An Overview of the Mechanisms Against “Candidatus Liberibacter asiaticus”: Virulence Targets, Citrus Defenses, and Microbiome

Abstract

Citrus Huanglongbing (HLB) or citrus greening, is the most destructive disease for citrus worldwide. It is caused by the psyllid-transmitted, phloem-limited bacteria “CandidatusLiberibacter asiaticus” (CLas). To date, there are still no effective practical strategies for curing citrus HLB. Understanding the mechanisms againstCLas can contribute to the development of effective approaches for combatting HLB. However, the unculturable nature ofCLas has hindered elucidating mechanisms againstCLas. In this review, we summarize the main aspects that contribute to the understanding about the mechanisms againstCLas, including (1)CLas virulence targets, focusing on inhibition of virulence genes; (2) activation of citrus host defense genes and metabolites of HLB-tolerant citrus triggered byCLas, and by agents; and (3) we also review the role of citrus microbiome in combattingCLas. Finally, we discuss novel strategies to continue studying mechanisms againstCLas and the relationship of above aspects.