American Journal of Potato Research

, Volume 87, Issue 4, pp 337–349 | Cite as

Evidence that Cell Death is Associated with Zebra Chip Disease in Potato Tubers

  • Godfrey P. Miles
  • Marcus A. Samuel
  • Jianchi Chen
  • Edwin L. Civerolo
  • Joseph E. Munyaneza


Zebra chip (ZC) is an established and highly destructive disease of potato (Solanum tuberosum L.) that occurs in several southwestern states of the United States, Mexico, Central America, and New Zealand. The causal agent for this disease has not been identified. However, the bacterium “Candidatus Liberibacter solanacearum” and the potato psyllid, Bactericera cockerelli (Šulc), its insect vector, are associated with the disease. Tubers from ZC-affected potato plants exhibit dramatic browning of vascular tissue concomitant with “necrotic flecking” both of which can affect the entire tuber. Upon frying, these tubers develop a characteristic striped pattern of discoloration rendering them unmarketable. These characteristic ZC symptoms in the tubers have been suggested to be associated with general cell death, though no evidence to confirm this hypothesis has been shown. In order to determine if cell death is associated with ZC disease, a series of experiments were undertaken. Cell death was initially quantified by comparing cellular ion leakage from ZC-affected and ZC-free tubers. Levels of ion leakage were found to be significantly higher in ZC-affected tubers compared to ZC-free tubers. To examine further the association of cell death with ZC disease, ZC-affected and ZC-free tubers were compared using classical histochemical staining methods in conjunction with optical microscopy, which revealed layers of dead cells surrounding numerous, small, irregularly-shaped lesions throughout the parenchymatic medullary region, vascular ring and cortex of ZC-affected tubers. This cell death was confirmed using high-resolution, field-emission scanning electron microscopy (FE-SEM) of fresh-cut tuber tissue.


Bactericera cockerelli Potato psyllid Candidatus Liberibacter solanacearum Solanum tuberosum Cultivar Atlantic FE-SEM 


Zebra chip (ZC) es una enfermedad establecida y altamente destructiva de papa (Solanum tuberosum L.) que se presenta en varios estados del suroeste de los Estados Unidos, México, América Central y Nueva Zelandia. El agente causal de esta enfermedad no ha sido identificado. No obstante, la bacteria “Candidatus Liberibacter solanacearum” y el psílido de la papa Bactericera cockerelli (Šulc), su insecto vector, están asociados con la enfermedad. Los tubérculos de plantas afectadas por ZC presentan oscurecimiento dramático del tejido vascular concomitante con “pecas necróticas” que en ambos casos pueden afectar al tubérculo completo. Al freírse, estos tubérculos desarrollan un patrón característico de rayado haciéndolos no comerciales. Se ha sugerido que estos síntomas característicos en los tubérculos estén asociados con muerte general de las células, aún cuando no se ha mostrado evidencia para confirmar esta hipótesis. Se llevaron a cabo varios experimentos a fin de determinar si la muerte de las células está asociada con la enfermedad de ZC. La muerte celular se cuantificó inicialmente comparando el lixiviado iónico celular de tubérculos con y sin ZC. Se encontró que los niveles de iones lixiviados fueron significativamente más altos en tubérculos afectados con ZC comparados con los libres de ZC. Para examinar mas la asociación de la muerte de la célula con la enfermedad ZC, a tubérculos infectados y a libres de ZC se les comparó usando los métodos de la clásica tinción histoquímica, junto con microscopía óptica, lo cual reveló capas de células muertas rodeando a numerosas lesiones pequeñas, de forma irregular, a través de la región medular parenquimatosa, el anillo vascular y el cortex de tubérculos afectados por ZC. Esta muerte celular se confirmó usando microscopía electrónica de barrido de alta resolución (FE-SEM) de tejido de cortes de tubérculo fresco.



We thank Jeremy Buchman, Dan Hallauer, Blaine Heilman, and Millie Heidt (USDA-ARS Laboratory in Wapato, WA); Andy Cruz (USDA-ARS Research Farm in Weslaco, TX.); Michael Laffin (University of Calgary, Canada); Darlene Hoffmann (USDA-ARS Laboratory in Parlier, CA); and Valerie Lynch-Holm and Christine Davitt (Franceschi Microscopy and Imaging Center, Washington State University for their technical assistance. We would like to give special thanks to Valerie Lynch-Holm for her invaluable assistance with potato tissue preparation, histochemical staining (toluidine blue and PAS) and training on the FE-SEM. We are also grateful to Drs. Dave Horton, Eugene Miliczky, and Roy Navarre for their critical reading of this manuscript. Financial support for this work was partially provided by Frito Lay, Inc., Texas Department of Agriculture, and the USDA-ARS State Cooperative Potato Research Program.


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Copyright information

© Potato Association of America 2010

Authors and Affiliations

  • Godfrey P. Miles
    • 1
  • Marcus A. Samuel
    • 2
  • Jianchi Chen
    • 3
  • Edwin L. Civerolo
    • 3
  • Joseph E. Munyaneza
    • 1
  1. 1.Yakima Agricultural Research LaboratoryUSDA-ARSWapatoUSA
  2. 2.Department of Biological SciencesUniversity of CalgaryCalgaryCanada
  3. 3.San Joaquin Valley Agricultural Sciences CenterUSDA-ARSParlierUSA

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