Combinatorial interactions of ethanol extract and essential oil from Citrus reticulata Blanco peels for plant protection product against Xanthomonas citri

Abstract

Peels of Citrus reticulata Blanco are a large amount of waste in agriculture. In order to take advantage of this source for a sustainable agricultural development, total polyphenol content, antibacterial activity of ethanol extract (EE) and essential oil (EO) from peels against plant pathogenic Xanthomonas citri were evaluated. Compared with EE, the EO exhibited slightly higher TPC with 65.08 ± 0.10 mg GAE/mL and more effectively inhibitory effect on X. citri growth as well at 30% for MIC and 40% for MBC. Overall, the antibacterial activities of both against X. citri were relatively weak, therefore combinatorial interactions between EE and EO were then investigated by Checkerboard assay. Among inhibitory combinations, most were detected as indifference (FICindex from 1.25 to 3), no synergism, one additional effect detected with FICindex as 1.0 (EE MIC/2 + EO MIC/2). A peel EO-based product against X. citri was formulated at MBC and ex-vivo tested on Kumquats. The results demonstrated that the product was effective in prevention more than for treatment, especially as it could inhibit 97.59% in 6 days before X. citri infection . This study exhibited a promising application of peel essential oil for a plant protection product against X. citri in agriculture.