ITS and secondary biomarkers in fungi: review on the evolution of their use based on scientific publications

In this review, we investigated the progress in the use of ribosomal DNA internal transcribed spacer (ITS) and other widely used biomarkers for fungal studies. To achieve this goal, qualitative and quantitative large-scale data mining from the literature and sequence-based searches in public databases was performed. Our survey indicates that the most relevant studies for the fungal barcoding area were published between 2012 and 2015. The ITS region was the most used biomarker within our dataset; however, a significant amount of studies have used ITS associated with other biomarkers, especially the 28S and 18S subunits. Despite the undoubted importance and usefulness of ITS, this genomic region cannot be considered a universal genomic marker for fungi. For some taxonomic groups, a conclusive identification at species level is not achieved using ITS and then another biomarker must be associated.