Evaluation of ochratoxin A production by Aspergillus ochraceus group isolated from pistachio orchards
2012
Sedaghati, E. | Khodaygan, P. | Kocsube, S. | Varga, J. | Nadi, M.
Pistachio is one of the main agricultural products and non-petroleum exports of Iran. The main problem concerning export of pistachio nuts is contamination of nuts by mycotoxins. Contamination of food and feed with mycotoxins represents a high risk for human and animal health. Aspergillus species cause not only physical damage on pistachio nuts but also reduce the quality of pistachio based on the production of secondary toxic metabolites such as aflatoxins, ochratoxins and fumonisin. One of the mycotoxins that have been considered during the last decade is ochratoxin A (OTA). OTA is believed to be produced in nature mainly by some species belonging to the genera of Aspergillus and Penicillium such as A. ochraceus (Section Circumdati), A. niger, A. carbonarius (section Nigri), Penicillium verrucosum. In order to study the capability of OA production in species of Aspergillus section Circumdati, samples including: fresh fruits, dried fruits, leaves; new and old wastages were taken from pistachio orchards. For purification of the isolates, single conidial heads were taken according to the phenotype, and subcultured repeatedly on Malt Extract Agar media until complete purification. According to the morphological characteristics 15 isolates were identified from different samples. Molecular identification was done based on the Calmodulin gene sequence. Overall, A. melleus, A. ochraceus and A. muricatus were detected with different frequency. To assay ocharatoxin production, isolates were cultured on yeast extract sucrose medium for 14 days. Ochratoxin A was detected using chloroform extraction and thin layer chromatography method. The results showed that 9 of 10 isolates of A. ochraceus, and all isolates of A. melleus were ochratoxigenic. None of A. muricatis isolates produced OTA.
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