Relative susceptibility of pistachio kernel to Aspergillus flavus among different commercial cultivars and wild species

Aflatoxins are carcinogenic secondary metabolites that are mainly produced by several different species of Aspergillus in a variety of foods. The problem of pistachio contamination with A. flavus and aflatoxin is a serious health threat that affects the export and trade of pistachios in the world. This study assessed the susceptibility of 12 commercial pistachio cultivars (Pistacia vera) and 2 wild pistachio species (Pistacia atlantica) to the colonization of A. flavus in vitro.

In the present study, 40 pistachio kernels samples were prepared from each cultivar and inoculated in four replications with spore suspension of A. flavus IPRC30 isolate. After one week, the percentage of fungal colonization on the surface of pistachio kernels and its penetration into pistachio kernel tissue were measured. The experiments were performed with four replications in a completely randomized experimental design. The data were analyzed by SAS software and the means were compared using Duncan's new multiple range test at the significance level of 0.05.

The results indicated that the fungal colonization on most cultivars was equally 60-80%. The lowest rate of colonization was related to wild Pistacia atlantica species with less than 15%. The percentage of colonization of internal tissue of pistachio kernel was variable. The highest percentage of fungal penetration was found in Ohadi cultivar (70%) and no penetration was observed in Sarakhs cultivar.

The results of this study can have some implications for selecting resistant cultivars in seed breeding programs.