Plectosphaerella cucumerina: a new pathogen on wild rocket in Italy.
In the spring 2012, plants belonging to wild [Diplotaxis tenuifolia (L.) D.C.] rocket grown in commercial greenhouses in Campania (Southern-Italy), showed symptoms of a new leaf spot. Affected plants showed black-brown leaf spot of irregular shape (1 mm) confluent to 10 mm in diameter, surrounded by a yellow halo, that were located on the foliar limb, rib and petiole of leaves. At later stages leaves may turn rot. The disease was severe under high humidity conditions at air temperature of 20-26°C, causing severe production losses. Severe losses were manifested after packaging. White to orange colonies with a ropy mycelium were consistently isolated on potato dextrose agar from leaf tissues of symptomatic plants. The ITS region (Internal Transcribed Spacer) of rDNA was amplified using the primers ITS1/ITS4. The nucleotide sequence has been assigned the GenBank Accession JX185769. The 519 bp segment obtained showed that the pathogen belong to Plectosphaerella cucumerina. Symptoms of this disease are reported, as well as the morphological and molecular identification of the pathogen. This is the first report of Plectosphaerella cucumerina on wild rocket in Italy as well as worldwide.