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

Plant breeding relies on genetic variability generated by meiotic recombina tion. Control of recombination frequencies is not yet possible, but would s ignificantly extend the options for plant-breeding strategies. A prerequisi te would be variability of recombination frequencies. In this study, 15 tra nsgenic kanamycin (K-R) and hygromycin (H-R) resistance gene insertions map ping to the five Arabidopsis thaliana chromosomes were used as genetic mark ers. Recombination frequencies were determined from the frequencies of resi stance phenotypes within populations segregating for linked K-R and H-R mar kers. Recombination frequencies of marker pairs were compared among these f our ecotypes, among F(1)s in both reciprocal forms derived from these ecoty pes, and between F(1)s and their parent lines. On average, the recombinatio n 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 he terozygosity influences recombination in plant breeding, and cannot be igno red in genetic mapping of genomes.