بهينه سازي يك روش زيست سنجي براي ارزيابي توليد زرالينون در قارچ ها و كاربرد آن در مورد جدايه هاي ايراني

OPTIMIZATION OF A BIOASSAY METHOD FOR EVALUATION OF ZEARALENONE PRODUCTION IN FUNGI AND ITS APPLICATION TO IRANIAN ISOLATES OF FUSARIUM GRAMINEARUM

In this investigation, a rapid zearalenone (ZON) extraction method from fungal culture (a 5 nun disk) was developed using 50% ethanol and freezing-thawing procedure. In addition, a rapid and inexpensive bioassay method for evaluation of zearalenone production in fungi was calibrated and used to screen for ZON production in lranian isolates of Fusarium graniinearum ,the causal agent of wheat headblight. This bioassay, which is based on Beta-galactosidase induction in a genetically engineered Saccharoniyces cerevisiae in response to an estrogenic substance like ZON, was calibrated using seven fungal species as negative and positive controls and pure ZON (Sigma) as standard. Gibberella fujikuroi, F. sporosrichoides, F. oxysporum, F. o. cucumerimrm, F. solani and F. subglutinans as negative controls showed no difference from mock preparation(50% ethanol). An isolate of F. graminearum and a pure sample of ZON effectively induced Beta-galactosidase and considered as positive control. Eighty-eight Iranian isolates of F. gmminearum collected from various parts of the country were screened using this bioassay method. The results showed that 32% of isolates tested produced ZON in various degrees. This is the first report of application of this bioassay method for evaluating ZON production in fungi. This method can potentially be used in rapid screening of many fungal mutants as an attractive low-cost tool for monitoring ZON production. Since ZON producer isolates were presented in all area of FHB distribution, monitoring of contamination of agrifoods and determining of acceptable daily intake (ADI) are mandatory.