(1) Understand the molecular basis for fungal responses to conditions encountered during invasion of crops in order to identify and modify the factors in corn and other crops that could induce or impede aflatoxin formation or fungal development. Accomplishment of objective 1 could lead to generic approaches to enhance resistance in all crops vulnerable to aflatoxin contamination. (2) Determine, by genetic and physiological studies of diverse aflatoxin producing species, whether aflatoxin production provides an adaptive advantage for fungal survival and invasion of crops, particularly because many natural isolates of A. flavus do not produce aflatoxins. (3) Determine the molecular responses of aflatoxin producing fungi to stress factors, particularly with regard to developing an understanding of the ability of the fungi to adapt and produce toxins. (4) Undertake and utilize newly available sequences of genomic DNA from Aspergillus species to develop rapid and highly sensitive PCR based tests to identify aflatoxigenic fungi and their toxins in contaminated food products.