Characterisation of Armillaria species based on pectic isozyme analyses

Abstract

Armillaria spp. are the causal agents of Armillaria root rot on a wide variety of mainly woody plants. Identification of these fungi using morphological characteristics is complicated by the fact that fruiting structures are uncommon and often ephemeral. Pectic isozyme analysis has been successfully applied in taxonomic studies of Armillaria species. This technique, however, has never been used in a study that included a collection of species from across the world. In the present study, 36 Armillaria isolates, representing 17 Armillaria spp. from different hosts and geographic regions were characterised using isozyme patterns for pectin lyase (PL), pectin methylesterase (PME) and polygalacturonase (PG). Isozyme patterns were determined directly from culture filtrates through electrophoresis in polyacrylamide gels stained in ruthenium red. The majority of species could clearly be separated from one another and isolates belonging to the same species had similar banding patterns, grouping them together after cluster analysis. Results from this study showed that pectic enzyme analysis can be an effective tool in the identification of Armillaria species. Furthermore the isozyme analysis supports previous observations regarding the relationships between Armillaria species.