Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/15/2013
Publication Date: 1/6/2014
Publication URL: http://handle.nal.usda.gov/10113/58248
Citation: Cooper, W.R., Sengoda, V.G., Munyaneza, J.E. 2014. Localization of 'Candidatus Liberibacter solanacearum' in Bactericera cockerelli (Hemiptera: Triozidae). Annals of the Entomological Society of America. 107(1):204-210. Interpretive Summary: Zebra chip is an important disease that infects potato. The bacterium that causes zebra chip disease is spread by the potato psyllid, but the interactions between the pathogen and the insect are poorly understood, preventing the development of ecologically-based methods to control zebra chip disease. Scientists at the USDA-ARS laboratory in Wapato, Washington developed and applied a technique to observe the pathogen in dissected organs of potato psyllids. They determined that the pathogen moves from the insect’s gut to colonize the insect’s hemolymph, salivary glands, and bacteriome (specialized organ that harbors beneficial symbiotic bacteria). They also determined that the pathogen is less likely than adults to infect psyllid nymphs than adults, and that nymphs are less likely to transmit the pathogen to new host plants. This new information on the epidemiology of zebra chip disease of potato will be useful to developing new approaches to controlling this disease.
Technical Abstract: ‘Candidatus Liberibacter solanacearum’ is a pathogen of solanaceous crops (Solanales: Solanaceae) that causes zebra chip disease of potato (Solanum tuberosum L.) and plant dieback in tomato (S. lycopersicum L.) and pepper (Caspicum spp.). This pathogen is vectored by the potato/tomato psyllid Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), but little is known about the interactions between B. cockerelli and ‘Ca. Liberibacter solanacearum.’ Fluorescent in situ hybridization was used to assess the incidence of ‘Ca. Liberibacter solanacearum’ in the hemolymph, bacteriomes, alimentary canals, and salivary glands of B. cockerelli. Liberibacter was observed in 66% of alimentary canals, 39% of salivary glands, and 40% of bacteriomes dissected from adult psyllids. Compared with adults, the organs of fifth instars appeared less likely to harbor Liberibacter, which was observed in 52% of alimentary canals, 10% of salivary glands, and 6% of bacteriomes dissected from the nymphs. Results of real-time PCR confirmed that fewer fifth instars were infected with Liberibacter compared with adults, and indicated that fifth instars were less likely to transmit the pathogen to non-infected host plants. These observations of the localization of ‘Ca. Liberibacter solanacearum’ in the organs and tissues of B. cockerelli adults and nymphs will aid the study of Liberibacter – psyllid interactions and of the epidemiology of ‘Ca. Liberibacter solanacearum.’