Records of Pseudomonas syringae pv. actinidiae on Actinidia spp. in Trentino (North-East Italy)

During 2012-2015, extensive field surveys were performed in new and old kiwifruit orchards located in the province of Trento (North-East of Italy). Symptoms resembling those incited by Pseudomonas syringae pv. actinidiae (Psa) (i.e, leaf spotting, twig wilting) were observed mainly on Actinidia deliciosa cv. Hayward and in a new orchard planted with A. chinensis cv. Soreli. The incidence of the disease ranged from 1% to 80%, and some old Hayward orchards (i.e., 35 years old) resulted severely damaged. From all infected orchards, samples were collected and, subsequently, processed in the laboratory for isolation by following routinely procedures (Ferrante and Scortichini, 2009). Bacterial isolates were obtained from all infected kiwifruit orchards; they were identified according to the techniques described by Ferrante and Scortichini (2010). Upon repetitive-sequence PCR using BOX, ERIC and REP primer sets, their fingerprint pattern perfectly matched that shown by the pandemic Psa 3 strain CRA-FRU 8.43. In addition, with isolates representative of all the sites from where the samplings were obtained, pathogenicity tests were carried out by artificially inoculating one-year-old, pot-cultivated A. deliciosa cv. Hayward plants according to the techniques described by Ferrante and Scortichini (2009, 2010). All the isolates induced, upon 10-15 days from the inoculation, the leaf spot and wilting symptoms. On the basis of these results, we conclude that P. s. pv. actinidiae was the causal agent of the field symptoms observed in green-fleshed and yellow-fleshed kiwifruit orchards located in Trentino. This is the first record of the disease in this region