‘Candidatus Liberibacter’ is a genus of gram-negative bacteria composed of three species–‘Ca. Liberibacter asiaticus’, ‘Ca. Liberibacter africanus’ and ‘Ca. Liberibacter americanus’ (5,13). They are transmitted in the field by psyllids (2,9,17), colonize the phloem of the infected plant (7), and cause an important citrus disease named huanglongbing (HLB). The disease is also known as greening i...