First report of grapevine black rot in Sardinia.

Grapevine black rot disease is caused by Guignardia bidwellii. It originated from North America but is now widespread all over the world. In Italy, it was reported only in northern regions like Friuli Venezia Giulia, Veneto, Liguria and Piedmont where infections are variable and rarely reach a high level of severity. In 2010 in northern Sardinia (Oschiri) symptoms resembling black rot were observed on young cv. Sultanina vines. The basal leaves of some shoots showed necrotic reddish brown spots with dark red margins and small black dots which were sometimes concentric. The canes were asymptomatic and the affected plants were few and contiguous. In spring 2011, the same symptoms were observed on cv. Cannonau in central Sardinia (Oliena). Infections were more severe and did not affect only the basal leaves but were also present in the axis of green shoots, petioles and rachis of several plants in the same vineyard. Some spots on the leaves were observed also in other vineyards in the same area. Microscopical observations revealed the presence of asexual fruiting structures, i.e. pycnidia containing one-celled, hyaline ovoid conidia with an apical hyaline appendage that measured 5.4±0.66 x 9.42±0.82 μm. All parameters were in accordance with those of Phyllosticta ampelicida, anamorph of G. bidwellii. According to typical symptoms and microscopic characters the disease was identified as black rot. Further studies are in progress to characterize the fungus and to assess its pathogenicity.