Morphological characteristics and aflatoxin production of pistachio strains of Aspergillus flavus in Kerman

Aflatoxin contamination of pistachio nuts is undoubtedly an important economic problem for Iran. The European Union's 1997 ban on pistachio imports from Iran because of high levels of aflatoxin. Existence of aflatoxins and fungal producing aflatoxins in pistachio were reported from Iran on 1970. Since then several research were conducted to find the fungal species produced aflatoxins, it was reported that up to 13 species were isolated from pistachio kernels and shells collected from orchard. The probability of contamination incidence in orchard, processing stages , at storage and shipment were studied. Throughout this project pistachio nuts were collected from the different storages and terminals of pistachio producing areas of Kerman province including Rafsanjan, Zarand, Kerman, Noogh nd Sirjan. 122 isolates of A. flavus collected using suspension of surfactant contamination of pistachio nuts. To detect fungal contamination at different parts of pistachio nuts, 51 samples of shells and kernels collected from 51 different storages were disinfected using hypochlorite 0.5 % and cultured on artificial media separately. 86% of the samples were contaminated to A. flavus in a range of 0- 100 %.Due to aflatoxin contamination, 32% of the samples had aflatoxin more than 2 ppb and 68% less than 2 ppb. Morphological and several physiological characters of the collected A. flavus isolates were studied and grouped based on common characters. Representative isolates of each group selected, cultured on rice medium and evaluated toxicologically using TLC scanner method. 27% of isolates produced sclrotia. All of isolates which studied toxicologically produced aflatoxin B1 with average rate of 11±0.52 µg/g and aflatoxin B2 with average rate 6.2±0.41 µg/g. No isolate produced aflatoxin G1 or G2. A criterion morphological character related to aflatoxin production was not found in studied isolates.