Genetic diversity and genomic distribution of homologs encoding NBS-LRR disease resistance proteins in sunflower

Osman Radwan, Sonali Gandhi, Adam Heesacker, Brett Whitaker, Chris Taylor, Alex Plocik, Richard Kesseli, Alexander Kozik, Richard W Michelmore, Steven J. Knapp

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


Three-fourths of the recognition-dependent disease resistance genes (R-genes) identified in plants encode nucleotide binding site (NBS) leucine-rich repeat (LRR) proteins. NBS-LRR homologs have only been isolated on a limited scale from sunflower (Helianthus annuus L.), and most of the previously identified homologs are members of two large NBS-LRR clusters harboring downy mildew R-genes. We mined the sunflower EST database and used comparative genomics approaches to develop a deeper understanding of the diversity and distribution of NBS-LRR homologs in the sunflower genome. Collectively, 630 NBS-LRR homologs were identified, 88 by mining a database of 284,241 sunflower ESTs and 542 by sequencing 1,248 genomic DNA amplicons isolated from common and wild sunflower species. DNA markers were developed from 196 unique NBS-LRR sequences and facilitated genetic mapping of 167 NBS-LRR loci. The latter were distributed throughout the sunflower genome in 44 clusters or singletons. Wild species ESTs were a particularly rich source of novel NBS-LRR homologs, many of which were tightly linked to previously mapped downy mildew, rust, and broomrape R-genes. The DNA sequence and mapping resources described here should facilitate the discovery and isolation of recognition-dependent R-genes guarding sunflower from a broad spectrum of economically important diseases.

Original languageEnglish (US)
Pages (from-to)111-125
Number of pages15
JournalMolecular Genetics and Genomics
Issue number2
StatePublished - Aug 2008


  • Compositae
  • Helianthus
  • Lactuca
  • Resistance genes

ASJC Scopus subject areas

  • Genetics


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