Plectosphaerella cucumerina: a new pathogen of rocket in Italy.
In April 2012, in a mutitunnel in the province of Salerno, some plants of wild rocket (Diplotaxis muralis and D. tenuifolia) showed severe foliar deformations never seen before on this plant. The leaves of affected plants had necrotic areas of irregular shape, often confluent and surrounded by chlorotic halos to the apex and leaf margins. Even the veins and petioles had punctate necrotic areas. Under high relative humidity, affected leaves gradually took on a soft consistency, the same rot observed on the packaged product compromising their marketing. At temperatures between 20 and 26°C, the spread of the pathogen appeared high with values varying between 25 and 35% of affected leaves predominantly located in more humid areas of the tunnel. Based on morphological observations and sequence analysis of the DNA internal transcribed spacer region, the causal agent was identified as Plectosphaerella cucumerina [Monographella cucumerina]. This is thought to be the first report of P. cucumerina on wild rocket in Italy and in the world.