Enhancing local meiotic crossovers in Arabidopsis and maize through juxtaposition of heterozygous and homozygous regions.

Meiotic crossovers, which exchange DNA between homologous chromosomes, are vital for accurate segregation and generate genetic diversity. In plant breeding, they help create new haplotypes by combining beneficial alleles. In Arabidopsis, heterozygous regions in an otherwise homozygous background attract more crossovers than in full F hybrids-a phenomenon so far observed only in this self-fertilizing species. Here we report a similar effect in outcrossing maize: local crossover rates increase up to threefold in regions where polymorphism is spatially confined compared to full hybrids. This stimulation occurs in both male and female meiosis and is strongest when heterozygous regions fully span the measured area, likely due to crossover redistribution. As Arabidopsis and maize represent distantly related plant lineages (eudicots and monocots), this shared phenomenon suggests a conserved mechanism. Importantly, it provides a tool for breeding, offering a way to boost recombination and accelerate the introgression of desired traits using interhomologue polymorphism.