A new method for estimating karyotype asymmetry
TL;DR: Two numerical parameters are used to estimate the karyotype asymmetry in twenty-two taxa of the tribe Aveneae (Gramineae) from the Iberian Peninsula and Baleares and when karyograms or idiograms are available.
Abstract: Summary Two numerical parameters are used to estimate the karyotype asymmetry in twenty-two taxa of the tribe Aveneae (Gramineae) from the Iberian Peninsula and Baleares. The new method is useful when there are only slight differences in karyotype asymmetry and when karyograms or idiograms are available.
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TL;DR: The investigation of seven different methods of evaluating karyotype asymmetry reveals that the intervals used by Stebbins to separate the different types of karyotypes are very broad and only one quantitative parameter, the A2 index, correctly describes the variation in chromosome length in a complement.
Abstract: In literature seven different methods of evaluating karyotype asymmetry – the TF%, the As K%, Stebbins' classification, the Rec and the Syi, the A1 and the A2, the DI, and the A – are used for the elucidation of phylogenetic relationships and taxonomic treatments within a particular group or taxon The investigation of these seven methods reveals that the intervals used by Stebbins to separate the different types of karyotype asymmetry are very broad and only one quantitative parameter, the A2 index, correctly describes the variation in chromosome length in a complement A new asymmetry index (AI) is proposed to measure karyotype asymmetry and a new parameter, the CVCI, is offered, that precisely assesses the relative variation in centromere position in a complement The AI index, the CVCI and the CVCL (=A2 × 100) have the potential to display even minor karyotypic variations Thus, these three indices together increase the precision of results in comparison with other existing methods All this has important consequences as regards the interpretation of the results of karyological studies
303 citations
TL;DR: This work addresses a critical review of the methods so far proposed for estimation of karyotype asymmetry, using both artificial and real chromosome datasets, and shows definitively what and how to measure to correctly infer karyotypes asymmetry.
Abstract: One of the most popular, cheap and widely used approaches in comparative cytogenetics – especially by botanists – is that concerning intrachromosomal and interchromosomal karyotype asymmetry. Currently, there is no clear indication of which method, among the many different ones reported in literature, is the most adequate to infer karyotype asymmetry (especially intrachromosomal), above all in view of the criticisms recently moved to the most recent proposal published. This work addresses a critical review of the methods so far proposed for estimation of karyotype asymmetry, using both artificial and real chromosome datasets. It is shown once again how the concept karyotype of asymmetry is composed by two kinds of estimation: interchromosomal and intrachromosomal asymmetries. For the first one, the use of Coefficient of Variation of Chromosome Length, a powerful statistical parameter, is here confirmed. For the second one, the most appropriate parameter is the new Mean Centromeric Asymmetry, where Centromeric Asymmetry for each chromosome in a complement is easily obtained by calculating the difference of relative lengths of long arm and short arm. The Coefficient of Variation of Centromeric Index, strongly criticized in recent literature, is an additional karyological parameter, not properly connected with karyotype asymmetry. This shows definitively what and how to measure to correctly infer karyotype asymmetry, by proposing to couple two already known parameters in a new way. Hopefully, it will be the basic future reference for all those scientists dealing with cytotaxonomy.
188 citations
TL;DR: Overall, the large-scale analyses of karyotype features within a well-supported phylogenetic framework enabled the most likely patterns of chromosome evolution in Liliaceae to be reconstructed, highlighting diverse modes of kARYotype evolution, even within this comparatively small monocot family.
172 citations
TL;DR: It is confirmed that Arachis ipaensis was the most probable B genome donor for A. hypogaea, and a group of other closely related species are identified.
Abstract: Arachis hypogaea is an allotetraploid species with low genetic variability. Its closest relatives, all of the genus Arachis, are important sources of alleles for peanut breeding. However, a better understanding of the genome constitution of the species and of the relationships among taxa is needed for the effective use of the secondary gene pool of Arachis. In the present work, we focused on all 11 non-A genome (or B genome sensu lato) species of Arachis recognized so far. Detailed karyotypes were developed by heterochromatin detection and mapping of the 5S and the 18S–25S rRNA using FISH. On the basis of outstanding differences observed in the karyotype structures, we propose segregating the non-A genome taxa into three genomes: B sensu stricto (s.s.), F and K. The B genome s.s. is deprived of centromeric heterochromatin and is homologous to one of the A. hypogaea complements. The other two genomes have centromeric bands on most of the chromosomes, but differ in the amount and distribution of heterochromatin. This organization is supported by previously published data on molecular markers, cross compatibility assays and bivalent formation at meiosis in interspecific hybrids. The geographic structure of the karyotype variability observed also reflects that each genome group may constitute lineages that have evolved through independent evolutionary pathways. In the present study, we confirmed that Arachis ipaensis was the most probable B genome donor for A. hypogaea, and we identified a group of other closely related species. The data provided here will facilitate the identification of the most suitable species for the development of prebreeding materials for further improvement of cultivated peanut.
108 citations
Cites methods from "A new method for estimating karyoty..."
...The intrachromosomal and interchromosomal asymmetry index was determined using the A1 and A2 indices (Romero Zarco 1986)....
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TL;DR: Phenetic distance and principal component analysis showed that in spite of the differences observed among entities, they can be grouped in clusters that coincide with the taxonomic sections established by F. K. Kupicha and with the life cycle of the species.
Abstract: The karyotypes of 10 species and one variety of South American Lathyrus were determined and compared with those obtained of five entities from the Northern Hemisphere. Although all the species have a chromosome number of 2n = 14, they could be differentiated by their karyotype formula and quantitative parameters of the karyotypes. Phenetic distance and principal component analysis showed that in spite of the differences observed among entities, they can be grouped in clusters that coincide with the taxonomic sections established by F. K. Kupicha and with the life cycle of the species. South American species form a homogeneous group and can be distinguished by the presence of a subtelocentric pair, which has a macrosatellite in the long arm, and the lack of a short metacentric pair characteristic of most species of the Northern Hemisphere. From an evolutionary point of view, variation in total chromosome length without major changes in the karyotype formula suggests that changes in the amounts of genomic DNA are proportional to the relative length of each chromosome arm and that species of Notolathyrus evolved in a concerted fashion. Variation in genome size, however, is congruent with morphological variation of some reproductive organs as well as with the life cycle and minimum generation time, as predicted by the nucleotype hypothesis.
98 citations
References
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01 Jan 1984
TL;DR: Se estudian cariológica, anatómica y taxonómicamente las especies de Avenu1a (Gramineae) de la Península Ibérica e Islas Baleares, donde this género tiene su más importante centro secundario de dispersión.
Abstract: espanolSe estudian cariologica, anatomica y taxonomicamente las especies de Avenula (Gramineae) de la Peninsula Iberica e Islas Baleares, donde este genero tiene su mas importan-te centro secundario de dispersion. Avenula presenta un conjunto de complejos poliploides de los que se estudian las relaciones entre los taxones y sus numeros cromosomicos. Se estudian cariolo-gicamente por primera vez ocho taxones, y se indican para otros cinco nuevos niveles de ploidia comprendidos entre 2x y 18x. En los niveles diploide, tetraploide y exaploide los cariotipos son bastante simetricos. La estructura anatomica de las hojas basales, asi como la morfologia de sus epidermis, muestran una estrecha relacion con la clasificacion del genero adoptada. Se reconocen para la Peninsula Iberica e Islas Baleares un total de 26 tazones pertenecientes a diez especies, incluyendo un hibrido interespecifico. Se describen como nuevos diez de dichos taxones y se propo-nen seis nuevas combinaciones. Se incluye una clave para la separacion de los tazones, y para cada uno de ellos se da el nombre correcto, sinonimias comprobadas, descripcion, tipo y distribucion geografica. EnglishA taxonomic revision of Avenula (Gramineae) from the Iberian Peninsula and the Balearic Islands is made, including caryology, anatomy and morphology of the studied taxa. Karyologically, Avenula represent a group of poliploid complexes. Eight taxa are studied karyolo-gically for the first time, and new ploidy levels, from 2x to 18x, are given for five taxa. The di-ploid, tetraploid and hexaploid plants show rather symmetric karyotypes. Anatomical data on structure and epiderms of basal leaves are provided. Twenty seven taxa are recognized, eleven of which are new, grouped into ten species. A key to the species is given, together with the correct narre, synonymy, description, type when traced, distribution and a list of selected localities for each recognized taxon.
31 citations
01 Dec 1985
TL;DR: Morphology, leaf Anatomy and Caryology of Arrhenatherum taxa (Gramineae) from Iberian Peninsula are studied and species delimitation and natural hybrids are discussed.
Abstract: espanolSe estudia la morfologia, anatomia foliar y cariologia de los taxones del genero Arrhenatherum Beauv. (Gramineae) de 1a Peninsula Iberica. Se reconocen seis taxones agrupados en dos especies. Se describe A. elatius subsp. baeticum Romero Zarco y se separan en A. album (Vahl) W.D.Clayton dos variedades, proponiendose una nueva combinacion, A. album var. erianthum (Boiss. e Reuter) Romero Zarco. Para cada taxon se indican sinonimia, distribucion y, cuando ha sido posible, tipificacion. Se discuten la delimitacion de las especies y los hibridos naturales. EnglishMorphology, leaf Anatomy and Caryology of Arrhenatherum taxa (Gramineae) from Iberian Peninsula are studied. Six taxa arranged in two species are recognized. A. elatius subsp. baeticum Romero Zarco is described, and two varieties are recognized in A. album (Vahl) W.D. Clayton, proposing a new combination, A. album var. erianthum (Boiss. E Reuter) Romero Zarco. Synonymy, distribution and, when posible, typification, are given far every taxa. Species delimitation and natural hybrids are discussed.
20 citations
01 Jan 1985
TL;DR: Cariology, foliar anatomy and taxonomy of the species of Pseudarrhenatherum Rouy (Gramineae) from the Iberian Peninsula have been studied which provide additional evidence for the separation of this genus within the tribe Aveneae Nees.
Abstract: espanolSe estudia la Cariologia, Anatomia foliar y Taxonomia de dos especies del genero Pseudarrhenatherum Rouy (P. longifolium y P. pallens). Se aportan nuevas pruebas para la delimitacion taxonomica del genero dentro de la tribu Avenae Nees y para la separacion de sus especies. Para cada una de ellas se indica sinonimia, descripcion y distribucion EnglishCariology, foliar anatomy and taxonomy of the species of Pseudarrhenatherum Rouy (Gramineae) from the Iberian Peninsula (P. longifolium and P. pallens) have been studied which provide additional evidence for the separation of this genus within the tribe Aveneae Nees, as well as for the delimitation of both species. For each species, the correct name, synonymy, description and distribution are provided.
12 citations