Molecular reassessment of diaporthalean fungi associated with strawberry, including the leaf blight fungus, Paraphomopsis obscurans gen. et comb. nov. (Melanconiellaceae)

Authors: UDAYANGA, DHANUSHKA - University Of Sri Jayewardenepura; MIRIYAGALLA, SHANEYA - University Of Sri Jayewardenepura; MANAMGODA, DIMUTHU - University Of Sri Jayewardenepura; Lewers, Kimberly; GARDIENNET, ALAIN - Mycological Society; Castlebury, Lisa

Submitted to: IMA Fungus
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2021
Publication Date: 6/22/2021
Citation: Udayanga, D., Miriyagalla, S.D., Manamgoda, D.S., Lewers, K.S., Gardiennet, A., Castlebury, L.A. 2021. Molecular reassessment of diaporthalean fungi associated with strawberry, including the leaf blight fungus, Paraphomopsis obscurans gen. et comb. nov. (Melanconiellaceae). IMA Fungus. https://doi.org/10.1186/s43008-021-00069-9.
DOI: https://doi.org/10.1186/s43008-021-00069-9

Interpretive Summary: Fungi that have been known in the genus Gnomonia occur on many different plant hosts and several are known to cause diseases on strawberries. Because these fungal species have similar microscopic appearances, they are often difficult to identify correctly. In this study, three species of strawberry pathogens were isolated and characterized using DNA sequences and cultural characteristics. Results revealed that one species should be referred to under a different name and that one represented an entirely new genus. New images and descriptions of all three species were provided. This research will be used by extension agents, plant breeders, plant pathologists, and plant quarantine officials to implement management strategies and to accurately determine the presence of these species in the United States and other countries to enhance the control of strawberry diseases.

Technical Abstract: Phytopathogenic fungi in the order Diaporthales (Sordariomycetes) cause diseases on numerous economically important crops worldwide. In this study, we reassessed the diaporthalean species associated with prominent diseases of strawberry, namely leaf blight, leaf blotch, root rot and petiole blight, based on molecular data and morphological characters using fresh and herbarium collections. Combined analyses of four nuclear loci, 28S ribosomal DNA/large subunit rDNA (LSU), ribosomal internal transcribed spacers 1 and 2 with 5.8S ribosomal DNA (ITS), and partial sequences of second largest subunit of RNA polymerase II (RPB2) and translation elongation factor 1-a (TEF1), were used to reconstruct a phylogeny for these pathogens. Results confirmed that the leaf blight pathogen formerly known as Phomopsis obscurans belongs in the family Melanconiellaceae and is not congeneric with Diaporthe (syn. Phomopsis). A new genus Paraphomopsis is introduced herein with a new combination, Paraphomopsis obscurans, to accommodate the leaf blight fungus. Gnomoniopsis fragariae comb. nov. (Gnomoniaceae), is introduced to accommodate Gnomoniopsis fructicola, the cause of leaf blotch of strawberry. Fresh collections and new molecular data were incorporated for the recently typified species, Paragnomia fragariae (Sydowiellace), which causes petiole blight and root rot of Fragaria spp. and is distinct from the above taxa. An updated multi-locus phylogeny for the Diaporthales is provided to place and distinguish the leaf blight and leaf blotch pathogen, as well as the species associated with petiole blight and root rot of strawberry.