Molecular approaches to differentiate subpopulations or formae speciales of the fungal phytopathogen Microbotryum violaceum

Microbotryum violaceum infects more than 200 species of Caryophyllaceae, although individual isolates of the fungus are Limited in host range to one or a feu species. The goal of the present study was to establish a molecular profile of individual haploid M. violaceum strains from different host species and to evaluate different methods for producing such profiles. Eighteen different sporidial strains from seven different host species were examined for electrophoretic karyotype, for random amplification of polymorphic DNA (RAPD) profile, by phylogenetic analysis of intron sequences in the gamma-tubulin gene, and by parsimony analysis of melting curves of total genomic DNA (DNA thermal profiles). While no one method could resolve all isolates from closely related host species, together the results obtained with these methods were able to group isolates based on their host species of origin. Taken together, host range/host species of origin and the genetic differences indicated by die molecular methods in this study would appear to define pathovars or formae speciales of this fungus.