Influence of genetic background and heterozygosity on meiotic recombination in Arabidopsis thaliana

Plant breeding relies on genetic variability generated by meiotic recombination. Control of recombination frequencies is not yet possible, but would significantly extend the options for plant-breeding strategies. A prerequisite would be variability of recombination frequencies. In this study, 15 transgenic kanamycin (K-R) and hygromycin (H-R) resistance gene insertions mapping to the five Arabidopsis thaliana chromosomes were used as genetic markers. Recombination frequencies were determined from the frequencies of resistance phenotypes within populations segregating for linked K-R and H-R markers. Recombination frequencies of marker pairs were compared among these four ecotypes, among F(1)s in both reciprocal forms derived from these ecotypes, and between F(1)s and their parent lines. On average, the recombination frequencies in F-1 crosses were substantially higher (up to 2-fold) than in the homozygous parental ecotypes. A strong negative correlation between genetic similarities of ecotypes and recombination frequencies was detected for two adjacent marker pairs located on the long arm of chromosome 3, but not for marker pairs in other genomic regions. Our results suggest that heterozygosity influences recombination in plant breeding, and cannot be ignored in genetic mapping of genomes.