Fusarium amaranthuense sp. nov. from amaranth is an emergent species closely related to Fusarium circinatum.

Amaranth (Amaranthus spp. L) is not native to South Korea but cultivated in small scales for ornamental purposes as well as leafy vegetables and pseudo cereals. In this study, a new species within the genus Fusarium was isolated from amaranth, showing stem rot symptoms from a farmer field in Hwaseong, South Korea. The disease is characterized by dark-brown spots with black borders, leading to withering. Phylogenetic analysis based on concatenated sequences of translation elongation factor 1-alpha (TEF1), beta-tubulin (tub2), calmodulin (cmdA), RNA polymerase largest subunit (RPB1) and RNA polymerase II second largest subunit (RPB2) genes, revealed that the obtained isolates were formed a distinct clade within the Fusarium fujikuroi species complex and closely related to F. circinatum. Cultural and morphological characteristics and pathogenicity on healthy amaranth plants (stem and leaves) were examined. The isolates readily differentiated from F. circinatum based on 1-5 septate macroconidia and the absence of sterile hyphae. Based on molecular and morphological characteristics, this fungus is demonstrated to be a new species and is described here as Fusarium amaranthuense, the causal agent of stem rot of amaranth in South Korea.