Control of Aspergillus and related aflatoxin production by using different plant extracts

Pistachio is an important export product in Iran. This product is constantly threatened by Aspergillus flavus and its aflatoxin. Researchers are now looking to use alternative non-hazardous methods instead of other methods of management of plant diseases, such as the use of chemical pesticides. Plant extracts as an environmentally friendly method can be a good alternative to chemicals. In this study, the effect of plant extracts including lavender (Lavandula stoechas), thyme (Thymus vulgaris), fennel (Foeniculum vulgare) and savory (Satureja hortensis) on the amount of degradation and aflatoxin production in vitro, by paper disk methods and mixing the extract with the culture medium, as well as in the storage conditions and on pistachio were investigated. The results showed that using of 2000 mg/L methanol extract reduced the growth of pathogenic fungus by 65.63%. In the tests of using the extracts on the paper disc as well as mixing the extracts with the culture medium, aqueous extract of lavender with a concentration of 2000 μg/ml prevented the growth of pathogen by 39.31 and 55.96%, respectively, and thyme extract with a concentration of 2000 μg/ml inhibited the fungal growth by 29.33% and 39.54%, respectively. These extracts had the highest effect on the pathogen growth. When the extracts were applied directly to aflatoxin, the results showed that the concentration of 4000 mg/L lavender prevented the aflatoxin production in the culture medium by 91.18%. Finally, aqueous extract of lavender at 4000 mg/L showed the highest effect (76.95% compared to control) in reducing the amount of spores produced by pathogenic fungi on pistachio fruit. The results of aflatoxin content in pistachio showed that both studied plants (lavender and thyme) at concentrations of 2000 and 4000 mg/L significantly reduced the amount of aflatoxin produced. Due to the remarkable and good effect of plant extracts on pistachio fruit under both in vitro and in the storage, the studied extracts, especially lavender and thyme, are natural compounds with high fungicidal effect and environmentally friendly effects.