Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2007
Publication Date: 7/1/2007
Citation: Sabba, R.P., Bussan, A.J., Michaelis, B.A., Hughes, R., Drilias, M.J., Glynn, M.T. 2007. Effect of Planting and Vine-kill Timing on Sugarss, Specific Gravity and Skin Set Processing Potato Cultivars. American Journal of Potato Research. 84(3):205-215. Interpretive Summary: Potato losses from storage are a serious problem for the potato industry and typically exceed 30 million cwt annually. Successful potato storage depends on crop maturity at harvest. Tuber maturity is composed of three components: chemical, physiological, and physical. Chemical maturity refers to the concentration of sugars in tubers. Chemically mature tubers have low concentrations of reducing sugars at harvest and process well from storage. Tuber sugar concentration is dependent on cultivar, and both pre- and postharvest storage factors. In this paper, the effects of planting and vine-kill dates. Data reported indicate that chemical maturity was enhanced by early planting and delayed vine-kill.
Technical Abstract: Quality and storability of potato tubers harvested for storage are affected by their chemical, physiological and physical maturity. The sucrose concentration in potato tubers is indicative of the chemical maturity of the crop and of the potential processing quality of the crop after storage. High reducing sugar concentrations result in undesirable discoloration of fried potato products. Sucrose does not directly contribute to the discoloration of tuber tissue upon frying, but influences reducing sugar concentrations during storage. Physiologically mature tubers have maximized their dry matter content resulting in high specific gravities that are desirable for most aspects of potato processing. We examined the effect of different planting and vine-kill dates on the sucrose and glucose concentrations and specific gravity of five russet potato varieties grown in repeated experiments at Hancock, WI, during 2002 and 2003. Planting date rarely affected sugar content and specific gravity of tubers at harvest, but greater sucrose and glucose concentrations and specific gravities were found with later vine-kill dates. Although planting date had little effect on sugar content at harvest, both bud-end sucrose and glucose content decreased with earlier planting date at vine-kill. Of particular concern for processing, stem-end glucose concentrations consistently exceeded bud-end glucose concentrations for all cultivars, regardless of the cultural parameters utilized. Physically immature tubers have poor skin-set and are prone to skinning and mechanical damage during harvest, which renders them more vulnerable to dehydration and infection by rotting pathogens in storage. Skin-set of Russet Burbank tubers in 2003 improved with earlier planting date and delayed vine-kill timing. Our data indicate that chemical maturity does not necessarily correlate with either physiological or physical maturity in russet cultivars, rendering the use of cultural practices to improve tuber maturity at harvest problematic.