Identification of Cacao TIR-NBS-LRR Resistance Gene Homologues and Their Use as Genetic Markers

in Journal of the American Society for Horticultural Science
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  • 1 Department of Biological Sciences, Florida International University, University Park Campus, Miami, FL 33199
  • | 2 USDA-ARS, Subtropical Horticulture Research Station, 13601 Old Cutler Rd., Miami, FL 33158

Identifying genetic markers linked to disease resistance in plants is an important goal in marker-assisted selection. Using a candidate-gene approach, we have previously developed genetic markers in cacao (Theobroma cacao L.) for two families of genes involved in disease resistance: non-TIR-NBS-LRR (Toll/Interleukin-1 Receptor-nucleotide binding site-leucine rich repeat) resistance gene homologues and WRKY transcription factor genes; however, we failed to isolate TIR-NBS-LRR genes. Using a novel algorithm to design degenerate primers, we have now isolated TIR-NBS-LRR loci as determined by DNA sequence comparison. These loci have been developed as genetic markers using capillary array electrophoresis (CAE) and single-strand conformational polymorphism (SSCP) analysis. We have mapped three distinct TIR-NBS-LRR loci in an F2 population of cacao and demonstrated that one is located on linkage group 3 and the other two on linkage group 5.

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