Genetic control of synapsis and recombination in Lolium amphidiploids.
Homologous bivalent formation in amphidiploids of Lolium is promoted during meiosis by diploidising genes carried by A-chromosomes, and by supernumerary B-chromosomes. The site and mode of action of these diploidising factors were investigated by comparing the relative frequencies of pairing configurations at meiotic prophase and metaphase I in several different hybrid genotypes. The results indicate that diploidising genes act predominantly by increasing the stringency of synapsis at early stages of meiotic prophase. By contrast, B-chromosomes appear to promote bivalent formation by ensuring that homoeologously paired chromosome segments within multivalents do not crossover. The results show that the additive effects of diploidising genes and B-chromosomes are to a certain extent separable in terms of their mode of action and timing during meiosis.
Institute of Biological Sciences, Sir George Stapledon Building, University of Wales, Aberystwyth, Dyfed, SY23 3DD, UK.
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G
Jenkins
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G
Jimenez
D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004171:Diploidy; D005838:Genotype; D008129:Lolium / Q000166:cytology / Q000235:genetics*; D008540:Meiosis; D008854:Microscopy, Electron; D011058:Pollen / Q000648:ultrastructure; D011995:Recombination, Genetic; D013573:Synaptonemal Complex / Q000502:physiology*