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Potatoes tolerant of ‘Candidatus Liberibacter solanacearum’ infection do not undergo changes in tuber physiology associated with zebra chip disease
C. WALLIS (1), J. Munyaneza (2), R. Novy (3). (1) USDA-ARS San Joaquin Valley Agricultural Sciences Center, Parlier, CA, U.S.A.; (2) USDA-ARS Yakima Agricultural Research Laboratory, Wapato, WA, U.S.A.; (3) USDA-ARS Small Grains and Potato Germplasm Research Unit, Aberdeen, ID, U.S.A.

Zebra chip disease (ZC), caused by the bacterium ‘<i>Candidatus </i>Liberibacter solanacearum’ (Lso), is of increasing concern to potato growers throughout the western United States and elsewhere. New potato cultivars are being developed that are tolerant of Lso and therefore infected tubers do not express ZC symptoms. Previous studies have observed that ZC symptoms are associated with increased tuber levels of amino acids, sugars, and phenolics. Therefore, this study examined whether or not increases of amino acids, sugars, and phenolics occurred in Lso-infected commercial or potentially ZC-tolerant potato cultivars. Lso-infected tubers from the commercial, susceptible potato variety ‘Atlantic’ exhibited strong ZC symptoms. Levels of many amino acids, sugars, and phenolics were greater in infected ‘Atlantic’ tubers compared to those that were non-infected. By contrast, Lso-infected tubers from three tolerant cultivars, designated ‘M5’, ‘ZC73’, and ‘ZC74’, did not exhibit ZC symptoms. Levels of amino acids, reducing sugars, and phenolics were not significantly different between non-infected and Lso-infected tubers from the three tolerant cultivars. These results provide evidence that potato cultivars that do not have physiological changes in response to Lso infection are unlikely to develop ZC symptoms. Thus, tolerance, rather than immunity, may be sufficient to mitigate effects of ZC disease.

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