Jenipapo, Genipa americana L., essential oil and Curvularia lunata control: Potential mode-of-action; plant immune responses and selectivity against beneficial non-target organisms

The Curvularia leaf spot, caused by the phytopathogen Curvularia lunata L., is one of the most relevant foliar diseases in Neotropical fields of corn, Zea mays L. The management of C. lunata infection still is heavily dependent on the use of synthetic compounds. However, due to increasing numbers of control failure reports and the unintended environmental hazards caused by synthetic products, the use of bioactive molecules that combine fungicidal and plant protective activities have been suggested as promising alternative management tools. Here, we assessed the chemical composition and the potential of Jenipapo, Genipa americana L., essential oil for controlling C. lunata in corn leaves. We further evaluated whether the essential oil treatment would modify the plant immune responses (e.g., the activity of defense enzymes, soluble proteins, and foliar pigments) or cause any potential undesired effects in the beneficial fungi Trichoderma asperellum and the ladybeetles Coleomegilla maculata. Chemical composition analysis revealed that the aldehyde (E)-2-decenal was the major component (85.4 %) of the essential oil. The essential oil treatment controlled C. lunata in a preventive way, increased the plant-immunity responses in a concentration manner, and did not cause any detrimental effect on the T. asperellum growth rate nor on the ladybeetles’ survival and predatory abilities. In silico analyses further demonstrated the molecular interactions between the (E)-2-decenal and the C. lunata fungal tyrosine-tRNA ligase as a potential mode of action. Collectively, our findings indicate that Jenipapo essential oil has the potential to be used in the management of C. lunata infection.