Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2007
Publication Date: 2/29/2008
Citation: Suttle, J.C. 2008. Effects of Synthetic Phenylurea and Nitroguanidine Cytokinins on Dormancy Break and Sprout Growth in Russet Burbank Minitubers. American Journal of Potato Research. 85:121-128. Interpretive Summary: For an indeterminate period of time following harvest, potatoes will not sprout and are physiologically dormant. Dormancy is gradually lost during postharvest storage and the resultant sprouting is detrimental to the nutritional and processing qualities of potatoes destined for human consumption. However for seed potatoes, lengthy dormancy is a disadvantage and can result in poor plant stands and reduced yields. The research being conducted in this lab is directed towards 1.) identifying key physiological processes that naturally regulate tuber dormancy and, ultimately, 2.) manipulating these processes to suit the needs of producers of table, process, and seed potatoes. Cytokinins are the principal regulators of tuber dormancy exit and initial sprout growth and may therefore be useful to prematurely terminate dormancy and promote sprout growth in seed potatoes. In this paper, the effects of two types of synthetic cytokinins on tuber dormancy were determined. Both synthetic cytokinins rapidly ended tuber dormancy and promoted sprout growth. In contrast, a naturally occurring cytokinin was much-less effective. Unlike currently used sprout stimulators that often cause excessive sprout elongation, cytokinin treatment results in short thick sprouts that may be more resistant to breakage during seed handling.
Technical Abstract: Treatment of dormant Russet Burbank minitubers with the synthetic cytokinins N-2-chloro-4-pyridyl)-N'-phenylurea (CP) or 1-(alpha-ethylbenzyl)-3-nitroguanidine (NG) resulted in the premature termination of tuber dormancy. In contrast, treatment with the thidiazoyl-urea cytokinin thidiazuron did not stimulate sprouting. Both CP and NG were more effective than the naturally occurring cytokinin zeatin and, unlike zeatin, both stimulated sprouting in minitubers during early storage. Unlike treatment with gibberellic acid (GA) which often induced excessive sprout growth, sprouts developing from minitubers treated with either cytokinin were short, thick, and robust. Upon transfer to room temperature, the endogenous content of abscisic acid in apical bud periderm discs isolated from control minitubers declined more than 40% over a 15 day period. Treatment with either CP or NG had no appreciable effect on this decline while treatment with GA diminished the decrease in ABA content. Treatment with either synthetic cytokinin resulted in a large and sustained increase in endogenous ethylene production that was detectable immediately prior to visible sprout growth. In contrast, GA treatment resulted in a much smaller increase that was observed after sprout growth commenced. These results indicate that either CP or NG treatment can be effectively used to prematurely terminate tuber dormancy and induce sprout growth.