ARS | Publication request: Tuber Water and Pressure Potentials Decrease and Sucrose Contents Increase in Response to Moderate Drought and Heat Stress

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 9, 2009
Publication Date: November 1, 2009
Citation: Bethke, P.C., Sabba, R.P., Bussan, A.J. 2009. Tuber Water and Pressure Potentials Decrease and Sucrose Contents Increase in Response to Moderate Drought and Heat Stress. American Journal of Potato Research. 86(6):519-532.

Interpretive Summary: Environmental stresses, such as drought and high temperatures, can reduce the quality of stored potatoes. Sugar end defect is a serious quality concern for growers and processors of russet potatoes that is initiated by drought or heat stress. French fries and other fried products made from sugar end defect potatoes are excessively dark on one end, and may have an unpleasant, bitter taste. This darkening is caused by an accumulation of the sugar glucose on the stem end of the tuber. To gain a better understanding of how environmental stresses bring about the sugar end defect, we exposed Russet Burbank potatoes to two-week long periods of heat, drought, or heat and drought stress, and measured changes in tuber water status and tuber composition. Our data show that stress during early tuber growth causes larger perturbations to several of the measured parameters, especially the contents of sucrose and glucose in the tuber. These changes at the end of the stress period were reflected in tuber composition at harvest. Stem end glucose content was higher in tubers from plants that had been stressed early compared to those that had been stressed later.

Technical Abstract: Environmental stress during the growing season can reduce the quality of stored Solanum tuberosum (potato) tubers. Sugar end defect is a serious quality concern for growers and processors of russet potatoes that is initiated by drought or heat stress. Changes in tuber water potential and tuber composition following two-week long periods of drought, heat, or drought and heat stress were characterized for the Russet Burbank cultivar. Decreases in leaf and tuber water potential were observed following drought stress treatments. Tuber sucrose and glucose contents increased with the severity of stress. Changes in tuber malic acid content were also observed. Stress during early tuber bulking had a larger effect on tuber sugars than stress during mid-bulking. Stem end glucose content of tubers at harvest was higher in tubers from plants that had been stressed at early bulking compared to mid bulking.