The influence of ecophysiological factors on growth, aflR gene expression and aflatoxin B1 production by a type strain of Aspergillus flavus.

Maize is prone to infection by Aspergillus flavus , which can contaminate the product with aflatoxins. The objective of this study was to examine the impact that interactions between water activity (a w ) and temperature may have on growth, the expression of a biosynthetic regulatory gene ( aflR ) and aflatoxin B 1 (AFB 1 ) production by a strain of A. flavus on a maize-based medium. Results showed that there were some differences between lag phases and growth rates of A. flavus . The optimum growth rate for A. flavus was at 30 °C and 0.99 a w . No growth occurred at 0.90 a w and 20 °C. Both temperature and a w had an influence on the relative aflR gene expression and AFB 1 production by A. flavus ; however, the results for AFB 1 production were not consistent with the effects on gene expression or growth. These findings provide data that are useful to better understand the conditions which represent higher risks from AFB 1 production. However, the aflR expression was not a good indicator of AFB 1 production alone. Thus, further molecular studies of other AF-related genes should be done. These results are discussed in the context of harvesting and storage of maize and the prevailing environmental conditions to minimise AFB 1 contamination. [ABSTRACT FROM AUTHOR]