8 research outputs found
Ploidía en 39 entradas y variación del diámetro de grano de polen en 30 entradas de Ipomoea trifida (Kunth) g. Don. (Convolvulaceae) del banco de germoplasma del Centro Internacional de la Papa
El nivel de ploidía y su relación con el diámetro de grano de polen fueron
analizados en entradas de Ipomoea trifida, procedentes de Colombia, Cuba,
Guatemala, México, Nicaragua, y Venezuela del Banco de Germoplasma del
Centro Internacional de la Papa. En 39 entradas se determinó el nivel de ploidía
mediante el conteo de cromosomas en meristemo apical de raíz. En 30 de estas
entradas se estudió la relación del diámetro de polen con el nivel de ploidía,
usándose controles diploide, tetraploide y hexaploide. Se evaluó también la
producción de polen gigante y la viabilidad del polen comparados con los
controles diploide y tetraploide. Las 39 entradas evaluadas por conteo de
cromosomas fueron diploides con 2n=2x=30 cromosomas. Mediante un análisis
de varianza de factores anidados y prueba de Tukey, con un nivel de
significación del 0.05, se determinó que sólo en 16 entradas existía homogenidad
del diámetro de polen en cada individuo de cada una de las entradas. Lo mismo
ocurrió con los controles diploides y tetraploides. Al comparar las dieciséis
entradas con los controles diploide, tetraploide y hexaploides se encontró que
existe correlación (r=0.92) del diámetro de polen con el nivel de ploidía. La
viabilidad fue cercana al 100% en la mayoría de los individuos. Solamente se en
siete entradas se encontró producción de polen gigante entre 0.04% y 2.37% por
individuo. El nivel de ploidía presenta correlación con el diámetro de polen pero
no puede ser usado como determinante para deducir éste. Ipomoea trifida
presentó baja producción de polen gigante en las condiciones evaluadas
Two possible scenarios about the origins of <i>Ipomoea batatas.</i>
<p>a) Scenario A which represents according to us, the most parsimonious scenario explaining the clear-cut phylogeographical pattern inferred from both nuclear and chloroplast data: 1) Multiple independent events of autopolypoidy within several polymorphic and pre-differentiated wild populations (phylogeographical differentiation), and then 2) multi-local domestication within each polyploid population, followed by 3) gene flow between the two cultivated genepools and between cultivated and wild forms. b) Scenario B: 1) Hybridization between differentiated conspecific wild populations (in contact because of potential climate-induced or human-induced range shift) and polyploidization, followed by 2) the domestication of these polyploids forms and then 3) patterns of post-domestication human expansion may have been responsible for the clear-cut phylogeographical pattern found within cultivated <i>I. batatas</i> in tropical America. Finally, 4) Gene flow between the two cultivated genepools and between cultivated and wild forms may also have occurred.</p
Taxa boundaries as accessed with DAPC analysis for nuclear SSR data.
<p>Diagram representing the proportion of membership probabilities in nuclear five clusters (K1, K2, K3, K4 and K5) as determined by the DAPC analysis. Each individual is represented as a vertical bar, with colours corresponding to membership probabilities to the five clusters.</p
Genetic diversity of the four geographically well-sampled taxa as revealed by nuclear SSRs.
<p>Values for the number of alleles (<i>NA</i>), its rarefied value over 25 individuals (1000 resamplings; <i>Ar</i>) and the observed and expected heterozygosities <i>Ho</i> and <i>He</i>, are provided both per locus and as mean values averaged over all loci. <i>D</i> corresponds to the intra-taxon mean Lynch distance between genotypes.</p
Contingency table comparing cpDNA haplotype “lineages” with DAPC clusters among the different taxa <i>I. batatas</i>, <i>I. trifida</i>, <i>I. triloba</i>, <i>Ipomoea</i> sp. (including <i>I. tabascana</i>).
<p><i>I. trifida</i> haplotypes correspond to hap2, 5, 9, 10, 14, 15, 16, 17 and <i>I. triloba</i> haplotypes to hap3, 8 and 18.</p
Sampling geographical distribution.
<p>Location of <i>I. triloba</i>, <i>I. trifida</i>, <i>I. batatas</i> and polyploid <i>Ipomoea</i> sp. accessions used in the present study and current taxon distribution ranges, as determined from GBIF records (<a href="http://data.gbif.org/species/" target="_blank">http://data.gbif.org/species/</a>) are provided. Accessions with no geographical information are not shown; details on sampling are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062707#pone.0062707.s005" target="_blank">Tables S1</a>.</p
Genetic relationships of <i>I. batatas</i>, five wild relatives and <i>Ipomoea</i> sp. accessions based on chloroplast DNA analyses.
<p>Statistical Parsimony Network of rpl32-trnL(UAG) haplotypes. Circle size is proportional to the number of individuals per haplotype. Substitutions and inversions are represented using full lines and indels are displayed using broken lines. Intermediate, unsampled haplotypes appear as dots. The posterior probability of two nodes, as obtained through a Bayesian tree reconstruction (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062707#pone.0062707.s001" target="_blank">Figure S1</a>), is reported in italics. The ploidy level of <i>Ipomoea</i> sp. accessions is indicated.</p