A FAMILY OF LRR SEQUENCES IN THE VICINITY OF THE CO-2 LOCUS FOR ANTHRACNOSE RESISTANCE IN PHASEOLUS-VULGARIS AND ITS POTENTIAL USE IN MARKER-ASSISTED SELECTION

Molecular markers offer new opportunities for breeding for disease res istance. Resistance gene pyramiding in a single cultivar, as a strateg y for durable resistance, can be facilitated by marker-assisted select ion (MAS). A RAPD marker, ROH20(450), linked to the Mesoamerican Co-2 anthracnose resistance gene, was previously transformed into a SCAR ma rker, SCH20, In the present paper we have further characterized the re levance of the SCH20 SCAR marker in different genetic backgrounds. Sin ce this SCAR marker mas found to be useful mainly in the Andean gene p ool, we identified a new PCR-based marker (SCAreoli) for indirect scor ing of the presence of the Co-2 gene. The SCAreoli SCAR marker is poly morphic in the Mesoamerican as well as in the Andean gene pool and sho uld be useful in MAS. We also report that PvH20, the cloned sequence c orresponding to the 450-bp RAPD marker ROH20(450), contains six imperf ect leucine-rich repeats, and reveals a family of related sequences in the vicinity of the Co-2 locus. These results are discussed in the co ntext of the recent cloning of some plant resistance genes.