Evaluation of Contamination of Aspergillus flavus and Aflatoxin Production in Pistachio Cultivars and Investigation of a Chemical Controlling Method

In order to study the contamination of Aspergillus flavus and aflatoxin production in pistachio cultivars in the Semnan province, eight cultivars of pistachio were collected from major pistachio growing areas. Using the serial dilution method, ground pistachio kernels were inoculated on plates containing AFPA medium and incubated at 28° C. This experiment was performed using three replications in a completely randomized design. After three to seven days, the number of A. flavus colonies were identified and enumerated.  Also, aflatoxin B1, B2, G1 and G2 contents of the samples were analyzed by HPLC method. On the other hand, the effect of two chemical fungicidesas a control method on the growth of Aspergillus flavus and aflatoxin production in pre-harvest pistachio cultivars was assessed under in vivo conditions. For this purpose, an orchard that was under cultivation by the most contaminated cultivar was selected, and a completely randomized design was carried out in the field. Two fungicides (tebuconazole 25% and mancozeb 80%) were applied at an application rate of 1 and 2 L or Kg ha-1, respectively. Aflatoxin B1 and B2 contents of the samples were analyzed using the HPLC method. The obtained results showed that there was a significant difference in A. flavus colonies number in different pistachio cultivars. Among these cultivars, Owhadi had the highest amount of contamination, and Akbari had the lowest contamination. The results showed that the contents of aflatoxin B1 and B2 were observed in Owhadi cultivar. , Tebuconazole 25% and mancozeb 80% reduced A. flavus growth compared to the control. However, this reduction was not significant. The obtained results of aflatoxin analysis showed that these two fungicides reduced the amount of aflatoxins B1 and B2 in pistachio cultivar, though there was not a significant reduction.It was concluded that the use of chemical fungicides were ineffective in preventing A. flavus growth and aflatoxin production in pistachio cultivars under in vivo conditions.