Polygalacturonase production by virulent and avirulent isolates of Sclerotium bataticola in culture and in sunflowers

Abstract

Three isolates of Sclerotium bataticola virulent on sunflowers and one moderately virulent induced symptoms and were reisolated from all plants 30 days after inoculation. Two avirulent isolates produced no symptoms but were reisolated from some inoculated plants after 30 days. Dialyzed culture filtrates of all isolates showed exopolygalacturonase (exo-PG) and endopolygalacturonase (endo-PG) activity. Activity was highest in filtrates from virulent cultures. Exo-PG activity was detected in dialyzed extracts from sunflower plants 12 h after toothpick inoculation (TPI) with two of four virulent isolates and 42 h after unwounded stem base inoculation (USBI) with all four virulent isolates. Endo-PG activity in plant extracts was detected 12 h after TPI with three of four virulent isolates and 19 h after USBI with all four virulent isolates. No PG activity was detected in extracts from plants inoculated with two avirulent isolates or from uninoculated plants.