Novel bacterium vectored by the tomato psyllid to Solanaceous plants

A new Candidatus Liberibacter species is genetically and ecologically characterized, and the bacterium is designated as “Candidatus Liberibacter psyllaurous”. Interestingly, all three known bacterial species belonging to the genus Candidatus Liberibacter are associated with citrus-green disease (Huanglongbing, HLB) and are vectored by a psyllid. Liberibacter psyllaurous infects the psyllid Bactericerca cockerelli and its solanaceous host plants potato and tomato. In vector-transmission trials, potato plants and tomato plants inoculated with infected psyllids were positive for C. L. psyllaurous infection and showed signs of yellowing, whereas control plants were negative for the bacterium and showed no signs of yellowing. Using PCR detection of C. L. psyllaurous and egg-transfer experiments, the bacterium is vertically as well as horizontally transmitted in the psyllid. In addition, bacterial infection frequencies of psyllids are variable between psyllid life stages and the host plants potato and tomato. Higher infection frequencies are found in eggs, 1st, and 2nd instar nymphs isolated from potato host plants relative to nymphs isolated from tomato host plants. Implications of these findings for disease management of potato and tomato plants are substantial, because C. L. psyllaurous may be the cause of “psyllid yellows”, a psyllid associated disease that has been a mystery to scientists for over a century. Moreover, since this bacterium has over 97% 16s rRNA sequence similarity to other HLB-associated Liberibacter species, Bactericerca cockerelli and L. psyllaurous may be a novel system to study to help combat HLB, the most serious disease of citrus around the world.