Role of ‘Candidatus Liberibacter solanacearum’ and the potato psyllid, Bactericera cockerelli, in ZC incidence, severity, and seed transmission

Authors: Swisher Grimm, Kylie; MUSTAFA, TARIQ - Washington State University; Cooper, William - Rodney; Munyaneza, Joseph - Joe

Submitted to: American Journal of Potato Research
Publication Type: Abstract Only
Publication Acceptance Date: 7/22/2018
Publication Date: 7/15/2019
Citation: Swisher Grimm, K.D., Mustafa, T., Cooper, W.R., Munyaneza, J.E. 2019. Role of ‘Candidatus Liberibacter solanacearum’ and the potato psyllid, Bactericera cockerelli, in ZC incidence, severity, and seed transmission. American Journal of Potato Research. 96:334. https://doi.org/10.1007/s12230-019-09723-w.
DOI: https://doi.org/10.1007/s12230-019-09723-w

Interpretive Summary: Zebra chip disease of potato has affected much of the potato growing region across the United States, Mexico, Central America, and New Zealand. There are two distinct genetic populations of 'Candidatus Liberibacter solanacearum', the pathogen associated with zebra chip, as well as four different genetic populations of Bactericera cockerelli, the insect vector of the pathogen. Researchers at the USDA-ARS research unit in Wapato and Prosser, WA, in collaboration with Washington State University, compared the disease incidence, severity, and seed transmission between the two different pathogen populations, and three different insect populations. Generally, differences were identified in disease incidence and tuber yield between the pathogen populations, but not the insect populations. Emergence rates were lower in infected tubers compared to control tubers, but no daughter tubers produced zebra chip symptoms. The difference in disease epidemiology between pathogen populations is important, and future studies must indicate which population is being used.

Technical Abstract: ‘Candidatus Liberibacter solanacearum’ (Lso) is the causal agent of the economically devastating zebra chip disease, and is transmitted to potato by the psyllid, Bactericera cockerelli. In the United States, there are four genetically distinct populations of the potato psyllid, as well as two genetically distinct populations of Lso. Prior to this study, it was not known whether the psyllid or Lso haplotype could affect zebra chip disease severity, incidence, or even seed transmission in potato. In a two year field cage study, disease severity and incidence were compared between both Lso haplotypes A and B, and three psyllid populations common in the Pacific Northwest. Lso haplotypes A and B were both able to induce severe zebra chip symptoms, regardless of the psyllid population that transmitted the bacteria. In general, Lso haplotype B-infected plants produced a higher incidence of zebra chip, and resulted in lower tuber yield compared with Lso haplotype A. In a separate three year field cage study, emergence dates, percent emergence, tuber yield, and tuber symptoms were compared between mother tubers infected with either Lso haplotype A or B, and control plants. In general, plants with either Lso haplotype A or B emerged later in the season compared to control plants, and with lower overall emergence. Daughter tubers harvested from the Lso haplotype A or B infected tubers did not show any zebra chip symptoms. All together, these results highlight differences in the epidemiology in Lso haplotype A and B, and suggest that future studies of this pathogen need to indicate the genetic population used.