Cloning of the Race-Non-Specific Late Blight Resistance Gene(s) RB from Solanum bulbocastanum Song, J., J.M. Bradeen, S.K. Naess, J.A. Raasch, G.T. Haberlach, S.M. Wielgus, S. Austin-Phillips, C.R. Buell, J. Jiang, J.P. Helgeson

Plant & Animal Genome XI (San Diego, CA Jan 2003)

The wild diploid Mexican species S. bulbocastanum confers durable race-non-specific resistance to late blight. To pursue the positional cloning of the RB gene(s), we constructed three BAC libraries and developed a BAC contig encompassing the RB locus. The S. bulbocastanum plant used for BAC library construction is heterozygous for the RB locus. Using the CAPS markers developed for fine mapping, we have determined the homolog origin for each BAC clone at the RB locus. Two BAC clones containing the entire genetically defined resistance region, derived from both the resistant and susceptible homologs, were completely sequenced. Four complete and one truncated R gene analogs of the CC-NB-LRR class of plant R gene were identified within 40-kb. Complementation studies with a DNA fragment encompassing the entire 40-kb region and individual candidate genes are underway.