A first approach to the use of hexanoic acid as a resistance inducer against Xanthomonas citri

Abstract: Nowadays, one of the most severe pathogens affecting citrus plants is canker disease. As there are no effective treatments, damage to fruit yield and quality causes huge economic loss every year. Current control measures are based mainly on SAR inducers, or on massive applications of copper which can be toxic for plants and the environment. In recent years we have been working on strategies based on natural compounds and we have recently described the effect of carboxylic acids as an inducer of resistance on citrus plants against fungus.Application of 1 mM of hexanoic acid in irrigation water or spray on 1-year-old citrus plants clearly reduced lesions and the number of bacteria on leaves. We observed that some of the most important mechanisms involved in induced resistance were affected by hexanoic application. The results obtained show enhanced callose deposition in treated and infected plants and an induction of JA marker genes, such as AOS. The mechanism of action seems to act by enhancing the JA pathway and promoting callose deposition, as previously described in tomato (Vicedo et al., 2009) and in citrus against A. alternata (Llorens et al., 2013). These findings highlight the effectiveness of the JA-mediated pathway in alleviating outbreaks of citrus cankers, which provides valuable clues to design alternative preventive approaches to combat this devastating disease.