"Candidatus Liberibacter solanacearum" Associated With the Psyllid, Bactericera maculipennis (Hemiptera: Triozidae).

The psyllid Bactericera maculipennis (Crawford) (Hemiptera: Triozidae) often cohabits field bindweed (Convolvulus arvensis, Solanales: Convolvulaceae) and other plants with the congeneric psyllid, Bactericera cockerelli (Sulc), in the Pacific Northwestern United States. Bactericera cockerelli is a vector of "Candidatus Liberibacter solanacearum," the pathogen associated with zebra chip disease of potato (Solanales: Solanaceae). Because B. maculipennis and B. cockerelli both naturally occur on certain plants, we surveyed B. maculipennis adults collected from Washington and Idaho for presence of "Ca. L. solanacearum" to determine whether this psyllid also harbors this pathogen. Liberibacter was present in 30% of field-collected B. maculipennis and in 100% of colony-reared psyllids. Sequences of 16S rDNA and microsatellite markers revealed that "Ca. L. solanacearum" from B. maculipennis was closely related to Liberibacter haplotype B from B. cockerelli. Results of laboratory assays demonstrated that Liberibacter can be transmitted between B. cockerelli and B. maculipennis on plants within the Convolvulaceae. Potato plants challenged with Liberibacter-infected B. maculipennis did not become infected, apparently because potato is not a suitable host for the psyllid. We therefore conclude that B. maculipennis is not a direct threat to potato production, despite its association with Liberibacter. We are the first to report that "Ca. L. solanacearum" is associated with a psyllid other than B. cockerelli in North America. Results of our study demonstrate the importance of understanding the complete ecology of psyllids-including interactions with other psyllids on non-crop hosts-in predicting what crops or regions are potentially susceptible to the spread of Liberibacter.

Horizontal Transmission of "Candidatus Liberibacter solanacearum" by Bactericera cockerelli (Hemiptera: Triozidae) on Convolvulus and Ipomoea (Solanales: Convolvulaceae).

"Candidatus Liberibacter solanacearum" (Proteobacteria) is an important pathogen of solanaceous crops (Solanales: Solanaceae) in North America and New Zealand, and is the putative causal agent of zebra chip disease of potato. This phloem-limited pathogen is transmitted to potato and other solanaceous plants by the potato psyllid, Bactericera cockerelli (Hemiptera: Triozidae). While some plants in the Convolvulaceae (Solanales) are also known hosts for B. cockerelli, previous efforts to detect Liberibacter in Convolvulaceae have been unsuccessful. Moreover, studies to determine whether Liberibacter can be acquired from these plants by B. cockerelli are lacking. The goal of this study was to determine whether horizontal transmission of Liberibacter occurs among potato psyllids on two species of Convolvulaceae, sweet potato (Ipomoea batatas) and field bindweed (Convolvulus arvensis), which grows abundantly in potato growing regions of the United States. Results indicated that uninfected psyllids acquired Liberibacter from both I. batatas and C. arvensis if infected psyllids were present on plants concurrently with the uninfected psyllids. Uninfected psyllids did not acquire Liberibacter from plants if the infected psyllids were removed from the plants before the uninfected psyllids were allowed access. In contrast with previous reports, PCR did detect the presence of Liberibacter DNA in some plants. However, visible amplicons were faint and did not correspond with acquisition of the pathogen by uninfected psyllids. None of the plants exhibited disease symptoms. Results indicate that horizontal transmission of Liberibacter among potato psyllids can occur on Convolvulaceae, and that the association between Liberibacter and Convolvulaceae merits additional attention.