Development of Molecular Markers Closely Linked to the Potato Leafroll Virus Resistance Gene, Rlr etb , for use in Marker-Assisted Selection

Potato leafroll virus (PLRV) is a major pathogen of potato with worldwide impact on seed and commercial production of potato. In North America, the primary potato cultivars grown by industry are not resistant to PLRV and require the application of insecticides to control the aphid vector of PLRV, so as to prevent PLRV infection of the crop. The Solanum etuberosum- derived dominant gene Rlr (etb) confers resistance to PLRV and has been mapped to chromosome 4. The previous closest marker to Rlr (etb) , C2_At1g42990, was mapped 13.6 cM from the gene in a BC3 population. Cleaved amplified polymorphic sequence markers were developed in the region surrounding C2_At1g42990 and mapped along with Rlr (etb) in 102 BC4 progeny. Sixteen markers were identified surrounding Rlr (etb) , with flanking markers at 2.1 and 9.3 cM. Two markers, 1367-8a and DMB32-11, both 2.1 cM from Rlr (etb) , are shown to be well suited for marker assisted selection. The development of additional molecular markers more closely linked to Rlr (etb) will greatly facilitate its use in potato breeding and its continued introgression into cultivated potato for the development of PLRV-resistant cultivars.