Fusarium xyrophilum, sp. nov., a member of the Fusarium fujikuroi species complex recovered from pseudoflowers on yellow-eyed grass (Xyris spp.) from Guyana

ABSTRACT

We report on the discovery and characterization of a novel Fusarium species that produced yellow-orange pseudoflowers on Xyris spp. (yellow-eyed grass; Xyridaceae) growing in the savannas of the Pakaraima Mountains of western Guyana. The petaloid fungal structures produced on infected plants mimic host flowers in gross morphology. Molecular phylogenetic analyses of full-length RPB1 (RNA polymerase largest subunit), RPB2 (RNA polymerase second largest subunit), and TEF1 (elongation factor 1-α) DNA sequences mined from genome sequences resolved the fungus, described herein as F. xyrophilum, sp. nov., as sister to F. pseudocircinatum within the African clade of the F. fujikuroi species complex. Results of a polymerase chain reaction (PCR) assay for mating type idiomorph revealed that single-conidial isolates of F. xyrophilum had only one of the MAT idiomorphs (MAT1-1 or MAT1-2), which suggests that the fungus may have a heterothallic sexual reproductive mode. BLASTn searches of whole-genome sequence of three strains of F. xyrophilum indicated that it has the genetic potential to produce secondary metabolites, including phytohormones, pigments, and mycotoxins. However, a polyketide-derived pigment, 8-O-methylbostrycoidin, was the only metabolite detected in cracked maize kernel cultures. When grown on carnation leaf agar, F. xyrophilum is phenotypically distinct from other described Fusarium species in that it produces aseptate microconidia on erect indeterminate synnemata that are up to 2 mm tall and it does not produce multiseptate macroconidia.

KEYWORDS:

• Floral mimicry
• MAT idiomorphs
• molecular phylogenetics
• morphology
• RPB1
• RPB2
• synnemata
• TEF1
• whole genome
• 1 new taxon

ACKNOWLEDGMENTS

The authors thank Gail Doehring, Amy McGovern, Nathane Orwig, and Deborah S. Shane for skilled technical assistance. The authors also thank Mark Strong (SI) for the Xyris identifications. The authors are also indebted to the reviewers and associate editor for numerous suggestions for improving this submission.

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Funding

The US Department of Agriculture Agricultural Research Service (USDA-ARS) National Program for Food Safety and National Science Foundation (NSF; DEB-1655980) provided funding for this study. This research was supported in part by an appointment to the ARS Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the US Department of Energy (DOE) and the US Department of Agriculture (USDA). ORISE is managed by ORAU under DOE contract number DE-SC0014664. All opinions expressed in this paper are the authors’ and do not necessarily reflect the policies and views of USDA, DOE, or ORAU/ORISE. Field work by Kenneth J. Wurdack was supported by the National Geographic Society/Waitt Grants Program (Karen Redden, Principal Investigator) and the Biological Diversity of the Guiana Shield Program, Smithsonian Institution.