Purification and characterization of pectolytic enzymes produced by virulent and hypovirulent isolates of Rhizoctonia solani Kuhn

Four pectolytic enzymes were purified from an isolate of Rhizoctonia solani (No. 82, AG-4) virulent on a wide range of hosts (Ichielvich-Auster et al. 1985, Phyloparasilica vol. 13, 103–112). The enzymes designated as endopolygalacturonase I and II (endoPG-I and endoPG-II), pectinesterase (PE) and endopectinlyase (endoPL) have been purified to homogeneity by a single chromatographic step on a cross linked polypectate column. These enzymes were identified also in two virulent isolates of R. zeae and two virulent binucleate Rhizoctonia spp. The endoPG-I, endoPG-II and PE but not endoPL were identified in three hypovirulent isolates of R. solani and two of R. zeae. These enzymes were purified to homogeneity from R. solani (No. 521, AG-4). The molecular weight (mol.wt), pH optimum, isoelectric point (pI) and optimal temperature (T) for each enzyme were endoPG-I, mol.wt 34 000, pH 4·8, pI 6·8, T 50°C); endoPG-II, mol.wt 37 000, pH 5·4, pI 7·4, T 42°C; PE, mol.wt 26 000, pH 7·7, pI 6·2, T 48°C; and endoPL (mol.wt. 45 500, pH 8·4, pI 8·1, T 53°C.