Emergence of Leaf Spot Disease on Leafy Vegetable and Ornamental Crops Caused by Paramyrothecium and Albifimbria Species

The genera and have been established from the former genus and they generally comprise common soil-inhabiting and saprophytic fungi. Within these genera, only two fungi have been recognized as phytopathogenic thus far: and , both of which cause necrotic leaf spots and plant collapse. Severe leaf necrosis and plant decay have been observed in Northern and Southern Italy on leafy vegetable crops. Thirty-six strains of and -like fungi were isolated from affected plants belonging to eight different species. Based on morphological characteristics, 19 strains were assigned to , whereas the remaining strains, which mostly resembled like fungi, could not be identified precisely. Molecular characterization of six loci (internal transcribed spacer [ITS], β-tubulin [ ], calmodulin [ ], translation elongation factor 1-alpha [ ], large subunit ribosomal RNA [LSU], and mitochondrial ATP 6synthase 6 [ ]) of the 36 new isolates and three previously ITS-characterized isolates assigned all strains to four species: , , , and Single and concatenated phylogenetic analyses were conducted, and they clearly distinguished the isolated fungi into four different groups. , , , and were able to induce leaf necrosis singly, and they were confirmed to be the causal agents of the leaf spot disease through pathogenicity assays. The involvement of fungi previously considered saprophytic (i.e., and ) in the development of plant disease for the first time deserves particular attention because of the possibility of their transmission by seeds and the limited knowledge of their management with chemicals.