Xanthomonas citri subsp. citri: host interaction and control strategies

Citrus is one of the most ancient fruit crops cultivated in the world. For many countries, citrus production is an important source of revenues. However, despite the richness of citrus production worldwide, fruit yields are constantly threatened by diseases that cause serious economic and social impacts to growers and consumers. One such example is citrus canker, a disease that affects all commercial citrus varieties and for which there is no cure. Currently, control measures for citrus canker are restricted to the application of copper-based compounds and the elimination of infected trees to prevent pathogen spreading in the field. However, new alternatives for the control of this disease are being developed, spanning through transgenic plants to innovative chemicals and biological control. New genome editing approaches and a repertoire of plant defense-related genes have been exploited to produce citrus lineages more tolerant to X. citri. In addition, a series of new molecules have been tested to not only inhibit X. citri growth but to also boost the plant immune system to suppress disease progression. In this review, we provide the state of art of all citrus canker control measures in use today, highlighting their utility and drawbacks and commenting on novel strategies to better control this important citrus disease.