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Title: LC-MS Analysis of Phenolic Compounds in Tubers Showing Zebra Chip Symptoms

item Navarre, Duroy - Roy
item Holden, Margaret
item Crosslin, James

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2008
Publication Date: 2/1/2009
Citation: Navarre, D.A., Shakya, R., Holden, M., Crosslin, J. 2009. LC-MS Analysis of Phenolic Compounds in Tubers Showing Zebra Chip Symptoms. American Journal of Potato Research. 86:88-95.

Interpretive Summary: This work shows that the economically damaging symptoms associated with the Zebra Chip disorder are likely caused by increases in phenolic compounds. Tyrosine levels were found to be substantially higher in tubers showing ZC symptoms and this compound is well-documented to be associated with browning in potatoes. Numerous other phenolic compounds increased substantially in ZC tubers. The defense compound salicylic acid also increased in ZC tubers. Collectively these results suggest that the cause of ZC disorder is pathogen related and that the browning seen in tubers is due to major changes in phenolic compounds..

Technical Abstract: A new potato disorder called zebra chip (ZC) has been identified in the United States and has been especially problematic in Texas where substantial economic losses have been incurred. Upon frying, ZC tubers develop a dark “zebra chip” pattern of discoloration. LC-MS analysis of symptomatic tubers revealed major alterations in aromatic amino acids and phenolic compounds. Tyrosine concentrations increased over 8-fold in some symptomatic tubers, reaching up to 3 mg/g DW and this increase may be a major component of the browning of ZC tubers. No marked differences in chlorogenic acid concentrations were found, but differences in other caffeoyl derivatives, including caffeoylpolyamines, were observed. Salicylic acid, a key regulator of plant defenses, was present at very high concentrations in ZC tubers, which is consistent with what would be expected from tubers mounting a defense response to a pathogen. ZC tubers may be a useful model to study how plant-microbe/pest or plant-environment interactions affect tuber physiology.