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The Late Blight Resistance Locus Rpi-blb3 from Solanum bulbocastanum Belongs to a Major Late Blight R Gene Cluster on Chromosome 4 of Potato

¹Graduate School Experimental Plant Sciences, Laboratory of Plant Breeding, Department of Plant Sciences, Wageningen University, Binnenhaven 5, 6709 PD, Wageningen, The Netherlands; ²Agrico Research, P.O. Box 40, 8300 AA, Emmeloord, The Netherlands; ³Plant Research International BV, P.O. Box 16, 6700 AA, Wageningen, The Netherlands

Late blight, caused by Phytophthora infestans, is one of the most devastating diseases in cultivated potato. Breeding of new potato cultivars with high levels of resistance to P. infestans is considered the most durable strategy for future potato cultivation. In this study, we report the identification of a new late-blight resistance (R) locus from the wild potato species Solanum bulbocastanum. Using several different approaches, a high-resolution genetic map of the new locus was generated, delimiting Rpi-blb3 to a 0.93 cM interval on chromosome 4. One amplification fragment length polymorphism marker was identified that cosegregated in 1,396 progeny plants of an intraspecific mapping population with Rpi-blb3. For comparative genomics purposes, markers linked to Rpi-blb3 were tested in mapping populations used to map the three other late-blight R loci Rpi-abpt, R2, and R2-like also to chromosome 4. Marker order and allelic conservation suggest that Rpi-blb3, Rpiabpt, R2, and R2-like reside in the same R gene cluster on chromosome 4 and likely belong to the same gene family. Our findings provide novel insights in the evolution of R gene clusters conferring late-blight resistance in Solanum spp.

Additional keywords: BAC library , bulked segregant analysis , chromosome walking , synteny .