Progress 09/01/04 to 08/04/09
Outputs
Progress Report Objectives (from AD-416) To determine the normal and molecular processes that control the initiation, maintenance and termination of potato bud dormancy and regulate early sprout growth wound healing and skin set suberization. Approach (from AD-416) Identify physiological/biochemical mechanisms that control potato tuber dormancy/sprout growth and wound-healing/skin set. Determine the roles of endogenous hormones in tuber dormancy progression and identify the biochemical mechanisms governing hormone homeostasis in tubers as related to dormancy. Identify and characterize genes controlling tuber dormancy/sprout growth and wound-healing/skin set. Identify hormones and endogenous elicitor systems initiating and regulating wound-healing in harvest-damaged and cut-seed tubers. Determine biochemical changes in tuber periderm cell wall conferring resistance to excoriation (skinning during maturation.) Significant Activities that Support Special Target Populations Following application of the radio-labeled cytokinin isopentenyladenosine to potato tuber meristems, a total of six metabolites have been identified. The major metabolite was adenosine which is a product of cytokinin oxidase activity. The pattern of metabolites was not affected by tuber dormancy status. Using degenerate primers to known ABA-8�- hydroxylase genes, six full-length copies of ABA-8�-hydroxylase have been cloned from potato tuber tissues. Preliminary studies have demonstrated both tissue-specific and time-dependent expression patterns in tuber tissues. Following wounding, the content of jasmonic acid (JA) increases two to five-fold within 6 hours, declines to near initial levels by twelve hours and remains constant thereafter. Tuber age has limited impact on the pattern of JA accumulation and destruction. Using degenerate primers, one partial extension gene has been cloned from wounded tuber tubers and a second partial extension-like gene has also been cloned. Successful completion of these studies will result in new information that will lead to improved potato storage management and enhanced economic return to producers. Technology Transfer Number of Active CRADAS: 1 Number of New/Active MTAs(providing only): 1
Impacts
(N/A)
Publications
- Suttle, J.C. 2007. Dormancy and sprouting. In: Vreugdenhil, D., Bradshaw, J., Gebhardt, C., Govers, F., Taylor, M.A., MacKerron, D.K.L., Ross, H.A. Potato Biology and Biotechnology: Advances and Perspectives. 1st Edition. Amsterdam. Elsevier. p. 287-309.
- Lulai, E.C. 2008. Skin-Set and Wound-Healing/Suberization. Potato Research. 50:387-390. doi 10.1007/s11540-008-9067-4.
- Lulai, E.C. 2007. Skin-set, Wound-Healing, and Related Defects. In: Vreugdenhil, D., Bradshaw, J., Gebhardt, C., Govers, F., MacKerron, D.K.L., Taylor, M.A., Ross, H.A. Potato Biology and Biotechnology: Advances and Perspectives. 1st Edition. Amsterdam. Elsevier. p. 471-500.
- Campbell, M.A., Segear, E., Beers, L., Knauber, D.C., Suttle, J.C. 2008. Dormancy in potato tuber meristems: chemically induced cessation in dormancy matches the natural process based on transcript profiles. Functional and Integrative Genomics. 8:317-328. doi:10.1007/s10142-008- 0079-6.
- Horvath, D.P., Chao, W.S., Suttle, J.C., Anderson, J.V., Thimmapuram, J. 2008. Transcriptome analysis identifies novel responses and potential regulatory genes involved in seasonal dormancy transitions of leafy spurge (Euphorbia esula L.). Biomed Central (BMC) Genomics. 9:536. DOI:10. 1186/1471-2164-9-536.
- Lulai, E.C., Suttle, J.C. 2009. Signals Involved in Tuber Wound-Healing. Plant Signaling & Behavior. 4(7):620-622.
- Suttle, J.C. 2009. Ethylene Is Not Involved in Hormone- and Bromoethane- Induced Dormancy Break in Russet Burbank Minitubers. American Journal of Potato Research. 86:278-285. doi:10.1007/s12230-009-9081-3.
- Suttle, J.C. 2008. Symposium Introduction: Enhancing the Nutritional Value of Potato Tubers. American Journal of Potato Research. 85:266.
- Lulai, E.C., Suttle, J.C., Pederson, S.M. 2008. Regulatory involvement of abscisic acid in potato tuber wound-healing. Journal of Experimental Botany. 59(6):1175-1186.
- 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.
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) To determine the normal and molecular processes that control the initiation, maintenance and termination of potato bud dormancy and regulate early sprout growth wound healing and skin set suberization. Approach (from AD-416) Identify physiological/biochemical mechanisms that control potato tuber dormancy/sprout growth and wound-healing/skin set. Determine the roles of endogenous hormones in tuber dormancy progression and identify the biochemical mechanisms governing hormone homeostasis in tubers as related to dormancy. Identify and characterize genes controlling tuber dormancy/sprout growth and wound-healing/skin set. Identify hormones and endogenous elicitor systems initiating and regulating wound-healing in harvest-damaged and cut-seed tubers. Determine biochemical changes in tuber periderm cell wall conferring resistance to excoriation (skinning during maturation.) Project has been classified as "Exempt" by the rating Institutional Biosafety Committee, ltr dated 6-12-02. Accomplishments Potato Storage Disorder: Potato growers and processors sustain tens of millions of dollars in total losses each year from a disorder of unknown origin loosely referred to as pink eye. In research conducted by the Sugarbeet & Potato Research Unit, Northern Crop Science Laboratory, Fargo, ND and university colleagues over a period of five years, the pink eye syndrome was analyzed in tubers of diverse genotypes from major U.S. production areas. These studies determined that pink eye is a result of aberrant periderm (skin) development resulting from incomplete cell wall formation thereby rendering tubers more susceptible to rot and other storage defects. Having determined the physiological basis for pink eye syndrome, this research has laid the foundation to identify methods to mitigate the deleterious and costly effects of this disorder. This research addresses the goals of NP 306 Quality and Utilization of Agricultural Products. Technology Transfer Number of Active CRADAS and MTAS: 3 Number of Non-Peer Reviewed Presentations and Proceedings: 2
Impacts
(N/A)
Publications
- Lulai, E.C., Weiland, J.J., Suttle, J.C., Sabba, R.P., Bussan, A.J. 2006. Pink Eye is an Unusual Periderm Disorder Characterized by Aberrant Suberization: A Cytological Analysis. American Journal of Potato Research. 83(5)409-421.
- Destefano Beltran, L.J., Knauber, D.C., Huckle, L.L., Suttle, J.C. 2006. Effects of postharvest storage and dormancy status an ABA content, metabolism, and expression of genes involved in ABA biosynthesis and metabolism in potato tuber tissues. Plant Molecular Biology. 61(4-5):687- 697.
- Jha, A.K., Dahleen, L.S., Suttle, J.C. 2006. Eythylene influences green plant regeneration from barley callus. Plant Cell Reports. 26:285-290.
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter? In 2001, world-wide production of potatoes exceeded 311.8 million MT (FAO est.). In the same year, U.S. production exceeded 438 million cwt (USDA- NASS est.). Roughly 70% of the fall potato crop is placed into medium- long term storage to meet the demands of consumers and processors. Unlike other major food crops, the potato is stored in a fully hydrated highly perishable form. Annual postharvest losses in the U.S. typically amount to about 10-15% of the harvested crop but can be as high as 30%. Maintenance of postharvest quality is of prime concern for potato producers and processors. Failure to maintain product quality can result in commercially unacceptable product for the processor and financial ruin for the producer. Postharvest quality losses in stored potatoes can occur through
both physiological and disease-related processes. Of the physiological processes affecting potato storage and market quality, two of the most important are dormancy/sprouting and wound-healing/skin set. Uncontrolled postharvest sprouting or incomplete wound-healing results in increased levels of highly toxic glycoalkaloids, increased respiration and transpiration, accelerated starch breakdown with concomitant accumulation of undesirable reducing sugars and decreased vitamin content. All of these changes adversely affect potato market quality and nutritional value resulting in lower producer prices or even complete market rejection. In addition to these direct impacts, many of these physiological changes promote disease susceptibility in stored tubers, thereby resulting in even greater financial loss to the industry. At harvest, and for an indeterminate period thereafter, potato tubers will not sprout and are physiologically dormant. Optimum storage conditions vary depending on
intended end-use. With the exception of seed potatoes (stored at 2-4oC), optimum storage temperatures (>4oC) do not prevent sprouting and the resultant deterioration. Temperatures below 4oC will suppress (but not prevent) sprouting but result in the accumulation of reducing sugars which, above a certain threshold, are unacceptable to the processing industry. As a result, chemical sprout suppressants are extensively used. These agents do not directly affect tuber dormancy but act by inhibiting sprout growth (i.e., herbicidal activity). For a variety of reasons, it would be desirable to replace existing synthetic sprout inhibitors with either genetic dormancy control or with other natural (presumably benign) sprout-control agents. The successful long-term storage of potatoes is completely dependent on the physical and physiological integrity of the harvested tuber which is dependent on the proper maturation of the skin prior to harvest (skin-set) and on the rapid healing of any
physical injuries incurred during harvesting, handling, and storage (wound healing). Long-term storage of immature or damaged tubers is often impossible due to the accelerated progression of numerous postharvest disorders and diseases. Fully mature, unwounded or fully healed tubers and cut seed are remarkably resistant to pathogen attack. Disease and defects, resulting from incomplete skin- set and tuber wounding during harvest and transit are serious problems for all facets of the potato industry. Presently, there are no methods to reduce these defects other than chemical vine killing (which may hasten tuber skin maturation) and by subjective adjustment of harvester operation. Erosion of market quality during postharvest handling and storage represent the most devastating type of losses a producer can experience both economically and psychologically. At harvest, the crop represents the cumulative outcome of all the producer's efforts and input costs throughout the growing
season. Despite the severity of these losses to the potato industry, the management strategies and technologies employed to combat these problems are several decades old and do not effectively meet today's consumer and industry demands. The goals of the proposed research are to identify critical biochemical and physiological mechanisms controlling tuber dormancy/sprout growth and wound- healing/skin-set and, ultimately, to manipulate these rate-limiting processes to develop improved potato storage technologies. The stated goals of this research directly address principal components of NP 306: Quality and Utilization of Agricultural Products, Problem Areas 1a (Definition and Basis for Quality) and 1c (Factors and Processes that Affect Quality). In addition, the fundamental nature of research proposed in this project addresses Component II of NP 302 (Biological processes that determine plant productivity and quality). New information on the physiological processes controlling tuber
dormancy/sprouting and wound-healing/excoriation will result in decreased postharvest losses and enhanced nutritional quality of stored potatoes. Maintenance of market quality is of prime importance to the potato industry. Cognate processes that control critical biological mechanisms directly related to quality characteristics are largely unknown and this ignorance greatly hinders the identification and development of improved postharvest storage practices. Loss of market quality is accompanied by loss of nutritional components (vitamins, etc.) critical to human health. Improved control of tuber dormancy and enhanced wound-healing will obviate or dramatically reduce the need for postharvest application of synthetic agrochemicals (sprout inhibitors, fungicides) and will greatly reduce the endogenous accumulation of toxic glycoalkaloids and mycotoxins that occur following sprouting and/or pathogen invasion. Furthermore from a broader perspective, issues related to meristem dormancy
and wound- healing are not unique to the potato industry but pertain to many segments of agriculture especially fruit and vegetable production and handling and weed control. Therefore, other segments of agriculture will be positively impacted by the proposed research. 2. List by year the currently approved milestones (indicators of research progress) FY 2004: 1. Complete studies on identification of cytokinin oxidase inhibitors. Prepare manuscript for publication. 2. Complete studies on histone acetylation changes during dormancy. Prepare manuscript for publication. 3. Prepare and submit manuscript on ethylene involvement in wound- induced suberization. 4. Complete studies on cell wall immunochemistry during maturation. Prepare manuscript for publication. 5. Initiate studies on involvement of ABA in wound-healing: determine ABA levels in wounded tuber tissues. FY 2005: 1. Collect tissue samples, optimize analytical methods, and begin year 1 determinations of jasmonic
acid (JA) content in tubers during dormancy progression. 2. Continue studies on involvement of ABA in tuber wound-healing: determine effects of an ABA biosynthetic inhibitor on ABA content and wound-healing kinetics. 3. Initiate studies determining the effects of cytokinin oxidase inhibitor(s) on cytokinin content and metabolism in tubers during dormancy. 4. Isolate, characterize and clone key regulatory genes involved in ABA biosynthesis. 5. Initiate search for molecular markers of skin set in potatoes: identify candidate genes. 6. Initiate studies on involvement of phenolics in tuber dormancy: screen bioassays for suitability. FY2006: 1. Continue JA studies: collect 2nd year tissue and analyze JA content, initiate JA inhibitor studies. 2. Complete studies on ABA involvement in wound-healing. 3. Complete studies on cytokinin oxidase inhibitors, prepare manuscript. 4. Determine changes in ABA biosynthetic gene expression during tuber dormancy. 5. Initiate studies on role of
ABA catabolism during tuber dormancy: identify optimum inhibitor. 6. Determine expression patterns of candidate molecular markers during tuber skin set, continue search for additional gene markers. 7. Initiate studies on involvement of phenolics in tuber dormancy: optimize bioassays for detection. 8. Initiate studies on involvement of JA in tuber wound-healing: optimize analytical and JA treatment techniques. 2007: 1. Complete studies on JA involvement in tuber dormancy and prepare manuscript. 2. Prepare manuscript on ABA involvement in tuber wound-healing. 3. Complete studies on changes in ABA biosynthetic gene expression during dormancy, prepare manuscript. 4. Continue studies on role of ABA catabolism during tuber dormancy: determine effects of inhibitors on endogenous ABA content and tuber dormancy progression. 5. Determine utilitiy of molecular markers for skin set, validate results. 6. Continue studies on involvement of phenolics in tuber dormancy: identify bioactive
compounds and initiate quantitative analyses of their contents during dormancy. 7. Continue JA wound-healing studies: collect tissues and analyze parenchyma JA content, determine JA wound-response effects and efficacy of JA biosynthetic inhibitors. 2008: 1. Complete studies on changes in bioactive phenolic content during tuber dormancy. 2. Complete studies on involvement of JA in tuber wound-incuded suberization and prepare manuscript. 3. Continue studies on the role of ABA catabolism in tuber dormancy: isolate, characterize and clone gene encoding key catabolic enzymes. 4. Prepare manuscript on identification of molecular markers of tuber skin set. 4a List the single most significant research accomplishment during FY 2006. First Report of Molecular Cloning of Key ABA Biosynthetic Genes. The plant hormone abscisic acid (ABA) controls many agronomically important stages of plant development and plays a central role in the regulation of potato tuber dormancy, wound-healing, and
disease resistance. Research from the Sugarbeet & Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) is directed toward the identification of the internal mechanisms controlling tuber dormancy and wound-healing with emphasis on the roles of endogenous plant hormones in these processes. Recently completed research from this project has identified, cloned, and characterized genes encoding enzymes catalyzing all key steps in the biosynthesis of ABA in potato tubers. This is the first report of the molecular cloning of these critically important genes from tuber tissues and will permit the genetic manipulation of ABA content in tuber tissues with the goal of improving postharvest storage characteristics and market quality of potatoes destined for human consumption. The stated goals of this research directly address principal components of NP 306: Quality and Utilization of Agricultural Products, Problem Areas 1a (Definition and Basis for Quality) and 1c (Factors
and Processes that Affect Quality). In addition, the fundamental nature of research proposed in this project addresses Component II of NP 302 (Biological processes that determine plant productivity and quality). 5. Describe the major accomplishments to date and their predicted or actual impact. Over 70% of current U.S. potato production is placed into long-term storage to meet the needs of consumers and processors. Annual losses during storage vary between 10-30% of the harvested crop and represent an enormous erosion of producer revenue. Research to improve postharvest storage of potatoes will benefit all segments of the potato industry and will provide consumers with a year-round supply of high-quality nutritious potatoes. Previous research from this laboratory has established essential roles for two classes (abscisic acid, and ethylene) of endogenous hormones, has implicated an essential role for a third class (cytokinins). The biochemical processes that affect the content and
activities of these hormones have been partially determined and key metabolic pathways controlling hormone content in tubers during dormancy have been identified. Current research is directed toward determination of specific enzymatic reactions that regulate these pathways and the genes encoding these regulatory enzymes. The first reported molecular cloning of an entire plant hormone biosynthetic pathway from tuber tissues will permit the identification of the genetic control of ABA biosynthesis that will, in turn, allow the genetic manipulation of the critical regulatory of tuber development. The cellular and molecular bases for dormancyimposed growth arrest in tuber eyes are also under investigation. The recently completed research on the role of chromatin composition (DNA methylation and histone acetylation) in dormancy control take knowledge of the cellular bases of meristem dormancy to a molecular level. These results are the first to describe changes in chromatin composition in
dormant organs and have moved us closer to the eventual identification of the specific genetic determinants of potato tuber dormancy and to the development of novel and improved methods to regulate dormancy duration. Rapid and complete wound-healing and skin set are critical to maintenance of potato quality in storage but the internal mechanisms controlling these processes are largely unknown. Previous research has identified specific cell wall changes occurring during wound-healing that are critical for the development of disease resistance in stored tubers. Current research has determined that the wound hormone ethylene does not control tuber wound-healing and other signals must be involved. Additional research has identified specific cell layer involved in tuber skinning injury resistance and the on-going characterization of changes in cell wall chemistry and architecture provides new insight into this harvest-related disorder and may lead to improved technologies to reduce the
economic impact of this injury. This research directly addresses principal components of NP 306: Quality and Utilization of Agricultural Products, Problem Areas 1a (Definition and Basis for Quality) and 1c (Factors and Processes that Affect Quality). In addition, the fundamental nature of research proposed in this project addresses Component II of NP 302 (Biological processes that determine plant productivity and quality). 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The results of these studies have been made available to interested parties (customers, stake-holders, and partners) through a combination of scientific articles, trade/popular journals and public presentations at professional meetings, fielddays and producer sponsored crop
expositions. In addition, numerous private contacts between interested parties and ourselves have been made during the past year. The utilization of the information obtained during our research to improve the postharvest storage of potatoes is hampered by a neartotal ignorance of the biochemical bases for the observed physiological processes. Addressing this lack of fundamental knowledge is the primary focus of this research program. 7. List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below). Potato Research at the Red River Valley Agricultural Research Center. Valley Potato Grower 71, No. 163, pg 22-23, 2006. Tuber dormancy control during storage. International Crop Expo, Grand Forks, ND (Feb. 16, 2006).
Impacts
(N/A)
Publications
- Lulai, E.C. 2005. Non-wound induced Suberization of Tuber Parenchyma Cells: A Physiological Response to the Wilt Disease Pathogen Verticillium Dahliae. American Journal of Potato Research. 82(6):433-440.
- Sabba, R.P., Lulai, E.C. 2005. Immunocytological analysis of potato tuber periderm and changes in pectin and extensin epitopes associated with periderm maturation. Journal of the American Society for Horticultural Science. 130(6):936-942.
- Campbell, M.A., Beers, L.A., Huckle, L.L., Suttle, J.C. 2005. Chemically forced and natural dormancy progression in potato tubers induces similar patterns of gene expression [Abstract]. American Society of Plant Biologists. Abstract No. 691-230.
- Jha, A.K., Dahleen, L.S., Suttle, J.C. 2005. Effects of ethylene in barley (Hordeum vulgare L.)tissue culture regeneration. Poster P-2000. In Vitro Biology Meeting. Issue 41:35-A.
- Suttle, J.C., Mornet, R. 2005. Mechanism-based irreversible inhibitors of cytokinin dehydrogenase. Journal of Plant Physiology. 162(11):1189-1196
- Destefano Beltran, L.J., Knauber, D.C., Huckle, L.L., Suttle, J.C. 2006. Chemically forced dormancy termination mimics natural dormancy progression in potato tuber meristems by reducing ABA content and modifying expression of genes involved in regulating ABA synthesis and metabolism. Journal of Experimental Botany. 57(11):2879-2886.
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Progress 10/01/04 to 09/30/05
Outputs
1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? In 2001, world-wide production of potatoes exceeded 311.8 million MT (FAO est.). In the same year, U. S. production exceeded 438 million cwt (USDA- NASS est.). Roughly 70% of the fall potato crop is placed into medium- long term storage to meet the demands of consumers and processors. Unlike other major food crops, the potato is stored in a fully hydrated highly perishable form. Annual postharvest losses in the U.S. typically amount to about 10-15% of the harvested crop but can be as high as 30%. Maintenance of postharvest quality is of prime concern for potato producers and processors. Failure to maintain product quality can result in commercially unacceptable product for the processor and financial ruin for the producer. Postharvest quality losses in stored potatoes can occur through both
physiological and disease-related processes. Of the physiological processes affecting potato storage and market quality, two of the most important are dormancy/sprouting and wound-healing/skin set. Uncontrolled postharvest sprouting or incomplete wound-healing results in increased levels of highly toxic glycoalkaloids, increased respiration and transpiration, accelerated starch breakdown with concomitant accumulation of undesirable reducing sugars and decreased vitamin content. All of these changes adversely affect potato market quality and nutritional value resulting in lower producer prices or even complete market rejection. In addition to these direct impacts, many of these physiological changes promote disease susceptibility in stored tubers, thereby resulting in even greater financial loss to the industry. At harvest, and for an indeterminate period thereafter, potato tubers will not sprout and are physiologically dormant. Optimum storage conditions vary depending on intended
end-use. With the exception of seed potatoes (stored at 2-4oC), optimum storage temperatures (>4oC) do not prevent sprouting and the resultant deterioration. Temperatures below 4oC will suppress (but not prevent) sprouting but result in the accumulation of reducing sugars which, above a certain threshold, are unacceptable to the processing industry. As a result, chemical sprout suppressants are extensively used. These agents do not directly affect tuber dormancy but act by inhibiting sprout growth (i.e., herbicidal activity). For a variety of reasons, it would be desirable to replace existing synthetic sprout inhibitors with either genetic dormancy control or with other natural (presumably benign) sprout-control agents. The successful long-term storage of potatoes is completely dependent on the physical and physiological integrity of the harvested tuber which is dependent on the proper maturation of the skin prior to harvest (skin-set) and on the rapid healing of any physical
injuries incurred during harvesting, handling, and storage (wound healing). Long-term storage of immature or damaged tubers is often impossible due to the accelerated progression of numerous postharvest disorders and diseases. Fully mature, unwounded or fully healed tubers and cut seed are remarkably resistant to pathogen attack. Disease and defects, resulting from incomplete skin- set and tuber wounding during harvest and transit are serious problems for all facets of the potato industry. Presently, there are no methods to reduce these defects other than chemical vine killing (which may hasten tuber skin maturation) and by subjective adjustment of harvester operation. Erosion of market quality during postharvest handling and storage represent the most devastating type of losses a producer can experience both economically and psychologically. At harvest, the crop represents the cumulative outcome of all the producers efforts and input costs throughout the growing season. Despite
the severity of these losses to the potato industry, the management strategies and technologies employed to combat these problems are several decades old and do not effectively meet todays consumer and industry demands. The goals of the proposed research are to identify critical biochemical and physiological mechanisms controlling tuber dormancy/sprout growth and wound- healing/skin-set and, ultimately, to manipulate these rate-limiting processes to develop improved potato storage technologies. The stated goals of this research directly address principal components of NP 306: Quality and Utilization of Agricultural Products, Problem Areas 1a (Definition and Basis for Quality) and 1c (Factors and Processes that Affect Quality). In addition, the fundamental nature of research proposed in this project addresses Component II of NP 302 (Biological processes that determine plant productivity and quality). New information on the physiological processes controlling tuber dormancy/sprouting
and wound-healing/excoriation will result in decreased postharvest losses and enhanced nutritional quality of stored potatoes. Maintenance of market quality is of prime importance to the potato industry. Cognate processes that control critical biological mechanisms directly related to quality characteristics are largely unknown and this ignorance greatly hinders the identification and development of improved postharvest storage practices. Loss of market quality is accompanied by loss of nutritional components (vitamins, etc.) critical to human health. Improved control of tuber dormancy and enhanced wound-healing will obviate or dramatically reduce the need for postharvest application of synthetic agrochemicals (sprout inhibitors, fungicides) and will greatly reduce the endogenous accumulation of toxic glycoalkaloids and mycotoxins that occur following sprouting and/or pathogen invasion. Furthermore from a broader perspective, issues related to meristem dormancy and wound- healing
are not unique to the potato industry but pertain to many segments of agriculture especially fruit and vegetable production and handling and weed control. Therefore, other segments of agriculture will be positively impacted by the proposed research. 2. List the milestones (indicators of progress) from your Project Plan. 2004: 1. Complete studies on identification of cytokinin oxidase inhibitors. Prepare manuscript for publication. 2. Complete studies on histone acetylation changes during dormancy. Prepare manuscript for publication. 3. Prepare and submit manuscript on ethylene involvement in wound- induced suberization. 4. Complete studies on cell wall immunochemistry during maturation. Prepare manuscript for publication. 5. Initiate studies on involvement of ABA in wound-healing: determine ABA levels in wounded tuber tissues. 2005: 1. Collect tissue samples, optimize analytical methods, and begin year 1 determinations of jasmonic acid (JA) content in tubers during
dormancy progression. 2. Continue studies on involvement of ABA in tuber wound-healing: determine effects of an ABA biosynthetic inhibitor on ABA content and wound-healing kinetics. 3. Initiate studies determining the effects of cytokinin oxidase inhibitor(s) on cytokinin content and metabolism in tubers during dormancy. 4. Isolate, characterize and clone key regulatory genes involved in ABA biosynthesis. 5. Initiate search for molecular markers of skin set in potatoes: identify candidate genes. 2006: 1. Continue JA studies: collect 2nd year tissue and analyze JA content, initiate JA inhibitor studies. 2. Complete studies on ABA involvement in wound-healing, prepare manuscript. 3. Complete studies on cytokinin oxidase inhibitors, prepare manuscript. 4. Determine changes in ABA biosynthetic gene expression during tuber dormancy. 5. Initiate studies on role of ABA catabolism during tuber dormancy: identify optimum inhibitor. 6. Determine expression patterns of candidate
molecular markers during tuber skin set, continue search for additional gene markers. 7. Initiate studies on involvement of phenolics in tuber dormancy: optimize bioassays for detection. 8. Initiate studies on involvement of JA in tuber wound-healing: optimize analytical and JA treatment techniques for wound-healing tissue. 2007: 1. Complete studies on JA involvement in tuber dormancy and prepare manuscript. 2. Complete studies on changes in ABA biosynthetic gene expression during dormancy, prepare manuscript. 3. Continue studies on role of ABA catabolism during tuber dormancy: determine effects of inhibitors on endogenous ABA content and tuber dormancy progression. 4. Determine utility of molecular markers for skin set, validate results. 5. Continue studies on involvement of phenolics in tuber dormancy: identify bioactive compounds and initiate quantitative analyses of their contents during dormancy. 6. Continue JA wound-healing studies: determine tuber JA wound-response and
effects of various JA inhibitors on wound-induced suberization. 2008: 1. Complete studies on changes in bioactive phenolic content during tuber dormancy. 2. Complete determination of JA requirement for wound-induced suberization and prepare manuscript. 3. Continue studies on the role of ABA catabolism in tuber dormancy: isolate, characterize and clone gene encoding key catabolic enzymes. 4. Prepare manuscript on tuber skin-set biology and identification of molecular markers. 3a List the milestones that were scheduled to be addressed in FY 2005. For each milestone, indicate the status: fully met, substantially met, or not met. If not met, why. 1. First-year tuber samples for JA aalysis have been collected. GC-MS and LCS-MS instruments are being compared for amximum sensitivity and initial JA determinations are underway. Milestone Fully Met 2. The effect of the ABA biosynthesis inhibitor fluridone on tuber wound- induced ABA content and periderm healing are being determined.
Milestone Fully Met 3. The effects of selected cytokinin oxidase inhibitors on tuber cytokinin content and metabolism are being determined. Milestone Fully Met 4. Isolate, characterize and clone key regulatory genes involved in ABA biosynthesis. Milestone Fully Met 5. Several candidate marker genes have been identified from cDNA libraries and are being cloned and characterized. Milestone Fully Met 3b List the milestones that you expect to address over the next 3 years (FY 2006, 2007, and 2008). What do you expect to accomplish, year by year, over the next 3 years under each milestone? 2006: 1. Continue JA studies: collect 2nd year tissue and analyze JA content, initiate JA inhibitor studies. 2. Complete studies on ABA involvement in wound-healing, prepare manuscript. 3. Complete studies on cytokinin oxidase inhibitors, prepare manuscript. 4. Determine changes in ABA biosynthetic gene expression during tuber dormancy. 5. Initiate studies on role of ABA catabolism during tuber
dormancy: identify optimum inhibitor. 6. Determine expression patterns of candidate molecular markers during tuber skin set, continue search for additional gene markers. 7. Initiate studies on involvement of phenolics in tuber dormancy: optimize bioassays for detection. 8. Initiate studies on involvement of JA in tuber wound-healing: optimize analytical and JA treatment techniques for wound-healing tissue. 2007: 1. Complete studies on JA involvement in tuber dormancy and prepare manuscript. 2. Complete studies on changes in ABA biosynthetic gene expression during dormancy, prepare manuscript. 3. Continue studies on role of ABA catabolism during tuber dormancy: determine effects of inhibitors on endogenous ABA content and tuber dormancy progression. 4. Determine utility of molecular markers for skin set, validate results. 5. Continue studies on involvement of phenolics in tuber dormancy: identify bioactive compounds and initiate quantitative analyses of their contents during
dormancy. 6. Continue JA wound-healing studies: determine tuber JA wound-response and effects of various JA inhibitors on wound-induced suberization. 2008: 1. Complete studies on changes in bioactive phenolic content during tuber dormancy. 2. Complete determination of JA requirement for wound-induced suberization and prepare manuscript. 3. Continue studies on the role of ABA catabolism in tuber dormancy: isolate, characterize and clone gene encoding key catabolic enzymes. 4. Prepare manuscript on tuber skin-set biology and identification of molecular markers. 4a What was the single most significant accomplishment this past year? A. Single Most Significant Accomplishment during FY 2004. First Report of Suicide Inhibitors of Key Plant Hormone Enzyme. The internal factors that control potato tuber dormancy/sprouting are presently unknown and this ignorance precludes the development of improved methods to control economically devastating tuber sprouting during storage. Research
from the Sugarbeet & Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) has been directed toward the identification of the internal mechanisms controlling tuber dormancy and early sprout growth with emphasis on the role of endogenous plant hormones in this process. Previous research from this lab has demonstrated that cytokinins control the onset of sprout growth that signals the end of tuber dormancy. In the past year, research has identified a new class of compounds that irreversibly inhibit a key enzyme controlling cytokinin levels in plants. This is the first report of a potent inhibitor of this class of enzymes and will permit the manipulation of endogenous cytokinin content in plant tissues without the use of transgenic technologies. This class of inhibitors will also permit determination of the role of this enzyme in tuber dormancy control and other key agronomically important physiological processes. 4b List other significant accomplishments, if any.
Tuber Disease Elicits Wound-like Response. Tuber infection by Verticillium spp. results in internal discoloration of vascular tissue that severely reduces market quality and prevents sale of raw product for consumption. Research conducted by the Sugarbeet & Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) has determined that the disease-induced vascular discoloration is associated with an aberrant wound response and deposition of polymers normally found only in tuber native periderm and wound periderm. A laboratory model was developed that will greatly facilitate future research on this important and costly disease. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. Over 70% of current U.S. potato production is placed into long-term storage to meet the needs of consumers and processors. Annual losses during storage vary between 10-30% of the harvested crop and represent an enormous erosion of
producer revenue. Research to improve postharvest storage of potatoes will benefit all segments of the potato industry and will provide consumers with a year-round supply of high-quality nutritious potatoes. Previous research from this laboratory has established essential roles for two classes (abscisic acid, and ethylene) of endogenous hormones, has implicated an essential role for a third class (cytokinins). The biochemical processes that affect the content and activities of these hormones have been partially determined and key metabolic pathways controlling hormone content in tubers during dormancy have been identified. Current research is directed toward determination of specific enzymatic reactions that regulate these pathways. The identification of a novel inhibitor of one of these pathways (cytokinin oxidation) will permit the determination of the role of this pathway in cytokinin physiology and tuber dormancy. The cellular and molecular bases for dormancyimposed growth
arrest in tuber eyes are also under investigation. The recently completed and current research on the role of chromatin composition (DNA methylation and histone acetylation) in dormancy control take knowledge of the cellular bases of meristem dormancy to a molecular level. These results are the first to describe changes in chromatin composition in dormant organs and have moved us closer to the eventual identification of the specific genetic determinants of potato tuber dormancy and to the development of novel and improved methods to regulate dormancy duration. Rapid and complete wound-healing and skin set are critical to maintenance of potato quality in storage but the internal mechanisms controlling these processes are largely unknown. Previous research has identified specific cell wall changes occurring during wound-healing that are critical for the development of disease resistance in stored tubers. Current research has determined that the wound hormone ethylene does not control
tuber wound-healing and other signals must be involved. Additional research has identified specific cell layer involved in tuber skinning injury resistance and the on-going characterization of changes in cell wall chemistry and architecture provides new insight into this harvest-related disorder and may lead to improved technologies to reduce the economic impact of this injury. The research reported is conducted under National Program 306, Quality and Utilization of Agricultural Products, and directly contributes to research component I, Quality Characterization, Preservation, and Enhancement. Research activities are further related to ARS Strategic Plan Goal 1, Enhance Economic Opportunities for Agricultural Producers; Objective 1.1, Provide the science-based knowledge and technologies to generate new or improved high-quality, value-added products and processes to expand domestic and foreign markets for agricultural commodities. 6. What science and/or technologies have been
transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The results of these studies have been made available to interested parties (customers, stake- holders, and partners) through a combination of scientific articles, trade/popular journals and public presentations at professional meetings, fielddays and producer sponsored crop expositions. In addition, numerous private contacts between interested parties and ourselves have been made during the past year. The utilization of the information obtained during our research to improve the postharvest storage of potatoes is hampered by a near total ignorance of the biochemical bases for the observed physiological processes. Addressing this lack of fundamental knowledge is the primary focus of this research program. 7. List your most important publications
in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below). New ways found to manipulate dormancy of potato tubers. 2005. Potato Storage International 2(2):40. Sabba, R.L., Lulai, E.C. 2005. Biochemical and physical changes in tuber periderm upon skin-set. Valley Potato Grower 70(158):8, 22-23. Suttle, J.C. 2005.Plant hormone analogs as novel sprout-control agents. Valley Potato Grower 70(159):20-21.
Impacts
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Publications
- Suttle, J.C. 2004. Physiological regulation of potato tuber dormancy. American Journal of Potato Research. 81:253-262.
- Destefano Beltran, L.J., Knauber, D.C., Huckle, L.L., Suttle, J.C. 2005. Changes in aba biosynthetic and metabolism-related gene expression during meristem dormancy in potato tubers [ abstract.] Plant Sciences Institute "Meristems 2005." Abstract No. 25 p.34.
- Law, R.D., Suttle, J.C. 2005. Chromatin remodeling in plant cell culture: patterns of DNA methylation and histone H3 and H4 acetylation vary during growth of asynchronous potato cell suspensions. Plant Physiology and Biochemistry. 43:527-534.
- Lulai, E.C., Suttle, J.C. 2004. The involvement of ethylene in wound- induced suberization of potato tuber (Solanum tuberosum l.): a critical assessment. Postharvest Biology and Technology. 34(1)105-112.
- Lulai, E.C., Suttle, J.C. 2005. Potato tuber absisic acid: concentration dynamics and invovlement in wound response. 16th Triennial Conference of the European Association for Potato Research. Poster 81. p.775-777.
- Suttle, J.C., Destefano Beltran, L.J., Knauber, D.C., Huckle, L.L. 2005. Changes in aba content, metabolism and expression of genes involved in aba biosynthesis and degradation in potato (solanum tuberosum l.) tuber meristems during chemically forced dormancy termination. 16th Triennial Confeence of the European Association for Potato Research. Poster 148. p. 994-996.
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