Infection by the different haplotypes of Candidatus Liberibacter solanacearum, and their influence on its vector, Bactericera cockerelli, and tomato host

The potato psyllid, Bactericera cockerelli (Hemiptera:Triozidae), is economically detrimental to cultivated solanaceous crops. B. cockerelli causes direct damage by feeding on phloem using piercing-sucking mouthparts, however, the most significant damage is caused by the transmission of ‘Candidatus Liberibacter solancearum’ (Lso), the causative agent of Zebra chip disease of potatoes. Recently, two Lso haplotypes (A and B) were identified.  In this study, we investigated the effects of the each Lso haplotype (A or B) on psyllid vectors and tomato hosts. Haplotype B infected psyllids had significantly lower fecundity and nymphal survival rate than haplotype A and non-infected psyllids (p-value<0.05). A similar phenomenon was also noticed in its tomato hosts. Tomato inoculated with haplotype B showed fatal symptoms (died at 9-week after inoculation) while Lso density increased along the incubation period, however, haplotype A infected tomato had slower growth rate than non-infected tomato, without fatal symptom.  Interestingly, we also noticed that Lso density in haplotype A infected tomato declined over the incubation time. This study provides useful information to investigate the pathogenesis associated with the two Lso haplotypes (A and B) in insect vectors and plant hosts.