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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Publications at this Location » Publication #353370
Research Project: Developing New Potatoes with Improved Quality, Disease Resistance, and Nutritional Content

Location: Temperate Tree Fruit and Vegetable Research

Title: Identification of a new haplotype of ‘Candidatus Liberibacter solanacearum’ in Solanum tuberosum

Author
item Swisher Grimm, Kylie
item Garczynski, Stephen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2018
Publication Date: 1/10/2019
Citation: Swisher Grimm, K.D., Garczynski, S.F. 2019. Identification of a new haplotype of ‘Candidatus Liberibacter solanacearum’ in Solanum tuberosum. Plant Disease. 103:468-474.

Interpretive Summary: Zebra chip of potato is an economically devastating disease in the United States. In 2017, researchers at the USDA-ARS Temperate Tree Fruit and Vegetable Research Unit in Washington State received tuber samples suspected of being infected with the causal agent of zebra chip disease. Visual tuber analysis and molecular diagnostic analysis identified a single tuber as positive for the causal agent, ‘Candidatus Liberibacter solanacearum’. Sequence analysis of three different genes confirmed the presence of ‘Candidatus Liberibacter solanacearum’ in the tuber, but did not identify the sample as one of the five known strains of the pathogen. This result indicated that a new strain of ‘Candidatus Liberibacter solanacearum’ was identified, designated here as haplotype F.

Technical Abstract: In 2017, potato tubers suspected of being infected with the bacterium, ‘Candidatus Liberibacter solanacearum,’ were received from the Animal and Plant Health Inspection Service in the United States. A total of 368 chipping tubers were observed for internal symptoms of zebra chip disease, which is associated with ‘Candidatus Liberibacter solanacearum’ infection in the United States, Mexico, Central America, and New Zealand. A single tuber sliced at the stem end showed classic zebra chip symptoms of darkened medullary rays, with streaking and necrotic flecking. The symptomatic tuber was confirmed positive for the bacterium by polymerase chain reaction targeting three different ‘Candidatus Liberibacter solanacearum’ genes. Sequence analysis of these three genes, and subsequent BLAST analysis identified the pathogen with 99%, 98%, and 97% identity to ‘Candidatus Liberibacter solanacearum’ for the 16S ribosomal RNA gene, 50S ribosomal proteins L10/L12 genes, and the outer membrane protein gene, respectively. Sequence analysis did not identify the sample as one of the five known haplotypes of ‘Candidatus Liberibacter solanacearum,’ indicating that a sixth haplotype of the pathogen was identified. This new haplotype, designated haplotype F, is now the third haplotype of the bacteria that infects Solanum tuberosum in the United States.