ARS | Publication request: Sugar End Defect in Stressed Russet Burbank Potatoes Grown Under Controlled Environment Conditions

Submitted to: American Journal of Potato Research
Publication Type: Abstract
Publication Acceptance Date: March 21, 2008
Publication Date: March 1, 2009
Citation: Bethke, P.C., Sabba, R., Bussan, A.J. 2009. Sugar End Defect in Stressed Russet Burbank Potatoes Grown Under Controlled Environment Conditions. American Journal of Potato Research. 86(2):136.

Technical Abstract: Sugar end defect results from an accumulation of reducing sugars at the stem end of the tuber. Such tubers turn dark at the stem end when fried and may not be acceptable to processors. Sugar end defect is thought to be caused by heat and/or drought stress during tuber growth, and may be promoted by insufficient or excess nitrogen. Although stress during the growing season causes sugar end defect, elevated reducing sugars may not be apparent until weeks after harvest. We are investigating the causes of sugar end defect and the physiological changes that are associated with sugar end production. Russet Burbank potatoes were grown in temperature controlled greenhouses and irrigated daily with nutrient solution. These were subjected to two-week long periods of water stress and/or heat stress. Data were collected on soil water content, leaf water potential, tuber water potential, tuber yield, tuber solids, and tuber sugars at the end of the stress period, at harvest, and after 3 months of storage at 13°C. There was a strong correlation between leaf and tuber water potential, but little evidence that sugar accumulation participated in osmotic adjustment of tubers. The data confirm earlier reports that sugar end defect is associated with stress, and support prior suggestions that sugar ends are associated with low starch content. Our data suggest a mechanism for sugar end production in which net conversion of starch to sugar is greater in the stem end than in the bud end.