Morphological and biochemical characterization of Armillaria isolates from Zimbabwe.

Variations in cultural and biochemical characteristics have been used to group 20 Armillaria isolates collected from different hosts and regions in Zimbabwe. Morphological features, including colony type and rhizomorph characteristics in vitro, rhizomorph characteristics from inoculum buried in soil, and features of basidiocarps produced in vitro on wood, millet and oranges, divided the Zimbabwean isolates into three morphologically distinct groups, designated I, II and III. Biochemical attributes involving isozyme and protein patterns studied by electrophoresis and isoelectric focusing also indicated three groups which corresponded precisely with the three groups observed for morphological studies. Isozyme analyses of pectin lyase (PL), pectin methylesterase (PME), beta-1,3-glucanase, nonspecific esterases and putative suberinases were important in grouping the isolates. Pectin lyase and pectin methylesterase patterns gave the clearest and mostly easily interpreted results. Total protein patterns by SDS–polyacrylamide gel electrophoresis also showed some group-specific bands. Cluster and principal component analyses of the data confirmed the separation of the Zimbabwean Armillaria isolates into three distinct groups.