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The epidemiology of Xanthomonas campestris pv. vitians causal organism of Bacterial Leaf Spot of lettuce [electronic resource] /

Source: OAI

ABSTRACT ABSTRACT: Several factors were investigated that may be involved in the epidemiology of Bacterial Leaf Spot (BLS) caused by Xanthomonas campestris pv. vitians in lettuce. These include the effect of temperature on development of disease, the role of epiphytic populations on different plant species, the effect of wounding on disease development, and the determination of internal dynamics in selected plant species. Dr. Ken Pernezny contributed data on the infectivity of X. c. pv. vitians. Temperature studies were performed on cos lettuce plants. In this study, optimal disease development occurred at 22.7⁰C. Wounding experiments were performed on lettuce, the known host plant, as well as nine other plant species from seven different plant families. Non-wounded and wounded plants were statistically different from each other in which wounding was associated with less disease compared to non-wounded plants. ABSTRACT: A second study involved infiltrating lettuce, tomato, pepper, cilantro, parsley, and beets with 10⁵ cells per gram of leaf tissue and assaying for internal populations of X. c. pv. vitians. Populations of X. c. pv. vitians followed a typical bacterial growth curve in lettuce, pepper, and cilantro. In trial 1, populations peaked at 3.6x10⁸, 5.8x10⁶ and 1.6 x10⁵ CFU/cm² in those crops, respectively, then dropped to 1.0x10⁶, 3.2 x10⁵ and 3.3 x10³ CFU/cm² of leaf tissue on the final day of sampling. Bacterial populations in tomato increased slightly to 2.1x10⁵ CFU/cm² and remained there. Bacterial populations in beet and parsley followed a different growth curve by making a drastic dip at Day 0 of the sampling period and growing slowly to 2.0 x10⁵ and 8.4 x10⁶ CFU/cm². Respectively, in Trial 2, bacterial populations in lettuce and pepper again followed a curve with peaks at 1.35x10⁸ and 5.5 x 10⁶ CFU/cm², respectively. Bacterial populations in tomato rose to 3.8 x 10⁵ CFU/cm2. ABSTRACT: Bacterial populations in parsley, cilantro, and beet had high populations of 1.85 x 10⁵, 1.3 x 10⁵, and 5.4 x 10³ CFU/cm², respectively. Epiphytic populations were measured in a field trial on the Pine Acres Research Center in Marion County, FL. Cos lettuce, tomato, parsley, cilantro, endive and beets were evaluated for epiphytic populations of X. c. pv. vitians. Lettuce was shown to support higher epiphytic populations for compared to all other host species 5 out of 6 weeks that were sampled. Of these crops tomato was the only one to support populations of X. c. pv. vitians in the final sampling date. Statistically higher populations were found on lettuce, tomato, and endive compared to cilantro, parsley and beets at two Weeks After Inoculation (WAI). This research shows that pepper and tomato may harbor relatively higher populations of X. c. pv. vitians making them possible alternative hosts. Optimum temperature for development of BLS on lettuce was determined to be 22.7⁰C. Wounding data were inconclusive. Text (Electronic thesis) in PDF format. System requirements: World Wide Web browser and PDF reader. Mode of access: World Wide Web. Title from title page of source document. Thesis (M.S.)--University of Florida, 2003. Includes vita. Includes bibliographical references.

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