Rehydrated wheat was place in sterile 9-cm Petri dishes to form a monolayer of grains (?20 g). Then a 3-mm-diameter agar disk was taken from the margin of a 7-day-old growing colony of each isolate on synthetic nutrient agar (Gerlach and Nirenberg, 1982) at 25 -C and transferred face down to the centre of each plate. To maintain the correct equilibrium relative humidity inside the boxes, Petri plates containing grains of the same aW were enclosed in plastic containers together with two beakers of glycerol –water solution of the same aW as the treatments. Containers were incubated at 5, 15, 25 and 30 -C and the experiment consisted of a fully replicated set of treatments with three replicates per treatment and the whole set carried out twice. Grain layers were checked to ensure that the appropriate target aW (T0.005) was achieved