Genetic Architecture of Recombination Rate Variation in Wheat Revealed By Analyzing a Nested-Association Mapping Population and Reverse Genetic Screens

Recombination is essential for meiosis and have profound impact on the rates with which new haplotypes originate in populations and change in frequency over time. The constraints imposed on recombination rate variation across genome affect our ability to map genes and the efficiency of selection in crop breeding. Previous studies showed significant recombination rate variation among individuals in populations. Here we used a nested association mapping population developed by crossing 32 diverse founders with broadly adapted cultivar Berkut to investigate the genetic basis of recombination rate variation in wheat. The population consists of 2,400 individuals that is comprised of 32 separate mapping populations of 75 recombinant inbred lines each. Genetic maps for each population were constructed with nearly 50,000 markers per map with about 235,000 markers genotyped across the entire population. Joint linkage mapping of QTL for recombination rate revealed 42 QTL, encompassing multiple candidate genes known to affect this trait in plants and animals. The effects of candidate genes on recombination rate have been validated in the TILLING populations of both tetraploid and hexaploid wheat. The identified genes were shown to be parts of the conserved network of genes controlling recombination in different organisms. While the epistatic interaction was demonstrated for several genes, the majority of recombination rate controlling genes acted additively suggesting the possibility of manipulating the recombination rate in wheat by combining multiple allelic variants of these genes. An integrated view of the gene network affecting recombination rate variation in wheat will be presented and discussed.