Isozyme analysis of Plasmopara halstedii using cellulose‐acetate gel electrophoresis

Abstract

Isozyme analysis by cellulose‐acetate gel electrophoresis was used for the first time on Plasmopara halstedii, the causal agent of sunflower downy mildew. Forty‐five isolates originating from sunflower, cocklebur and Helianthus × laetiflorus were used, comprising 10 field isolates and 35 single‐spore lines of an additional 30 field isolates representing 10 different virulence phenotypes. Sixteen isozyme systems were analysed, of which three, isocitrate dehydrogenase, malate dehydrogenase and phosphoglucomutase, resulted in clear, reproducible banding patterns and revealed some polymorphism among the isolates. Phosphoglucomutase differentiated two groups among the isolates collected from cultivated sunflower, while the other enzymes were polymorphic between isolates from the different hosts. Polymorphisms were not related to virulence phenotype.