Alexander Helen M, Emry D Jason, Pace Brian A, Kost Matthew A, Sparks Kathryn A, Mercer Kristin L
Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045 USA.
Department of Biology, Washburn University, Topeka, Kansas 66621 USA.
Am J Bot. 2014 Jul;101(7):1176-1188. doi: 10.3732/ajb.1400088. Epub 2014 Jul 11.
• Premise of the study: The fitness of an offspring may depend on its nuclear genetic composition (via both parental genotypes) as well as on genetic maternal effects (via only the maternal parent). Understanding the relative importance of these two genetic factors is particularly important for research on crop-wild hybridization, since traits with important genetic maternal effects (e.g., seed size) often differ among crops and their relatives. We hypothesized that the effects of these genetic factors on fitness components would change across the life cycle of hybrids.• Methods: We followed seed, plant size, and reproductive traits in field experiments with wild and four crop-wild hybrids of sunflower (Helianthus annuus), which differed in nuclear genetic composition and maternal parent (wild or F1 hybrid).• Key results: We identified strong genetic maternal effects for early life cycle characteristics, with seeds produced on an F1 mother having premature germination, negligible seed dormancy, and greater seedling size. Increased percentages of crop alleles also increased premature germination and reduced dormancy in seeds produced on a wild mother. For mature plants, nuclear genetic composition dominated: greater percentages of crop alleles reduced height, branching, and fecundity.• Conclusions: Particular backcrosses between hybrids and wilds may differentially facilitate movement of crop alleles into wild populations due to their specific features. For example, backcross seeds produced on wild mothers can persist in the seed bank, illustrating the importance of genetic maternal effects, whereas backcross individuals with either wild or F1 mothers have high fecundity, resulting from their wild-like nuclear genetic composition.
• 研究前提：后代的适合度可能取决于其核基因组成（通过双亲基因型）以及遗传母体效应（仅通过母本）。了解这两种遗传因素的相对重要性对于作物-野生杂交研究尤为重要，因为具有重要遗传母体效应的性状（如种子大小）在作物及其近缘种之间往往存在差异。我们假设这些遗传因素对适合度组成部分的影响会在杂种的生命周期中发生变化。
• 方法：我们在田间试验中跟踪了野生向日葵（Helianthus annuus）以及四个向日葵作物-野生杂种的种子、植株大小和繁殖性状，这些杂种在核基因组成和母本（野生或F1杂种）方面存在差异。
• 关键结果：我们确定了早期生命周期特征存在强大的遗传母体效应，F1母本产生的种子具有过早萌发、种子休眠可忽略不计以及更大的幼苗大小。野生母本产生的种子中，作物等位基因比例增加也会增加过早萌发并降低休眠。对于成熟植株，核基因组成起主导作用：作物等位基因比例增加会降低株高、分枝和繁殖力。
• 结论：杂种与野生种之间的特定回交可能因其特定特征而不同程度地促进作物等位基因向野生种群的转移。例如，野生母本产生的回交种子可以在种子库中存留，这说明了遗传母体效应的重要性，而与野生或F1母本杂交产生的回交个体具有较高的繁殖力，这是由于其类似野生种的核基因组成。
