Identification of three new ‘Candidatus Liberibacter solanacearum’ haplotypes in four psyllid species (Hemiptera: Psylloidea)

Authors: Swisher Grimm, Kylie; Horton, David; Lewis, Tamera; GARCZYNSKI, STEPHEN - Former ARS Employee; JENSEN, ANDREW - Northwest Potato Research Consortium; CHARLTON, BRIAN - Oregon State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2022
Publication Date: 11/30/2022
Citation: Swisher Grimm, K.D., Horton, D.R., Lewis, T.M., Garczynski, S., Jensen, A., Charlton, B. 2022. Identification of three new ‘Candidatus Liberibacter solanacearum’ haplotypes in four psyllid species (Hemiptera: Psylloidea). Scientific Reports. 12. Article 20618. https://doi.org/10.1038/s41598-022-24032-9.
DOI: https://doi.org/10.1038/s41598-022-24032-9

Interpretive Summary: ‘Candidatus Liberibacter solanacearum’ is known to cause quality and yield losses in solanaceous and apiaceous crops around the globe, including the economically important zebra chip disease of potato. In an effort to identify the insect vector of a newly identified genetic variant of this pathogen found in potato in Southern Oregon, researchers at the USDA Agricultural Research Service in Washington state, in collaboration with Oregon State University and Northwest Potato Research Consortium scientists screened psyllid species collected on sticky traps placed near potato fields in the Klamath Basin of Oregon and California for the pathogen. Testing of over 2700 psyllid specimens trapped in 2018 and 2019 led to the discovery of three new genetic variants of ‘Ca. L. solanacearum’ in four different psyllid species. Taxonomic and molecular tools were used to identify the psyllid species, three of which belong to the poorly describe Aphalara genus. These finding indicate that ‘Ca. L. solanacearum’ genetic diversity, and their plant hosts and psyllid vectors, are greater than what is currently known, and further research is needed to determine what effect these ‘Ca. L. solanacearum’ variants might have on crops in the region.

Technical Abstract: Eleven haplotypes of the bacterium, ‘Candidatus Liberibacter solanacearum’, have been identified worldwide, several of which infect important agricultural crops. In the United States, haplotypes A and B are associated with yield and quality losses in potato, tomato, and other crops of the Solanaceae. Both haplotypes are vectored by potato psyllid, Bactericera cockerelli. Recently, a third haplotype, designated F, was identified in Southern Oregon potato fields. To identify the vector of this haplotype, psyllids of multiple species were collected from yellow sticky cards placed near potato fields during two growing seasons. Over 2700 specimens were tested for ‘Ca. L. solanacearum’ by polymerase chain reaction. Forty-seven psyllids harbored the bacterium. The infected specimens comprised four psyllid species in two families, Aphalaridae and Triozidae (Hemiptera: Psylloidea). Nucleic acid and/or amino acid sequence analysis of the ‘Ca. L. solanacearum’ 16S RNA, 50S ribosomal proteins L10/L12, and outer membrane protein identified three new haplotypes of the bacterium, designated as Aph1, Aph2 and Aph3, including two variants of Aph2 (Aph2a and Aph2b). The impact of these new haplotypes on solanaceous or other crops is not known. The vector of ‘Ca. L. solanacearum’ haplotype F was not detected in this study and remains unknown.