Alternaria alternata causes bud blight of rose (Rosa sp.) in Cotopaxi, Ecuador

Grey mould, caused by Botrytis cinerea, is a common necrotrophic plant pathogen that infects the petals of ornamentals. In 2017–18 we collected, from a farm located in the Ecuadorian province of Cotopaxi, 30 buds of the rose ‘Vendela’ that showed petal lesions similar to those caused by grey mould. For causal agent isolation and morphological characterization, the infected tissue was incubated on potato dextrose agar (PDA). Isolated fungal colonies grown on PDA showed grey-olive to dark green mycelium and conidia borne in chains with zero to three longitudinal septa and two to six transversal septa, indicating the presence of an Alternaria sp. A multilocus Bayesian inference phylogenetic analysis, including the internal transcribed spacer (ITS), RNA polymerase II (RPB2), and translation elongation factor 1-alpha (TEF1) gene regions, indicated that the isolates clustered with isolates of A. alternata. After pathogenicity analysis, A. alternata-inoculated rose petals showed similar symptoms to botrytis blight. To fulfill Koch’s postulates, the pathogen was re-isolated successfully. Here, we report that A. alternata is causing disease symptoms in rose buds/petals in Ecuador.