Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Definition of the role of ecological factors on Aspergillus Section Nigri on growth and OTA production

The study examined, for the first time, the detailed effect of temperature x aw conditions on germination and germ tube extension of spores of A.carbonarius. This is critical in defining the capacity of contaminant spores to become established on grapes and subsequently grow and produce OTA. Germination occurs very rapidly in vitro suggesting that a wide range of aw x temperature levels over which infection could occur. Studies on grape tissue and grape skin confirmed that at >85% ERH conducive conditions occur for spore germination and establishment on grapes if insect damage or cracking of the skin surface occurs. This study has been the first to confirm that optimum environmental conditions for OTA production by A.carbonarius isolates are very different from the optimum for germination and growth. Thus optimum OTA production was at 15-20°C depending on isolate, with optimum aw conditions of 0.95-0.98. The amount of OTA produced varied markedly between isolates from different countries. The fact that partitioning of OTA results in a greater accumulation in spores than fungal biomass or medium suggests that sometimes the presence of large numbers of spores on the grape surface but largely passively present could result in OTA contamination despite no skin damage.

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