|Swisher Grimm, Kylie|
|MUSTAFA, TARIQ - Washington State University|
|Cooper, Rodney - William|
|Munyaneza, Joseph - Joe|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2018
Publication Date: 8/9/2018
Citation: Swisher Grimm, K.D., Mustafa, T., Cooper, W.R., Munyaneza, J.E. 2018. Role of ‘Candidatus Liberibacter solanacearum’ and Bactericera cockerelli haplotypes in zebra chip incidence and symptom severity. American Journal of Potato Research. 95:709-719.
Interpretive Summary: Zebra chip disease of potato is an economically damaging disease found in the western United States, and is caused by a pathogen called 'Candidatus Liberibacter solanacearum'. Researchers at USDA-ARS in Wapato and Prosser, Washington, in collaboration with a Washington State University scientist, assessed the role of two different populations, A and B, of Ca. Li. solanacearum, and three different populations (central, northwestern, and western) of the insect vector (Bactericera cockerelli), in zebra chip disease incidence and symptom severity. Interestingly, the Ca. Li. solanacearum B population was found to trigger higher zebra chip incidence, lower tuber yield, and more severe symptoms as compared to the A population. All three B. cockerelli insect populations were able to transmit the pathogen and produce severe zebra chip symptoms. This study is the first trial to compare pathogen and insect population effects on zebra chip disease in field cages, and highlights the role specific pathogen populations play in overall zebra chip disease epidemiology.
Technical Abstract: Zebra chip disease of potato is an economically devastating disease in the United States, Mexico, Central America, and New Zealand. Research to understand the disease epidemiology has identified two different haplotypes of the causal agent, ‘Candidatus Liberibacter solanacearum,’ and four different haplotypes of the insect vector, Bactericera cockerelli, within the United States. It is not known whether severity or incidence of disease symptoms is influenced by haplotype of the pathogen or the insect vector. This field cage study analyzed the role of two haplotypes of ‘Candidatus Liberibacter solanacearum’ (haplotypes 'A' and 'B') transmitted by three haplotypes of B. cockerelli (central, western, and northwestern), on disease severity and incidence in eight different potato cultivars grown in the United States. Both haplotypes of ‘Candidatus Liberibacter solanacearum’ induced zebra chip symptoms in tubers, irrespective of the haplotype of B. cockerelli used to transmit the pathogen. In general, infection with haplotype B of ‘Candidatus Liberibacter solanacearum’ caused a higher incidence of zebra chip symptoms, and caused a greater reduction in tuber production compared with haplotype A. Haplotype B of ‘Candidatus Liberibacter solanacearum’ was also associated with more severe tuber symptoms, producing fewer tubers with mild or moderate zebra chip symptoms than haplotype A. ‘Candidatus Liberibacter solanacearum’ haplotype A was therefore associated with less severe tuber symptoms overall, despite being able to induce severe symptoms in some tubers. Disease incidence, tuber yield, and symptom severity ratings did not appear to be dependent upon the psyllid haplotype used to transmit the pathogen. Results from this study indicate the necessity for future research to clearly identify the ‘Candidatus Liberibacter solanacearum’ haplotype used in each experiment, and clearly indicate the impact either haplotype has in the study.