Concomitant reiterative BAC walking and fine genetic mapping enable physical map development for the broad-spectrum late blight resistance region, RB

J. M. Bradeen, S. K. Naess, J. Song, G. T. Haberlach, S. M. Wielgus, C. R. Buell, J. Jiang, J. P. Helgeson

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The wild potato species Solanum bulbocastanum is a source of genes for potent late blight resistance. We previously mapped resistance to a single region of the S. bulbocastanum chromosome 8 and named the region RB (for "Resistance from S. Bulbocastanum"). We now report physical mapping and contig construction for the RB region via a novel reiterative method of BAC walking and concomitant fine genetic mapping. BAC walking was initiated using RFLP markers previously shown to be associated with late blight resistance. Sub-contig extension was accomplished using new probes developed from BAC ends. Significantly, BAC end and partial BAC sequences were also used to develop PCR-based markers to enhance map resolution in the RB region. As they were developed from BAC clones of known position relative to RB, our PCR-based markers are known a priori to be physically closer to the resistance region. These markers allowed the efficient screening of large numbers of segregating progeny at the cotyledon stage, and permitted us to assign the resistance phenotype to a region of approximately 55 kb. Our markers also directed BAC walking efforts away from regions distantly related to RB in favor of the 55-kb region. Because the S. bulbocastanum genotype used in BAC library construction is heterozygous for RB (RB/rb), codominant PCR-based markers, originally developed for fine-scale mapping, were also used to determine homolog origins for individual BAC clones. Ultimately, BAC contigs were constructed for the RB region from both resistant (RB) and susceptible (rb) homologs.

Original languageEnglish (US)
Pages (from-to)603-611
Number of pages9
JournalMolecular Genetics and Genomics
Issue number5
StatePublished - Aug 1 2003

Bibliographical note

Funding Information:
Acknowledgements This work was funded in part by NSF Plant Genome Project #DBI-9975866. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the USDA, and does not imply its approval to the exclusion of other products and vendors that might also be suitable

Copyright 2008 Elsevier B.V., All rights reserved.


  • Cleaved Amplified Polymorphic Sequences (CAPS)
  • General resistance
  • Reiterative mapping
  • Solanum bulbocastanum


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