LA REVOLUCIÓN DE LAS TÉCNICAS MOLECULARES EN EL ESTUDIO DE HONGOS. CAMPOS EXPLORADOS Y FUTURAS DIRECCIONES

Mª Paz Martín. Real Jardín Botánico de Madrid. CSIC.

The traditional method to characterize the fungi that grow in a particular region or habitat, as well as the community changes over time, was based during many years exclusively on morphological characters. However, since the last two decades molecular methods based on the Polymerase Chain Reaction (PCR) help to species identification not only from sporocarps, but also from pure cultures, mycelia, mycorrhizas or, for example, directly from soil. The polymorphism of the ITS1 and ITS2 (Internal Transcribed Spacers) regions of the nuclear ribosomal DNA is used for the identification of the fungi to the species level. First, the characterisation of fungi was done comparing the patterns obtained after digesting the amplimer with restriction enzymes (RFLP: Restriction Fragment Length Polymorphisms), but year after year the cost of sequencing was cheaper, allowing to known almost exactly the position of every nucleotide in a amplified fragment. Many published papers are based on comparing homologous regions among specimens to identify species. Members of CBOL (Consortium for the Barcode of Life) have agreed that the ITS1 and ITS2 could be the best barcode region for fungi; but selection of a second standardized region of the genome that allow an accurate delimitation and identification has not been finalized, and more loci, such as protein-coding regions (RPB1, RPB2 or ATP6) are being analyzed.

In this talk some examples of our contribution to the international barcoding initiative from projects at the Real Jardín Botánico-CSIC1 related to Basidiomicota will be shown, paying attention to the importance of integrating molecular tools with morphology and ecology, as well as the reference collections and to keep voucher specimens in secure repositories (museums, herbaria and culture collections).

Now, the process of barcoding (matching an unidentified specimen to a known species) takes a few hours and few euros, but when an unknown specimen does not return a close match to existing records in the barcode database (at this moment the GenBank or UNITE databases to fungi), the barcode sequence does not qualify the unknown specimen for designation as a “new species”. Instead, such specimens are flagged for thorough taxonomic study that is usually much slower that barcoding analysis. Since the number of trained taxonomists capable of describing biodiversity incorporating morphological characters is in decline, one of the main objectives in the future of fungi research should be to attract students to be involved in taxonomic studies, since the naming of the species and the assignment of specimens to species are of fundamental importance in conservation. The threatened or endangered status of an individual species can only be determined if the species itsef is recognized and identified.