Bacterial Citrus Diseases: Major Threats and Recent Progress

Abstract

Citriculture is an important, highly organized, and competitive sector of the Brazilian economy. Nonetheless, citrus production is constantly threatened by pathogens that cause considerable economic losses and severe social impacts. Among the major citrus diseases are citrus canker (CCK), citrus variegated chlorosis (CVC), and Huanglongbing (HLB), caused by members of the bacterial species Xanthomonas citri (Xcc), Xylella fastidiosa (Xfa), and ‘Candidatus Liberibacter’ (CaL), respectively. During the last years, management practices for CVC and HLB in Brazil have provided good results, maintaining the disease incidence at low levels. In contrast, CCK re-emerged as the main citrus disease because of the inefficacy of the current eradication program. In this review, we discuss about the biology of the plant-pathogen interactions, several controversial aspects on the taxonomy of the causal agents, the molecular mechanisms they use to cause disease in citrus plants, the strategies used for disease management and their limitations, and some emerging control alternatives that may be available for commercial production in the future, including transgenic and genome-edited plants with enhanced resistance. Keywords: