Characteristics of stationary-phase variation affecting virulence in Xanthomonas oryzae pv. oryzae

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Abstract
Xanthomonas oryzae pv. oryzae is the causal agent of bacterial leaf blight, a serious disease of rice. Spontaneous loss of virulence in X. oryzae pv. oryzae is associated with mutants that produce reduced levels of extracellular polysaccharide. Evidence is presented that these mutants accumulate in long-term stationary phase cultures but are not obtained from exponentially growing cultures. A number of independent spv (stationary-phase variation) mutants have been isolated and characterized. These mutants differ from each other with respect to the stability of the mutant phenotype, extent of loss of virulence, ability to outcompete wild type cells in stationary-phase cocultures, and hypersensitivity to hydrogen peroxide.Key words: stationary-phase variation, spontaneous loss of virulence, Xanthomonas oryzae.