SSR-based genetic map of apple. M: male parent (cv. ‘Golden Delicious’), F: female parent (cv. ‘Jonathan’), and LG: linkage map. The consensus map is shown in centre, and distances shown in the maps are measured in centimorgans (cM). The number of linkage groups corresponds to the number of the haploid chromosomes of the draft apple genome sequence . Segregation-distorted markers clustered within the chromosomal region are indicated in gray.