Epiphytic Populations of Xanthomonas campestris pv. vesicatoria on Tomato Cultigens Resistant and Susceptible to Bacterial Spot. Raymond G. McGuire, Former Postdoctoral Associate, Gulf Coast Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 5007 60th Street East, Bradenton 34203. Jeffrey B. Jones, and John W. Scott. Associate Professor, and Associate Professor, Gulf Coast Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 5007 60th Street East, Bradenton 34203. Plant Dis. 75:606-609. Accepted for publication 27 November 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0606.

Populations of Xanthomonas campestris pv. vesicatoria were monitored over four seasons on leaves of two tomato cultivars and five genotypes selected for various levels of resistance to the pathogen. Populations on all five genotypes were consistently below those on the very susceptible Lyconorma, but only those on Hawaii 7998 were significantly below numbers of the susceptible cultivar Walter in every test. Rankings of cultigens based on support of epiphytic populations of X. c. pv. vesicatoria mirrored those based on defoliation over two seasons. Significant interactions in repeated measures analyses of variance between cultigen and sampling day indicated differences in population and disease development over time. By analyzing the slopes of regression equations, which compared epiphytic populations or defoliation with time, population and disease development were confirmed to be slowest on leaves of the genotypes Campbell 28, Ohio 4013, and Hawaii 7998.