Zebra chip-diseased potato tubers are characterized by increased levels of host secondary metabolites, amino acids, and defense-related proteins

Authors: Wallis, Christopher; Chen, Jianchi; Civerolo, Edwin

Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2012
Publication Date: 2/26/2012
Citation: Wallis, C.M., Chen, J., Civerolo, E.L. 2012. Zebra chip-diseased potato tubers are characterized by increased levels of host secondary metabolites, amino acids, and defense-related proteins. Physiological and Molecular Plant Pathology. Available: http://dx.doi.org/10.1016/j.pmpp.2012.02.001

Interpretive Summary: Zebra chip disease, associated with infection by ‘Candidatus Liberibacter solanacearum’, is a serious threat to potato production in the United States, Mexico, and New Zealand. Symptoms of the disease are not likely due to presence of the causal agent(s) itself, but rather due changes in host physiology associated with defense response of the plant to the pathogen. This work examined differences in host chemistry and pathogenesis-related proteins between healthy and diseased tubers. Changes in host chemistry were related to zebra chip symptom severity. Higher levels of phenolic compounds were observed in diseased tubers than in healthy tubers. Greater levels of phenolics and polyphenol oxidase in diseased tubers likely resulted in increased browning of freshly-cut tubers. Elevated levels of six amino acids were present in diseased tubers compared to healthy tubers. Collectively, these results suggest that host defense responses against the bacterium could affect tuber chemistry, resulting in zebra chip symptom formation.

Technical Abstract: Zebra chip disease, a serious threat to potato production in the United States and elsewhere, is associated with 'Cadidatus Liberibacter solacearum'. Little is known about host chemistry effects on zebra chip disease symptom development in potatoes (Solanum tuberosum). This research compared chemical profiles and defense-related enzyme levels between non-diseased and zebra chip-diseased potato tubers. Most phenolics, six amino acids, peroxidase, polyphenol oxidase, chitanase, and ß-1,3-glucanase levels were found in greater levels in diseased tubers than healthy tubers, and many of these were significantly positively associated with zebra chip disease severity. Thus, host defense responses against the bacterium could affect tuber chemistry, resulting in the formation of zebra chip symptoms both prior to and after frying.