Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: 6/9/2015
Publication URL: http://handle.nal.usda.gov/10113/60968
Citation: Cooper, W.R., Garczynski, S.F., Horton, D.R. 2015. Relative abundance of Carsonella ruddii (Gamma Proteobacterium) in females and males of Cacopsylla pyricola (Hemiptera: Psyllidae) and Bactericera cockerelli (Hemiptera: Triozidae). Journal of Insect Science. 15:65.
Interpretive Summary: Pear psylla and potato psyllid are important pests of pear and potato, respectively. The bacterium Carsonella lives inside pear psylla and potato psyllid providing these insects with essential nutritional needs. Carsonella could be targeted to develop new ways to control psyllids if accurate methods to measure Carsonella numbers were available. Researchers at the USDA-ARS in Wapato, WA developed two new methods to measure Carsonella in psyllids. One method estimates Carsonella densities in bacteriocytes, which are specialized insect cells that contain the bacterium. The other method uses qPCR to measure Carsonella abundance in whole insects. Using these two methods, we determined that Carsonella is more abundant in females than in males of both psyllid species. Results of this study will provide researchers with a means of measuring and confirming the destruction of Carsonella, which is one approach at controlling the psyllids.
Technical Abstract: Carsonella ruddii (Gamma Proteobacterium) is an obligate bacterial endosymbiont of psyllids that produces essential amino acids that are lacking in the insect’s diet. Accurate estimations of Carsonella populations are important to studies of Carsonella/psyllid interactions and to developing ways to target Carsonella for control of psyllid pests including pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae) and potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae). We developed two methods using fluorescence in situ hybridization and qPCR to estimate relative abundance of Carsonella in bacteriocytes and whole bodies of psyllids, respectively. Using these two methods, we compared Carsonella populations between female and male insects. Estimations using fluorescence in situ hybridization indicated that Carsonella was more abundant in bacteriocytes of female C. pyricola than in those of males, but Carsonella abundance in bacteriocytes did not differ between sexes of B. cockerelli. Analyses by qPCR using whole-body specimens indicated Carsonella was more abundant in females than in males of both psyllids. Neither fluorescence in situ hybridization nor qPCR indicated that Carsonella populations differed in abundance among adults of different ages (0 to 3 weeks after adult eclosion). Using fluorescence in situ hybridization, Carsonella was observed in ovarioles of newly emerged females, and formed an aggregation in the posterior end of mature oocytes. Results of our study indicate that female psyllids harbor greater populations of Carsonella than do males, and that sex should be controlled for in studies which require estimations of Carsonella populations.