Phylogenomic analysis supports the transfer of Coniothyrium glycines, a soybean pathogen and USDA Select Agent, to the genus Aristastoma.

Red leaf blotch, caused by Coniothyrium glycines, is a major leaf spot disease of soybean in Africa. Because of its unique morphological characteristics, C. glycines has been placed in numerous genera since its description in 1957, and recent phylogenetic evidence has suggested that its current placement within Coniothyrium is incorrect. To provide nomenclatural stability, we reevaluated its evolutionary history and taxonomy using a phylogenomic approach. We produced draft genomes for 13 close relatives of C. glycines and generated a consensus tree from 4643 BUSCO genes in these species and related Dothideomycetes. We show that Coniothyrium is not monophyletic and C. glycines is closely related to Aristastoma oeconomicum, a once prevalent leaf spot pathogen of cowpea in the eastern United States. Similarities in morphology and disease symptomology, along with genome distance estimations and a phylogeny based on internal transcribed spacer (ITS) and partial nuclear 28S rDNA (D1-D2) data, support the transfer of C. glycines and another species, Coniothyrium dolichi, to Aristastoma. The inclusion of this species in Aristastoma expands the morphological concept of this genus to include species that produce sclerotia and have aseptate conidia. The improved systematics and genomic resources generated with this study will advance the development of diagnostics and detection assays of this high-consequence plant pathogen.