Antibacterial activity of Cymbopogon species essential oils against Xanthomonas citri and their use in post-harvest treatment for citrus canker management

Abstract

Citrus canker is a disease caused by the gram-negative bacterium Xanthomonas citri subp. citri (X. citri), which affects all commercially important varieties of citrus and can lead to significant losses. Fruit sanitization with products such as chlorine-based ones can reduce the spread of the disease. While effective, their use raises concerns about safety of the workers. This work proposes essential oils (EOs) as viable alternatives for fruit sanitization. EOs from Cymbopogon species were evaluated as to their antibacterial activity, their effect on the bacterial membrane, and their ability to sanitize citrus fruit. The in vitro assays revealed that the EOs from C. schoenanthus and C. citratus had a lower bactericidal concentration at 312 mg L−1, followed by 625 mg L−1 for C. martini and C. winterianus. Microscopy assay revealed that the bacterial cell membranes were disrupted after 15 min of contact with all EOs tested. Regarding the sanitizing potential, the EOs with higher proportions of geraniol were more effective in sanitizing acid limes. Fruit treated with C. shoenanthus and C. martini showed a reduction of ∼68% in the recovery of viable bacterial cells. Therefore, these EOs can be used as viable natural alternatives in citrus fruit disinfection. Impact Statement The disinfection of citrus fruit is a demanded step to prevent the spread of the bacterium Xanthomonas citri, the causer of citrus canker. Recent trends are pointing agricultural practices to a greener, and sustainable approach. In this light, this work evaluated essential oils from the Cymbopogon genus, commonly known as lemongrass, as alternatives to traditional chlorine-based products. Results obtained reveal significant antibacterial actions of essential oils from C. schoenanthus and C. martini, pointing out that these natural products could be used as fruit disinfectants for X. citri contamination, and possibly as active agents in future biopesticides.