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  • 1970-1974  (2)
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  • 1
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Diploid populations of Aegilops mutica and Aegilops speltoides containing B chromosomes have been used as male parents in crosses with aneuploid genotypes of Triticum aestivum to investigate the effect of B chromosomes on meiotic homologous and homoeologous chromosome pairing. F1 hybrids of T. aestivum/Ae. mutica and T. aestivum/Ae. speltoides segregated into four classes with regard to the degree of meiotic chromosome pairing, irrespective of the presence of B chromosomes. The B chromosomes do not introduce factors altering the level of pairing other than that due to the natural allelic and gene variation occurring in the diploids. Similarly no reduction in pairing of homologous chromosomes was observed in genotypes in which pairs of homologues co-existed with B chromosomes. However, a significant drop in chiasma frequency was observed in F1 hybrids of T. aestivum × Ae. mutica with B chromosomes and T. aestivum × Ae. mutica nullisomic for wheat chromosome 5D with B chromosomes, in temperature regimes of 12° C. No asynapsis occurred in similar hybrids in the absence of Mutica B chromosomes at low temperatures. The low-temperature sensitive phase lies early in the pre-meiotic interphase. In this instance the Mutica B chromosomes are interacting with specific gene loci of the A chromosomes. Synaptic pairing has been observed between A and B chromosomes in Ae. mutica. A high frequency of pollen mother cells with twice the number of chromosomes was observed in hybrids in the presence of Mutica B chromosomes due to failure of spindle formation at the last pre-meiotic mitosis. Meiotic spindle irregularities occurred in hybrids containing Speltoides B chromosomes. Hybrids of Ae. speltoides + B's X Ae. mutica + B's displayed the mitotic and meiotic spindle abnormalities introduced by the presence of the B chromosomes of each parent.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Transfer of stem rust resistance from diploid wild einkorn, Triticum boeoticum, to susceptible Mindum and Spelmar, varieties of cultivated T. durum, was achieved by means of a triploid hybrid bridge and subsequent backcrossing to the tetraploid parent. Seedlings of the second hybrid generation segregated for resistance to race 14 of Puccinia graminis f.sp. tritici which was used as test race in this investigation. The F3 and F4 progenies included segregants which displayed seedling resistance also to races 17, 19, 21, 40, 53, 194, 222, 315 and 322. Since these were the same races which proved avirulent to the T. boeoticum donor but virulent to the T. durum recipients, it was concluded that the full pattern of resistance determined in the wild diploid parent of this cross was transferred to the tetraploid durum-like hybrid derivatives.
    Type of Medium: Electronic Resource
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