Genome size variation and morphological differentiation within Ranunculus parnassifolius group (Ranunculaceae) from calcareous screes in the Northwest of Spain (original) (raw)
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Annals of Botany, 2006
Background and Aims Intraspecific genome size variability of Festuca pallens occurring on relict rocky steppes in Central Europe was studied on two ploidy levels and three geographical scales: (1) local scale of 24 populations, (2) landscape scale of three transects in river canyons or hill systems, and (3) global scale of 160 samples covering the whole distribution area. Methods DAPI flow cytometry of homogeneously cultivated samples (>1 year), measured randomly with two internal standards, Lycopersicon esculentum and Pisum sativum. Differences in DNA content were confirmed (1) by the double peaks of simultaneously measured samples, (2) based on measurements carried out in different seasons, and (3) by additional measurements with propidium iodide. Key Results On a global scale, the relative DNA content ranged between 1Á170-fold in diploids and 1Á164-fold in tetraploids. A maximum difference of 1Á088-fold between the mean relative DNA content of nearby populations was found. In 16 of 24 populations significant variability was shown (P < 0Á001, 1Á121-fold as maximum). For both ploidy levels, the relative genome size had the same range and geographical pattern, correlated with geographical coordinates (P < 0Á01). Diploids with larger genomes occur on relict habitats (P < 0Á01), and in areas of periglacial steppes (20 000 years ago; P < 0Á02). In tetraploids, the relative DNA content differs among the three previously recognized geographical types (Alpine, Pannonian and Scabrifolia, P < 0Á001). Tetraploids have a relative DNA content smaller than twice that of the diploids (P < 0Á001). An influence of microhabitat on DNA content variation was not confirmed. Conclusions Genome size variability occurs over all spatial scales: intrapopulation, landscape and global. Correlation between geographical coordinates and palaeovegetation type, concomitant with diploids and tetraploids, and no influence of microhabitat were found. Genome size decreases in tetraploids. Lower CVs, and thus higher accuracy, resolution and reproducibility, favour DAPI measurements for the study of intraspecific genome size variability.
Plant DNA Flow Cytometry and Estimation of Nuclear Genome Size
Background DNA flow cytometry describes the use of flow cytometry for estimation of DNA quantity in cell nuclei. The method involves preparation of aqueous suspensions of intact nuclei whose DNA is stained using a DNA fluorochrome. The nuclei are classified according to their relative fluorescence intensity or DNA content. Because the sample preparation and analysis is convenient and rapid, DNA flow cytometry has become a popular method for ploidy screening, detection of mixoploidy and aneuploidy, cell cycle analysis, assessment of the degree of polysomaty, determination of reproductive pathway, and estimation of absolute DNA amount or genome size. While the former applications are relatively straightforward, estimation of absolute DNA amount requires special attention to possible errors in sample preparation and analysis.
Plant Science, 2013
Crop wild relatives constitute a broad pool of potentially useful genetic resources for plant breeders. The genus Beta L. (Amaranthaceae) is an important source of crops, primarily for sugar production. Until recently, species within Section Beta were mostly cytogenetically uniform, with diploidy being prevalent. Still, with the discovery of tetraploid individuals of the wild B. macrocarpa in the Canary Islands, a large-scale study was necessary to evaluate the cytogenetic diversity within the wild Beta. For that, genome size and ploidy level of B. vulgaris subsp. maritima and B. macrocarpa from 21 populations across Portugal mainland and islands, including all know populations of the later taxon, were estimated using propidium iodide flow cytometry. This work revealed a cytogenetically diverse scenario. The analyzed populations were mostly diploid, except for one population of B. vulgaris subsp. maritima that presented both diploid and tetraploid individuals, and for two populations of B. macrocarpa where two or three cytotypes (diploids, tetraploids and/or hexaploids) were found. The nuclear DNA content of diploid individuals was estimated as 1.44 ± 0.035 and 1.41 ± 0.027 pg/2C for B. vulgaris subsp. maritima and B. macrocarpa, respectively. Also, leaves of both species presented variable levels of endopolyploidy. The obtained results are discussed within the context of interspecific hybridization and cryptic diversity and constitute significant data for the conservation of these wild Beta crop relatives.
Determination of Ploidy Level and Nuclear DNA Content in Tunisian Populations of Atriplex halimus L
Genetic Resources and Crop Evolution, 2005
2C-values of nine species of the genus Drosera, and two monotypic genera Aldrovanda and Dionaea were estimated to provide an overview of the genome diversity and chromosome differentiation in the Droseraceae. The measured DNA contents of all species used in this study ranged over nine-fold from 2C=0.63 pg in D. burmannii to 5.67 pg in D. anglica. In the genus Drosera, even though the polyploid species were excluded, the difference of the 2C DNA contents among diploid species was still high, ranging 4.3-fold from 0.66 pg in D. spatulata to 2.85 pg in D. intermedia. In subgenus Drosera, especially the polyploidal group, two chromosome types were identified by means of their size; this therefore made it possible to discriminate two groups of the genomes: one group was of a smaller genome size (S genome group) consisting of a total of 10 small-sized chromosomes (x=10s), and the other group was of a larger genome size (M genome group) consisting of a total of 10 middle-sized chromosomes (x=10 m). The Cx-value of the S genome group was less than 0.4 pg (ca. 400 Mbp). On the other hand, the Cx-value of the M genome group showed a range of 1.3-1.5 pg (1270-1470 Mbp). Moreover, the 2C DNA content of the hexaploid species D. tokaiensis (2n=6x=20 m+40s, 2C= 3.57 pg), which originated from naturally occurring interspecific hybridization event between D. rotundifolia (2n=2x=20 m, 2C=2.73 pg) and the tetraploid D. spatulata (2n=4x=40s, 2C=1.38 pg), was less (86.9%) than the sum of their putative parental species.
American Journal of Botany, 2007
DNA ploidy levels were estimated using DAPI-flow cytometry of silica-dried specimens of the European mountain plant Senecio carniolicus (Asteraceae), covering its entire distribution area in the Eastern Alps (77 populations, 380 individuals) and the Carpathians (five populations, 22 individuals). A complex pattern of ploidy level variation (2x, 4x, 5x, 6x, and 7x cytotypes) was found in this species, which has been considered uniformly hexaploid. Hexaploids predominated in the Eastern Alps and was the only cytotype found in the Carpathians, while odd ploidy levels (5x, 7x) constituted a small fraction of the samples (,1.3%). Tetraploids occurred in two disjunct areas, which correspond with putative Pleistocene refugia for silicicolous alpine plants. Diploids occurred in large portions of the Alps but were absent from areas most extensively glaciated in the past. Intrapopulational cytotype mixture was detected in 22 populations-the majority involving diploids and hexaploids-with intermediate ploidy levels mostly lacking, suggesting limited gene flow and the evolution of reproductive isolation. Significant and reproducible intracytotype variation in nuclear DNA content was observed. Higher genome size in western diploids might be due to ancient introgression with the closely related S. incanus or to different evolutionary pathways in the geographically separated diploids.
Modern Phytomorphology, 2016
Aconitum in Europe is represented by ca. 10% of the total number of species and the Carpathian Mts. are the center of the genus variability in the subcontinent. We studied the chloroplast DNA intergenic spacer trnL(UAG)-rpl32-ndhF (cpDNA) variability of the Aconitum subgen. Aconitum in the Carpathians: diploids (2n=16, sect. Cammarum), tetraploids (2n=32, sect. Aconitum) and triploids (2n=24, nothosect. Acomarum). Altogether 25 Aconitum accessions representing the whole taxonomic variability of the subgenus were sequenced and subjected to phylogenetic analyses. Both parsimony, Bayesian and character network analyses showed the two distinct types of the cpDNA chloroplast, one typical of the diploid and the second of the tetraploid groups. Some specimens had identical cpDNA sequences (haplotypes) and scattered across the whole mountain arch. In the sect. Aconitum 9 specimens shared one haplotype, while in the sect. Camarum one haplotype represents 4 accessions and the second – 5 acces...
Canadian Journal of Botany, 2005
Hawthorns and medlars are closely related genera in Rosaceae subfamily Maloideae, whose taxonomy remains poorly understood. Gametophytic apomixis occurs in polyploids, and diploids are sexual out-crossers, so ploidy level is of great interest, but suitable material for chromosome counts is of limited availability each year. The promise of flow cytometry is that it permits rapid measurement of nuclear DNA amounts from most tissues, and ploidy level can be inferred if climatic and taxonomic differences do not interfere. Our DNA measurements cover most of the taxonomic series in Crataegus, adding cultivated and naturalized Eurasian plants to the many wild plants collected mainly from south-central Canada and the southeastern and northwestern United States. We found that some variation in DNA amount per genome copy distinguishes certain taxa, but ploidy-level estimates are at least as clear as the published chromosome counts, especially in the most common diploid-triploid-tetraploid range, and to the single published higher (hexaploid) chromosome count, we add evidence of pentaploids. By comparing ploidy evaluations to morphology, we hypothesize that both autopolyploidy and allopolyploidy contribute to the taxonomic complexity. We compared DNA amounts in Maloideae with those in Gillenia, a likely sister genus to the subfamily, which has a smaller chromosome number.
Determination of ploidy and nuclear DNA content in populations of Atriplex halimus (Chenopodiaceae)
Botanical Journal of the Linnean Society, 2005
Nuclear DNA contents were determined by flow cytometry for 20 populations of the perennial C 4 shrub Atriplex halimus L. (Chenopodiaceae) originating from the Mediterranean basin and Fuerteventura (Canary Islands). Two populations were also analysed for chromosome number: one (from Ibiza, Spain), with a 2C nuclear DNA content of 2.40 pg, was shown to be diploid (2 n = 2 x = 18), whilst the other (from Sicily, Italy), with 5.11 pg, was tetraploid (2 n = 2 x = 36). With respect to nuclear DNA content, two groups of populations were detected, diploids with 2.40-2.44 pg and tetraploids with 4.77-5.13 pg. The diploid populations were mainly from the western Mediterranean (Spain and France) and Fuerteventura, whereas tetraploids were generally, but not exclusively, from more arid areas in North Africa and the eastern Mediterranean. In general, the diploid and tetraploid populations corresponded to the subspecies halimus and schweinfurthii , respectively. For certain populations having morphologies intermediate between those considered typical of these two subspecies, nuclear DNA contents showed them to be tetraploid. There was significant variation in nuclear DNA content among the tetraploid populations, with greater values in the more easterly populations.