ARS | Publication request: Zebra chip disease symptoms are positively associated with pathogenesis-related protein activity and phenolic compound levels in tubers

Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2011
Publication Date: June 1, 2011
Citation: Wallis, C.M., Chen, J. 2011. Zebra chip disease symptoms are positively associated with pathogenesis-related protein activity and phenolic compound levels in tubers. Phytopathology. 101:S184.

Technical Abstract: Zebra chip disease, putatively caused by the bacterium 'Candidatus Liberibacter solanacearum', is an emerging problem for potato growers throughout North America. However, little is known about the physiological changes that occur in diseased plants beyond the eponymous zebra chip symptom. One physiological change that occurs in diseased plants, presumably as a response to pathogen infection, is increased production of pathogenesis-related (PR) proteins including beta-glucanases, exo-chitanases, peroxidases, and polyphenol oxidases. Increased production of phenolic compounds also occurs. The levels of these proteins and phenolics were compared between healthy and zebra-chip diseased tubers. PR protein levels were quantified based on relative enzymatic activity, whereas phenolic compounds were extracted in methanol and analyzed by high-performance liquid chromatography. Diseased tubers, compared with non-diseased tubers, had twice the levels of beta-glucanase, exo-chitanase, and polyphenoxidase; and eight times the levels of peroxidase. Protein concentrations were also positively correlated with disease assessment ratings. Phenolic levels were much greater in diseased tubers, especially levels of chlorogenic acid derivatives and precursors. Zebra chip diseased tubers could exhibit increased browning when cut or fried because of these observed increases in enzyme levels and phenolic content.