Lemon essential oil for controlling Alternaria alternata (Fr: Fr.) Keissler f. sp. Citri

Abstract

The increasing incidence of diseases in tangerine orchards, including alternaria brown spot (ABS) caused by Alternaria alternata, has led to significant production losses, which requires the development of new disease control strategies. This study aimed to evaluate the effect of essential oils (EOs)extracted from the peels of different lemon genotypes at several concentrations and application methods on the ABS control. The experiments were conducted at the Sylvio Moreira Citrus Research Center, Cordeiropolis - São Paulo state,Brazil. An in vitro experiment was set up in a completely randomized design (CRD) with a 2×4×5 factorial scheme, including two control methods (preventive and curative),four lemon genotypes for EO extraction (Amber IAC 269, Eureka IAC 644, Harvey IAC 641 e IAC 262 Siciliano), and five EO concentrations (0, 2, 4, 8, and 16µL mL-1), with three replicates. Each replicate consisted of a Petri dish containingthree young Murcott tangor leaves. An in vivo experiment was also conducted in a CRD with a 2×4×3 factorial scheme, including two control methods (preventive and curative), four lemon genotypes for EO extraction, and three EO concentrations(0,8, and 16 µL mL-1), with three replicates. Each replicate consisted of one Murcott tangor plant, with four leaves from three different branches of the same plant.Disease severity assessments were conducted over seven days following fungal inoculation. The Area Under the Disease Progress Curve (AUDPC) was calculated using severity data. Data were submitted to analysis of variance, Tukey’s test(p<0.05), and regression analysis. The preventive method was more effective in controlling the fungus. The Amber genotype, at concentration of 16 µL mL-1,showed the best ABS control.