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  • Avena sativa  (1)
  • sexual polyploidization  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 81 (1995), S. 1-6 
    ISSN: 1573-5060
    Keywords: Avena ; 2n gametes ; binucleate cell ; evolution ; sexual polyploidization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sexual polyploidization via the action of 2n gametes (gametes with the sporophytic chromosome number) has been identified as the most important evolutionary mode of polyploidization among plant genera. This study was conducted to determine whether 2n gametes are present in the tetraploid level of the genus Avena (2n=4×=28) Twenty tetraploid Avena lines, representing four species and one interspecific hybrid, were screened for pollen grain size in order to differentiate between n and 2n pollen. Avena vaviloviana (Malz.) Mordv. line PI 412767 was observed to contain large pollen grains at a 1.0% frequency. Cytogenetic analyses of pollen mother cells of PI 412767 revealed cells with double the normal chromosome number (i.e., 56 chromosomes at metaphase I and anaphase I). The mode of chromosome doubling was found to be failure of cell wall formation during the last mitotic division that preceded meiosis. The resulting binucleate cells underwent normal meiotic divisions and formed pollen grains with 28 chromosomes. Based on the formation and function of 2n gametes, three models involving diploid and tetraploid oat lines are proposed to describe possible evolutionary pathways for hexaploid oats. If stable synthetic hexaploid oat lines could be developed by utilizing 2n gametes from diploid and tetraploid oat species through bilateral sexual polyploidization, the resulting hexaploids could be used in breeding programs for transferring genes from diploids and tetraploids to cultivated hexaploids.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 83 (1995), S. 103-108 
    ISSN: 1573-5060
    Keywords: oat ; Avena sativa ; pollen grain size ; chromosome number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pollen grain size in many genera positively correlated with chromosome number. In this study, oat (Avena) pollen grain size was examined in diploids (2×=14, one species, for accessions), tetraploids (4×=28, five species, 20 accessions), hexaploids (6×=42, one species, eight cultivars), and in 10 octoploid (8×=56) accessions. Mature anthers ready to dehisce pollen were sampled from one to six plants per accession, and pollen grains were squeezed out of the anther with tweezers. Oat pollen grains are slightly elliptical, and the length of the major axis was found to be highly correlated with the minor axis width (r=0.94**). Pollen grain length, 39.3 μm for diploids, 41.3 μm for tetraploids, 47.0 μm for hexaploids, and 48.8 μm for octoploids, was positively correlated (r=0.86**) with ploidy level. No genomic or species effects appeared to influence this trait. Only tetraploidAvena vaviloviana accession PI 412767 produced two distinct class sizes of pollen grains, 99% normal (43.0 μm) and 1% large (52.7 μm).
    Type of Medium: Electronic Resource
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