VIEW ARTICLE

Physiology and Biochemistry

A Comparison of the Quantities of Exopolysaccharide Produced by Xanthomonas campestris pv. malvacearum in Susceptible and Resistant Cotton Cotyledons During Early Stages of Infection. Margaret L. Pierce,Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater 74078-0454; Margaret Essenberg, and Andrew J. Mort. Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater 74078-0454. Phytopathology 83:344-349. Accepted for publication 22 October 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-344.

Two pairs of susceptible and highly resistant lines of Gossypium hirsutum were compared for their influence on Xanthomonas campestris pv. malvacearum extracellular polysaccharide (EPS) production during the early stages of infection. Quantities of EPS in intercellular washing fluid from inoculated cotton cotyledons were measured and related to the bacterial population densities in those same cotyledons. The presence of pyruvylated mannose in EPS from X. c. malvacearum, as in xanthan gum from X. c. campestris, allowed accurate quantitation of EPS without interference from polysaccharides of plant origin. During the period when bacterial population densities were similar in susceptible and resistant cotyledons, the quantity of EPS present per bacterium was equal. Thus, no evidence was found for suppression by the resistant lines of EPS production by the bacteria. We conclude that perturbation in bacterial EPS production during the initial 48 h after infection is not required for the hypersensitive response of cotton foliar tissue to occur.