Protium heptaphyllum, a tree native to the Atlantic Forest, is a potential source of compounds against important...

Given the growing demand for sustainable agricultural practices with less environmental impact, plant-derived essential oils (EOs) have gained attention as promising alternatives to control phytopathogens. Protium heptaphyllum Aubl. Marchand (amescla) is a tree species widely distributed in fragments of the Atlantic Forest, whose resin is rich in EOs. Different bioactivities have been attributed to the EO of P. heptaphyllum, mainly associated with antimicrobial activity in human health applications. However, there are still no studies investigating its potential to control plant diseases, especially pathogens of cacao (Theobroma cacao L.) This study evaluated the efficiency of P. heptaphyllum EO on the development of Moniliophthora perniciosa, the causal agent of witches' broom disease in cacao, as well as its effect on modulating its proteome. The chemical composition of the essential oil, determined by GC/MS, revealed predominance of monoterpenes, with emphasis on α-pinene (39.57%), δ-carene (21.42%), and β-pinene (9.56%). The antifungal activity assay was conducted in a completely randomized design, composed of different concentrations of the essential oil (0.05-12.8%) and two controls (PDA - potato dextrose agar and 1% Tween 80 on the surface of solidified PDA), with five replicates per treatment. The essential oil had a significant inhibitory effect on the mycelial growth of M. perniciosa at all concentrations evaluated (0.05-12.8%), compared to the controls. The greatest concentration tested (12.8%) resulted in the highest fungistatic activity, with a PIC (percentage of mycelial growth) of 73.8%. Hyphae treated with 0.8% essential oil (EO) showed intense red fluorescence after staining with propidium iodide (PI), in comparison with the control, indicating greater permeability of the cell membrane. Quantitative analysis of the PI-stained hyphae showed that approximately 97% exhibited red fluorescence, evidencing compromised plasma membrane integrity. In general, P. heptaphyllum essential oil, ha a low inhibitory effect on Lactuca sativa in all parameters evaluated (germination, root length, shoot length, fresh weight, dry weight, and electrical conductivity) without compromising seedling development. Proteomic analysis revealed modulation of the fungal proteome, highlighting ribosomal proteins, structural proteins, glycolytic metabolism proteins, and antioxidant response proteins. The results indicated that P. heptaphyllum essential oil is a promising sustainable alternative for the control of M. perniciosa.