Leah McHale

In collaboration with Celera, a lettuce EST database of over 66,000 sequences has been established. Two genotypes of lettuce were used to generate the ESTs, a cultivar and the wild progenitor of cultivated lettuce. To identify more resistance gene candidates (RGCs), I searched the database for sequences with the NBS-LRR motifs as well as other possible resistance genes. I also mined the EST database for candidate genes functioning downstream of the resistance genes. These genes include signal transduction genes, such as EDS1 and NPR1, as well as disease response genes, such as the PR genes. Markers have been designed based on the EST sequences, and we are generating mapping data. To determine the potential function of these genes, I will look for genetic cosegregation of the genes that I have identified with phenotypic data generated by others in the lab who are mapping resistance to a variety of pathogens.

In addition, I am conducting a loss-of-resistance mutant screen on the M2 generation of fast neutron and gamma irradiated lettuce. Several different genotypes were irradiated. Each genotype contains different resistance genes. By screening seedlings for a loss of resistance, I have identified plants with mutations in one to several resistance genes or downstream signal transduction genes. Each loss-of-resistance mutant will be analyzed genetically to place them in complementation groups. Panels of these potential deletion mutants will be screened for the candidate RGC sequences and other genes involved in resistance to determine whether any of these candidate genes function in the resistance specificity that has been lost.