|Cooper, Rodney - William|
|ACALA, PIEDAD - Heritage University|
|BARCENAS, NINA - Heritage University|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2014
Publication Date: 2/25/2015
Publication URL: http://handle.nal.usda.gov/10113/60422
Citation: Cooper, W.R., Acala, P.E., Barcenas, N.M. 2015. Relationship between plant vascular architecture and within-plant distribution of 'Candidatus Liberibacter solanacearum' in potato. American Journal of Potato Research. 92:91-99.
Interpretive Summary: Liberibacter is the bacterial pathogen associated with zebra chip disease of potato, and is transmitted among potato plants by the potato psyllid. Detecting this pathogen in plants before the onset of visible symptoms is difficult because the bacteria can be present in some leaves yet absent in others. USDA-ARS researchers in Wapato, WA, along with researchers at Heritage University in Toppenish, WA, assessed whether vascular connectivity among leaves influences the distribution of the pathogen in plants. They found that the distribution of Liberibacter in plants is dependent upon vascular connectivity; Liberibacter was located in leaves with direct connectivity with the inoculation leaf more often than in leaves with partial or minimal connectivity with the inoculation leaf. These findings will improve methods to sample and diagnosis Liberibacter-infection in plants before the development of visible symptoms.
Technical Abstract: “Candidatus Liberibacter solanacearum” is an important pathogen of Solanaceous crops that causes zebra chip disease of potato. This pathogen is transmitted among plants by the potato psyllid Bactericera cockerelli. Within-plant variability in Liberibacter infection impedes the ability to detect Liberibacter in plants before the onset of visible symptoms. The goal of our study was to test whether vascular architecture of potato contributes to uneven distribution of Liberibacter from inoculated leaves. The movement of rhodamine B from an export leaf was used to identify vascular connectivity among leaves. Three weeks after inoculating a single leaf with Liberibacter, the pathogen infected significantly more leaflets that had direct vascular connectivity with the inoculated leaf than leaflets with minimal connectivity. In a separate study, significantly more psyllids that were confined to whole leaves with direct vascular connectivity with a Liberibacter-infected leaf acquired the pathogen than did psyllids confined to leaves with indirect or partial connectivity to the infected leaf. Using fluorescence in situ hybridization, the pathogen was observed in the inner and outer phloem above and below the export leaf, respectively, corresponding with passive movement of Liberibacter in the phloem. Results of this study indicate that the distribution of Liberibacter in potato is at least partly limited by vascular architecture. This knowledge should improve the design of sampling methods to detect Liberibacter in asymptomatic plants.