Genetic Diversity of Lettuce for Resistance to Bacterial Leaf Spot Caused by Xanthomonas campestris pv. vitians

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. Accepted for publication 17 May 2007. Published 17 September 2007.