Aspergillus section Nigri and ochratoxin A in Argentinian wine grapes

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

Sicilia, Italia

Congreso; International workshop Ochratoxin A in grapes and wine: prevention and control; 2005

Caviro, Faculty of Africulture paicenza, ISPA

The evolution of contamination with 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 of early maduration (Tempranillo). The vineyards were set 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) media (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 medium (2% yeast extract, 15% sucrose).  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 contamination with Aspergillus section Nigri. The main species isolated belonged to A. niger aggregate.  From 246 strains evaluated 24% were ochratoxigenic,. The levels of toxin produced ranged from 1.3 to 50 ng/mL of culture medium. OTA was not detected in grapes during the survey, considering a detection limit of 1 ng/g. The climatic conditions were recorded and were quite different from those recorded in a survey carried out in Italy. It appears that the climatic differences among different grape-growing areas may be responsible for differences in OTA contamination in grapes.