Pistachio nuts (Pistaciavera, Anacardiaceae) have long beencherished as the symbol of health since ancient times. The kernels of pistachioare enriched with many health-benefiting nutrients essential for optimumhealth. Pistachio kernels are a rich source of many antioxidant phytochemical substances,such as carotenes, vitamin-E, and polyphenolic antioxidant compounds. They arethe storehouse of minerals such as copper, manganese, potassium, calcium, iron,magnesium, zinc, and selenium.
Regular consumption of pistachio in the diet mayhelp lower total as well as bad LDL-cholesterol and increase goodHDL-cholesterol levels in the blood (1). Pistachio isthe only edible crop of 11 species in the genus Pistacia. The pistachiois native to western Asia, where still found growing wildly in Turkey, Syria,Iran, Iraq, India, Lebanon, Palestine, southern Europe, Asia, and Africa (2).
Iran is the main producer of pistachio inthe world. Most of this product isexported to other countries. The European Union (EU) has traditionally been oneof the major destinations for Iran’s pistachio. Contamination of agriculturalproducts with mycotoxins including a?atoxins, ochratoxin, and fumonisin is oneof the major challenges encountered by producers (3). Speciesof the Aspergillus are responsible for various plant and food secondaryrot, with the consequence of possible accumulation of mycotoxins (a secondarymetabolite that has powerful teratogenic, mutagenic and hepatocarcinogeniceffects (4). They can contaminate agricultural products at different stages,including pre-harvest, harvest, processing, and handling.
Changes due tospoilage by Aspergillus species can be ofsensorial, nutritional, and qualitative nature, including pigmentation,discoloration, rotting, development of off-odors, and off-flavors (4). This fungus is common all over the world as anair and soil mycoflora found in live and dead animal and plant organisms. It isparticularly interested in colonizing nut kernels and oily cereals.
Peanut,corn, wheat, rice, pistachio, and almond are the major products infected bythis fungus. Iran has about 316,000 hectares of pistachio orchards and producesabout %57 of the world pistachio. More than %60 of the world pistachio exportis done from Iran to other countries, well showing the economic significance ofthis product for the country. Iran is also recognized as the biggest and mostimportant producer and exporter of pistachio in the world, among otherpistachio producing countries (5). Contamination of pistachio nut by Aspergillusspecies and their mycotoxins are the most serious challenge for pistachioproduction, consumption, and exportation in the world. Factors influencinginfection of pistachio nuts to mycotoxin include cracking of pistachio nuts(especially early hull splitting pistachios), environmentalfactors, cultural practices, frequency and time of irrigation, animalmanures, and harvesting date (6). Aspergillus species not only cause physical damages topistachio nuts but also reduce the quality of pistachio since they producetoxic secondary metabolites, such as aflatoxins, ochratoxins, and fumonisin(6).
Ochratoxin A(OTA) was discovered as a secondary metabolite of a strain of Aspergillusochraceus. OTA exhibits intestinal fragility, nephrotoxicity,immunosuppression, teratogenicity, carcinogenicity, and cytotoxicity in hepaticcell lines (7). The OTA inhibits carboxypeptidase A, renalphosphoenolpyruvate carboxykinase, phenylalanine tRNA synthetase, andphenylalanine hydroxylase activity. Formation of free radicals has beenconsidered as one of the mechanisms for the carcinogenic/toxic effects of OTA (8).
Fungi from two genera are known to produceochratoxins. In the genus Penicillium, OTA is produced by P.verrucosum and P. nordicum, and in the genus Aspergillus by A.ochraceus, A.
melleus, A. auricomus, A. ostianus, A. petrakii, A.
sclerotiorum,and A. sulphureus, all in section Circumdati (formerly the A. ochraceus group). Aspergillusalliaceus and Aspergillus albertensis, formerly placed insection Circumdati but recently shown to be more closely related tosection Flavi, have also been described as OTA producers (9). Some members of Aspergillus section Nigri(formerly the Aspergillus niger group) such as Aspergillusniger var.
niger and Aspergillus carbonarius have beenreported as ochratoxigenic fungi (7). Several food products worldwide face therisk of OTA contamination, including coffee, cereal grains, processed foods,beer, grapes, wine, cocoa, nuts, and dried fruits (10). A survey on contaminant fungal flora of somenuts showed that 49% of market pistachio have fungal contamination, and Penucillium,Mucor and Aspergillus with 26, 24, and 20% were found to be themost dominant spoilage agents, respectively (11). This study was conducted to evaluate theincidence and prevalence of Aspergillus species in the main pistachioorchards of Iran and OTA production potential of Section circumdatiisolates in vitro.