Identification and Characterization of Neodidymelliopsis cynanchi, the Causal Agent of Milkweed Leaf Lesions

Calotropis procera is a shrub or small tree growing in tropical regions of the southern provinces in Iran. The economic benefits of the shrub include the use of latex and extract in traditional medicine. In a survey conducted in the southern provinces of Iran, leaf lesion symptoms were observed on C. procera shrubs. The purpose of the current study was to identify and characterize putative pathogens causing these symptoms. Isolations from the symptomatic tissues yielded predominantly a fungus belonging to the Didymellaceae family of Ascomycota. The causal agent was identified as Neodidymelliopsis cynanchi, based on morphological characteristics, and multilocus phylogenetic analysis using ITS, LSU, rpb2, and tub2 sequences. Pathogenicity tests on four-month-old seedlings of C. procera revealed that the isolates caused typical leaf lesions on the host. To the best of our knowledge, this is the first report of N. cynanchi causing disease on C. procera worldwide and the first report of the occurrence of this species in Iran.