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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Mycology and Nematology Genetic Diversity and Biology Laboratory » Research » Publications at this Location » Publication #337355

Research Project: Systematics and Diagnostics of Emerging and Quarantine-Significant Plant Pathogenic Fungi

Location: Mycology and Nematology Genetic Diversity and Biology Laboratory

Title: Juglanconis gen. nov. on Juglandaceae, and the new family Juglanconidaceae (Diaporthales)

item Voglmayr, Hermann
item Castlebury, Lisa
item Jaklitsch, Walter

Submitted to: Persoonia: Molecular Phylogeny and Evolution of Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2017
Publication Date: 1/19/2017
Citation: Voglmayr, H., Castlebury, L.A., Jaklitsch, W.M. 2017. Juglanconis gen. nov. on Juglandaceae, and the new family Juglanconidaceae (Diaporthales). Persoonia: Molecular Phylogeny and Evolution of Fungi. 38(1):136-155. doi: 10.3767/003158517X694768.

Interpretive Summary: Each year in the United States, fungi destroy billions of dollars of crops, agricultural products, and ornamental and forest trees. In order for scientists to study and control these fungi, it is necessary to have accurate names. Fungi in the genus Melanconis occur on many different tree hosts with some species causing disease and other co-existing with their host plants without causing disease. It was recently discovered that some species placed in the genus Melanconis infecting walnut trees had different DNA sequences and should be given a new name. This research will be used by extension agents, plant breeders, plant pathologists, and plant quarantine officials to implement management strategies for diseases caused by these species and to accurately determine the presence of these species in the United States and other countries.

Technical Abstract: Molecular phylogenetic analyses of ITS-LSU rDNA sequence data demonstrate that Melanconis species occurring on Juglandaceae are phylogenetically distinct from Melanconis sensu stricto, and the new genus Juglanconis is described. Morphologically, the genus Juglanconis differs from Melanconis by light to dark brown conidia with irregular verrucae on the inner surface of the conidial wall, while in Melanconis sensu stricto they are smooth. Juglanconis forms a separate clade not affiliated with a described family of Diaporthales, and the family Juglanconidaceae is described. A phylogenetic relationship to the highly supported Melanconidaceae-Gnomoniaceae clade receives high support. Macro- and microscopic morphology and phylogenetic multigene analyses of partial nuSSU-ITS-LSU rDNA, cal, his, ms204, rpb1, rpb2, tef1 and tub2 sequences revealed 4 distinct species of Juglanconis. Comparison of the markers revealed that tef1 introns are the best performing markers for species distinction, followed by cal, ms204 and tub2. The ITS, which is the primary barcoding locus for fungi, is amongst the poorest performing markers analysed, due to the comparatively low number of informative characters. Melanconium juglandinum (=Melanconis carthusiana), M. oblongum (=Melanconis juglandis) and M. pterocaryae are formally combined into Juglanconis, and J. appendiculata is described as a new species, which is well distinct from the other species by ascospores with short cylindrical appendages and narrow, light brown, pip-shaped conidia. Melanconium juglandinum and Melanconis carthusiana are neotypified and M. oblongum is lectotypified. A short description and illustrations of the holotype of Melanconium ershadii from Pterocarya fraxinifolia are given, but it is not considered to belong to Juglanconis; due to the lack of sequence data its phylogenetic position within Diaporthales remains unresolved. A key to all treated species of Juglanconis is provided. The European Juglanconis appendiculata and J. juglandina are co-occurring on the same hosts (Juglans regia, J. nigra), often even on the same branches.