Submitted to: American Journal of Potato Research
Publication Type: Abstract only
Publication Acceptance Date: 3/21/2008
Publication Date: 3/1/2009
Citation: Bethke, P.C., Sabba, R., Higgins, C., Bussan, A.J. 2009. Stem End Defect in Chipping Potatoes From Production Fields and Temperature-Controlled Greenhouses. American Journal of Potato Research. 86(2):136. Interpretive Summary:
Technical Abstract: Stem end defect is a highly localized darkening at the stem end after frying. This defect is a significant quality concern for chip potatoes, but there is little published literature on the nature of the defect or its causes. Although stress during the growing season is thought to be involved in stem end defect formation, there is little agreement as to what the stress is or when it is most effective in causing the defect. In 2007, we evaluated chip potatoes grown in commercial fields and in greenhouses with the goals of (1) describing stem end defect in an unambiguous, consistent way (2) identifying environmental conditions or management practices that are associated with stem end defect (3) evaluating the hypothesis that stem end defect can be attributed primarily to localized accumulation of reducing sugars, (4) determining if stem end defect can occur while tubers are in storage and if reconditioning can be used to remove the defect, and (5) determining if stem end defect can be found in tubers harvested from plants grown in the greenhouse under favorable or stressful conditions. Our data to date are inconsistent with the hypothesis that stem end defect is associated with pathogen stress, as defect tubers were harvested from fields where vines were healthy late in the season, and from healthy plants grown in the greenhouse. Stem end defect was found to be associated with the tuber vasculature, but was not restricted to those tissues. Stem end defects, covering the range from mild to severe, were observed in greenhouse grown tubers, and stem end glucose content in those tubers was significantly higher than that on the bud end, giving support to the hypothesis that reducing sugars are important in stem end formation.