Aspergillus section Nigri and ochratoxin A in Argentinean wine grapes

PONSONE, L.; COMBINA, M.; DALCERO, A.M.; CHULZE, S.N

Sicilia, Italia

Workshop; International Workshop “Ochratoxin A in grapes and wine: Prevention and Control”; 2005

The evolution of contamination whit Aspergillus section Nigri and ochratoxin A occurrence was evaluated in four vineyards located at Mendoza province, Argentina during 2003-2004. The survey included two grape varieties, one of late maduration (Bonarda) and other ofearly maduration (Tempranillo). The vineyards where setting under conventional and organic cropping systems. Bunches of grapes at different growth stages were collected, and berry samples were plated on petri dishes containing dichloran 18% glycerol agar (DG18) and Dichloran Rose Bengal Chloramphenicol agar (DRBC) medio (Pitt and Hocking 1997). After a incubation period of 7 days at 25 ºC ± 1 ºC, the mycoflora belonging to Aspergillus section Nigri was identified. The ability to produce ochratoxin A (OTA) by the potential ochratoxigenic species was evaluated on YES (2% yeast extract, 15% sucrose) medium. The cultures were incubated at 30 ºC ± 1ºC   for 10 days in darkness.  The OTA content of the grapes was determined by HPLC. Through the different growth stages, from setting to harvest, the grapes increased the level of Aspergillus section Nigri. The main species isolated belonged to A. niger aggregate.  From 246 strains evaluated 24% were ochratoxigenic. OTA was not detected in grapes during the survey. Key Words: Aspergillus section Nigri, Ochratoxin A, grapes