New variety of zebra chip disease threatens potato production in southwestern Oregon

The disease, caused by the bacterium 'Candidatus Liberibacter solanacearum,' has been economically damaging commercial crops, including potato, tomato, and pepper, in the central and western United States, Mexico, Central America, and New Zealand since the early 2000s.

In a three-year period in the mid-2000s, chemical management of the disease in Texas cost an estimated $25.86 million. The Pacific Northwest spends an estimated $11 million a year on chemical management.

"The economic impact of zebra chip disease on the U.S. potato industry cannot be taken lightly," write K. D. Swisher Grimm and S. F. Garczynski, authors of "Identification of a New Haplotype of 'Candidatus Liberibacter solanacearum' in Solanum tuberosum," an article in Plant Disease.

Swisher Grimm and Garczynski received potato tubers from the Klamath Basin in Oregon that were suspected of being infected with the casual bacteria of zebra chip disease. When they analyzed the tubers, they confirmed the presence of the pathogen but did not identify the sample as one of the six known varieties (haplotypes).

Prior to this discovery, "only haplotypes A and B were known to cause zebra chip symptoms in potato," explains Swisher. This research identified a new haplotype, designated haplotype F, as the third haplotype of the bacterium that infects potatoes in the United States.

There is more to learn about haplotype F -- research must be done to determine host range and identify the insect that transmits this pathogen. As this is the first time zebra chip disease has been identified in the Klamath Basin, it is important to identify the dynamics and geographic overlaps of haplotypes A, B, and F. In-depth surveys are necessary to determine the potential impact of the novel haplotype on the potato industry of Southwestern Oregon.