Polyploid polymorphism in Andropogon gerardii

Abstract

1987. Polyploid polymorphism in Andropogon gerardii. Genome, 29: 374-379. The relationship between nuclear DNA content and chromosome number was investigated in Andropogon gerardii. The distribution of cytotypes in a natural population of this grass was also examined. Nuclear DNA content was determined using flow cytometry rather than the traditional method of Feulgen microphotometry. Our results demonstrate the increased accuracy and speed of this new method in the detection and study of polyploidy. Nuclear DNA content is strongly correlated to chromosome number in Andropogon gerardii ( r = 0.97 1, P < 0.01 ). The natural population of this grass was found to consist of plants with 2N = 60 chromosomes (hexaploid cytotype) and 2N = 80 chromosomes (octoploid cytotype), in equal proportions. Intermediate cytotypes were lacking in the natural population, although three progeny plants grown in the greenhouse from wild-collected seed show intermediate values of nuclear DNA content and have 2N = 70 chromosomes. The two coexisting cytotypes are intermingled and show no difference in microhabitats. The absence of septaploids in the natural population suggests that the two cytotypes are probably reproductively isolated. . 1987. Polyploid polymorphism in Andropogon gerardii.Genome, 29 : 374-379. La relation entre la teneur en ADN nucleaire et le nombre de chromosomes a ete investiguke chez Andropogon gerardii. La distribution des cytotypes chez une population naturelle de cette graminee a aussi 6t6 examinee. La teneur en ADN nucliaire a 196 determinee par cytomCtrie en mouvement continu, plut6t que par la mkthode conventionnelle de microphotographie au Feulgen. Nos r6sultats montrent un accroissement de la precision de cette nouvelle mkthode et sa rapidit6 pour la detection et I'itude de la polyploidie. La teneur en ADN nucleaire est fortement corr6lCe au nombre de chromosomes chez Andropogon gerardii ( r = 0,97 1, P < 0,Ol). La population naturelle de cette graminie s'est avCr6e Etre constituee de plantes a 2N = 60 chromosomes (cytotype hexaploide) et a 2N = 80 chromosomes (cytotype octoploi'de), en proportions igales. Cette population naturelle ne comportait pas de cytotypes intermkdiaires, bien que trois lignies dirivees de graines de plantes sauvages, croissant en serres, ont present6 des valeurs intermediaires de teneur en ADN nucleaire et le nombre de chromosomes Ctait de 2N = 70. Les deux cytotypes coexistants sont entremglks et ne presentent aucune difference relativement a leurs microhabitats. L'absence de septaploides chez cette population naturelle suggkre que les deux cytotypes sont probablement isolCs sur le plan de la reproduction.Mots cle's : polyploi'die, teneurs en ADN, cytometrie en mouvement continu, polymorphisme.[Traduit par la revue]

Determination of ploidy level and nuclear DNA content in blueberry by flow cytometry

“…Chromosome number has often been found to be significantly correlated with nuclear DNA content (Verma and Rees 1974;Black and Beckman 1983). In this regard, DNA flow cytometry has been used to determine ploidy levels in plants (De Laat et al 1987;Keeler et al 1987;De Rocher et al 1990) or sex in dioecious species (Costich et al 1991) using nonflowering materials. Moreover, the estimation of nuclear DNA content is important for plant genome mapping as well as for developing strategies for plant gene isolation (Arumuganathan and Earle 1991a).…”

Cytometry and plant sciences: A personal retrospective

“…Now, flow cytometric methods are used routinely for all of these measurements and forms the major methodologic underpinning of the searchable database of plant nuclear DNA contents established at the Royal Botanical Gardens at Kew (http:// www.rbgkew.org.uk/cval/homepage.html). The ease of sampling means that large populations can be routinely analyzed, and we extended the method to the analysis of haploids in tissue culture (14), of natural variation in cytotype distributions (15), and for addressing issues in angiosperm evolution (16). Flow cytometry also can be used for quality control monitoring of the ploidy of commercial seeds and of different germ plasm accessions, for analysis of novel crosses and identification of wide-hybrids, and for monitoring euploidy in plants emerging from protoplast fusion, tissue culture, and genetic engineering procedures; for a complete discussion, see Galbraith et al (17).…”

Population biology of intraspecific polyploidy in grasses

“…Variation in ploidy level occurs within many grass species (Federov, 1974;Lewis, 1980;Keeler & Kwankin, 1989; Table 7.2). Of the grass species listed in the floras of the Great Plains (Sutherland, 1986) and California (Hickman, 1993) about 21'% of the species were reported to have intraspecific polyploidy (Table 7.3).…”

“…In Dactylis glomerata there is sufficient data to suggest that patterns are deterministic not random (Stebbins & Zohary, 1959;Lumaret et al, 1987;Roy & Lumaret, 1987;Bretagnolle & Thompson, 1996), while for Andropogon gerardii, the lack of match between patterns at different scales (Keeler et al, 1987;Keeler, 1990Keeler, , 1992 could reasonably result from stochastic effects.…”

“…For Daetylis, levels of mixing vary greatly across its range (Lumaret, 1988b). Andropogon gerardii is mainly hexaploid in the eastern part of its extensive range, but the populations in the west have roughly equal frequencies of 60 and 90 chromosome plants, thoroughly intermingled (Keeler et al, 1987;Keeler, 1990, 1992. Mixing of the cytotypes of Anthoxanthum odoratum has been enhanced by human activities (Hedberg, 1967).…”