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Physiology and Biochemistry

Polygalacturonases Associated with Infection of Valencia Orange by Penicillium italicum. J. Hershenhorn, Department of Botany, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; S. Manulis(2), and I. Barash(3). (2)Department of Plant Pathology, A.R.O., The Volcani Center, Bet Dagan, Israel; (3)Department of Botany, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel, Department of Plant Pathology, A.R.O., The Volcani Center, Bet Dagan, Israel. Phytopathology 80:1374-1376. Accepted for publication 28 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-1374.

Three forms of polygalacturonase (PG), designated PG-I, PG-II, and PG-III, were purified to homogeneity from culture filtrate of Penicillium italicum. PG-I was characterized as an exoenzyme, whereas PG-II and PG-III were characterized as endoenzymes. All three enzymes were present in orange peel infected by P. italicum. Exo-PG-I was the predominant enzyme in infected tissue and constituted 69% of the total PG activity as compared with 4% in the culture filtrate. Endo-PG-II and endo-PG-III constituted only 24 and 7%, respectively, of the activity in the infected tissues, as compared with 71 and 25% in culture filtrate. The demonstration of high exo-PG activity in infected tissue suggests that it may be responsible for the excessive accumulation of d-galacturonic acid which occurs during blue mold infection.