Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2016
Publication Date: 8/18/2016
Publication URL: http://handle.nal.usda.gov/10113/5454516
Citation: Cooper, W.R., Horton, D.R., Unruh, T.R., Garczynski, S.F. 2016. Gut content analysis of a phloem-feeding insect, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae). Environmental Entomology. 45:938-944. Interpretive Summary: Potato psyllid is a vector of the pathogen associated with zebra chip disease of potato. This insect relies upon the use of weed hosts to survive during parts of the year when potato plants are not available, but it is unclear what weeds serve as important sources of infective psyllids colonizing fields of potato. Scientists at the USDA-ARS laboratory in Wapato, WA developed molecular methods to identify host plants previously fed upon by psyllids, by detecting in psyllids regions of plant DNA which serve as barcodes for plant species. This study is the first to show that plant DNA can be detected in a psyllid, and provides a means to study the landscape-level movements of potato psyllid. Continuing studies using these methods will enable growers to identify fields at risk of being colonized by psyllids carrying the zebra chip pathogen, and to make more informed pest management decisions.
Technical Abstract: Potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae) is a key pest of potato (Solanum tuberosum L., Solanales: Solanaceae) and a vector of "Candidatus Liberibacter solanacearum," the pathogen associated with zebra chip disease. In addition to its presence on cultivated crops, the psyllid regularly occurs on numerous uncultivated annual and perennial species within the Solanaceae. A better understanding of landscape-level ecology of B. cockerelli would substantially improve our ability to predict which potato fields are most likely to be colonized by infected psyllids. We developed three PCR-based methods of gut content analysis to identify what plant species B. cockerelli had previously fed upon. These methods included 1) sequencing PCR amplicons of regions of plant-derived internal transcribed spacer (ITS) or the chloroplast trnL gene from psyllids, 2) high-resolution melting analysis of ITS or trnL real-time PCR products, and 3) restriction enzyme digestion of trnL PCR product. Each method was used to test whether we could identify psyllids that had been reared continuously on potato versus psyllids reared continuously on the perennial nightshade, Solanum dulcamara. All three methods of gut content analysis correctly identified psyllids from potato and psyllids from S. dulcamara. Our study is the first to demonstrate that plant DNA can be detected from a phloem-feeding insect. Gut content analysis, in combination with other landscape ecology approaches, could help elucidate patterns in landscape-level movements and host plant associations of B. cockerelli.