Survey of the presence of ochratoxin A-producing fungi and ochratoxin A in grapes grown under organic and integrated systems in Umbria, central Italy.

A survey was conducted in 2013 on a total of five Umbrian organic and integrated vineyards in order to determine the occurrence of mycotoxigenic fungi in grapes, to identify the isolated species and to assess their ochratoxin A (OTA) production in vitro. Four integrated vineyards were located at Magione (plain) and Castel Rigone (hill) (Perugia, central Italy) and included a white (Chardonnay) and a red (Cabernet Sauvignon) variety, while the organic vineyard, located at Cannara (Perugia, central Italy), included three red grape varieties (Cabernet Sauvignon, Sangiovese, Sagrantino) and one white grape variety (Grechetto). Grapes were collected from mid-June to September at four development stages: fruit set, pea-size berries, veraison and harvest. Small pieces from each bunch were transferred into moist chambers while eight berries were plated on PDA and MEA nutritive media. Vineyard phytosanitary conditions were also monitored throughout the growing season by the use of moist chambers which revealed that vines were affected by downy and powdery mildew due to incorrect and inadequate use of control measures. Alternaria, Penicillium, Cladosporium, Aspergillus were the most frequent isolated genera from grapes from setting to harvest. In particular, Alternaria spp., Penicillium spp. and Cladosporium sp. were abundant over the entire season while Aspergillus spp. populations increased from veraison to harvest. Aspergillus colonization was prevalent on the secondary branches and berries of the bunch. The incidence of Aspergillus spp. increased with berry ripening on all wine cultivars. Botrytis cinerea colonization was low during the grape growing season but severe attacks were noticed at harvest on Cabernet Sauvignon in an integrated vineyard located in the plain. Fifty-three Aspergillus spp. were isolated from berries collected in the integrated (26) and organic (27) vineyards. Based on molecular identification, most of Aspergillus isolates were identified as A. niger sensu stricto, A. tubingensis and A. japonicus. Other black aspergilli were identified as belonging to A. niger aggregate. A. carbonarius, reported as the main OTA producer, was never isolated. According to ELISA assays, all Aspergillus isolates produced OTA in vitro with concentrations varying from 2.1 µgL-1 to 77.5 µgL-1.