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Characterization of Endopolygalacturonase Produced by Rhizoctonia solani in Culture and During Infection of Cotton Seedlings. L. W. Brookhouser, Former graduate assistant, Department of Plant Pathology, University of California, Berkeley 94720; J. G. Hancock(2), and A. R. Weinhold(3). (2)(3)Professors, respectively, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 70:1039-1042. Accepted for publication 6 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1039.

An isolate of anastomosis group 4 of Rhizoctonia solani produced endopolygalacturonase (endoPG) in culture in response to cotton seed exudates and in infected cotton seedlings 18 hr after inoculation. No other depolymerizing type of pectic enzyme was detected during fungal growth under these conditions. EndoPG from these sources had pH optima of 5.2 and molecular weights of ~42,000 daltons. Enzyme preparations from culture and infected seedlings readily macerated cotton hypocotyl sections. However, by using isoelectric focusing techniques, it was found that the endoPG produced by R. solani in response to seed exudates had a single isoelectric point (pI) of 7.1 whereas endoPG from infected hypocotyls had a major peak at pI 7.8 and a minor peak at 7.1. Differences in elution patterns were observed when preparations from the two sources were purified by ion exchange chromatography. Results of this study suggest that R. solani produces different forms of endoPG and that the ionic properties of the predominant form produced during pathogenesis differ from those of the single-peak form produced in culture.