Taxonomic clarification of two Cercospora spp. causing leaf spots on Neomarica spp. in Brazil

Abstract

Neomarica is a genus of the Iridaceae with several ornamental species, including Neomarica caerulea (walking iris) and N. longifolia (yellow iris). Little is known about fungal diseases of members of the genus Neomarica. In June 2017, N. longifolia plants growing in a garden at Antonio Carlos were observed bearing leaf spots symptoms. A cercosporoid hyphomycete was associated with the necrotic tissues. It was conjectured that the fungus involved might be the same described causing leaf spots on N. caerulea in Brazil. Examination of the type of the species concerned (Cercospora neomaricae) revealed that this specimen was in very poor condition and inadequate for comparison. This prompted us to re-collect the fungus from the type locality for epitypification. Besides designating an epitype, a pure culture of C. neomaricae was obtained (ex-epitype culture) and a molecular study of this isolate together with the molecular and morphological analysis of the fungus on N. longifolia was performed. The fungus on N. longifolia was found to be morphologically and genetically clearly distinct from C. neomaricae. Analyses of the ITS, CAL and ACT regions indicated that the fungus on N. longifolia belongs to the Cercospora sp. H, which is an unresolved species complex, including several isolates obtained from various hosts.