Resolving the Phoma enigma.

Area of Science:

• Mycology
• Plant Pathology
• Fungal Taxonomy

Background:

• The fungal family Didymellaceae, established in 2009, includes important plant pathogens, saprobes, and endophytes.
• Distinguishing between Ascochyta and Phoma genera is challenging due to morphological similarities, complicating their classification within Didymellaceae.
• Past taxonomic studies have linked species from Ascochyta and Phoma to Didymella sexual morphs, necessitating a clearer generic delimitation.

Purpose of the Study:

• To resolve the generic boundaries within the Didymellaceae family.
• To provide a robust phylogenetic framework for Didymellaceae classification.
• To update the taxonomy of Ascochyta, Didymella, and Phoma, including emending generic descriptions.

Main Methods:

• Multi-locus phylogenetic analyses using ITS, LSU, rpb2, and tub2 sequence data.
• Morphological examination of fungal specimens.
• Taxonomic revisions including the designation of epitypes and neotypes.

Main Results:

• Phylogenetic analyses identified 17 well-supported monophyletic clades within Didymellaceae.
• Nine new genera, three new species, two new names (nomina nova), and 84 new combinations were introduced.
• Ascochyta, Didymella, and Phoma were delineated as distinct genera, with emended generic circumscriptions for Ascochyta, Didymella, Epicoccum, and Phoma.
• The genus Microsphaeropsis was found to be basal to Didymellaceae, leading to the establishment of the new family Microsphaeropsidaceae.

Conclusions:

• The study provides a refined generic delimitation for Didymellaceae based on molecular and morphological data.
• The revised taxonomy enhances the understanding of fungal diversity and relationships within this important family.
• The establishment of Microsphaeropsidaceae reflects the distinct phylogenetic position of Microsphaeropsis outside the Didymellaceae.