Citrus sinensis waste as a source of essential oils for crop protection

Citrus production is one of the major agricultural activities worldwide, due to their typical aroma and nutritional value [1]. Over the years, the Citrus processing industry has concentrated on producing fruit juices and essential oils (EOs), generating approximately 60 million tons of waste annually worldwide [2]. Therefore, it is necessary to explore the possibility of converting this waste into commercially valuable products. Citrus species are well-known for their high EOs content. In preliminary screening tests, EOs of sweet orange (C. sinensis) demonstrated antifungal activities. In this study, two varieties of C. sinensis (“Navel” and “Tarocco” orange) were selected to test the effectiveness of EOs obtained from citrus peel waste against Fusarium oxysporum fsp. radicis lycopersici (FORL), a fungus responsible for serious crop diseases. The development of FORL infection is particularly problematic because roots start to lose their functionalities, including water absorption and nutrients from the soil, leading to crop deterioration [3]. The efficacy of different treatments was evaluated through a 24-well plate assay. The study aimed to determine the ability of EOs to inhibit fungal growth and prevent the blackening of root seedlings. Different concentrations were tested. For each well, a conidial suspension of FORL combined with EOs at the desired concentration was prepared; after 10 minutes of incubation, seeds were immersed in the solution. After 5 days, the presence of root necrosis was evaluated. The results will provide insights into the antimicrobial efficacy of EOs against FORL infections in crops.