Location: Sugarbeet and Potato Research
2020 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.
Objective 3: Determine the effects of postharvest storage on process quality and nutritional composition of advanced breeding lines in collaboration with public potato breeding programs (non-hypothesis driven).
Sub-objective 3.1: Determine storage and processing characteristics of advanced breeding lines.
Sub-objective 3.2: Screen advanced potato breeding lines for cold storage potential.
Objective 4: Determine the total antioxidant and ascorbic acid (vitamin C) contents of advanced breeding clones at harvest and during temperature-controlled storage (non-hypothesis driven).
Objective 5: Identify and characterize the physiological and molecular mechanisms that regulate and maintain meristem dormancy in potato tubers and evaluate strategies to inhibit tuber sprouting during storage.
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
This is the final report for this project. Research investigating the physiological mechanisms impacting suberin development and wound healing was advanced (Sub-objectives 1.3 and 2.2). Tuber suberin production is critical for developing a protective barrier and is required for mitigating postharvest quality losses in storage. Research identified critical steps in polyamine biosynthesis limited suberin levels by restricting cellular hydrogen peroxide concentrations (Sub-objective 2.2). Enhancement of hydrogen peroxide production in this regulatory pathway may facilitate wound healing and reduce costly post-harvest wound-related losses. Research on wound-induced changes in phytohormone profiles revealed that cytokinin (CK) and indole acetic acid (IAA) are required in the regulation of cell division and periderm formation; wound healing involves tight CK mediated regulation; significant changes in IAA content, when cell division processes are fully initiated, suggested that its regulatory role was less sensitive (Sub-objective 1.3). These results provide new insight into the regulation of wound periderm formation, which is critical in the development of new technologies to hasten wound healing. Studies investigating the role of nitric oxide (NO) revealed that NO is essential in potato tuber wound healing to protect harvested tubers from infection and deterioration (Sub-objective 2.2). These results hold promise in the development of innovative technologies to reduce potato disease and associated losses through enhanced NO formation and possible treatment in potato storage facilities.
Significant progress was made in the non-hypothesis driven Objectives 3 and 4. Cooperative research has been fostered among university breeding programs, USDA-ARS potato breeding programs, and potato industry grower and processing stakeholders. Annual processing quality evaluations throughout storage were performed among advanced breeding clones and new potato varieties representing public breeding programs (Objective 3.1). Potato clones possessing excellent processing quality and cold storage potential were identified (Objective 3.2). Processing quality of fry and chip clones were assessed among Potatoes USA sponsored National Chip and Fry field and processing trials (Objective 3.1). Tuber antioxidant (vitamin C) concentrations and anti-quality compounds including glycoalkaloids were quantified among new potato clones at harvest and throughout storage (Objective 4). This cooperative evaluation process has streamlined the introduction of new potato cultivars with superior processing characteristics in storage.
Accomplishments
1. Potato post-harvest quality evaluations and release of new potato cultivars. Acceptable processing quality after storage is an essential attribute of a successful potato variety. The standardized evaluation procedures developed and used by ARS scientists in East Grand Forks, Minnesota, a worksite of the Fargo, North Dakota, location, have been an important component of the overall process for evaluation and release of new cultivars by federal and state cooperators nationwide. In the past year, in support of federal and non-federal public breeding/screening programs, 139 advanced breeding lines were analyzed for storage/processing quality at multiple storage temperatures and durations. Since 2015, 17 chip clones and 14 fry processing clones identified in East Grand Forks to have superior storage quality have advanced through rigorous national variety testing platforms aimed at providing potato industry stakeholders a high-quality processed potato product throughout storage. Data from these analyses have contributed to the national release of new potato varieties with superior processing quality throughout storage.
2. Potato cultivars with reduced acrylamide concentration identified. Acrylamide is an unwanted and potentially toxic by-product produced when carbohydrate-rich foods are processed at high temperatures. ARS scientists in East Grand Forks, Minnesota, a worksite of the Fargo, North Dakota, location, identified several clones exhibiting excellent processing characteristics, including very low acrylamide levels among entries in the National Fry Processing Trials. Since 2015, 40 fry processing clones with excellent processing characteristics and reduced acrylamide concentrations have been advanced through national variety trials. These clones are being evaluated in more detailed trials and are candidates to replace currently used varieties in commercial production. Adoption of these clones with reduced acrylamide concentrations ensures processed potato products are a safe food source for consumers.
