Plant & Animal Genomes XIII Conference Plant & Animal Genomes XIII ConferenceJanuary 15-19, 2005
Town & Country Convention Center
San Diego, CA
Leah K McHale , Tadeusz Wroblewski , Urszula Piskurewicz , Keri Cavanaugh , Barnaly Pande , Alexander Kozik , Maria Jose Truco , Oswaldo E Ochoa , Dean O Lavelle , Richard W Michelmore
We are conducting a comprehensive analysis of disease resistance at the phenotypic and molecular levels to understand the genomic distribution of different types of resistance genes and to provide tools for crop improvement. Over 23 loci for resistance to seven pathogens have been identified in lettuce and mapped using several mapping populations. In addition, diverse lettuce genotypes are being screened for their ability to recognize effector proteins from Pseudomonas spp. using Agrobacterium tumefaciens mediated transient assays. When effector recognition varies between the parents of a mapping population, the genetic determinants of this response are being mapped. Several different types of genes may determine the outcome of a plant-pathogen interaction. Intra-specific variation in any of these genes may result in variation of the resistance phenotype. Using the Compositae Genome Project EST database (http://compgenomics.ucdavis.edu/), approximately 350 sequences with similarity to resistance (R) genes, genes involved in resistance signal transduction, and defense response genes have been identified. These candidate genes are being mapped to an F7:8 Recombinant Inbred Line (RIL) population. RNAi is being used to determine the resistance function of candidate genes that cosegregate with phenotypic resistance loci or effector recognition loci. Divergent selection is a characteristic of genes that encode proteins involved in host pathogen interactions. R genes and genes involved in signal transduction are being sequenced from a diverse set of lettuce genotypes and analyzed using maximum likelihood methods to search for an evolutionary signal of divergent selection.