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% ...