BIOCHEMICAL AND MOLECULAR TOOLS FOR THE DIFFERENTIATION OF AGGRESSIVE AND NONAGGRESSIVE ISOLATES OF THE OILSEED RAPE PATHOGEN, PHOMA-LINGAM

A number of aggressive and non-aggressive isolates of the rape seed (Brassica napus) pathogen Phoma lingam (teleomorph: Leptosphaeria maculans) were analyzed by three different biochemical approaches: the quantitative measurement of extracellular enzymes, which are believed to be involved in plant attack, the electrophoretic analysis of fungal surface proteins, and the analysis of restriction fragment length polymorphisms (RFLPs) in Southern blot experiments. Aggressive strains show elevated activity levels for cellulase, alpha- and beta-glucanase as well as for polygalacturonase. Furthermore, aggressive and non-aggressive isolates can clearly be characterized by their pattern of surface associated proteins and by RFLP analysis in Southern type experiments, using molecular probes for actin, ubiquitin, ribosomal RNA and the gene for elongation factor EF1 (TEF). Seven out of nine aggressive isolates but only one out of eleven non-aggressive strains contained plasmid-like DNA.