WATER RELATIONS OF ASPERGILLUS-FLAVUS AND CLOSELY-RELATED SPECIES

The water relations of three isolates representative of each of the closely related species Aspergillus flavus, A. nomius, A. oryzae and A, parasiticus were examined at three temperatures, 25 degrees C, 30 degrees C and 37 degrees C. Media were prepared over a wide range of water activity (a(w)) from 0.996 to 0.75, controlled by a mixture of glucose and fructose. Water relations of A. flavus, A. oryzae and A. parasiticus were very similar. The minimum a(w) for germination and growth of each of these three species was 0.82 at 25 degrees C, 0.81 at 30 degrees C and 0.80 at 37 degrees C. A. nomius was slightly less xerophilic, with minimum a(w) values for germination and growth of 0.83 at 25 and 30 degrees C, and 0.81 at 37 degrees C. Reported differences in water relations between A. flavus and A. parasiticus were not substantiated. The ''domestication'' of A. oryzae has not affected its water relations.