Location: Small Grain and Food Crops Quality Research
2023 Annual Report
Objectives
Objective 1: Resolve the underlying changes in transcriptome and metabolome profiles, and identify regulatory genes, gene-networks and metabolic pathways responsible for wound-healing and tuber sprouting in potato during postharvest storage.
Sub-objective 1.A: Determine the effects of exogenous ethylene treatment on tuber dormancy progression and identify molecular mechanisms regulating dormancy/sprout growth by utilizing integrated transcriptome, phytohormone, and metabolome analyses.
Sub-objective 1.B: Determine the effects of exogenous DMN and CIPC treatment on tuber dormancy progression and identify genes and metabolic pathways regulating dormancy/sprout growth by utilizing integrated transcriptome, phytohormone, and metabolome analyses.
Sub-objective 1.C: Determine changes in transcriptome and metabolome profiles in tuber tissues following mechanical wounding to identify regulatory genes and metabolic pathways involved in periderm development and wound-healing processes.
Objective 2: Evaluate and report the effects of postharvest storage on intrinsic processing quality and nutritional composition of advanced breeding lines in collaboration with public breeding programs, as a USDA-ARS direct mission of research support (non-hypothesis driven).
Sub-objective 2.A: Determine cold storage (< 7°C) potential and processing characteristics of advanced breeding lines.
Sub-objective 2.B: Screen advanced potato breeding lines for vitamin C and anti-quality compounds impacting food end-use.
Approach
Potato (Solanum tuberosum) ranks fourth among major food crops with annual global production exceeding 368 million metric tons (FAOSTATS, 2018). United States potato production exceeds 450 million hundredweight (cwt; USDA-NASS, 2018), of which 400 million cwt (~90%) with an estimated value of over $2 billion, are harvested in the fall. Because postharvest losses through physiological and disease-related processes routinely reach 10-15%, maintenance of postharvest quality is of prime concern to the potato industry. Current management strategies employed to combat these problems are several decades old and do not effectively meet today’s consumer or industry demands to control physiological deteriorations. Moreover, chemistries utilized to manage storage issues are under regulatory scrutiny and may not be available in coming years. Two physiological processes that adversely affect postharvest tuber quality are dormancy/sprouting and wound-healing. Further improvements in postharvest storage technologies are hindered by limited empirical information on biological processes underlying tuber meristem dormancy and wound-healing. Thus, the proposed research project is essential to identify the critical molecular, biochemical, and physiological mechanisms controlling tuber dormancy/sprouting and wound-healing and, ultimately, to manipulate these rate-limiting processes to reduce postharvest deteriorations of potato (Figure 1). Studies will be conducted to achieve the following objectives: (a) investigate effects of exogenous postharvest treatments (i.e., ethylene, 1,4-dimethylnaphthalene, and isopropyl-N-(3-chlorophenyl) carbamate) on tuber dormancy progression and sprouting using distinct cultivars for dormancy characteristics and utilize transcriptome and metabolome profiling to determine changes induced by these treatments, (b) identify the molecular mechanisms associated with mechanical wounding and wound-healing processes by utilizing transcriptome and metabolome profiling, and using a natural elicitor (water soluble chitosan) and distinct cultivars for periderm development and wound-healing characteristics. Equally important to the potato industry is development of superior germplasm for introducing new varieties with proven storage characteristics. Effective evaluation of new clones requires high-throughput screening facilities, specialized equipment, and resources. Therefore, we collaborate with public breeding programs to screen advanced breeding material for the postharvest storage potential, food quality and safety characteristics.
Progress Report
In Fiscal Year 2023, significant progress was made towards Objective 1. Partnering with potato stakeholders, potato tubers were obtained in the fall of 2022 for postharvest physiology research. Several collaborations were established, and grant proposals were submitted to attain external funding for complementing the Objective 1. Certified seed potato tubers were grown by potato producers according to the industry standards. After harvest, potato tubers were cured and placed in cold storage for four weeks. Then, tubers were subjected to sprout suppressing treatments. One experiment included ethylene treatment (Sub-objective 1.A), and another experiment included chlorpropham and dimethylnapthalene treatments (Sub-objective 1.B). Tuber tissue samples were collected at three-week intervals for four months and samples were processed to conduct molecular assays. Using a subset of tubers, sprout growth was recorded weekly to assess the impact of treatments on dormancy progression. To complement the Sub-objective 1.A-B, research continued with the university cooperators to determine effects of essential oil treatments on tuber sprout growth. Initially, three essential oils (organic spearmint, organic oregano, and organic sweet orange) were selected for an efficacy trial. After optimizing the treatment conditions, two potato cultivars with contrasting dormancy characteristics were selected for a follow up experiment. Overall, the three essential oils showed the ability to physically damage sprouts and suppress sprout development. Oregano oil appeared more effective at causing peeping eyes to be damaged after application and showed promise as a “rescue treatment” to potatoes that had broken dormancy with substantially elongated sprouts. In another experiment, potato tubers were treated with dimethylnaphthalene or jasmonic acid to evaluate their impact on tuber meristem dormancy, and tissues were for molecular analyses. In Fiscal Year 2023, experiments continued to investigate the efficacy of elicitor treatments for accelerating wound-healing responses in potato tubers (Sub-objective 1.C). Certified seed tubers of three potato cultivars were obtained from potato producers, and elicitor treatments were applied to mechanically wounded tissues. Wound-healing ratings were determined histologically, and subsets of treated tuber tissues were prepared for molecular assays. Additional projects were conducted to complement the Sub-objective 1.C. One experiment included five potato cultivars and another experiment included fifteen cultivars to elucidate their wound-healing responses with and without elicitor treatments. Results indicated improvement in wound-healing responses in most potato cultivars with optimized elicitor treatment.
In Fiscal Year 2023, significant progress was made in the non-hypothesis driven Objective 2. 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 were performed throughout storage among advanced breeding clones and new potato varieties representing the United States public breeding programs. Potato clones possessing improved processing quality and cold storage potential were identified (Sub-objective 2.A). Processing quality of fry and chip clones was assessed among Potatoes USA sponsored National Chip and Fry field and processing trials (Objective 2.A). Tuber antioxidant (vitamin C) concentrations and anti-quality compounds impacting food end-use (such as, glycoalkaloids and acrylamide) were quantified among new potato clones at harvest and throughout storage (Sub-objective 2.B). This cooperative evaluation process has streamlined the introduction of new potato cultivars with superior processing characteristics in storage, and has been considered gold-standard by the potato industry and stakeholders in the U.S.
Accomplishments
1. Using oregano essential oil to mitigate tuber sprouting. As potato tubers age, they develop sprouts and lose their nutritional quality. Commercial storage facilities usually integrate cold storage and sprout inhibitors to prevent premature sprouting of tubers. But commonly used tuber sprout inhibitors have been under regulatory scrutiny, prompting the continued search for alternative and safe methods. ARS scientists in Fargo, North Dakota, in cooperation with University of Idaho scientists, determined that organic spearmint, oregano, and sweet orange essential oils can be instrumental for controlling sprout growth. Our results indicate that all three essential oils have the ability to suppress sprout development, and particularly oregano oil resulted in consistent sprout suppression after thermal application. Additional research will focus on the optimization of application and potential use of oregano oil in the potato industry.
2. Improved tuber wound healing with elicitor treatments. Unintended wounding of potato tubers can occur during harvest or postharvest operations and can cause significant crop losses. Finding safe and effective treatment strategies is essential to ensure better tuber quality and minimize postharvest crop losses. ARS scientists in Fargo, North Dakota, along with North Dakota State University scientists, optimized natural elicitor treatments to improve wound-healing responses in cut and bruised potato tubers using several agronomically significant cultivars. Our results reveal novel information about the regulation of wound healing responses at the molecular level, and ultimately will lead to developing effective management strategies to hasten wound healing.
3. Evaluation of potato processing quality in storage. 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 evaluation process, contributing to the 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, 156 advanced breeding lines were analyzed for storage/processing quality after storage at multiple temperatures and durations. Data from these analyses will contribute to the release of new potato varieties. These improved varieties offer significant benefits to both producers and processors and should be widely adopted by the potato industry.
4. Potato cultivars with reduced acrylamide levels. Acrylamide is an unwanted and potentially toxic by-product produced when carbohydrate-rich foods are processed at high temperatures. Among entries in the National Fry Processing Trials, several clones exhibiting excellent processing characteristics and very low acrylamide levels were identified by ARS scientists in East Grand Forks, Minnesota, a worksite of the Fargo, North Dakota location. These clones will be evaluated in more detailed trials and may be candidates to replace currently used varieties in the commercial production of processed potato products. Eventual adoption of these clones and consequent reduction in the acrylamide concentration of potato products will benefit both producers and consumers.
5. Examining glycoalkaloid concentrations of new potato varieties. Glycoalkaloids are a naturally occurring secondary metabolite found in potato tissues, but tuber concentrations exceeding 20 mg/100 g fw-1 are not safe for human consumption (bitterness). ARS scientists in East Grand Forks, Minnesota, a worksite of the Fargo, North Dakota location, measured glycoalkaloid concentrations in 194 potato cultivars representing 8 public breeding programs. Data reported to breeders will help ensure new potato varieties meet glycoalkaloid concentrations that are safe for human consumption.
Review Publications
Chintha, P., Sarkar, D., Ramakrishna, R., Dogramaci, M., Lulai, E.C., Shetty, K. 2023. Biological elicitors to enhance wound healing responses in cut potato tubers. Scientia Horticulturae. https://doi.org/10.1016/j.scienta.2023.112152.
Akpinar, B.A., Muslu, T., Ozturk-Gokce, Z.N., Reddy, G.V., Dogramaci, M., Budak, H. 2023. Wheat long noncoding RNAs from organelle and nuclear genomes carry conserved microRNA precursors which may together comprise intricate networks in insect responses. International Journal of Molecular Sciences. 24(3). Article 2226. https://doi.org/10.3390/ijms24032226.
Fugate, K.K., Finger, F.L., Lafta, A.M., Dogramaci, M., Khan, M.F. 2023. Wounding rapidly alters transcription factor expression, hormonal signaling, and phenolic compound metabolism in harvested sugarbeet roots. Frontiers in Plant Science. https://doi.org/10.3389/fpls.2022.1070247.
Chintha, P., Sarkar, D., Pecota, K., Dogramaci, M., Hatterman-Valenti, H., Shetty, K. 2023. Phenolic bioactive-linked antioxidant, anti-hyperglycemic, and antihypertensive properties of sweet potato cultivars with different flesh color. Journal of Horticulture, Environment and Biotechnology. https://doi.org/10.1007/s13580-023-00515-0.
De Sousa Santos, M.N., Araujo, N.O., De Araujo, F.F., Da Silva, M.A., Pereira, O.L., Dogramaci, M., Finger, F.L. 2023. Sprout-suppressing 1,4-dimethylnaphthalene treatment reduces dry rot infection in potato tubers during postharvest storage. Postharvest Biology and Technology. https://doi.org/10.1016/j.postharvbio.2023.112485.
