Sensitivity to Lippia alba (Mill.) NE Br Essential Oil of two Aspergillus flavus Strains Isolated from Peanut Seeds (Arachis hypogaea L.) Collected from Two Agroecological Zones in Senegal

Abstract

Aspergillus flavus is most often associated with acute or chronic aflatoxicosis due to its ability to produce aflatoxin. These recent years, many studies have been conducted to identify biopesticides able to mitigate the aflatoxinogenic strains in soils and crops. Then, essential oils naturally contain various bioactive molecules whose antifungal properties offer promising prospects for mitigating the dangers posed by aflatoxins. This study aims to determine the chemical composition of Lippia alba essential oil and to assess its effectiveness on 2 strains of A. flavus isolated from peanut seeds in Senegal. Chemical analysis by GC-MS of the essential oil (EO) of Lippia alba revealed more oxygenated monoterpenes (84.3%) than hydrocarbons (8.4%) and oxygenated (2.4%) sesquiterpenes. Neral (34.6%) and geranial (46.6%) were also identified as major and distinctive biochemical components present in the essential oil extracted from Lippia alba plants in Senegal. Furthermore, the biological activity of this EO, at three different doses (100, 500, and 1000 ppm), was more effective in inhibiting the mycelial growth of the two isolates of Aspergillus flavus (TN and V), compared to Azoxystrobin (Positive control). The inhibition rates recorded with the highest dose (1000 ppm) reached 91.4% on the TN isolate (Peanut Basin isolate) and 84.6% on the V isolate (Casamance isolate). In contrast, after 11 days of incubation, Azoxystrobin at 1000 ppm produced 34.3% and 66.9% inhibition rates, respectively, on the TN and V isolates. Due to their chemical composition, essential oils are positioned as an alternative to synthetic pesticides and in the fight against crop pests and mycotoxins. However, for the practical use of this EO as a fungicide, future research would need to include searching for a suitable carrier appropriate inert material, allowing the development of a biopesticide formula directly applicable to peanut seeds without any negative impact on their physico-chemical, functional, and organoleptic properties.