Enhancing the relevance of fungal taxonomy to plant pathology: phylogenetics, molecular diagnostics, and long-term memory

Fungal taxonomy is moving from subjective morphology-based concepts to phylogenetic DNA-based concepts. This enables development of rapid, broad-scale, and accurate molecular diagnostics but does not put taxonomists out of business. Present trends indicate that most fungal species are delimited too broadly. As the age of molecular diagnostics emerges, a renewed era of species discovery has also begun. The two must develop together if the molecular assays are to be sufficiently precise. The phytopathogenic and mycotoxin-producing genus Fusarium illustrates this point. Species considered synonyms by morphologists are often shown to be different by phylogenetic studies, meaning that old names must be reconsidered before new species are described. Commercially viable molecular diagnostics focus on species of present economic importance, but as new species are delimited and their ecological roles are elucidated, the interactions between all groups of microorganisms can be investigated, irrespective of taxonomic group or a priori perceptions of significance. Total ecosystem profiling, involving the detection, identification, and quantification of all organisms present in an ecosystem irrespective of their kingdom or phylum, is an important goal for enhancing the relevance of taxonomy to plant pathology.