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

We report on the discovery and characterization of a novel <i>Fusarium</i> species that produced yellow-orange pseudoflowers on <i>Xyris</i> 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 <i>RPB1</i> (RNA polymerase largest subunit), <i>RPB2</i> (RNA polymerase second largest subunit), and <i>TEF1</i> (elongation factor 1-α) DNA sequences mined from genome sequences resolved the fungus, described herein as <i>F. xyrophilum</i>, sp. nov., as sister to <i>F. pseudocircinatum</i> within the African clade of the <i>F. fujikuroi</i> species complex. Results of a polymerase chain reaction (PCR) assay for mating type idiomorph revealed that single-conidial isolates of <i>F. xyrophilum</i> had only one of the <i>MAT</i> idiomorphs (<i>MAT1-1</i> or <i>MAT1-2</i>), which suggests that the fungus may have a heterothallic sexual reproductive mode. BLASTn searches of whole-genome sequence of three strains of <i>F. xyrophilum</i> indicated that it has the genetic potential to produce secondary metabolites, including phytohormones, pigments, and mycotoxins. However, a polyketide-derived pigment, 8-<i>O</i>-methylbostrycoidin, was the only metabolite detected in cracked maize kernel cultures. When grown on carnation leaf agar, <i>F. xyrophilum</i> is phenotypically distinct from other described <i>Fusarium</i> 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.