Behavior of an atoxigenic strain of Aspergillus flavus on sterile wheat: insights related to field use

摘要

Strains of A. flavus that do not produce aflatoxins (atoxigenic strains) are being applied to agricultural fields to reduce aflatoxin contamination in crops through competitive exclusion of aflatoxin producers. The atoxigenic strains are applied onsterile wheat seed that serves as a nutrient for the fungus. In Arizona, crops are grown under flood irrigation that may cause prolonged soil saturation and burial of the atoxigenic product. Influences of flooding and temperature on spore yield were assessed. Colonized seed was buried in non-sterile soil and flooded for 24 h at temperatures between 10 deg C and 42 deg C. Survival of the atoxigenic strain was highest below 25 deg C and decreased at 31 deg C and above. Increasing the duration of floodingdecreased survival of the atoxigenic strain with a concomitant increase in colonization by other fungi. Incubation period during product manufacture influenced product performance when it was subjected to flooding. Colonization for 20-24 hours was optimal while shorter colonization decreased sporulation and longer incubations, up to 72 hours, conferred no advantage. The initial concentration of spores, (1 X 10~7 spores/kg to 1 X 10~9 spores/kg) applied to the product during manufacture did not influenceproduct performance.