Physical overview of selected resistance loci. R2 (a), R3 (b), R1 (c) and Rpi-vnt1/Tm-2/Sw-5 (d). The directions towards the respective telomeres are shown. Boxed arrows symbolise NB-LRR genes and clusters are indicated by horizontal lines. Known genetic markers are shown. The distances between NB-LRR clusters are indicated above the gaps. Identifiers for single NB-LRRs are shown.