Aloysia Citriodora Essential Oil: Antimicrobial Potential and Induced Resistance in Controlling Tomato Black Spot Fungus

The objective of this work was to evaluate the antimicrobial and biochemical activity of Aloysia citriodora essential oil in controlling Alternaria linariae. Antimicrobial activity was tested in vitro with 0.0, 0.8, 1.8 and 2.4 μL mL−1 dosages of essential oil, and mycelial growth and the growth inhibition were evaluated thereafter. Furthermore, 2.5 and 5.0 μL mL−1 essential oil doses were tested in vivo, and severity, control efficiency, diseased and healthy areas, total leaf area, number of leaves and plant height were also subsequently evaluated. Plants grown in pots in a protected environment were used for biochemical analyzes. A 2.4 μL mL−1 dose of A. citriodora essential oil inhibited A. linariae growth in vitro and a dose of 2.5 μL mL−1 reduced the severity of the disease. Essential oil application to tomato plants induced resistance against tomato black spot fungus, mainly due to β-1,3 glucanase enzyme activity. The increase in guaiacol peroxidase activity was more evident in the presence of the pathogen with or without any treatment. Thus, the use of the A. citridiora essential oil is a promising option for controlling black spot fungus and to induce resistance in tomato plants, thereby promoting efficient and sustainable agriculture.