Reconsidering the taxonomy of Sclerotinia with special reference to S. sclerotiorum

Abstract

The taxonomy of Sclerotinia has remained largely unchanged since the last revision of the genus 45 years ago. This monographic revision by Linda Kohn evaluated potential Sclerotinia species on the basis of morphological differences, and was invaluable in stabilising the taxonomy of this important plant pathogenic genus. Since then, little has been done to bring Sclerotinia taxonomy into the phylogenetic age. This project sought to address this by generating sequence data from the type specimen of S. sclerotiorum, the generic type for Sclerotinia. This sequence then provided a foundation from which to evaluate the current molecular marker used for Sclerotinia identification, and to conduct the first multi-gene and phylogenomic evaluation of Sclerotinia. The first chapter of this dissertation is a review of the taxonomic history of Sclerotinia, with a focus on the monographic revision of the genus and the changes that have occurred since. Recommendations for future research in Sclerotinia taxonomy are also explored. In Chapter 2 an ITS sequence is generated from S. sclerotiorum lectotype material that is more than 160 years old. This sequence was then used in an evaluation of the informativeness of the ITS region for species identification in Sclerotinia. The final chapter investigates the taxonomy of Sclerotinia using both multigene and phylogenomic analyses, providing a phylogenetic framework for the genus which allowed for the evaluation of some of the changes made by Kohn. Additionally, gene regions which could serve as a more reliable marker for species delineation than ITS were evaluated.