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United States Department of Agriculture

Agricultural Research Service

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

Location: Systematic Mycology and Microbiology

Title: Diverse multilocus molecular signatures from Colletotrichum caudatum associated with warm-season grasses

Author
item Crouch, Joanne

Submitted to: IMA Fungus
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 25, 2014
Publication Date: March 11, 2014
Citation: Crouch, J. 2014. Diverse multilocus molecular signatures from Colletotrichum caudatum associated with warm-season grasses. IMA Fungus. 5:17-30.

Interpretive Summary: Fungi cause leaf spot diseases of warm season grasses including those used in golf courses and as turf grass. One of these fungi occurs on a wide range of hosts throughout the world. In this research isolates of this disease-causing fungus from four continents were examined to determine if they were correctly identified. Both morphological and molecular characteristics were determined for each isolate. It was discovered that, although these fungi appear to be slightly different on each continent, they are all considered to be a single species. This fungal species is well characterized using DNA markers. Plant pathologists will use this research to determine the accurate identification of the fungi causing leaf spot diseases on golf course and turf grasses.

Technical Abstract: Colletotrichum caudatum is a widespread fungal pathogen of warm-season grasses. The fungus is traditionally differentiated from related Colletotrichum species through the presence of a unique filiform appendage at the conidium apex. Phylogenetic analysis of four DNA sequence markers from 22 C. caudatum isolated from six grass hosts recovered the morphospecies as a well-supported monophyletic group. Although closely related to other Colletotrichum species pathogenic to warm-season grasses (e.g. C. sublineola, C. falcatum, C. navitas and C. graminicola), the sister taxa placement of C. caudatum remained unclear. Intraspecific lineage diversification of C. caudatum isolates was evident across the molecular phylogenies, with four major C. caudatum subgroups identified. Subgroups were divided according to the continent from which samples were collected (USA, Australia, Japan, India), but this pattern may have been a sampling artifact, or impacted by host origin. Incongruence between individual gene trees, reticulate intraspecific relationships, and evidence for recombination indicated that the C. caudatum subgroups are suitably recognized as members of a single species. An epitype strain consistent with the C. caudatum lectotype specimen collection on Sorghastrum nutans from the midatlantic region of the USA is designated and illustrated.

Last Modified: 7/28/2014
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