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Necrosis Induction in Cotton. D. G. Hopper, Former Research Associate, Department of Biochemistry, Oklahoma State University, Stillwater 74074, Currently Visiting Scientist, Department of the Air Force, Aerospace Research Laboratories (AFSC), Wright-Patterson Air Force Base, Ohio 45433; R. J. Venere(2), L. A. Brinkerhoff(3), and R. K. Gholson(4). (2)(4)Research Associate and Professor of Biochemistry, respectively, Department of Biochemistry, Oklahoma State University, Stillwater; (3)Research Professor, Langston University, Langston, Oklahoma 74052, and Professor, Department of Botany and Plant Pathology, Oklahoma State University, Stillwater 74074. Phytopathology 65:206-213. Accepted for publication 30 August 1974. DOI: 10.1094/Phyto-65-206.

The necrotic resistant response (hypersensitivity) of upland cotton Gossypium hirsutum to Xanthomonas malvacearum was examined. Necrosis induced by the antibiotics dactinomycin, chloramphenicol, cycloheximide, mitomycin C, and puromycin, and by the inorganic ions Hg++ and Cu++, is similar in appearance to that induced by X. malvacearum in resistant cotton cultivars. A necrotic lesion is also produced by sterile culture filtrates of X. malvacearum and several other Xanthomonas spp. grown on an autoclaved cotton leaf medium. The necrosis induction caused by the culture filtrates is correlated with the activity of enzymes which degrade the pectinaceous constituent of plant cell walls. No necrotic response is observed with culture filtrates from X. malvacearum grown on nutrient broth or on a basal salts medium containing any one of several purified carbon sources. The results suggest that the necrotic lesion produced in the cotton host infected with X. malvacearum may be initiated by the production of a polymethylgalacturonase by the invading bacteria.

Additional keywords: bacterial blight, host-pathogen interaction.