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Endopolygalacturonase: Evidence for Involvement in Verticillium Wilt of Cotton. Harry W. Mussell, Assistant Plant Pathologist, Boyce Thompson Institute for Plant Research, 1086 North Broadway, Yonkers, New York 10701; Phytopathology 63:62-70. Accepted for publication 19 July 1972. DOI: 10.1094/Phyto-63-62.

Endopolygalacturonase (endoPG) but not exopolygalacturonase (exoPG) purified from culture fluids of Verticillium albo-atrum was toxic to susceptible cotton leaves when assayed in a divalent salt solution. Leaf symptoms generated by this endoPG were identical to some of the symptoms observed in susceptible cotton after infection with V. albo-atrum. Symptoms similar to those generated by endoPG treatment were also observed after treatment of cotton leaves with several substrate-oxidase combinations which generated hydrogen peroxide. Symptom expression in endo PG-treated leaves could be blocked by pretreatment of the leaves with catalase or reduced by pretreatment with peroxidase. Hydrogen peroxide could be detected in solutions bathing endoPG-treated leaf tissue 30 min after treatment. The above results support a hypothesis that endoPG-induced leaf damage is mediated through hydrogen peroxide appearing intramurally in endoPG-treated cotton leaves.

Additional keywords: disease physiology, pathogenesis, cell death, defoliation, Gossypium hirsutum.