Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2007
Publication Date: 9/17/2007
Citation: Bull, C.T., Goldman, P.H., Hayes, R.J., Madden, L.V., Koike, S.T., Ryder, E.J. 2007. Genetic Diversity of Lettuce (Lactuca sativa) for Resistance to Bacterial Leaf Spot Caused by Xanthomonas campestris pv. vitians. Online:Plant Health Progress DOI:10.1094/PHP-2007-0917-02-RS. Interpretive Summary: Over 80% of the 890 million lbs of lettuce consumed annually by Americans is produced in the United States. Lettuce production in California accounts for 70-75% of the US total. This research has identified lettuce cultivars resistant to bacterial leaf spot, a plant disease that reduces market yield. Because the relative performance of cultivars with regard to disease resistance was correlated between field evaluations and assays developed for the greenhouse, the relatively rapid greenhouse assay can be used to facilitate research on the genetics of bacterial leaf spot resistance and the selection of resistant individuals. The techniques developed and lettuce cultivars identified are being used by private and federal breeding programs to breed commercial cultivars with resistance to the bacterial leaf spot pathogen.
Technical Abstract: Lettuce plants were artificially inoculated with three isolates of Xanthomonas campestris pv. vitians in field and greenhouse evaluations for genetic variation in resistance to bacterial leaf spot. The cultivar Little Gem had the least amount of disease, whether evaluated for disease severity or disease incidence. Disease severity levels for cultivar Batavia Reine des Glaces were not significantly different from those of Little Gem. Several cultivars including Vista Verde, Pybas 251, Pacific, Clemente, Salinas 88, and Sniper were highly susceptible. There was a strong correlation between results obtained in the greenhouse and those obtained in the field (r=0.77, P=0.009) indicating that greenhouse assays may be used to increase the number of cultivars evaluated and to speed breeding efforts.