Location: Sugarbeet and Potato Research
2016 Annual Report
Objectives
Objective 1: Delineate and integrate the molecular processes that control cytokinin content and their biological activities during tuber dormancy progression and wound-healing.
Sub-Objective 1-1: Determine changes in tuber meristem cytokinin content and expression of genes encoding cytokinin biosynthetic enzymes during dormancy progression.
Sub-Objective 1-2: Determine changes in the expression of cytokinin-responsive histidine kinase genes and the acquisition of cytokinin sensitivity during tuber dormancy progression.
Sub-Objective 1.3: Determine changes in cytokinin content and the expression of genes encoding key cytokinin metabolic enzymes in tuber tissues following mechanical wounding.
Objective 2: Quantify nitric oxide release during potato storage and handling and determine nitric oxide involvement in tuber dormancy progression and wound-healing.
Sub-Objective 2.1: Determine the release and role of NO in potato tuber dormancy exit.
Sub-Objective 2.2: Determine the release and role of NO in the potato tuber wound-healing response.
Objectives 1 and 2 build upon research findings secured during the previous project cycle and address current knowledge gaps in the regulatory processes controlling tuber dormancy progression and wound healing.
Approach
Worldwide, the potato ranks fourth among the major food crops. Global potato production exceeds 364 million metric tons (FAOSTAT, March, 2013) and U.S. production exceeds 437 million cwt (USDA-NASS, January, 2013) of which over 400 million cwt worth an estimated $2.01 billion are harvested in the fall. Over 70% of the fall potato crop is placed into storage for year-round use. Unlike other major food crops, potatoes are stored in a fully hydrated and highly perishable form. Postharvest losses routinely approach 10% of the stored crop and occur through both physiological and disease-related processes. Two of the most important physiological processes affecting potato storage and market quality are dormancy/sprouting and wound-healing. Despite the severity of these losses, management strategies and technologies employed to combat these problems were empirically derived, are several decades old and do not effectively meet today’s consumer or industry demands to control damage, minimize physiological deteriorations, and reduce disease problems. Further improvements in postharvest storage technologies are hindered by ignorance of the biological mechanisms underlying these physiological processes. The goals of this project are to identify critical molecular, biochemical and physiological mechanisms controlling tuber dormancy/sprout growth and wound-healing and, ultimately, to genetically, chemically, or physically manipulate these rate-limiting processes to develop improved methods to maintain potato nutritional and processing quality during storage. Specific goals are: 1) Identify the cognate processes that control cytokinin content and activity during postharvest storage/wound-healing, and 2) Determine the involvement of nitric oxide in tuber dormancy progression and wound-healing.
Progress Report
Previously initiated studies to determine the effect of inhibitors of polyamine (PA) biosynthesis and catabolism on wound-induced suberization (the development of barriers that block rot-type infections, shrinkage, and reduce nutritional losses and market quality defects) are now in process after several major equipment failures. Inhibitors of PA biosynthesis and catabolism, including triamine and tetramine PA oxidation but not inhibitors of diamine PA oxidation, inhibited the first phase of suberization. Replicated analyses are near completion. Studies of PA related nitric oxide production (NO) are following to determine the role of NO in mediating wound-induced suberization and ultimately reduce wound related rot and other losses. Retirement of the ARS scientist conducting research on tuber dormancy has delayed planned studies on the control of potato sprouting.
Accomplishments
1. Gibberellins are involved in 1,8-cineole-mediated inhibition of tuber sprout growth. At harvest and for an indeterminate period thereafter, potatoes are in a state of physiological dormancy and will not sprout. However, dormancy is lost during storage yielding sprout growth which is accompanied by changes in tuber physiology leading to loss of nutritional and processing quality. Suppression of sprout growth is essential in successful potato storage management. Unlike other registered sprout inhibitors, the natural product cineole is known to reversibly mediate inhibition of sprout growth, suggesting a non-herbicidal mechanism of action that may be related to exploitable hormonal control. ARS scientists in Fargo, North Dakota determined that cineole inhibits sprout growth, in part, through reversible inhibition of gibberellin biosynthesis. These results are important in the future development of modern technologies to control sprouting in bulk stored potatoes.
2. Wound healing in potatoes. Potato tubers are unavoidably skinned and bruised (wounded) during harvest/handling and require rapid wound-healing (WH) to avoid costly rot type infections, nutritional deterioration and other losses during storage. Currently, there are no means available to hasten WH; yet little is known about the biological mechanisms regulating the critical WH processes for rapid development of an initial protective barrier (suberin) and subsequent initiation of cell division required for development of a more durable protective wound periderm. ARS scientists in Fargo, North Dakota along with a Pennsylvania State University biologist, determined the wound-induced changes in hormones that are required for this cell division process. Although the hormones cytokinin (CK) and indole acetic acid (IAA) are required in the regulation of cell division, the existence of certain CK related products indicated that there was only a fleeting presence of biologically active CK during WH, which suggested tight CK mediated regulation. IAA content increased markedly at 7 days after wounding when cell division processes fully initiated, suggesting that its regulatory role was less sensitive. Notably, gibberellin hormones, which are typically involved in growth, were not present during WH and consequently do not play a role in WH processes. These results provide new insight into the regulation of wound periderm formation, which is critical in the development of new technologies to hasten WH and thereby reduce rot and nutritional/quality deterioration for growers, processors and consumers.
None
Review Publications
Lulai, E.C., Suttle, J.C., Olson, L.L., Neubauer, J.D., Campbell, L.G., Campbell, M.A. 2016. Wounding induces changes in cytokinin and auxin content in potato tuber, but does not induce formation of gibberellins. Journal of Plant Physiology. 191:22-28.
Suttle, J.C., Olson, L.L., Lulai, E.C. 2016. The Involvement of Gibberellins in 1,8-Cineole-Mediated Inhibition of Sprout Growth in Russet Burbank Tubers. American Journal of Potato Research. 93(1):72-79.
Suttle, J.C., Campbell, M.A., Olsen, N.L. 2016. Potato tuber dormancy and postharvest sprout control. In Pareek, S. Postharvest Ripening Physiology of Crops. CRC Press. 449-476.
