The Stability and Consequences of Recombination in Maize

Meiotic recombination varies by over 3 orders of magnitude within the genomes of many eukaryotic organisms, including crop species such as maize. Because plant breeders rely on meiotic cross-overs to introgress beneficial alleles and fine-map quantitative traits, the tremendous regional variation in cross-over rates fundamentally limits the practice of crop improvement. Population genetic theory further predicts that deleterious mutations should preferentially accumulate in low-recombination regions, particularly in historically outcrossing species such as maize. Here, we show that meiotic recombination is predictable across diverse maize crosses, with epigenetic indicators of open chromatin delineating the locations of recombination hotspots and sites of GC-biased gene conversion. We further demonstrate that the extant patterns of recombination are historically stable and tied to variation in the frequency of deleterious mutations. The ability of plant breeders to exploit recombination in purging segregating deleterious alleles will determine the efficacy of future crop improvement.