First report of Colletotrichum orchidophilum causing necrotic spots on flowers of Laelia tenebrosa.

Among the 2,692 orchid species endemic to Brazil, Laelia tenebrosa has significant economic value because of the beauty of its flowers and the size of the plant. Despite being listed as endangered, it is one of the most cultivated Laelia species. Anthracnose is one of the main diseases affecting orchids. The fungus responsible for the disease, Colletotrichum sp., can spread efficiently in orchid collections in Brazil owing to favorable temperature and humidity conditions. To date, 46 species of Colletotrichum have been identified as the causal agents of anthracnose in various orchid species worldwide. In December 2018, flowers of Laelia tenebrosa (Orchidaceae) with necrotic spots were collected from the orchidarium maintained at the coffee nursery of the Universidade Federal de Viçosa (UFV), State of Minas Gerais, Brazil. The fungus was identified based on morphological characteristics and phylogenetic analyses using Bayesian inference, and the maximum likelihood method was performed using sequences from each region (ACT, CHS, GAPDH, ITS, and TUB2) and concatenated sequences. The disease is caused by Colletotrichum orchidophilum, a species known to infect Bletilla striata in China, Cycnoches aureum in Panama, Dendrobium sp. in Thailand and the United States, Phalaenopsis sp. in the United Kingdom, x Ascocenda sp. in the United States, and Reunion Island as the causal agent of black spots on Vanilla planifolia. For the first time, C. orchidophilum was reported in Brazil and was the first to cause anthracnose in Laelia worldwide.