Unleashing meiotic crossovers in hybrid plants

Meiotic crossovers shuffle parental genetic information, providing novel combinations of alleles on which natural or artificial selection can act. However, crossover events are relatively rare, typically one to three exchange points per chromosome pair. Recent work has identified three pathways limiting meiotic crossovers in Arabidopsis thaliana , that rely on the activity of FANCM 1 , RECQ4 2 and FIGL1 3 , respectively. Here, we analyzed recombination in plants where one, two or three of these pathways were disrupted, in both pure line and hybrid contexts. The highest effect was observed when combining recq4 and figl1 mutations, which increased the hybrid genetic map length from 389 to 3037 centiMorgans. This corresponds to an unprecedented 7.8-fold increase in crossover frequency. Disrupting the three pathways do not further increases recombination, suggesting that some upper limit has been reached. The increase in crossovers is not uniform along chromosomes and rises from centromere to telomere. Finally, while in wild type recombination is much higher in male than in female meiosis (490 cM vs 290 cM), female recombination is higher than male in recq4 figl1 (3200 cM vs 2720 cM), suggesting that the factors that make wild-type female meiosis less recombinogenic than male wild-type meiosis do not apply in the mutant context. The massive increase of recombination observed in recq4 figl1 hybrids opens the possibility to manipulate recombination to enhance plant breeding efficiency.