Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2006
Publication Date: 6/23/2006
Citation: Kuhn, D.N., Narasimhan, G., Nakamura, K., Brown, J.S., Schnell II, R.J., Meerow, A.W. 2006. Identification of cacao tir-nbs-lrr resistance gene analogs and their use as genetic markers. Journal of the American Society for Horticultural Science.131(6):806-813. Interpretive Summary: The identification of genetic markers linked to disease resistance is a major goal in cacao improvement. We have used a candidate gene strategy to identify resistance genes in cacao by their nucleotide sequence similarity with known resistance genes in other plants. These genes have been turned into genetic markers using an assay that can detect sequence differences rapidly and reliably. These markers will aid us in breeding disease resistant cacao plants.
Technical Abstract: Identifying genetic markers linked to disease resistance in plants is an important goal in marker assisted selection. Using a candidate gene approach, we have developed genetic markers for non-TIR-NBS-LRR resistance gene analogs and WRKY transcription factor genes, both families involved in disease resistance, but were unable to isolate TIR-NBS-LRR genes. Using a novel algorithm to design degenerate primers for TIR-NBS-LRR genes, we have now isolated TIR-NBS-LRR loci as determined by DNA sequence comparison. These have been developed as genetic markers using capillary array electrophoresis (CAE) and single strand conformational polymorphism (SSCP) analysis. We have mapped three of the TIR-NBS-LRR loci in an F2 population of cacao and demonstrated that each is a single locus with TIR2 located on linkage group 3 and TIR3 and TIR4 located on linkage group 5.