Natural occurrence of aflatoxin contamination on soybeans was investigated. Thirty four samples from the 1986 crop (5.8% positive samples) and 60 samples harvested in 1987 (11.6% positive samples) were analyzed. Aflatoxin levels in positive samples were low, ranging from traces to 36 μg/kg of total aflatoxins.
Aflatoxin production by three isolates of Aspergillus flavus/A. parasiticus in 13 soybean varieties has been studied. Soybeans used for cultures were surface disinfected. Levels of aflatoxin formed were dependent both on the toxicogenic potential of the fungal isolate and on the variety of soybeans. Under laboratory conditions variety Prata was the most susceptible and variety SRF the less susceptible to aflatoxin formation.