Studies on the interaction between grape-associated filamentous fungi on a synthetic medium

Abstract

Eleven fungi isolated from grapes and sun-dried grapes (Alternaria alternata, Cladosporium herbarum, Eurotium amstelodami, Penicillium janthinellum, P. decumbens, Trichoderma harzianum, Candida sp., Aspergillus carbonarius OTA-negative, A. carbonarius OTA-positive, A. niger var. niger. and A. japonicus var. aculeatus), were grown in SNM medium at different water activities (0.82–0.97) and temperature (20–40 °C) levels for 18 days. Pairs of one Aspergillus faced with one non-Aspergillus were grown at 0.87–0.97 aw and at 20 and 30 °C. In single cultures, daily radii were recorded. In paired cultures radii were recorded and each A. section Nigri isolate was given a dominance score. At high temperatures and low water activities, Penicillium isolates, E. amstelodami and A. niger var. niger showed higher growth rates, while T. harzianum only grew well at the highest water activity. In addition, A. section Nigri was dominant in most paired assays, being only surpassed by T. harzianum at 0.97 aw and 20 °C. Thus, prevalence of A. section Nigri in sun-dried grapes can be explained by its adaptation to environmental conditions of sun-drying, and by its capability to dominate other fungal species when coming into contact with them.

The authors are grateful to the Spanish Government (CICYT, Comisión Interministerial de Ciencia y Tecnología, project AGL2004-07549-05-01, grant BES-2003-2180 and Ramon y Cajal program) and to the Catalonian Government (CeRTA strategic project 2005 – 2006 “ Seguridad biótica y abiótica de los ali- mentos ” , Generalitat de Catalunya) for their financial support.