Characterization and pathogenicity of Plectosphaerella spp. collected from basil and parsley in Italy

From 2012-2016 plants of basil (Ocimum basilicum L.) and parsley (Petroselinum sativum Hoffm.) showing decline symptoms were collected from local markets in Foggia Province (southern Italy) and assessed to determine their main fungal pathogens. These plants showed symptoms including leaf yellowing, necrotic lesions on stems, collar and roots, and in some cases, stunting of entire plants. Mycological analyses revealed fungal isolates mainly belonging to the Plectosphaerella genus. Molecular and morphological studies identified four species of Plectosphaerella: Plectosphaerella cucumerina, P. pauciseptata, P. plurivora, and P. ramiseptata. To understand the pathogenic roles of these fungi, and five other reference Plectosphaerella spp., pathogenicity tests were performed in vitro and in-vivo using, respectively, detached leaves and 30-d-old plants of basil (cv. Napoletano) and parsley (cv. Gigante di Napoli). All the fungal species isolated produced host symptoms, including necrotic spots, parenchymatic patches, hydropic areas, collar and root discolouration on leaves and young plants, with varying severity. The most aggressive species on both plants were P. pauciseptata and P. ramiseptata, while P. alismatis, P. citrulli, P. cucumerina, P. delsorboi, P. melonis, and P. plurivora gave less disease severity on both plants. This is the first report worldwide of P. cucumerina, P. pauciseptata, and P. ramiseptata as pathogens of parsley, and P. pauciseptata, P. plurivora, and P. ramiseptata as pathogens of basil.