First report of Cephaliophora tropica causing leaf spot on tomato (Solanum lycopersicum cv. Picus) in U.S.A

Abstract

A foliar disease characterized by tiny black spots developed on tomato cv. Picus in a greenhouse at The Ohio State University, Columbus, U.S.A in 2022. The related diseased tomato leaf samples were collected to identify the causal agent of the leaf spot disease. Colonies with consistent morphological characteristics to the genus Cephaliophora were isolated from the diseased lesions of tomato leaves. The pathogenicity test was performed by inoculating the isolates on tomato leaves (Picus variety) using the foliar spray method. The same symptom of black spots appeared on all the inoculated leaves in the greenhouse, which was the same as observed originally. The fungal colonies were re-isolated from the diseased leaves and examined under a microscope for morphological identification. Molecular sequencing was performed by amplifying the 18S rRNA gene and the large subunit (28S) of the rRNA gene of the representative isolates. The phylogenetic comparison was subsequently carried out with the sequences of the recognized species retrieved from Genebank. The phylogenetic analyses provided the basis for identifying the isolates as Cephaliophora tropica. To our knowledge, this is the first worldwide report of C. tropica causing leaf spots on tomato and the first record of this fungal pathogen in plant host in U.S.A.