Meiotic recombination and advances in quantitative trait locus mapping

In plants, meiotic crossovers preferentially occur near and within genes, reshuffling preexisting genetic variation from parental genomes and thereby generating diversity in offspring. However, crossovers are generally limited to one to three per chromosome pair, tend to be widely spaced, and are rare in heterochromatic pericentromeric regions. These constraints on crossover number and distribution limit the genetic variation available for crop improvement and hinder the fine mapping of quantitative trait loci (QTLs). Unleashing meiotic crossovers has, therefore, become a key objective in plant genetics and breeding. Here, we review recent findings on pro- and anti-crossover factors that regulate crossover numbers, along with epigenetic mechanisms that suppress pericentromeric crossover recombination. We then explore genetic strategies to manipulate these regulators to maximize crossovers in both chromosomal arms and pericentromeric regions. Finally, we consider the implications of substantially elevating crossover frequency for enhancing QTL mapping resolution and accelerating plant breeding.