First report of Cladosporium anthropophilum causing leaf spots on sourgrass (Digitaria insularis) in Brazil

Abstract

Sourgrass (Digitaria insularis L. Fedde) is one of the most aggressive agricultural weeds in the Americas, with widespread populations resistant to glyphosate and acetyl coenzyme A carboxylase (ACCase)–inhibiting herbicides. During a survey of the pathogenic mycobiota associated with sourgrass in Brazil, leaf spot symptoms were observed in December 2020 in Uberaba, Minas Gerais. Lesions were initially circular and later became elliptical, dark brown with a light brown center, occurring mainly on the adaxial leaf surface. A fungus was consistently isolated from necrotic leaf tissues and characterized based on morphological and molecular analyses. The isolate (COAD 3621; KDI 0118) exhibited morphological features typical of Cladosporium. Sequencing of the ITS, ACT, and TEF gene regions followed by BLASTn and multilocus phylogenetic analyses confirmed the identity of the fungus as Cladosporium anthropophilum. Pathogenicity tests conducted on healthy sourgrass plants resulted in severe leaf spot symptoms seven days after inoculation, and the pathogen was successfully reisolated, fulfilling Koch’s postulates. Cladosporium anthropophilum has been previously reported on other plant hosts; however, to our knowledge, this is the first report of C. anthropophilum causing leaf spots on D. insularis in Brazil. Studies evaluating the biocontrol potential of this isolate are currently in progress.