Genetic and environmental determinants of unreduced gamete production in Brassica napus, Sinapis arvensis and their hybrids

Unreduced gametes, sperm or egg cells with the somatic chromosome number, are an important mechanism of polyploid formation and gene flow between heteroploid plants. The meiotic processes leading to unreduced gamete formation are well documented, but the relative influence of environmental and genetic factors on the frequency of unreduced gametes remain largely untested. Furthermore, direct estimates of unreduced gametes based on DNA content are technically challenging and hence, uncommon. Here, we use flow cytometry to measure the contribution of genetic (hybridization) and environmental (nutrient limitation, wounding) changes to unreduced male gamete production in Brassica napus, Sinapis arvensis, and two hybrid lines. Treatments were applied to greenhouse grown plants in a random factorial design, with pollen sampled at two time intervals. Overall the frequency of unreduced gametes averaged 0.59% (range 0.06%-2.17%), plus a single outlier with 27%. Backcrossed hybrids had 39% to 75% ...不减数配子（Unreduced gametes），即携带体细胞染色体数的精子或卵细胞，是多倍体形成以及异倍体植物间基因流的重要机制。尽管学界已对介导不减数配子形成的减数分裂过程开展了充分研究，但环境与遗传因素对不减数配子发生频率的相对影响，目前仍未得到广泛验证。此外，基于DNA含量直接估算不减数配子的方法在技术层面存在较大挑战，因此相关研究较为少见。本研究借助流式细胞术（flow cytometry），以甘蓝型油菜（Brassica napus）、野芥菜（Sinapis arvensis）以及两个杂交株系为材料，探究遗传因素（杂交）与环境因素（营养限制、机械损伤）对雄性不减数配子产生的贡献。实验采用随机析因设计对温室栽培植株施加处理，并在两个时间间隔内采集花粉样本。整体而言，不减数配子的发生频率平均为0.59%（范围0.06%~2.17%），另有1个异常值达27%。回交杂交株系的发生频率介于39%~75%……