Mapping of the potato leafroll virus resistance gene, Rlr etb , from Solanum etuberosum identifies interchromosomal translocations among its E-genome chromosomes 4 and 9 relative to the A-genome of Solanum L. sect. Petota

Gene Rlr _etb , derived from the potato species Solanum etuberosum, confers resistance to potato leafroll virus (PLRV). Mapping of this gene would aid in developing marker-assisted selection protocols to facilitate its introgression into cultivated potato. One RFLP marker and 45 cleaved amplified polymorphic markers (CAPs) markers were used to screen an etuberosum-derived BC₃ family segregating for PLRV resistance conferred by Rlr _etb . Nine markers from linkage group 4 of the tomato map displayed linkage with Rlr _etb , however, eight additional markers from linkage group 4 that should have been syntenic with Rlr _etb were not. Instead they segregated with 12 markers previously mapped to linkage group 9 of the tomato map, indicative that chromosomes 4 and 9 of S. etuberosum have translocated regions relative to the potato and tomato genomes. These chromosomal translocations have placed Rlr _etb beyond the end of the published map of linkage group 4 of tomato with the closest marker, C2_At1g42990, mapping 13.6 cM from Rlr _etb .