Department of Agronomy, University of Wisconsin-Madison, 1575 Linden Drive, Madison, Wisconsin 53711 USA.
Am J Bot. 2004 Feb;91(2):174-83. doi: 10.3732/ajb.91.2.174.
Variation that arises in generations immediately following polyploidization may be important for the establishment, adaptation, and persistence of new polyploid species. We previously showed divergence for flowering time among lines from a resynthesized Brassica napus allopolyploid lineage derived from a cross of diploid B. rapa and B. oleracea. In this study, we more fully assess phenotypic differentiation of lines from the previously studied lineage and of lines derived from an additional resynthesized B. napus lineage. Nine polyploid lines and their diploid parents were grown under four growth conditions and measured for eight life-history traits. Polyploid lines within a lineage were expected to be genetically identical because they were derived from individual, chromosome-doubled amphihaploid plants. However, significant differences were found among lines within lineages for every phenotypic trait measured and in response to different growth conditions (genotype by environment interactions). When phenotypes of each polyploid line for each trait in each environment were compared with their diploid progenitors, approximately 30% were like one or the other parent, 50% were intermediate, and 20% were transgressive. Our results demonstrate extensive de novo variation in new polyploid lineages. Such changes could contribute to the evolutionary potential in naturally occurring polyploids.
在多倍体形成后立即出现的变异可能对新的多倍体物种的建立、适应和存续很重要。我们之前曾展示过由二倍体甘蓝型油菜和白菜杂交产生的拟南芥同源多倍体系的衍生系中开花时间的分化。在这项研究中，我们更全面地评估了之前研究的系和另一个合成的甘蓝型油菜系的衍生系的系中个体的表型分化。在四个生长条件下种植了 9 个多倍体系及其二倍体亲本，并测量了 8 个生活史性状。由于它们是从单个加倍的异源单倍体植物衍生而来，所以一个系内的多倍体系在遗传上应该是相同的。然而，在系内的个体之间，每个表型性状的差异都很显著，而且对不同的生长条件（基因型与环境的相互作用）也有不同的反应。当每个环境中每个多倍体系的每个性状的表型与它们的二倍体亲本进行比较时，大约 30%的表型与一个亲本相似，50%的表型是中间型，20%的表型是超越型。我们的结果表明，新的多倍体系中存在广泛的全新变异。这种变化可能有助于自然发生的多倍体的进化潜力。
