Differential Response of Sweet Corn Cultivars to Phytotoxic Water-Soluble Compounds from Culture Filtrates of Exserohilum turcicum. Bilha Bashan, Department of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel. Yehouda Levy, Department of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel. Plant Dis. 76:451-454. Accepted for publication 23 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0451.

Phytotoxic substances were isolated from culture filtrates of Exserohilum turcicum grown in Fries' medium, or from susceptible corn plants infected with the fungus. The substances significantly inhibited chlorophyll biosynthesis in corn seedlings susceptible to E. turcicum but not in those resistant to the fungus. The phytotoxic substances were extracted from culture filtrates of eight different isolates of E. turcicum. A positive correlation was found between lesion size of isolates and phytotoxic activity. Lesion size and infection efficiency of E. turcicum on susceptible excised leaves pretreated with one or more phytotoxic substances increased by 119 and 30%, respectively, indicating that these substances may be a virulence factor.