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Autotetraploids of Vicia cracca show a higher allelic richness in natural populations and a higher seed set after artificial selfing than diploids.

Abstract

BACKGROUND AND AIMS

Despite the great importance of autopolyploidy in the evolution of angiosperms, relatively little attention has been devoted to autopolyploids in natural polyploid systems. Several hypotheses have been proposed to explain why autopolyploids are so common and successful, for example increased genetic diversity and heterozygosity and the transition towards selfing. However, case studies on patterns of genetic diversity and on mating systems in autopolyploids are scarce. In this study allozymes were employed to investigate the origin, population genetic diversity and mating system in the contact zone between diploid and assumed autotetraploid cytotypes of Vicia cracca in Central Europe.

METHODS

Four enzyme systems resolved in six putative loci were investigated in ten diploid, ten tetraploid and five mixed-ploidy populations. Genetic diversity and heterozygosity, partitioning of genetic diversity among populations and cytotypes, spatial genetic structure and fixed heterozygosity were analysed. These studies were supplemented by a pollination experiment and meiotic chromosome observation.

KEY RESULTS AND CONCLUSIONS

Weak evidence of fixed heterozygosity, a low proportion of unique alleles and genetic variation between cytotypes similar to the variation among populations within cytotypes supported the autopolyploid origin of tetraploids, although no multivalent formation was observed. Tetraploids possessed more alleles than diploids and showed higher observed zygotic heterozygosity than diploids, but the observed gametic heterozygosity was similar to the value observed in diploids and smaller than expected under panmixis. Values of the inbreeding coefficient and differentiation among populations (ρST) suggested that the breeding system in both cytotypes of V. cracca is mixed mating with prevailing outcrossing. The reduction in seed production of tetraploids after selfing was less than that in diploids. An absence of correlation between genetic and geographic distances and high differentiation among neighbouring tetraploid populations supports the secondary contact hypothesis with tetraploids of several independent origins in Central Europe. Nevertheless, the possibility of a recent in situ origin of tetraploids through a triploid bridge in some regions is also discussed.

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  • Authors+Show Affiliations

    ,

    Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, CZ-128 01 Prague, Czech Republic.

    , ,

    Source

    Annals of botany 113:1 2014 Jan pg 159-70

    MeSH

    Alleles
    Czech Republic
    Diploidy
    Europe
    Genetic Variation
    Genetics, Population
    Heterozygote
    Isoenzymes
    Pollination
    Seeds
    Self-Fertilization
    Slovakia
    Tetraploidy
    Vicia

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    24232383

    Citation

    TY - JOUR T1 - Autotetraploids of Vicia cracca show a higher allelic richness in natural populations and a higher seed set after artificial selfing than diploids. AU - Eliášová,Anežka, AU - Trávníček,Pavel, AU - Mandák,Bohumil, AU - Münzbergová,Zuzana, Y1 - 2013/11/14/ PY - 2013/11/14/aheadofprint PY - 2013/11/16/entrez PY - 2013/11/16/pubmed PY - 2014/8/26/medline PY - 2015/1/1/pmc-release KW - Autopolyploidy KW - F-statistics KW - Vicia cracca KW - allozymes KW - artificial pollination KW - fixed heterozygosity KW - genetic differentiation KW - genetic diversity KW - heterozygosity KW - inbreeding depression KW - mating system KW - meiotic chromosomes SP - 159 EP - 70 JF - Annals of botany JO - Ann. Bot. VL - 113 IS - 1 N2 - BACKGROUND AND AIMS: Despite the great importance of autopolyploidy in the evolution of angiosperms, relatively little attention has been devoted to autopolyploids in natural polyploid systems. Several hypotheses have been proposed to explain why autopolyploids are so common and successful, for example increased genetic diversity and heterozygosity and the transition towards selfing. However, case studies on patterns of genetic diversity and on mating systems in autopolyploids are scarce. In this study allozymes were employed to investigate the origin, population genetic diversity and mating system in the contact zone between diploid and assumed autotetraploid cytotypes of Vicia cracca in Central Europe. METHODS: Four enzyme systems resolved in six putative loci were investigated in ten diploid, ten tetraploid and five mixed-ploidy populations. Genetic diversity and heterozygosity, partitioning of genetic diversity among populations and cytotypes, spatial genetic structure and fixed heterozygosity were analysed. These studies were supplemented by a pollination experiment and meiotic chromosome observation. KEY RESULTS AND CONCLUSIONS: Weak evidence of fixed heterozygosity, a low proportion of unique alleles and genetic variation between cytotypes similar to the variation among populations within cytotypes supported the autopolyploid origin of tetraploids, although no multivalent formation was observed. Tetraploids possessed more alleles than diploids and showed higher observed zygotic heterozygosity than diploids, but the observed gametic heterozygosity was similar to the value observed in diploids and smaller than expected under panmixis. Values of the inbreeding coefficient and differentiation among populations (ρST) suggested that the breeding system in both cytotypes of V. cracca is mixed mating with prevailing outcrossing. The reduction in seed production of tetraploids after selfing was less than that in diploids. An absence of correlation between genetic and geographic distances and high differentiation among neighbouring tetraploid populations supports the secondary contact hypothesis with tetraploids of several independent origins in Central Europe. Nevertheless, the possibility of a recent in situ origin of tetraploids through a triploid bridge in some regions is also discussed. SN - 1095-8290 UR - https://www.unboundmedicine.com/medline/citation/24232383/Autotetraploids_of_Vicia_cracca_show_a_higher_allelic_richness_in_natural_populations_and_a_higher_seed_set_after_artificial_selfing_than_diploids_ L2 - http://aob.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=24232383 ER -