Karyotypic Characteristics and Genetic Relationships of Apricot Accessions from Different Ecological Groups

The present study aims to reveal the karyotypic characteristics and genetic relationships of apricot (Prunus armeniaca L.) accessions from different ecological groups. Fourteen, 9, and 30 accessions from the Central Asian ecological group, North China ecological group, and Dzhungar-Ili ecological group, respectively, were analyzed according to the conventional pressing plate method. The results showed that all the apricot accessions from the different ecological groups were diploid (2n = 2x = 16). The total haploid length of the chromosome set of the selected accessions ranged from 8.11 to 12.75 μm, which was a small chromosome, and no satellite chromosomes were detected. All accessions had different numbers of median-centromere chromosomes or sub-median-centromere chromosomes. The karyotypes of the selected accessions were classified as 1A or 2A. Principal component analysis revealed that the long-arm/short-arm ratio (0.968) and the karyotype symmetry index (−0.979) were the most valuable parameters, and cluster analysis revealed that the accessions from the Central Asian ecological group and Dzhungar-Ili ecological group clustered together. In terms of karyotypic characteristics, the accessions from the Dzhungar-Ili ecological group and Central Asian ecological group were closely related.

Reconstruction of evolutionary trajectories of coffee chromosomes

Background Polyploidization is a widespread phenomenon in plants, especially in angiosperms. Because of the rearrangement of chromosomes and the loss of genes, the number of plant chromosomes will reduce. Studies have shown that core dicotyledons are derived from ancestors with seven proto-chromosomes, which triplicated in a core-eudicot-common hexaploidization. Therefore, dicotyledon with different chromosome numbers have evolved on the basis of 21 chromosomes. On this basis, we selected grape as the intermediate reference species to infer the karyotype evolutionary process of coffee. Results We found that all the chromosome fusion forms in grape were end-end joining, and 7 (70.0%) chromosome fusion forms in coffee were end-end joining. In the process of grape forming 19 chromosomes, there were three chromosome fusions and one chromosome fission. In the process of coffee 11 chromosomes formation, 10 chromosome fusions occurred. During the process, we inferred that satellite chromosomes formed by telomeres from the same or different chromosomes were produced; and the lost of them resulted in chromosome number reduction Conclusions Notably, we found that the major fusion mode of chromosomes in coffee is end-end joining, which is well explained by telomere-centric model, shared by grape and possibly by many other eudicots. This is contrastively different from the observation of monocot plants like grasses, in which nested chromosome fusions often occurred. The present work will help to understand the structural and functional innovations of plant chromosomes.

Localización de satélites y cromosomas NOR para la interpretación del cariotipo de Sesbania virgata (Papilionoideae, Sesbanieae) de dos poblaciones americanas

<p><strong>Background</strong>: Cytogenetic studies in the genus <em>Sesbania</em> show lack of agreement among the researchers about the precise number and position of secondary constrictions and satellites as well as their relation to the organization of the nucleolus. The lack of this information makes it difficult to carry out reliable comparative cytogenetic studies and chromosome evolution in this genus.</p><p><strong>Questions</strong>: Where are the secondary constrictions and satellites located in the chromosomes of <em>Sesbania</em> <em>virgat</em>a? Do these regions actively participate in the nucleolar organization?</p><p><strong>Study species</strong>: <em>Sesbania virgate</em> (Cav.) Pers.</p><p><strong>Study site</strong>: Municipality of Tlacotalpan, Mexico and Province of Salta, Argentina.</p><p><strong>Methods</strong>: Surface spreading and air-drying technique was applied to obtain chromosomes in prometaphase and typical metaphase from radicular meristems.</p><p><strong>Results</strong>: Each population exhibited a different karyotype and only two secondary constrictions associated with microsatellites in the short arms of the smallest chromosome pair and not in long arms as was suggested by other authors. The inclusion of secondary constrictions and satellites in the nucleolus of cells in prometaphase allowed to corroborate their active participation in the formation of this one. This information was used to reevaluate the position of the nucleolar organizer regions "NOR´s".</p><strong>Conclusions</strong>: Our results agree with the predominant point of view on the location of the "NOR´s" in the short arms of plant species, particularly in legumes. In addition, given that the populations under study are geographically isolated, we suggest that an active process of speciation manifested in the two found cytotypes whose differences are attributed to changes in the proportion of arms of the satellite chromosomes is favored.

Karyological studies on eight species of Onobrychis genus in Turkey

This study used karyological techniques to determine the chromosome numbers and morphology of eight species of Onobrychis L. (O. caput-galli (L.) Lam, O. aequidentata (Sibth. & Sm.) d’ Urv, O. fallax Freyn & Sint. var. fallax, O. lasiostachya Boiss, O. viciifolia Scop., O. oxyodonta Boiss. subsp. armena (Bois. & Huet) Aktoklu, O. hypargyrea Boiss. and O. cappadocica Boiss.). The results of this study determined the chromosome numbers of O. cappadocica as 2n = 16; O. viciifolia as 2n = 28 and the other species as 2n = 14 The karyotypes of species consisted of median-centromeric (m) or submedian-centromeric (sm) chromosomes. However, O. oxyodonta Boiss. subsp. armena (Bois. & Huet) Aktoklu was found to have only the median-centromeric (m) chromosomes. According to the results of the present study, of the eight Onobrychis taxa, only O. hypargyrea has a pair of satellite chromosomes (sat-chromosome). Furthermore, this study detected karyotype asymmetry.

Chromosome evolution in wild oat grasses (Aveneae) revealed by molecular phylogeny

Karyotype structures revealed by in situ hybridization with ribosomal and satellite DNAs and fluorochrome staining of AT- or GC-rich regions are reported for 23 diploid to tetraploid taxa of Aveneae genera Arrhenatherum , Avena , Helictotrichon , and Pseudarrhenatherum . Chromosomal features are compared with a molecular phylogeny generated on nuclear ribosomal (ITS, 5S) and chloroplast (matK) DNA sequences. Ancestral chromosomal character states are (1) two satellite chromosomes per set of x = 7, (2) 5S rDNA localized in nonsatellite chromosomes, (3) large chromosomes with (4) rather equal lengths of their respective chromosome arms, (5) sets with strong variance of chromosome lengths, (6) absence or small amounts of heterochromatin, and (7) absence or no detectable amplification of the satellite DNAs tested. Overall, most karyotype characteristics are species specific, but common patterns were found for the species of two large subgenera of Helictotrichon. Pseudarrhenatherum, although nested in the molecular phylogeny within Helictotrichon subgenus Helictotrichon, deviates strongly in karyotype characters such as Arrhenatherum as sister of Avena. The karyotype of Helictotrichon jahandiezii , sister to the clade of Helictotrichon subgenera Helictotrichon, Avena, and Arrhenatherum, strongly resembles that of Avena macrostachya . Karyotype features suggest that perennial A. macrostachya and H. jahandiezii are close to the C-genome species of annual Avena, whereas the Avena A genome resembles that of Arrhenatherum.

New cytogenetic information on Allium iranicum (Alliaceae) from Iran

Karyotype analysis and chromosome behaviour in tetraploid Allium iranicum is reported. The somatic karyotype 2n = 32, consists of 12 pairs of metacentric chromosomes, two pairs of submetacentric chromosomes and two pairs of submetacentric satellite chromosomes. Chromosome complement follows two sets of 16 pairs of homologous chromosomes. A detailed analysis of Pachytene, Diplotene and Metaphase I of meiosis in pollen mother cells in this taxon showed that the most common chromosome configurations were bivalents at all subphases mentioned. It is concluded that A. iranicum is most likely a natural allotetraploid and certainly differs from related species A. ampeloprasum, A. commutatum and A. porrum.

A CYTOGENETIC STUDY IN ALLIUM FISTULOSUM, A. CEPA, THEIR F1 HYBRID, AND BACKCROSS PROGENY

Cytogenetic studies were performed on Allium fistulosum, A. cepa. their F1 hybrid, and ten backcross (BC1) progenies [(A. fistulosum × A. cepa) × (A. cepa) 1. In meiosis the F1 hybrid showed 41 percent hetercmorphic bivalent pairing with 10.6 +. 1.8 `chiasmata per cell. Meiocytes were observed with one, two and three bridges and fragments, indicating at least three paracentric inversions. Multivalent associations indicate at least two translocations, one involving the satellite chromosome. The percentage of bivalent pairing, bridges and fragments, and multivalent associations varied in BC1 progenies. The F1 hybrid and all of the BC1 plants were either sterile or had very little seed set. The satellite chromosomes used as cytological markers showed variation in nucleolus position, degree of attachment and number.

Heterochromatin diversity and chromosome morphology in wheats analyzed by the HKG banding technique

Chromosome banding patterns in diploid, tetraploid, and hexaploid wheats were clearly revealed and compared by the HCl–KOH–Giemsa banding technique. Heterochromatin diversity of chromosomes 4A, 4B, 5B, and satellite chromosomes IB and 6B was shown at the centromeric, pericentric, telomeric, interstitial, and satellite regions. Quantitative comparisons were made of the amount of heterochromatin in chromosomes 4A, 4B, and 5B and among genomes of 'Chinese Spring' (Triticum aestivum). Genome relationships were evaluated in the extant diploid and polyploid wheat taxa. Modifications of the banding technique by hypotonic solution and water treatments and by changing air-drying time of slides influenced centromeric, interstitial, and nucleolar organizer region banding patterns, greatly increased the volume of chromosomes, produced different banding patterns, and significantly changed the nuclear morphologies.Key words: HKG-banding, diversity, chromosomes, genome relationships, Triticum.