Determination Of Chromosome Number Research Articles

The Chromosome Counts Database (CCDB).

For decades, plant biologists have been interested in the determination and documentation of chromosome numbers for extant taxa. This central cytological character has been used as an important phylogenetic marker and as an indicator for major genomic events such as polyploidy and dysploidy. Due to their significance and the relative ease by which chromosome numbers can be obtained, chromosome numbers have been extensively recorded across the plant kingdom and documented in a wide variety of resources. This makes the collection process a wearing task, often leading to partial data retrieval. In 2015, the Chromosome Counts Database (CCDB) was assembled, being an online unified community resource. This database compiles dozens of different chromosome counts sources, of which a significant portion had been unavailable before in a digitized, searchable format. The vast amount of data assembled in CCDB has already enabled a large number of analyses to examine the evolution of different plant hierarchies, as well as the application of various follow-up analyses, such as ploidy-level inference using chromEvol. CCDB ( http://ccdb.tau.ac.il/ ) encourages data sharing among the botanical community and is expected to continue expanding as additional chromosome numbers are recorded.

Documented chromosome number determinations in some Physaria species (Brassicaceae)

The determination of the chromosome numbers of species of Physaria (Brassicaceae) are of interest as part of a breeding program to develop new industrial oilseeds and to further our knowledge of the genus in general. Polyploid plants could be useful in generating novel and improved breeding populations. We report 47 meiotic chromosome number determinations for 19 species of Physaria. The first chromosome number is reported for P. kingii subsp. kaibabensis as 2n = 5 II, and the first report of polyploidy in Physaria kingii susbsp. latifolia with a tetraploid determination of 2n = 10 II. A determination of 2n = 23 II is reported for Physaria mendocina, which was previously reported as 2n = ca. 50, which results in a new base number for the genus of x = 23.

Segregation of the univalent X chromosome in the wide-footed treehopper Enchenopa latipes (Say 1824)

In metaphase I, autosomal bivalents align on the metaphase plate, while naturally-occurring univalent sex chromosomes can display a number of different behaviours depending on cellular conditions. Here we describe the behaviour of the univalent X chromosome in the wide-footed treehopper Enchenopa latipes (Say 1824). We confirm the chromosome number and sex determination method for this species, and that males possess a univalent X chromosome. We show that the univalent X chromosome forms a bipolar attachment to the spindle in metaphase I, and then segregates intact toward one spindle pole in late anaphase I (long after autosomes have initiated poleward movement). Movement of the univalent toward one pole is associated with loss of microtubule connections toward the opposite spindle pole.

Additional documented chromosome number determinations in Paysonia (Brassicaceae)

Thirteen meiotic chromosome number determinations are reported for seven species of Paysonia O’Kane & Al-Shehbaz (Brassicaceae). Our counts are in agreement with previous published numbers and we make new chromosome number reports for five counties.

Determination of Genetic Distance, Genome Size and Chromosome Numbers to Support Breeding in Ornamental Lavandula Species

Knowledge of phylogenetic relatedness and cytogenetic characteristics can facilitate breeding programs and interspecific hybridization in ornamentals. In this study genetic relationships, genome sizes and chromosome numbers were determined in a collection of 82 lavender genotypes, including 15 hybrids. Amplified Fragment Length Polymorphism (AFLP) marker analysis revealed 5 clusters, corresponding to the sections Lavandula, Stoechas, Dentatae, Pterostoechas and Subnudae. Genome sizes varied between 0.76 ± 0.02 pg 2C−1 and 4.80 ± 0.06 pg 2C−1 and chromosome numbers ranged from 2n = 22 to 2n = 100. Genome sizes of hybrids were intermediate to the progenitors genome sizes. All analyzed hybrid genotypes were characterized by even chromosome numbers, with 2n = 48 or 50. Using Principal Coordinate Analysis (PCoA) separate hybrid clusters were identified between the progenitor species clusters. Polyploidy and/or aneuploidy was observed in two hybrids genotypes: L. × intermedia ‘Heavenly Angel’ (2n = 100) and L. × heterophylla ‘Big Boy James’ (2n = 66). Results obtained in this study can be used to predict cross compatibility among different species, thus enabling targeted breeding towards the creation of new improved Lavandula cultivars.

Development and quality of pollen in Lachenalia cultivars with determination of genome size and chromosome number

The genus Lachenalia J. Jacq. ex Js. Murray (Asparagaceae) comprises 136 species endemic to South Africa and Namibia. These bulbous geophytes are considered to have excellent horticultural potential due to their morphological and genetic diversity, and thus have been chosen for the initiation of a breeding program to develop new cultivars that suitable for commercial use. From breeding perspective, studies on pollen viability and morphology are of great importance, since pollen quality represents an essential factor that influences crossbreeding processes. Therefore, to comprehensively characterize the pollen of selected Lachenalia cultivars, we conducted a multi-level analysis in which we investigated the processes of microsporogenesis and pollen grain development, as well as evaluated pollen morphology and viability. We also performed somatic chromosome counts and flow cytometry, thereby providing, for the first time, valuable cytogenetic data on the chromosome numbers and nuclear DNA contents of these cultivars. Morphologically, all the pollen grains were classified as medium-sized, subspheroidal in shape, and monosulcate with a single elongated aperture. Their exine ornamentation was categorized as reticulate with a heterobrochate reticulum. The pollen viability analysis revealed one of the cultivars to be nearly completely sterile, however, we were able to explain this phenomenon and found that this cultivar was affected by meiotic abnormalities associated with its triploid nature. Based on the obtained results, three of the studied cultivars may be considered as suitable pollinizers. From the perspective of applied research, the findings of our research offer important information for selecting appropriate donors for cross-pollination in the development of new Lachenalia cultivars.

Identification of putative origin of Iris pumila L. karyotype

Aim. The study was aimed at cytogenetic analysis of Iris pumila, I. attica, and I. pseudopumila, comparative study of the karyotypes of these species, as well as identification of putative origin of I. pumila karyotype. Methods. Cytogenetic analysis of root apical meristem, determination of chromosome number in mitotic metaphase plates, anaphase analysis. Results. The chromosome numbers observed were 2n=32 for I. pumila plants from different localities in Ukraine and 2n=16 for I. attica and I. pseudopumila plants from Greece and Italy, respectively. Some of the plants were mixoploids, the smallest proportion of mixoploids was in I. pseudopumila (10.9%) and the largest in I.pumila from all studied populations (60-80%). Anaphase analysis showed the presence of chromosomal aberrations in 2.6% of cells in roots of I. pseudopumila seedlings. The highest level of structural chromosomal aberrations (9.2%) was found in root apical meristem cells of I. pumila seedlings. Conclusions. The chromosome number was established as 2n=32 for I.pumila plants and 2n=16 for I. attica and I. pseudopumila plants. The high level of mixoploidy (60–80% of mixoploid plants) and anaphase chromosomal aberrations (up to 9.2%) was found in apical meristem of I. pumila seedlings. The amphidipiloid nature of I. pumila was established; the karyotype of the species could be formed as a result of a combination of chromosome sets from hypothetical ancestral species I. attica and I. pseudopumila.
 Keywords: Iris pumila L., Iris attica Boiss. & Heldr., Iris pseudopumila Tineo, chromosome number, amphidiploid, mixoploidy.

Research on native ornamental species from Mexico

Mexico is known as a megadiverse country, and its flora includes about 25,000 described species of vascular plants. Many of these have been bred to be used as ornamentals, examples of which include the genera Ageratum, Begonia, Cosmos, Dahlia, Euphorbia, Helianthus, Tagetes, Tigridia, Polianthes and Zinnia, among many others. The number of plants already developed for ornamental purposes is relatively low compared with the great diversity found in Mexico. For this reason, at the Centro de Investigacion y Asistencia en Tecnologia y Diseno del Estado de Jalisco A.C., efforts are being directed to introduce new cultivars and species into culture to be utilized as ornamentals. Selections were made of suitable genera and species, some of which include geophytes, from the genera Bessera, Habranthus, Hymenocallis, Milla, Polianthes, Sprekelia and Zephyranthes, and some perennials such as Eustoma. Chromosome number determination has been performed for most of the species, revealing a polyploid complex in the genus Sprekelia, where the diploid chromosome number is 2n=2x=60, and triploid, tetraploid and pentaploid forms have been found. In the genus Polianthes, several species have been analysed, and all of them showed a bimodal karyotype, consisting of ten big chromosomes and 50 small ones (2n=2x=60). In Habranthus longifolius, the chromosome number ranged from 34 to 36, showing one, two or three B chromosomes. Hymenocallis howardii has 96 chromosomes. The genus Eustoma has a chromosome number of 2n=2x=72. In order to generate genetic variation, interspecific hybridization has been performed in the genus Polianthes and in the genus Eustoma, resulting in hundreds of hybrids, which are being selected for further breeding programmes. In this work, the species and breeding programmes are described.

Introduction into in vitro culture and cytogenetic analysis of Iris attica Boiss. & Heldr. and Iris pseudopumila Tineo plants

Aim. The work was aimed at the development of conditions for introduction into in vitro culture of two species of irises, Iris attica and I. pseudopumila to obtain aseptic seedlings with subsequent reintroduction into natural environment, as well as at cytogenetic analysis of the obtained plants. Methods. In vitro seed germination and seedling cultivation. Cytogenetic analysis of cells of root meristem, determination of chromosome number and morphology in mitotic metaphase plates, anaphase analysis. Results. The plants of I. attica and I. pseudopumila were introduced in vitro. Aseptic seedlings were obtained, which were actively growing on MS/2 medium without phytohormones. The experiments on the adaptation of the plants to greenhouse conditions revealed the high survival rate for both species. The chromosome number 2n = 16 was established for the obtained plants of both I. attica and I. pseudopumila. Mixoploidy was detected in root meristem of some of the plants, the incidence of which was 10.9 % for I. pseudopumila and 30.4 % for I. attica. The frequency of cells with chromosomal rearrangements revealed by anaphase analysis in root meristem of I. pseudopumila seedlings was 2.6 %; in I. attica plants, chromosome aberrations were not detected. Conclusions. The plants of I. attica and I. pseudopumila were introduced into in vitro culture, aseptic seedlings were obtained, which showed a high survival level when adapted to greenhouse conditions. Chromosome number 2n = 16 was established for the obtained plants of both species. The root apical meristems of the seedlings were found to be mixoploid, with the incidence of mixoploidy in I. attica identified as three times higher than in I. pseudopumila plants.Keywords: I. attica Boiss. & Heldr., I. pseudopumila Tineo, aseptic seedlings, mixoploidy, anaphase aberration.

Inheritance of powdery mildew resistance in Aurotica’s introgressive lines

Aim. Frequency of alien chromatin inheritance in hybrids from crosses of common wheat and introgressive lines determines whether transfer of alien chromatin controlling desirable trait into common wheat genome would be successful. The paper presents results of introgressive lines assessment for frequency of transfer of alien dominant trait of powdery mildew resistance to their progeny in the crossing with recurrent genotype Aurora, which was a recipient cultivar in the development of these lines. Methods. Artificial hybridization of introgressive lines with common wheat, visual assessment of cross components and hybrids F1 and F2 for powdery mildew resistance. Determination of chromosome numbers and chromosome configurations in meiosis M1 of F1 plants. Results. Among F2 plants, from the crossing of resistant to powdery mildew introgressive lines of Aurotica and susceptible cultivar Aurora excess of susceptible plants was observed. In order to explain distortion of ratio susceptible : resistant plants in comparison with expected for monogenic segregation, we propose the determined fact of absence in meiosis M1 of MPC of bivalent chromosome conjugation, which results in formation of aneuploid gametes and zygotes with reduced viability. As the third parameter, the one that can influence the mentioned ratio, we propose d parameter, which quantitatively expresses excess of gametes without alien chromatin controlling resistance to powdery mildew. Conclusion. Model of inheritance, which best explains experimental data of F2 plants segregation for resistant and susceptible if the trait is controlled by one dominant gene, takes into account the following conditions for calculation of probabilities of resistant or susceptible plant formation: all female and only euploid male gametes function, nullisomic zygotes are not viable, during meiosis elimination of meiosis products with alien chromatin occurs with parameter d = 0,11–0,12.Received 11.06.2018

Hybridization and polyploidization within the Chenopodium album aggregate analysed by means of cytological and molecular markers

Hybridization and polyploidization represent an important speciation mechanism in the diploid-polyploid complex of the Chenopodium album aggregate. In the present study we successfully reconstructed the evolutionary histories of the majority of Eurasian representatives of the C. album aggregate, resulting in the most comprehensive phylogenetic analysis of this taxonomically intricate group of species to date. We applied a combination of classical karyology for precise chromosome number determination, genomic in-situ hybridization for the determination of genomic composition, flow cytometry for the estimation of genome size and sequencing of plastid (cpDNA) and nuclear (ribosomal internal transcribed spacer – ITS and the introns of the FLOWERING LOCUS T LIKE genes – FTL) markers for a phylogenetic reconstruction and the identification of parental genomes in polyploid taxa. The FTL markers identified eight well supported evolutionary lineages. Five of them include at least one diploid species, and the remaining three comprise solely the subgenomes of polyploids that probably represent extinct or unknown diploid taxa. The existence of eight basic diploid lineages explains the origin of seven Eurasian polyploid groups and brings evidence of a nearly unlimited number of subgenomic combinations. The supposed promiscuity generated new species wherever different diploid lineages met each other and gave rise to tetraploid species or whenever they met other tetraploid species to produce hexaploid species throughout their evolutionary history. Finally, we unravelled a surprisingly simple scheme of polyploid species formation within the C. album aggregate. We determined seven groups of polyploid species differing in their origin in either Eurasia or Africa and convincingly demonstrated that (1) all Chenopodium polyploid species under study are of allopolyploid origin, (2) there are eight major monophyletic evolutionary lineages represented by extant or extinct/unknown diploid taxa, (3) those monophyletic lineages represent individual subgenomes, (4) hybridization among the lineages created seven subgenomic combinations of polyploid taxa, (5) taxa represented by particular subgenome combinations were further subjected to diversification, and (6) the majority of species are relatively young, not exceeding the age of the Quaternary period.

Karyotypic Analysis of four Species of Genus Blumea (Asteraceae) from Nepal

In this study chromosome number determination and karyotype analysis of four species of genus Blumea from the family asteraceae was carried out. The specimen plants were collected from central parts of Nepal, namely Blumea fistulosa (Roxb.) Kurz, Blumea lacera var.glandulosa (DC.) Hook, Blumea lacera (Buem f.) DC. and Blumea laciniata DC were observed. The chromosome number in somatic cells were recorded to be 2n= 22 in Blumea fistulosa; 2n= 32 in Blumea lacera var.glandulosa; 2n=18 in Blumea lacera and Blumea laciniata. The range of chromosome length found to be 0.6 to 1.6 µm in Blumea fistulosa, 0.6 to 1.6µm in Blumea lacera var.glandulosa, 0.6 to 1.7 µm in Blumea lacera and 0.8 to 1.6 µm in Blumea laciniata. Karyotype formula for Blumea fistulosa is M12+ sm10, for Blumea lacera var. glandulosa is M14+sm14+ st4, for Blumea lacera is M14+ st2 and for Blumea laciniata is M12+ sm6 in Blumea laciniata. In this investigation a pair of satellite chromosome found in only one species Blumea fistulosa at the end of shot arm of chromosome. Mainly three types of chromosomes observed in this study having centromere at middle point, at sub-median region and at sub-terminal region. Numerical and structural variation in chromosome are evolutionary significance. Similarity in size of chromosomes and karyomorphology indicates the homogeneity of the taxa within this tribe. Int. J. Appl. Sci. Biotechnol. Vol 6(2): 115-121

Segregation of the amphitelically attached univalent X chromosome in the spittlebug Philaenus spumarius.

In meiosis I, homologous chromosomes combine to form bivalents, which align on the metaphase plate. Homologous chromosomes then separate in anaphase I. Univalent sex chromosomes, on the other hand, are unable to segregate in the same way as homologous chromosomes of bivalents due to their lack of a homologous pairing partner in meiosis I. Here, we studied univalent segregation in a Hemipteran insect: the spittlebug Philaenus spumarius. We determined the chromosome number and sex determination mechanism in our population of P. spumarius and showed that, in male meiosis I, there is a univalent X chromosome. We discovered that the univalent X chromosome in primary spermatocytes forms an amphitelic attachment to the spindle and aligns on the metaphase plate with the autosomes. Interestingly, the X chromosome remains at spindle midzone long after the autosomes have separated. In late anaphase I, the X chromosome initiates movement towards one spindle pole. This movement appears to be correlated with a loss of microtubule connections between the kinetochore of one chromatid and its associated spindle pole.

Characterization of interspecific hybrids of Petunia and Calibrachoa by multiplex PCR, DNA content, and chromosome number

ABSTRACTPetunia and Calibrachoa are ornamental plants of worldwide economic importance. Commercially, it is useful to combine desirable characteristics of Calibrachoa, including the large diversity of flower colors, with the pH tolerance and vigorous growth of Petunia. For investigation of interspecific hybrids between Petunia and Calibrachoa we used four different introns with flanking exon areas, each from a different gene and with a different sequence for Petunia and Calibrachoa, as genus-specific markers for chromosomes in interspecific hybrids. PCR primers specific for Petunia and Calabrachoa were made from the determined sequences and tested on a range of presumed hybrids using multiplex PCR, which confirmed that the hybrids were derived from these two species. Flow cytometry demonstrated that the hybrids were triploid, and determination of chromosome numbers showed that two of the chromosome sets were from Calibrachoa, i.e. that the other parent, Petunia, was diploid. Similar methods can be used for molecular characterization of other new hybrids made between closely related species or cultivars.

First karyotype description and nuclear 2C value for Myrsine (Primulaceae): comparing three species

Cytogenetic studies in Primulaceae are mostly available for herbaceous species, and are focused on the chromosome number determination. An accurate karyotype characterization represents a starting point to know the morphometry and class of the chromosomes. Comparison among species within Myrsine, associating these data with the nuclear 2C value, can show changes that led the karyotype evolution. Here, we studied three Myrsine species [Myrsine coriacea (Swartz, 1788) Brown ex Roemer et Schultes, 1819, Myrsine umbellata Martius, 1841 and Myrsine parvifolia Candolle, 1841] that show different abilities to occupy the varied types of vegetation within the Brazilian Atlantic Forest. Cytogenetic characterization showed some individuals with 2n = 45 chromosomes for Myrsine parvifolia and Myrsine coriacea, with most individuals of the three species having 2n = 46. The first karyograms for Myrsine were assembled and presented morphologically identical and distinct chromosome pairs. In addition, differences in the mean 2C nuclear value and chromosome morphometry were found. Therefore, the first description of the Myrsine karyotype has been presented, as well as the nuclear 2C value. The procedures can be applied to other Myrsine species for future investigations in order to better understand its effects on the differential spatial occupation abilities shown by the species in Brazilian Atlantic Forest.

In Vivo Ploidy Determination of Arabidopsis thaliana Male and Female Gametophytes.

Organ- or tissue-specific ploidy level determination is often used for answering biological, molecular, genetic, or evolutionary questions in plant sciences. However, current techniques for ploidy determination either cannot provide information on single cell level, require destructive sample preparation, or are laborious and time-consuming. Here, we present a new approach developed in Arabidopsis thaliana, which is not only less labor intensive but also allows in vivo ploidy determination on single cell level. The technique is based on the incorporation of a transgenic construct, consisting of the centromere-specific protein CENH3 fused to the fluorescent reporter GFP that specifically labels centromeric regions and hence allows for an accurate visual determination of the cell's chromosome number. Moreover, by combining the construct with a gametophyte-specific promoter, the technique enables accurate chromosome quantification in all individual gametophytic cell types formed during micro- and mega-gametogenesis. As such, CENH3-based centromere visualization provides an easy and straightforward method to monitor meiotic cell division integrity, gametophytic chromosome dynamics, and reproductive ploidy stability.

Comparison of different cytogenetic methods and tissue suitability for the study of chromosomes in Cimex lectularius (Heteroptera, Cimicidae).

In the article we summarize the most common recent cytogenetic methods used in analysis of karyotypes in Heteroptera. We seek to show the pros and cons of the spreading method compared with the traditional squashing method. We discuss the suitability of gonad, midgut and embryo tissue in Cimex lectularius Linnaeus, 1758 chromosome research and production of figures of whole mitosis and meiosis, using the spreading method.The hotplate spreading technique has many advantages in comparison with the squashing technique. Chromosomal slides prepared from the testes tissue gave the best results, tissues of eggs and midgut epithelium are not suitable. Metaphase II is the only division phase in which sex chromosomes can be clearly distinguished. Chromosome number determination is easy during metaphase I and metaphase II. Spreading of gonad tissue is a suitable method for the cytogenetic analysis of holokinetic chromosomes of Cimex lectularius.

Genome size, chromosome number, and rDNA organisation in Algerian populations of <em>Artemisia herba-alba</em> (Asteraceae), a basic plant for animal feeding facing overgrazing erosion

Artemisia herba-alba is a largely-distributed and often landscape-dominating taxon in arid areas of the Mediterranean and Irano-Turanian regions. In Algeria, in 2010 its communities covered 10% of the steppe territory, but its populations have been subjected to overgrazing. A karyological study based on 22 populations together with a cytogenetic characterisation of this species has been performed for the first time in Algerian materials, through genome size and chromosome number determination. Fluorescence in situ hybridisation (FISH) was also used to assess the rDNA loci number and distribution in the two ploidy levels detected. The studied accessions are diploid (2n = 2x = 18 chromosomes, 6 populations) or tetraploid (2n = 4x = 36 chromosomes, 15 populations). One population, occupying a more or less central geographic position among the studied area, presented both cytotypes. Genome size reflects well the two ploidy levels, with no evidence of downsizing with polyploidy. The karyotypes are rather symmetric (2A Stebbins’ class). FISH analyses detected four signals (2 loci) in diploid and eight signals (4 loci) in tetraploid cytotypes for both ribosomal DNA genes, which present an L-type (linked) organisation, i.e. with loci from both rDNA genes colocalised. The presence of two ploidy levels suggest a genomic dynamism and even a possible differentiation underlying the morphological uniformity and despite the dramatic decrease experienced by this plant in Algeria in terms of surface coverage.

Serendipities in medicine

Coincidences accompany our lives. This paper shows to which extent serendipity plays a role in important discoveries and developments in medicine. These include, among others, Mendel's laws, the determination of the human chromosome number, the discovery of DNA by Watson and Crick, the PAP test, or the discovery of X-rays and radioactivity. But also and especially in pharmacology, there are many examples of serendipity. Some go closely with serendipities in the discovery of bacteriology.

Recurrent Events of Polyploidy in Ficus carica L. (Moraceae)

Premise of research. The fig, Ficus carica (2n=26), is a widely cultivated tree of the Mediterranean region. Because of the scarcity of cytogenetic studies, intraspecific polyploidy in the fig has been overlooked until some years ago, when a few 2n=3x=39 genotypes were identified. This finding stimulated further explorations to learn more about the real extent of cytotypic diversity in this species and verify the presence of higher ploidy levels.Methodology. A total of 84 wild fig plants sampled from two different geographic areas was examined for the determination of chromosome numbers and karyotype analyses. The fluorescence in situ hybridization technique using rDNA sequences as probes was applied for a further characterization of the populations and polyploid genotypes discovered. The analysis of the nucleotide composition of 5S rDNA repeats was included in this study to acquire information on the intraspecific variability of F. carica and its genome constitution.Pivotal results. Chromosome counts led...