A monograph of Allantonectria, Nectria, and Pleonectria (Nectriaceae, Hypocreales, Ascomycota) and their pycnidial, sporodochial, and synnematous anamorphs

Authors: HIROOKA, Y. - University Of Maryland; Rossman, Amy; Samuels, Gary; LECHAT, C. - Collaborator; CHAVERRI, P. - University Of Maryland

Submitted to: Studies in Mycology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2011
Publication Date: 3/15/2012
Citation: Hirooka, Y., Rossman, A.Y., Samuels, G.J., Lechat, C., Chaverri, P. 2012. A monograph of Allantonectria, Nectria, and Pleonectria (Nectriaceae, Hypocreales, Ascomycota) and their pycnidial, sporodochial, and synnematous anamorphs. Studies in Mycology. 71:1-210.

Interpretive Summary: Fungi are a group of organisms that cause billions of dollars damage each year to agricultural and forest resources in the United States. One group of fungi includes fungal species that cause canker diseases on woody plants such as cherry and apple trees. In this research hundreds of specimens and living cultures of three genera of canker-causing fungi from around the world were examined to determine both their macroscopic and microscopic appearance. In addition molecular sequence data were analyzed to evaluate the relationships among the species. Of the 56 species included, thirteen species are new to science. All species of these three genera are described and illustrated with a key for their identification. This research will be used by plant pathologists and plant quarantine officials to identify the fungi that cause diseases on woody plants.

Technical Abstract: Although Nectria is the type genus of Nectriaceae (Hypocreales, Sordariomycetes, Pezizomycotina, Ascomycota), the systematics of the teleomorphic and anamorphic state of Nectria sensu Rossman has not been studied in detail. The objectives of this study were to 1) provide a phylogenetic overview to determine if species of Nectria with Gyrostroma, Tubercularia and Zythiostroma anamorphs form a monophyletic group; 2) define Nectria, segregate genera, and their species using morphologically infromative characters of teleomorphic and anamorphic states; and 3) provide descriptions and illustrations of these genera and species. To accomplish these objectives, phylogenetic analyses of DNA sequence data from six loci (i.e., act, ITS, LSU, rpb1, tef1 and tub), and integrated morphological characterizations of anamorphs and teleomorphs were completed. Results from the phylogenetic analyses demonstrate that species previously regarded as the genus Nectria having Gyrostroma, Tubercularia, and Zythiostroma anamorphs belong in two major paraphyletic clades. In the first major clade, Pleonectria clade contains 26 species with ascoconidia produced by ascospores in asci, perithecial walls having bright yellow scurf, and immersed or superficial pycnidial anamorphs (Zythiostroma = Gyrostroma). A lineage basal to the Pleonectria clade includes Nectria miltina having very small, aseptate ascospores and trichoderma-like conidiophores and occurring on monocotyledonous plants. These characteristics are unusual in Pleonectria, thus we recognize the monotypic genus Allantonectria with Allantonectria miltina. The second major clade comprises the genus Nectria sensu stricto including the type species, N. cinnabarina, and 28 additional species. Within the genus Nectria, four subclades exist. One subclade includes species with sporodochial anamorphs and another with synnematous anamorphs. The other two paraphyletic subclades include species that produce abundant stromata in which the large perithecia are immersed, large ascospores, and peculiar anamorphs that form pycnidia or sporodochia either on their natural substrate or in culture. In this study the evolution of species, morphology, and ecology of the three genera, Allantonectria, Nectria, and Pleonectria, are discussed based on the phylogenetic analyses. In addition, descriptions, illustrations, and keys for identification are presented for the 56 species in Allantonectria, Nectria, and Pleonectria.