Chromosomal organization of RGAs in Malus × domestica.
A: Phylogenetic analysis of NBS domain was carried out by neighbor-joining method  on RGAs protein sequences from M. domestica cultivar ‘Golden delicious’. Major phylogenetic clades (from CN1 to CN5 and from TN1 to TN6) correspond to the classification based on protein domains. TN1 (light blue): TIR-NBS-LRR; TN2 (light purple): TIR-NBS-LRR and TIR-NBS; TN3 (black): TIR-NBS-LRR; TN4 (blue): TIR-NBS-LRR, CC-TIR-NBS, and TIR-NBS; TN5 (orange): TIR-NBS-LRR, and TIR-NBS; TN6 (dark purple): TIR-NBS-LRR; CN1 (pink): CC-NBS-LRR; CN2 (red): CC-NBS-LRR and NBS-LRR; CN3 (light green): CC-NBS-LRR, NBS-LRR, NBS; CN4 (green): CC-NBS-LRR, NBS-LRR, NBS; CN5 (dark green): CC-NBS-LRR, NBS-LRR, NBS. B: RGAs assigned to chromosomes (Chr) are represented by dots with colors corresponding to major phylogenetic clades. The size of each chromosome is given in megabase (Mb, on the left side), whereas the markers of the genetic map are shown in black (on the right side). Resistance-related genes different from RGAs are shown in red. Known quantitative trait loci (QTL) for resistance to apple scab (brown), powdery mildew (green), aphids (light blue), fire blight (red) and rust mite (blue) are shown by bars on the left side of chromosomes –, together with the major resistance genes to apple scab (Vd3 and Rvi genes) –, powdery mildew (Pl1) , and aphids (Sd-1, Sd-2, Er1, Er2) , .