Progress 10/01/01 to 08/31/04
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 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 the milestones (indicators of progress) from your Project Plan. Note: Ad Hoc project approved for < 2 years. Replaced by new project 8/04. FY 2003: 1. Identify optimum inhibitor of cytokinin oxidase: determine in-vitro and in-vivo efficacy. 2. Complete analyses of changes in DNA cytosine methylation during tuber dormancy. 3. Initiate analyses of histone acetylation patterns in tuber tissues. 4. Determine involvement of ethylene in wound-induced suberization. 5. Initiate studies on changes in cell wall immuno-chemistry during maturation. 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. Identify optimum inhibitor of ABA metabolism. 6. Initiate studies on involvement of ABA in wound-healing: determine ABA levels in wounded tuber tissues. 3. Milestones: A. List the milestones that were scheduled to be addressed in FY 2004. How many milestones did you fully or substantially meet in FY 2004 and indicate which ones were not fully or substantially met, briefly explain why not, and your plans to do so. Project terminated mid-2004; new project initiated 8/04. 1. Cytokinin oxidase studies: completed and manuscript prepared for publication. Met. 2. Histone acetylation changes: completed, manuscript prepared, submitted and published. Met. 3. Ethylene suberization studies: manuscript prepared, submitted, and accepted for
publication. Met. 4. Cell wall immuno-chemistry studies: completed, manuscript prepared and submitted for publication. Met. 5. Identify ABA metabolism inhibitor(s). Negotiation for MTA-CRADA to obtain needed analogs underway but unresolved. Not met. 6. ABA wound-healing studies: Effects of wounding on endogenous ABA content determined. Met. B. List the milestones that you expect to address over the next 3 years (FY 2005, 2006, and 2007). What do you expect to accomplish, year by year, over the next 3 years under each milestone? This is a new CRIS project that was approved by OSQR/NPS and initiated 8/18/04. Due to significant delays in OSQR process, project goals have been adjusted to accurately reflect current time-lines. FY 2005: Initiate studies on JA involvement in tuber dormancy: complete year 1 determinations of JA content during tuber dormancy progression. Initiate in vitro JA ablation studies. Complete in vitro studies on role of cytokinin dehydrogenase in cytokinin
homeostasis. Complete studies on changes in ABA content during tuber wound healing. Determine changes in gene expression during tuber skin-set. FY 2006: Complete studies (year 2) on JA content during tuber dormancy. Develop in vitro system to manipulate JA levels. Initiate studies on involvement of phenolic acids (PA) in tuber dormancy: identify endogenous phenolic compounds present in periderm extracts. Initiate molecular cloning of key ABA biosynthetic genes (ZEP, NCED) from potato tuber tissues. Initiate studies on involvement of JA in tuber wound- healing: determine changes in JA content following wounding. Continue studies identifying molecular markers of tuber skin-set. FY 2007: Continue studies on involvement of PA in tuber dormancy: determine changes in periderm PA content during dormancy progression (Year 1). Identify chemical/genetic methods to manipulate JA content during wound-healing. Determine changes in ZEP and NCED gene expression during tuber dormancy
progression (year 1). Determine changes in expression of selected genetic markers during tuber skin-set. 4. What were the most significant accomplishments this past year? A. Single Most Significant Accomplishment during FY 2004. 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 processes and mechanisms controlling tuber dormancy and early sprout growth. In the past year, studies have determined changes in nuclear histone proteins that are known to regulate gene expression in all multi-cellular organisms and may play a pivotal role in tuber dormancy control. These studies are the first to describe histone-related changes during dormancy and, together
with earlier studies on changes in DNA methylation, demonstrate that chromatin composition and function are critical aspects of tuber dormancy control. B. Other Significant Accomplishment(s), if any. Although rapid suberization of potato tuber wounds and rapid skin-set development (resistance to skinning injury) are essential for maintaining quality and preventing a range of disease problems, the biochemical signals and regulatory mechanisms required to initiate and control these processes are largely unknown. Research conducted at the Sugarbeet and Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) has been directed toward the identification of internal factors/processes required for initiating/regulating wound-healing and marking the development of resistance to skinning injury. Immunolocalization experiments conducted on tuber periderm indicate that the deposition of certain pectins and extensin on phellogen cell walls are likely involved in skin-set
development and the reduction of associated tuber wounding during harvest. Differences in immunolocalization further indicated that wound periderm did not fully mimic native periderm as a model for skin- set research. These results are important because they identify potential biochemical markers for skin-set development for eventual use in potato breeding programs and they demonstrate that a commonly used model system for skin-set may not provide useful information. C. Significant activities that support special target populations. None D. Progress Report. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. This is a newly initiated project. The following describes major accomplishments of the terminated CRIS project. To date, 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)
and tentatively ruled out the involvement of a fourth class of native hormones (gibberellins). The biochemical processes that affect the metabolism and activities of these hormones have been partially determined and are currently under investigation. These results are the first to unequivocally establish a hormonal basis for potato tuber dormancy and have set the stage for the complete experimental dissection of the biochemical mechanisms that regulate the biosynthesis, metabolism and activities of these hormone systems during dormancy. Studies from this lab have begun to determine the cellular and molecular bases for dormancyimposed growth arrest in tuber eyes. The recently completed and current research on the role of chromatin composition in dormancy control take knowledge of the cellular bases of meristem dormancy to a more fundamental level. These results 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. A fluorescent histochemical probe was developed to detect deposition of suberin polyaliphatics in native and developing wound periderm. This probe provides a sensitive means of tracking the final phase of suberization which provides the periderm of the potato tuber with durable horizontal resistance to penetration by pathogens. With this and another technique developed in our laboratory, we determined that: 1) deposition of suberin polyphenolics is discretely followed by deposition of polyaliphatics on individual suberizing cell walls during wound-healing, and 2) the deposition of these suberin components correlates directly with the development of resistance to bacterial and then fungal infection during wound-healing of cut seed and stored potatoes. This technique and the information derived using it may be used by researchers to predict when wounds are sufficiently suberized to resist infection and in
determining how we may enhance wound-healing to reduce disease and defect development in stored potatoes. The identification of the 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. 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. Suttle, J.C. Hormone analogs as novel sprout-control agents. CD Rom of 2004 Potato Research Proceedings, Northern Plains Potato Growers Association. 2004. Saba, R.P., Lulai,E.C. Biochemical and physical changs in tuber perdiderm upon skin-set. CD Rom of 2004 Potato Research Proceedings, Northern Plains Potato Growers Association. 2004.
Impacts
(N/A)
Publications
- LAW, R.D., SUTTLE, J.C. CHANGES IN HISTONE H3 AND H4 MULTI-ACETYLATION DURING NATURAL AND FORCED DORMANCY BREAK IN POTATO TUBERS. PHYSIOLOGIA PLANTARUM. 2004. V. 120. P. 642-649.
- SUTTLE, J.C. INVOLVEMENT OF ENDOGENOUS GIBBERELLINS IN POTATO TUBER DORMANCY AND EARLY SPROUT GROWTH: A CRITICAL ASSESSMENT. JOURNAL OF PLANT PHYSIOLOGY. 2004. v. 161(2). P. 157-164.
- Campbell, M.A., Beers, L.A., Suttle, J.C. 2004. Gene expression changes associated with dormancy breakage by bromoethane in potato [abstract]. 2004 Anual Meeting of the American Society of Plant Biologist. p. 50. Abstract No. 37.
- Destefano Beltran, L.J., Suttle, J.C. 2004. Regulation of aba biosynthesis during potato tuber dormancy: molecular characterization of a putative potato ABA2 gene [abstract]. 2004 Annual Meeting of the American Society of Plant Biologists. p. 123. Abstract No. 481.
- Sabba, R.P., Lulai, E.C. 2004. Immunocytological comparison of native and wound periderm maturation in potato tuber. American Journal Of Potato Research. 81:119-124.
- Suttle, J.C. 2004. Breaking tuber dormancy with synthetic cytokinins [abstract.] American Journal of Potato Research. 82(1):92.
- Lulai, E.C. 2004. Potato tuber suberization [abstract.] American Journal of Potato Research. 82(1):79.
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Progress 10/01/02 to 09/30/03
Outputs
1. What major problem or issue is being resolved and how are you resolving it? Worldwide, the potato ranks among the top five food crops and in many countries, constitutes a major source of human nutrition. Global production of potatoes exceeds 290 million metric tons (FAO estimate). Annual U.S. production exceeds 440 million hundredweight (USDA estimate). Over 70% of the total U.S. annual potato crop is placed in short to long term storage for a stable yearround supply. Unlike cereals, oilseeds and pulses, potatoes are stored in a fully hydrated and highly perishable form. As such, postharvest losses from both physiological and pathological processes can be severe. Of the physiological processes that affect the quality of stored potatoes, two of the most important are dormancy/sprouting and woundhealing. Both uncontrolled postharvest sprouting in storage and incomplete woundhealing following harvest can severely reduce the nutritional and market quality of
stored potatoes both directly by affecting various aspects of tuber composition and indirectly by fostering accelerated attack by storage pathogens. At present, the biochemical/physiological mechanisms that naturally regulate these two processes are unknown and this ignorance precludes the development of improved storage technologies. The goals of this project are to determine and exploit the natural, cognate physiological mechanisms that regulate both sprout growth and woundhealing in order to develop benign yet effective technologies to reduce the impact of these processes on potato quality and value. 2. How serious is the problem? Why does it matter? In the U.S., total postharvest losses can range from 5 to 40% of the stored crop. This results in financial losses to producers and processors of over $300 million in addition to the loss of the nutritional quality of the most widely consumed vegetable in most U.S. diets. Currently, chemical sprout suppressants are the only
commercially viable means to limit the deleterious effects of uncontrolled postharvest sprouting. At present aside from attempts to limit harvestrelated tuber damage, there are no known methods to reduce woundrelated tuber damage. Clearly, there is considerable room for the development of improved technologies to control these two important physiological processes. 3. How does it relate to the National Program(s) and National Program Component(s) to which it has been assigned? National Program 306, Quality and Utilization of Agricultural Products (60%) National Program 302, Improving Plant Biological Molecular Processes (40%) This research identifies intrinsic physiological and biochemical mechanisms that regulate the speed and extent of key biological processes that adversely affect the storage life and marketability of potatoes thereby providing a rational basis for the development of improved storage technologies and/or the genetic improvement of the potato itself. 4. What were
the most significant accomplishments this past year? A. Single Most Significant Accomplishment during FY 2003: 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 native hormone systems regulating tuber dormancy and early sprout growth. In the past year, studies have examined the mechanism of action of naphthalene derivatives, a novel class of naturally occurring and synthetic sprout inhibitors with commercial potential. These studies are among the first to mechanistically determine the biological bases for observed sprout growth inhibition and have conclusively demonstrated that growth inhibition is independent of naphthalene-mediated ethylene biosynthesis and action.
B. Other Significant Accomplishment(s) if any: Although rapid suberization of potato tubers that are cut for seed or wounded during harvest is essential for maintaining quality and preventing disease, the biochemical signals and regulatory mechanisms required to initiate and control woundhealing are largely unknown. Research conducted at the Sugarbeet and Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) has been directed toward the identification of internal factors/processes required for initiating/regulating wound-healing. Research to determine the role(s) of ethylene in wound induced suberization was completed; these final results confirmed earlier conclusions and also showed that wound-induced ethylene production was not causally involved in the accumulation of suberin polyaliphatics on wound-healing cell walls (the accumulation of suberin polyaliphatics is critical for resistance to fungal infection). These results are of great importance because they
are the first to show that this well-known stress and wound-related hormone does not play a major role in the last and most crucial stage of suberization during tuber wound-healing and these results directly impact the application of new commercial ethylene blocking technologies that may be used to control deterioration of stored potatoes. C. Significant Activities that Support Special Target Populations D. Progress Report: 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. To date, 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) and tentatively ruled out the involvement of a fourth class of native hormones (gibberellins). The biochemical processes that affect the metabolism and activities of these hormones have been partially determined and are currently under investigation.
These results are the first to unequivocally establish a hormonal basis for potato tuber dormancy and have set the stage for the complete experimental dissection of the biochemical mechanisms that regulate the biosynthesis, metabolism and activities of these hormone systems during dormancy. Studies from this lab have begun to determine the cellular and molecular bases for dormancyimposed growth arrest in tuber eyes. The recently completed and current research on the role of chromatin composition in dormancy control take knowledge of the cellular bases of meristem dormancy to a more fundamental level. These results 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. A fluorescent histochemical probe was developed to detect deposition of suberin polyaliphatics in native and developing wound periderm. This probe provides a sensitive means
of tracking the final phase of suberization which provides the periderm of the potato tuber with durable horizontal resistance to penetration by pathogens. With this and another technique developed in our laboratory, we determined that: 1) deposition of suberin polyphenolics is discretely followed by deposition of polyaliphatics on individual suberizing cell walls during wound-healing, and 2) the deposition of these suberin components correlates directly with the development of resistance to bacterial and then fungal infection during wound-healing of cut seed and stored potatoes. This technique and the information derived using it may be used by researchers to predict when wounds are sufficiently suberized to resist infection and in determining how we may enhance wound-healing to reduce disease and defect development in stored potatoes. The identification of the 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. 6. What do you expect to accomplish, year by year, over the next 3 years? 1. Three inter-related research approaches will be taken to address the problem of potato tuber dormancy control. Studies determining the involvement of endogenous phenolics and jasmonic acid (JA) in tuber dormancy will be initiated. A second approach will be directed toward the identification of the metabolic processes that regulate the levels of cytokinins; a class of hormones previously implicated in tuber dormancy control. A third approach will examine changes in expression of ABA biosynthetic genes during tuber dormancy. FY 2004: Initiate studies on role of phenolic acids and JA in tuber dormancy: identify optimum bioassay for phenolic growth inhibition, develop chromatographic techniques for phenolic isolation/characterization,
quantify tuber JA contents during dormancy progression (year 1). Using in vitro microtubers, screen putative inhibitors of cytokinin oxidase. Using PCR, amplify, clone and sequence tuber genes coding for the rate-limiting ABA biosynthetic enzymes 'ZEP', 'NCED' and 'AO'. FY 2005: Continue studies on involvement of hormones in tuber dormancy: using LC/GC-MS, identify bioactive phenolics present in tuber extracts, determine endogenous JA levels during dormancy (year 2). Determine effects of cytokinin oxidase inhibitors on endogenous cytokinin content and metabolism. Using RT-PCR, determine changes in expression of ABA biosynthetic genes during natural dormancy progression (year 1). FY 2006: Determine endogenous contents of selected phenolics during natural and chemically forced tuber dormancy progression. Initiate studies on the role of N-glucosylation on cytokinin levels; determine optimum in-vitro cultural conditions and conduct preliminary screen of putative inhibitors. Complete
studies on ABA biosynthetic gene expression during natural and chemically forced dormancy progression. 2. Research will continue on the identification and characterization of the biochemical processes, signals and mechanisms that regulate the deposition of suberin during tuber wound-healing and the development of resistance to tuber skinning injury/wounds (skin-set development) for harvest. FY 2004: Initiate determination of role(s) of abscisic acid in wound- induced suberization. Initiate studies, using a model genotype, to identify molecular markers that help characterize and control the processes responsible for development of resistance to tuber skinning injury. FY 2005: Continue determination of the role(s) of abscisic acid and initiate determination of the signaling role(s) of jasmonic acid in wound- induced suberization. Reinitiate research to determine role(s) of coumarin compounds in suberization. Continue research on molecular markers for skin-set development by
determining expression of these clones (RNA transcripts) in susceptible and resistant tubers of the model genotype. FY 2006: Complete determination of the role(s) of abscisic acid in tuber wound healing/suberization. Continue studies to determine the role(s) of jasmonic acid, including the identification of affected biological processes, in initiating and regulating tuber wound-healing. Begin verification of the specificity of the molecular markers for skin-set by screening for their appearance in tubers from diverse genotypes during development of resistance to skinning injury. 7. 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 both 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. 8. List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: This does not replace your peer-reviewed publications listed below). USDA/ARS Article: 'Spud Hub' Tests Potatoes Fitness for Market. Jan Suszkiw. Agriulture Research Magazine. July 2003. v. 51(7) p. 20-22. AGWEEK Article: IS you Spud a Dud? AGWEEK
Newspaper. July 14, 2003. p. 31-32. Lulai, E.C. Researchers report progress on potato tuber wound- healing/suberization, skin-set. Valley Potato Grower Magazine. 2003. v. 68(138) p. 34-35. Suttle, J. C. Control research: recent progress in dormancy/sprout. Valley Potato Grower Magazine. 2003. v. 68(138) p. 22-24. Suttle, J.C. Minnesota storage research seeks to improve product. Spudman. 2003. v. 41(7) p. 10.
Impacts
(N/A)
Publications
- LULAI, E.C. THE ROLES OF PHELLEM (SKIN) TENSILE STRENGTH-RELATED FRACTURES AND PHELLOGEN SHEAR-RELATES FRACTURES IN SUSCEPTIBILITY TO TUBER SKINNING INJURY AND SKIN-SET DEVELOPMENT. AMERICAN JOURNAL OF POTATO RESEARCH. 2002. V. 79 P. 241-248.
- LULAI, E.C. RECENT RESEARCH PROGRESS ON POTATO TUBER WOUND- HEALING/SUBERIAZTION AND SKIN-SET. PROCEEDINGS MINNESOTA AREA II POTATO RESEARCH AND PROMOTION COUNCIL AND THE NORTHERN PLAINS POTATO GROWERS ASSOCIATION REPORTING CONFERENCE. 2003. P. 306-309.
- LAW, R.D., SUTTLE, J.C. TRANSIENT DECREASES IN METHYLATION AT 5'-CCGG-3' SEQUENCES IN POTATO (SOLANUM TUBEROSUM L.) MERISTEM DNA DURING PROGRESSION OF TUBERS THROUGH DORMANCY PRECEDE THE RESUMPTION OF SPROUT GROWTH. PLANT MOLECULAR BIOLOGY. 2003. V. 51. P. 437-447.
- SUTTLE, J.C. RECENT PROGRESS IN DORMANCY/SPROUT CONTROL RESEARCH. PROCEEDINGS OF MINNESOTA AREA II POTATO RESEARCH AND PROMOTION COUNCIL AND THE NORTHERN PLAINS POTATO GROWERS ASSOCIATION REPORTING CONFERENCE. 2003. P. 271-273.
- Suttle, J.C. Regulation of tuber dormancy. 87th Annual Meeting of the Potato Association of American. 2003. p. 26. Abstract No. S3.
- Sabba, R.P., Lulai, E.C. 2003. Immunocytological determination of rhamnogalacturonan and extensin cell wall polymers associated with skin- set. [abstract]. American Journal of Potato Research. 81(1):85-86.
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Progress 10/01/01 to 09/30/02
Outputs
1. What major problem or issue is being resolved and how are you resolving it? Worldwide, the potato ranks among the top five food crops and in many countries, constitutes a major source of human nutrition. Global production of potatoes exceeds 290 million metric tons (FAO estimate). Annual U.S. production exceeds 440 million hundred-weight (USDA estimate). Over 70% of the total U.S. annual potato crop is placed in short to long term storage for a stable year-round supply. Unlike cereals, oilseeds and pulses, potatoes are stored in a fully hydrated and highly perishable form. As such, postharvest losses from both physiological and pathological processes can be severe. Of the physiological processes that affect the quality of stored potatoes, two of the most important are dormancy/sprouting and wound-healing. Both uncontrolled postharvest sprouting in storage and incomplete wound-healing following harvest can severely reduce the nutritional and market quality of
stored potatoes both directly by affecting various aspects of tuber composition and indirectly by fostering accelerated attack by storage pathogens. At present, the biochemical/physiological mechanisms that naturally regulate these two processes are unknown and this ignorance precludes the development of improved storage technologies. The goals of this project are to determine and exploit the natural, cognate physiological mechanisms that regulate both sprout growth and wound-healing in order to develop benign yet effective technologies to reduce the impact of these processes on potato quality and value. 2. How serious is the problem? Why does it matter? In the U.S., total postharvest losses can range from 5 to 40% of the stored crop. This results in financial losses to producers and processors of over $300 million in addition to the loss of the nutritional quality of the most widely consumed vegetable in most U.S. diets. Currently, chemical sprout suppressants are the only
commercially viable means to limit the deleterious effects of uncontrolled postharvest sprouting. At present aside from attempts to limit harvest-related tuber damage, there are no known methods to reduce wound-related tuber damage. Clearly, there is considerable room for the development of improved technologies to control these two important physiological processes. 3. How does it relate to the national Program(s) and National Program Component(s) to which it has been assigned? National Program 306, New Uses, Quality & Utilization of Agricultural Products (60%) National Program 302, Improving Plant Biological & Molecular Processes (40%) This research identifies intrinsic physiological and biochemical mechanisms that regulate the speed and extent of key biological processes that adversely affect the storage life and marketability of potatoes thereby providing a rational basis for the development of improved storage technologies and/or the genetic improvement of the potato itself. 4.
What was your most significant accomplishment this past year? A. Single Most Significant Accomplishment during FY 2002: Although rapid suberization of potato tubers that are cut for seed or wounded during harvest is essential for maintaining quality and preventing disease, the biochemical signals and regulatory mechanisms required to initiate and control wound-healing are largely unknown. Research conducted at the Sugarbeet and Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) has been directed toward the identification of internal factors/processes required for initiating/regulating wound-healing. This research has shown that tuber wounding elicits the production of ethylene, a hormone/signaling compound associated with stress and ripening, but that ethylene does not initiate, enhance, inhibit or influence the suberization component of the wound- healing response. These studies are of great importance because they are the first to show that this well known
stress and wound related hormone does not play a role in the crucial process of suberization during tuber wound-healing; these results directly impact the application of new commercial ethylene blocking technologies that may be used to control deterioration of stored potatoes. B. Other Significant Accomplishment(s) if any: The internal factors that control potato tuber dormancy/sprouting are unknown and this ignorance precludes the development of improved methods to control economically devastating tuber sprouting during storage. Research from the Sugarbeet and Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) has been directed toward the identification of native hormone systems regulating tuber dormancy and to the internal processes regulating hormone activity during dormancy progression in storage. In the past year, the metabolic fate of cytokinins (previously demonstrated by us to control dormancy termination) was determined and the enzymatic bases
regulating cytokinin levels was identified. These results are the first to determine the importance of cytokinin metabolism (destruction) in tuber dormancy control and have identified potential enzymatic targets for dormancy manipulation during storage. Although the susceptibility of potato tubers to skinning injury at harvest is a serious and costly problem leading to disease and blemish defects that reduce marketability, there is limited information on the identity of the biochemical processes which may be manipulated to enhance the development of resistance to tuber skinning injury (skin-set). Research was conducted at the Sugarbeet and Potato Research Unit at the Northern Crop Science Laboratory (Fargo, ND) to identify key physical and biochemical changes in tuber periderm that provide resistance to skinning injury upon periderm maturation. Histological and immunolocalization studies showed that as periderm phellogen cells become non-meristematic during periderm maturation
their cell walls thickened and accumulated non- esterified pectins; both of which provided strength to tightly hold the skin in place and thereby make the tubers resistant to skinning injury. This identification of cells and characterization of cell wall changes responsible for resistance to tuber skinning injury has: (1) dispelled long held anecdotal theories, used by researchers and industry, which incorrectly characterized the physiology of skin-set and how it should be addressed, (2) produced a completely new structural model to correctly guide research on skin-set, (3) given rise to new research projects on periderm maturation in other potato growing countries, and (4) developed foundational information that is essential in the creation of technologies to enhance resistance to skinning injury and reduce market quality defects and disease in harvested potatoes. C. Significant Accomplishments/Activities that Support Special Target Populations: None 5. Describe your major
accomplishments over the life of the project, including their predicted or actual impact? To date, 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) and tentatively ruled out the involvement of a fourth class of native hormones (gibberellins). The biochemical processes that affect the metabolism and activities of these hormones have been partially determined and are currently under investigation. These results are the first to unequivocally establish a hormonal basis for potato tuber dormancy and have set the stage for the complete experimental dissection of the biochemical mechanisms that regulate the biosynthesis, metabolism and activities of these hormone systems during dormancy. Studies from this lab have begun to determine the cellular and molecular basis for dormancy- imposed growth arrest in tuber eyes. The recently completed and
current research on the role of chromatin composition in dormancy control take knowledge of the cellular bases of meristem dormancy to a more fundamental level. These results 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. A fluorescent histochemical probe was developed to detect deposition of suberin polyaliphatics in native and developing wound periderm. This probe provides a sensitive means of tracking the final phase of suberization which provides the periderm of the potato tuber with durable horizontal resistance to penetration by pathogens. With this and another technique developed in our laboratory, we determined that: 1) deposition of suberin polyphenolics is discretely followed by deposition of polyaliphatics on individual suberizing cell walls during wound-healing, and 2) the deposition of these suberin components correlates
directly with the development of resistance to bacterial and then fungal infection during wound-healing of cut seed and stored potatoes. This technique and the information derived using it may be used by researchers to predict when wounds are sufficiently suberized to resist infection and in determining how we may enhance wound-healing to reduce disease and defect development in stored potatoes. The identification of the specific cell layer involved in resistance/susceptibility to tuber skinning injury 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. 6. What do you expect to accomplish, year by year, over the next 3 years? 1. Research on potato tuber dormancy control will continue with emphasis on three inter-related topics. First, the role(s) of the plant hormone gibberellin in dormancy control will be
continued and completed using a gibberellin-deficient mutant obtained from ARS collaborators at Sturgeon Bay, WI. Second, the roles of cytokinin oxidation and glucosylation in controlling cytokinin levels and activities during tuber dormancy will be determined using specific enzyme inhibitors. Lastly, the effects of dormancy progression on chromatin composition and function will be continued with emphasis on histone acetylation dynamics. FY03: Continue studies on gibberellin involvement in tuber dormancy: identify optimum greenhouse conditions for plant growth and tuber induction, determine endogenous GA levels in normal and mutant plants using GC-MS, initiate in-vitro culture of normal and mutant plants. Begin studies on the role of cytokinin oxidation in cytokinin homeostasis: screen putative enzyme inhibitors for effectiveness, determine potential interference of inhibitors with cytokinin immunoassays. Complete studies on changes in histone acetylation during dormancy
progression and transcriptional activation. FY04: Complete studies with gibberellin-deficient mutant. Continue studies on the role of cytokinin oxidase in cytokinin homeostasis. Initiate studies on the role of cytokinin glucosylation in regulating cytokinin levels during tuber dormancy: screen putative enzyme inhibitors to determine potency, determine potential interference of selected inhibitors with immunoassays, identify chromatographic methods to minimize interference. FY05: Complete studies on role of cytokinin oxidase in cytokinin homeostasis in tubers. Continue studies on role of cytokinin glycosylation in cytokinin homeostasis: determine effects of selected inhibitors on cytokinin levels and metabolism, develop protocols for the extraction and characterization of the enzyme(s) responsible for N- glucosylation of cytokinins and determine effects of inhibitors on isolated enzymes. 2. Research will continue on the identification and characterization of the biochemical
processes, signals and mechanisms that regulate the deposition of suberin during wound-healing and the development of resistance to tuber skinning injury/wounds (skin-set development) for harvest. FY 2003: Complete studies on the of role of ethylene in wound-induced suberin polyphenolic and polyaliphatic accumulation; this research was moved ahead of schedule to coordinate with other team related experiments. Conduct additional immunolocalization studies of 1-4-D- Galactans in conjunction with 1-5-L-Arabinans in immature (skinning susceptible) and mature (skinning resistant) tuber periderm. FY 2004: Initiate determination of role(s) of abscisic acid in wound- induced suberization. Initiate identification of molecular markers and bioregulators that characterize and control the processes responsible for development of resistance to tuber skinning injury. FY 2005: Complete the determination of role of abscisic acid in suberization and the characterization of coumarin-mediated
inhibition of suberization. Initiate the determination of the role(s) of molecular marker related products in skin-set development by identifying potential linkage(s) with accumulation of polymers responsible for cell wall strengthening and development of resistance to skinning injury. 7. What technologies have been transferred and to whom? When is the technology likely to become available to the end user (industry, farmer other scientist)? What are the constraints, if known, to the adoption durability of the technology? 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 both professional meetings and field-days. 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. 8. List your most important publications and presentations, and articles written about your work (NOTE: this does not replace your review publications which are listed below) RRVARC Partnership meeting, Oct. 31, 2001, Fargo, ND. Overview of Sugarbeet & Potato Research Unit accomplishments and activities. Popular article written by Tamas Houlihan interviewing Ed Lulai about the NCSL postharvest research on tuber wound-healing and periderm maturation. Published in the Wisconsin vegetable industry trade magazine, "The Badger Common' Tater." 2002, January. v. 54(1). p. 6-7. Lulai, E.C. The suberization of tuber wounds. A 45 min. invited opening oral presentation to the Wisconsin Potato & Vegetable Growers Assn. Conference. Held in Stevens Point, Wisconsin, Feb.
12-14, 2002. Quad-State Potato Meetings, April 4, 2002, St. Paul, MN. Update on unit potato related research and EGF Potato Research Worksite capabilities. The peer reviewed scientific journal, "Annals of Botany", provided a special editorial review recognizing and describing our research, "Histological Analysis of the Maturation of Native and Wound Periderm in Potato (Solanum tuberosum L.) Tuber". This independent review was published under "Content Select" in the prefacing unnumbered pages of Annals of Botany, 2002, v. 90.
Impacts
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Publications
- Lulai, E.C., Freeman, T.P. The importance of phellogen cells and their structural characteristics in susceptibility and resistance to excoriation in immature and mature potato tuber (Solanum tuberosum L.) periderm. Annals of Botany. 2001. v. 88. p. 555-561.
- Knight, V.I., Wang, H., Lincoln, J.E., Lulai, E.C., Gilchrist, D.G., Bostock, R.M. Hydroperoxides of fatty acids induce programmed cell death in tomato protoplasts. Physiological & Molecular Plant Pathology. 2001. v. 59. p. 277-286.
- Lulai. E.C. Compendium of Potato Diseases. Stevenson, W.R., Loria, R., Franc G.D., and Weingartner D.P., editors. American Phytopathological Society Press, St. Paul, MN. Tuber periderm and disease resistance. 2001. p. 3-6.
- Lulai. E.C. Compendium of Potato Diseases. Stevenson, W.R., Loria, R., Franc G.D., and Weingartner D.P., editors. American Phytopathological Society Press, St. Paul, MN. Tuber respiration and storage environment. 2001. p. 6-7.
- Sabba, R.P., Lulai, E.C. Histological analysis of the maturation of native and wound periderm in potato (Solanum tuberosum L.) tuber. Annals of Botany. 2002. v.90 p. 1-10.
- Lulai, E.C., Suttle, J.C. The role of ethylene in wound-induced suberization of potato tuber (Solanum tuberosum L.). XXVIth International Horticultural Congress & Exhibition (IHC 2002), On-Site Program. 2002. Abstr# S03-P-85, p 127.
- Sabba, R.P., Lulai, E.C., Freeman, T.C. Changes in cell wall pectin associated with periderm maturation in potato tuber. XXVIth International Horticultural Congress & Exhibition (IHC 2002). On-Site Program. 2002. Abstr# S03-P-99. p 130.
- Suttle, J.C. Role of ethylene in naphthalene-mediated sprout growth inhibition. International Horticultural Congress. 2002. Abstr # S03-P-101. p. 130.
- Suttle, J.C. Dormancy related changes in cytokinin efficacy and metabolism in potato tubers during postharvest storage. Journal of Plant Growth Regulation. 2001. vol. 35 p.199-206.
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