First author: United States Department of Agriculture–Agricultural Research Service Crop Diseases, Pests and Genetics Research Unit 9611 S. Riverbend Avenue, Parlier, CA 93648; and second author: Department of Plant Pathology, North Dakota State University, Fargo 58108-6050.
An overview is provided for the aspects of history, biology, genomics, genetics, and epidemiology of zebra chip (ZC), a destructive disease of potato (Solanum tuberosum) that represents a major threat to the potato industries in the United States as well as other potato-production regions in the world. The disease is associated with a gram-negative, phloem-limited, insect-vectored, unculturable prokaryote, ‘Candidatus Liberibacter solanacearum’, that belongs to the Rhizobiaceae family of α-Proteobacteria. The closest cultivated relatives of ‘Ca. L. solanacearum’ are members of the group of bacteria known as the α-2 subgroup. In spite of the fact that Koch's postulates sensu stricto have not been fulfilled, a great deal of progress has been made in understanding the ZC disease complex since discovery of the disease. Nevertheless, more research is needed to better understand vector biology, disease mechanisms, host response, and epidemiology in the context of vector–pathogen–plant interactions. Current ZC management strategies focus primarily on psyllid control. The ultimate control of ZC likely relies on host resistance. Unfortunately, all commercial potato cultivars are susceptible to ZC. Elucidation of the ‘Ca. L. solanacearum’ genome sequence has provided insights into the genetic basis of virulence and physiological and metabolic capability of this organism. Finally, the most effective, sustainable management of ZC is likely to be based on integrated strategies, including removal or reduction of vectors or inocula, improvement of host resistance to the presumptive pathogen and psyllid vectors, and novel gene-based therapeutic treatment.