Mycopathologia 120: 183-188, 1992. 9 1992 Kluwer AcademicPublishers. Printedin the Netherlands. Assessment of aflatoxin and cyclopiazonic acid production by Aspergillus flavus isolates from Hungary J.L. Richard 1, Deepak Bhatnagar2, S. Peterson 1 & G. Sandor3 iNational Center for Agricultural Utilization Research, 1815N. University, Peoria, IL 61604, USA; 2Southern Regional Research Center, 1100 Robert E. Lee Boulevard, P.O. Box 19687, Room 3006, New Orleans, LA 70179, USA; 3Department of Pharmacology and Toxicology, University of Veterinary Science, P.O. Box 2, H-1400 Budapest, Hungary Received 31 March 1992; accepted 8 April 1992 Key words: Aflatoxins, Aspergillus flavus; cyclopiazonic acid, mycotoxins Abstract Thirty-two isolates of Aspergillus flavus were obtained from various sources in Hungary. All isolates were morphologically identified as A. flavus and three atypical variants were confirmed as A. flavus by comparing their DNA with an ex type culture of A. flavus. None of these isolates produced aflatoxins when tested on coconut agar or grown on rice medium and culture extracts examined by thin layer chromatography. Also, none of the isolates converted sterigmatocystin, O-methyl sterigmatocystin, norsolorinic acid, or sodium acetate to aflatoxin. However, 59% of the isolates produced cyclopiazonic acid based on thin layer chromatographic analysis of culture extracts. The isolates that lack the ability to produce both aflatoxin and cyclopiazonic acid are potential candidates for use in bicontrol studies. Introduction Typically, about one third of the naturally occur- ring Aspergillus flavus isolates from feed and veg- etative matter are aflatoxigenic [1]. In the United States, A. flavus and A. parasiticus cause aflatoxin contamination in the economically important commodities of corn, cottonseed, peanuts, and tree nuts [2]. Proper management practices can reduce crop aflatoxin contamination but these techniques do not eliminate aflatoxin occurrence [3]. Biological control is one of the likely aflatoxin control methods of the future. An attractive bi- ocontrol technique for the aflatoxins is the use of nonaflatoxigenic A. flavus or A. parasiticus strains as competitive biocontrol agents. The ultimate benefit would be attained when such biocontrol agents are extremely good competitors for the ecological niches of the toxigenic strains and com- petitively exclude those agents from the host. Currently there are efforts underway to deter- mine the efficacy of nonflatoxigenic A. flavus and A. parasiticus strains as biocontrol agents, parti- cularly in peanuts and cottonseed [3]. However, the nontoxigenic nature of the strains that are used as biocompetitive agents may be the result of ultraviolet light-induced mutants or the reason for their nontoxigenicity is unknown. Recent ob- servations [4] have important implications in the use of aflatoxin blocked strains as biocompetition agents because there is a possibility of cross-feed- ing of pathway intermediates during cofer-