Advancing the taxonomy of Sclerotinia (Helotiales, Sclerotiniaceae): a review and recommendations for an important plant-pathogenic genus

Sclerotinia is a fungal genus of both significant agricultural and scientific importance, as it contains multiple plant pathogens and provides an interesting case study for the mechanisms of host generalism. However, the taxonomy of this group is not settled, which hinders research into these pathogens. The last monographic treatment of Sclerotinia was published over 40 years ago and was centred on the morphological data available at the time. Here, we examine that revision alongside other pivotal publications to trace the taxonomic history of Sclerotinia and evaluate the morphological traits used to identify Sclerotinia species. We also briefly evaluate the composition of genera in the family Sclerotiniaceae , emphasising the need for a modern taxonomic investigation of the broader group. Thirteen new Sclerotinia species have been described since the last taxonomic revision, including Sclerotinia antarctica , S. asari , S. atrostipitata , S. cirsii-spinosissimi , S. ginseng , S. glacialis , S. himalayensis , S. nivalis , S. pseudoplatani , S. subarctica , S. tetraspora , S. trillii and S. verrucispora . These are evaluated here. Lastly, several recommendations are made for how future taxonomic research in Sclerotinia should embrace molecular data. We highlight potential obstacles and opportunities for this research, including the limitations of the internal transcribed spacer rDNA region (ITS) as a DNA barcode and the untapped resource present in genomic data for the genus. In outlining the gaps that need to be addressed, this review charts a course to creating a clearer understanding of the taxonomic relationships between Sclerotinia species. This understanding will simplify research endeavours into other aspects, such as pathogenicity and host generalism, which could ultimately help to manage the devastating diseases caused by these pathogens.