Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/2/2013
Publication Date: 2/1/2014
Citation: Wallis, C.M., Rashad, A., Wallingford, A.K., Paetzold, L., Workneh, F., Rush, C.M. 2014. Similarities and differences in physiological responses to ‘Candidatus Liberibacter solanacearum’ infection among different potato cultivars. Phytopathology. 104:126-133. Interpretive Summary: Zebra chip disease (ZC), caused by the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso), poses a threat to potato production in Mexico, New Zealand, and the United States as it renders tubers unmarketable. Current management for ZC involves chemical control of the potato psyllid vector of Lso, which costs growers roughly $700/hectare. The key to more cost-effective, long-term management of ZC lies in exploiting naturally occurring tolerance to this disease. Anecdotally, potatoes of the “fresh red” marketing class were considered more tolerant to Lso infection than russet or chipping marketing classes. Therefore, Red La Soda (of the fresh red potato marketing class), Russet Norkotah (of the russet marketing class), and FL 1867 (of the chipping marketing class) potatoes were inoculated with Lso at different times before harvest. Contrary to anecdotal reports, ZC symptoms were greater in Red La Soda tubers than Russet Norkotah or FL 1867 tubers. However, all cultivars expressed moderate to severe ZC symptoms, rendering tubers unmarketable. Lso concentration did not differ among cultivars. Further, all three cultivars had similar changes in tuber biochemistry following Lso infection that were associated with moderate to severe ZC symptoms. Taken together, these results revealed that major potato marketing types do not vary greatly in tolerance to Lso infection. Therefore, ZC-resistance breeding programs should consider using wild potato species to create resistant cultivars.
Technical Abstract: Zebra chip disease (ZC), putatively caused by ‘Candidatus Liberibacter solanacearum’ (Lso), is a threat to potato growers worldwide. However, little is known about biochemical shifts in different potato genotypes in response to Lso infection. To address this, Red La Soda, Russet Norkotah, and FL 1867 potatoes were infected with Lso four-, three-, two-, and one-week(s) before harvest to observe variability in cultivar responses to Lso infection. ZC symptoms, Lso titers, and tuber biochemistry were assessed. Red La Soda tubers exhibited greater symptoms when infected for four weeks than Russet Norkotah or FL 1867 tubers. Lso titers did not vary among cultivars. Tuber levels of amino acids, carbohydrates, and phenolics varied among cultivars, but no consistent trends were observed. Individual amino acids and phenolics were greater in FL 1867 than Red La Soda, whereas others were greater in Red La Soda or Russet Norkota than FL 1867. Most amino acids, carbohydrates, and phenolics were positively associated with infection duration, symptoms, and titers. However, asparagine, aspartic acid, glutamic acid, glutamine, and methionine levels were negatively associated with infection duration, symptoms, and titers. This study concluded potato cultivars from different marketing classes did not vary greatly in susceptibility to Lso infection.