Correlation of Aspergillus flavus Growth and Aflatoxin Production with Sugar and Lipid Content among Pistachio Cultivars

Aflatoxin is an important fungal contaminant in various crops. The substrate and its compounds are involved in the growth of fungus and the production of toxins. In order to investigate correlation between sugar and lipid content as the major chemical composition of pistachio kernels with Aspergillus flavus growth and aflatoxin production, the total sugar content was extracted by phenol-sulphoric method and estimated by spectrophotometry. The lipid was also extracted by Soxhlet method. A toxigenic A. flavus strain was used for the study of the fungal growth and aflatoxin B1 production. For that, 20 gram of kernels of different pistachio cultivars were inoculated with 1 ml of fungal spore suspension (2×10^6 spores/ml) in a completely randomized design with three replications. Eight days after inoculation, the average percent of fungal growth and colonization of A. flavus were calculated. The aflatoxin produced in inoculated pistachios was extracted by Best Foods (BF) method and measured by thin layer chromatography (TLC). The results showed that there was no significant difference in the amount of sugar content in different cultivars of pistachios kernel but the amount of total lipid content was different (P≤0.05). Results of statistical analysis showed that there was no significant correlation between sugar content with fungal growth and aflatoxin production in pistachio cultivars as well as lipid percentage and aflatoxin B1 production. Therefore, to find sources of resistance to A. flavus in commercial pistachio cultivars in aflatoxin management programs, these two factors cannot be used as a standard scale of resistance.