Incidence of Aspergillus species and Ochratoxin production potential in the main pistachio orchards of Iran

Background: Aspergillus species not only cause damage to the color of pistachio fruit but also reduce the value of this product since they produce toxic secondary metabolites such as aflatoxins, ochratoxins, and fumonisin. Materials and methods: In order to identify Aspergillus species associated with pistachio, 300 samples of fresh fruits, dried fruits, leaves, and fresh old wastages were collected from the main pistachio production area of Iran (in Kerman, Yazd, Semnan, and Ghazvin provinces). Fungal isolation was performed using single conidial: 220 isolates were identified based to morphological charachteristics. 22 species belonged to four subgenus and eight sections were identified according to morphological characteristics. The OTA-producing ability of the Aspergillus section Circumdati isolates was determined by the thin layer chromatography (TLC) method. Results: The results showed that Aspegillus tubingensis was the most prevalent species in pistachio orchards. Most isolates of A. ochraceous and A. melleus are OTA producer in vitro, but isolates of A. nakazawae and A. muricatus were not able to produce OTA. Conclusion: higher incidence of A. tubingensis as a not-dangerous mycotoxins producer species can ecologically lead to competition between this species and mycotoxigenic aspergillii and cause a decrease in mycotoxins contamination of pistachio nut.