Molecular markers are becoming more and more popular for species identification — a practice known as DNA barcoding. Researchers sequence a region of the genome from an organism of interest and search that sequence against a DNA database using BLAST. Such an analysis is contingent on a comprehensive database containing sequences from representatives of many diverse taxa.
We do not possess such a database for fungal species. Researchers have estimated that less than 5% of all fungal species have been identified, which means the chances are good that you may be the first person to sequence anything — let alone a common molecular marker — from a fungal species you are interested in identifying. Adding to the problem, a paper in PLoS ONE reports that approximately 20% of fungal sequences are misidentified (either containing incorrect or insufficient information) at the species level in the International Nucleotide Sequence Database.
The authors report that less that 1% of all fungal species have sequences from the internal transcribed spacer (ITS) of the ribosomal genes — a common molecular marker — deposited in the database. The issue of incorrect or insufficient information seems trivial compared to that of lack of information. Whereas the goal of a database of cytochrome c oxidase I (COI) genes (a locus in the mitochondrial genome) from all animal species in 15-20 years may be feasible, it’s unlike that fungi — a taxon far more evolutionarily diverse that animals — will be there anytime soon.