and from 2 to 6 35S rDNA loci. The three species have just one 5S rDNA locus at intercalary position on a separate chromosome pairs, except in the case of C. musimonum in which both rDNA loci were localized on the same chromosome. All rDNA loci were co-localized with CMA⁺ bands, except three 35S in C. musimonum. Genome size ranged from 2C = 1.66 to 2C = 2.86 pg in diploid species (C. musimonum and C. maroccana, respectively) and to 2C = 4.51 pg in tetraploid C. tougourensis subsp. tougourensis.     

Morphological,reproductive and karyological variability in <Emphasis Type="Italic">Allium oleraceum</Emphasis> in Lithuania

Morphological, reproductive and karyological variability were investigated in fifteen populations of Allium oleraceum transferred from natural populations in Lithuania to the field collection of medicinal and aromatic plants of the Institute of Botany of the Nature Research Centre in Vilnius. Nine populations were tetraploid (2n = 4x = 32), four pentaploid (2n = 5x = 40) and two consisted of both cytotypes. The greatest differences among the populations and between the ploidy levels were observed in stem height and mass of aerial bulbils per plant. The seed production was very low and did not differ significantly between the ploidy levels, while neither tetraploids nor pentaploids did produce any seed if insects were prevented from visiting their flowers. The means of the morphological characters were higher in pentaploids than in tetraploids. However, none of them provided the possibility of determining ploidy level without chromosome counting.     

Chromosome Localization of 5S and 45S Ribosomal DNA in the Genomes of Linum L. Species of the Section Linum (Syn. Protolinum and Adenolinum)

Fluorescence in situ hybridization (FISH) was for the first time used to study the chromosomal location of the 45S (18S–5.8S–26S) and 5S ribosomal genes in the genomes of five flax species of the section Linum (syn. Protolinum and Adenolinum). In L. usitatissimum L. (2n = 30), L. angustifolium Huds. (2n = 30), and L. bienne Mill. (2n = 30), a major hybridization site of 45S rDNA was observed in the pericentric region of a large metacentric chromosome. A polymorphic minor locus of 45S rDNA was found on one of the small chromosomes. Sites of 5S rDNA were colocalized with those of 45S rDNA, but direct correlation between signal intensities from the 45S and 5S rDNA sites was observed only in some cases. Other 5S rDNA sites mapped to two chromosomes in these flax species. In L. grandiflorum Desf. (2n = 16) and L. austriacum L. (2n = 18), large regions of 45S and 5S rDNA were similarly located on a pair of homologous satellite-bearing chromosomes. An additional large polymorphic site of 45S and 5S rDNA was found in the proximal region of one arm of a small chromosome in the L. usitatissimum, L. angustifolium, and L. bienne karyotypes. The other arm of this chromosome contained a large 5S rDNA cluster. A similar location of the ribosomal genes in the pericentric region of the pair of satellite-bearing metacentrics confirmed the close relationships of the species examined. The difference in chromosomal location of the ribosomal genes between flax species with 2n = 30 and those with 2n = 16 or 18 testified to their assignment to different sections. The use of ribosomal genes as chromosome markers was assumed to be of importance for comparative genomic studies in cultivated flax, a valuable crop species of Russia, and in its wild relatives.     

Wheat Neocentromeres Found in F1 Triticale × Tritordeum Hybrids (AABBRH<Superscript>ch</Superscript>) After 5-Azacytidine Treatment

The DNA hypomethylation effect of 5-azacytine (5-AC; a cytosine analog) is widely known. This agent has been used for rRNA gene expression studies of Triticeae amphiploids and hybrids regarding rye rRNA genes suppression caused by the wheat nucleolar dominance phenomenon. However, this situation is reverted by 5-AC treatment which activates rye rRNA gene expression as it has been intensively observed in triticale. For nucleolar dominance studies, we produced F1 multigeneric hybrids (AABBRH^ch; 2n = 6x = 42) from crosses between the triticale cultivar ‘Corgo’ (AABBRR; 2n = 6x = 42) and the tritordeum cultivars HT9 and HT31 (AABBH^chH^ch; 2n = 6x = 42). The hybrid seeds were germinated in a low concentration of 5-AC (treatment) and in distilled water (nontreated control plants). Silver nitrate staining performed in one 5-AC-treated F1 hybrid revealed a reduced number of interphase cells with seven nucleoli, metaphases with eight Ag-NORs, and neocentromeres in the long arm of three wheat chromosomes. Nontreated hybrids presented six Ag-NORs per mitotic metaphase cell and a maximum of six nucleoli per interphase because of the 1R Ag-NOR suppression. No neocentromere was found in the control F1 hybrid plants. Both treated and nontreated seedlings were subsequently evaluated by fluorescent in situ hybridization performed with genomic and repetitive DNA probes to identify H^ch and rye genomes, to confirm Ag-NORs location, and to detect inactive rDNA loci. DAPI counterstaining was also helpful for the detection of neocentromeres in the long arm of three wheat chromosomes. This study allowed us to suggest that 5-AC treatment specifically induced wheat neocentromeres in the F1 multigeneric triticale × tritordeum hybrids.