PHYSIOLOGICAL AND AGRONOMIC STUDIES TO MAXIMIZE THE PRODUCTIVITY AND POSTHARVEST QUALITY OF NEW POTATO CULTIVARS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0195310
• Project Start Date: Mar 1, 2010
• Project End Date: Feb 28, 2015
• Program Code: [(N/A)]- (N/A)

Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001

Performing Department
Horticulture

Non Technical Summary
Tuber maturity affects the quality of seed and processing potatoes. Environmental conditions interact with agronomic practices during production to dictate the physiological maturity of tubers at harvest. Understanding how these interactions influence seed productivity and the retention of processing quality in stored potatoes is key to developing best management practices for newly released cultivars. We have a major interest in defining how growing environment and in-season management interact with harvesting, handling and storage conditions to affect tuber maturity and the storability and quality of maincrop and seed potatoes. This project integrates our research in both areas, with a focus on newly released cultivars for which best management practices remain to be defined. Methods for predicting and manipulating seed productivity to control tuber size distribution for added value of newly released cultivars are being developed. The project also includes a service component that provides the WA industry information on an annual basis about the quality of seed imported from other states and provinces. Commercial potato production in WA relies on seed potatoes produced predominantly exterior to the state. For this reason, a side-by-side comparison of performance of seed potatoes from the various seed producing areas aids growers in understanding the variation in quality. This information complements data available through certification agencies and seed grower history and is helpful in selecting seed tuber lots that have potential for production of high yielding, high quality potatoes.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
203	1310	1000	25%
205	1499	1020	25%
206	2410	1050	25%
503	2410	1020	25%

Knowledge Area
206 - Basic Plant Biology; 205 - Plant Management Systems; 203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants; 503 - Quality Maintenance in Storing and Marketing Food Products;

Subject Of Investigation
1310 - Potato; 1499 - Vegetables, general/other; 2410 - Cross-commodity research--multiple crops;

Field Of Science
1000 - Biochemistry and biophysics; 1020 - Physiology; 1050 - Developmental biology;

Keywords

potato

solanum tuberosum

seed productivity

aging

storage

sweetening

wound healing

variety development

physiological maturity

postharvest

quality

physiological disorders

Goals / Objectives
SEED PHYSIOLOGY AND PRODUCTIVITY OBJECTIVES (N.R. Knowles). 1) Model stem number, tuber set, and tuber size distribution relationships to determine combinations that maximize returns for fresh, processing, and seed markets for new cultivars. 2) Investigate ways to regulate apical dominance to produce target stem numbers in seed lots. 3) Determine how accelerated aging resets the basal metabolic (respiration) rates of seed tubers to dictate their physiological age. Expected Impacts: The seed productivity studies will enable seed growers to manage seed lots to produce maximum yield and economic return potential. The work will result in recommendations for managing heat-unit accumulation by seed during maturation and storage, and for grouping compatible cultivars in seed storages in relation to the degree days needed to produce target stem numbers. Development of methods for handling Summit seed to overcome delayed emergence and low yield is prerequisite to using this cultivar commercially. Methods for rejuvenating older seed lots to optimize tuber size distribution will broaden management options for growers. REGULATION OF POSTHARVEST QUALITY AND NUTRITIONAL ATTRIBUTES OF PROCESSING POTATOES OBJECTIVES (N.R. Knowles). 1) Determine how tuber maturity affects wound-healing ability and changes in processing quality during storage. 2) Define genotype and maturity-dependent differences in periderm that affect resistance to desiccation and shrink in storage. 3) Investigate the biochemical bases for differences in resistance to cold-induced sweetening among newly released cultivars. 4) Characterize the onset and physiology of mottling and identify production factors that lead to the disorder. 5) Determine the mechanism(s) by which vit C declines in tubers following harvest. Expected Impacts: Defining how tuber maturity affects retention of processing quality will lead to recommendations for optimizing at-harvest and out-of-storage quality and thus profitability for growers. Elucidation of the biochemical bases for cultivar-dependent differences in LTS and mottling may reveal genetic markers for selection of cold tolerance. Understanding how tuber maturity affects wound-healing ability and resistance to desiccation and pathogens will lead to recommendations for end-of-season management to minimize shrink for these cultivars. The work will also facilitate the development of high ascorbate-retaining genotypes and storage protocols to reduce ascorbate loss. POTATO VARIETY DEVELOPMENT AND COMMERCIAL SEED LOT EVALUATION OBJECTIVES (M.J. Pavek, PI). 1) Determine the response of potato clones and cultivars that show promise for commercial production in WA to various cultural practice alternatives. 2) Test early generation clones for potential as fresh market and processing cultivars and determine their adaptability to WA growing conditions. 3) Demonstrate the incidence of seed-borne diseases in potato seed lots planted for commercial potato production in WA. 4) Provide an opportunity for personnel from WSU, WSDA Certification, and the potato industry to receive potato disease identification training and experience.

Project Methods
Seed-tubers will be acquired directly from seed growers at harvest. The tubers will be aged by storing at different temperatures at the beginning of the storage season, to produce a wide range of stem numbers the following season. Plant growth regulators will also be used to modify apical dominance. The relationships among stem numbers, tuber set, and tuber size distribution will be modeled, with a complete economic analysis of production and market opportunities for each cultivar. The importance of respiration as the pacemaker of aging will be determined by integrating the respiratory effort (output) of seed tubers over time and in response to treatments that alter physiological age and correlating this output with apical dominance, tuber set, and tuber size distribution (measures of age). Additional studies will involve storing tubers under low O2 to potentially mitigate the effects of prolonged high respiration on the aging process. The respiratory responses of tubers of cultivars that are highly sensitive (e.g. Russet Burbank), moderately sensitive (e.g. Russet Norkotah), and insensitive (e.g. GemStar Russet) to accelerated aging treatment will be correlated with subsequent effects on crop growth and development. Nitrogen (N) nutrition (rate and timing) will be manipulated to produce tubers of different maturities to study the importance of tuber maturity to the retention of processing quality of selected cultivars during storage. Changes in sweetening and processing quality during storage will be correlated with differences in at-harvest physiological maturity as induced by N level. Studies to assess the effects of tuber maturity on wound-healing potential and resistance to pathogens will be done toward the end of the growing season using tubers from field plots showing N-induced differences in degree of vine senescence (ranging from fully senesced, DV, to green, GV). The relative abilities of GV and DV tubers to produce the requisite antimicrobial oxidative burst in response to wounding will be compared. Temporal differences in gene expression and the activities of key enzymes involved in wound response and suberization, in relation to increasing resistance to desiccation over a 10-day healing interval (a measure of wound healing), will establish the mechanisms by which tuber maturity affects wound response and healing capacity. Cold sweetening will be induced by exposing tubers to precise temperature changes while monitoring key aspects of respiratory and carbohydrate metabolism. Temperature-induced changes in gene expression and activities of enzymes involved in starch, sucrose, glucose, and fructose metabolism will be compared among the cultivars. Potato clones and/or recently named cultivars that have shown potential in early generation trials will be grown in three to four row plots. Treatment variables include length of growing season, plant population, depth of planting, etc). Treatments will compare current industry practices with alternative cultural practices in an effort to optimize the genetic potential of the new cultivars.

Progress 03/01/10 to 02/28/15

Outputs
Target Audience: The target audience includes: potato growers (including seed and commercial growers of fresh and processing potatoes); processors; consultants; fertilizer, chemical and equipment manufacturers and applicators; scientists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The project contributed to the training of six graduate students and numerous personnel from state, federal and private industry. How have the results been disseminated to communities of interest? Through annual field days; regional, national and international conferences; refereed journal article publications and trade journal articles. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project focused heavily on advanced agronomic trials to further develop cultivars released by the Pacific Northwest Potato Variety Development Program (NWPVD). Additionally, germplasm from the NWPVD program offered a unique opportunity for fundamental research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses in potato. From 2009 through 2015, the NWPVD program released the following cultivars: Classic Russet (2009), Alpine Russet (2009), Clearwater Russet (2009), Owyhee Russet (2009), Red Sunset (2009), Crimson Red (2009), Purple Pelisse (2009), Sage Russet (2010), AmaRosa (2010), Teton Russet (2011), Palisade Russet (2011), Huckleberry Gold (2011), Yukon Nugget (2013). All varieties developed by the NWPVD Program have been licensed to the Potato Variety Management Institute (PVMI), a non-profit organization working on behalf of the program to promote and market varieties since 2005. Detailed information about these and other NWPVD varieties can be found at www.pvmi.org. Major goals of the research were to identify clones that are more efficient in producing yield and higher economic returns than the mainstay cultivar, Russet Burbank, and to develop best management practices (BMP) and 'sustainability indices' for the most productive and newest releases from the NWVDP. Research-based sustainability indices (e.g., N, P, and land and water use efficiencies) and BMP recommendations for the selected newly released cultivars are an improvement for WA growers over existing recommendations, which were based solely on management of Russet Burbank. The following studies were completed during the project: (1) Defined the growth and yield responses of Sage and Alpine Russet to in-season N; modeled the attainment of tuber physiological maturity and determined subsequent effects on retention of nutritional and process qualities during storage. (2) Evaluated the effects of soil temperature on tuber quality, postharvest physiology and storability of processing potatoes (Premier & Ranger Russet). (3) Tested the hypothesis that respiration is the 'pacemaker' of tuber aging and that inherent- and management-induced differences in tuber respiration are significant determinants of the ability to retain quality of seed and processing potatoes. Identified production factors that affect tuber metabolic rate & quality retention. Determined how the sensitivity of seed to temp-induced accelerated aging changes from vine kill through storage to planting. (4) Completed land use efficiency plant population trials for Premier Russet; Alturas, Umatilla Russet, Russet Burbank, Russet Norkotah, Chieftain, and Ranger Russet. (5) Established comparative N and P use efficiencies and management recommendations for Russet Burbank, Ranger, Umatilla, Classic Russet, Owyhee Russet, Teton Russet, Alpine Russet, Alturas, and Sage in the Columbia Basin. (6) Completed water use efficiency trials for a range of NWPVD program varieties.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: JC Miller Jr., Scheuring DC, Koym JW, Holm DG, Pavek JJ, Novy RG, Whitworth JL, Stark JC, Charlton BA, Yilma S, Knowles NR, Pavek MJ, Nunez JJ, Shock CC, and CR Brown. 2015. 11ATTX961014-1R/Y a.k.a. Sierra RoseTM: A Red-Skin, Yellow-Flesh Potato Cultivar for the Specialty/Gourmet Market. Am J Pot Res 91:447-458. DOI 10.1007/s12230-015-9460-x
• Type: Book Chapters Status: Published Year Published: 2014 Citation: Wohleb, CH, Knowles, NR and MJ Pavek. 2014. Plant Growth and Development. In The Potato Botany, Production and Uses, DA Navarre and MJ Pavek ed., 1st edition, CABI Press (invited chapter) ch 5 pp. 64-82.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: The target audience includes: potato growers (including seed and commercial growers of fresh and processing potatoes); processors; consultants; fertilizer, chemical and equipment manufacturers and applicators; scientists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Six graduate students were involved in various aspects of these trials. How have the results been disseminated to communities of interest? Results were reported to stakeholders at the WA/OR annual Potato Conference and Trade Show and the Western WA Potato Growers meetings in 2013 and 2014. Articles containing results from the project have been published in the Proceedings of the WA Potato Conference and Trade Show. Results have also been summarized in presentations at the annual potato industry field days (Othello, WA) and annually during the WA Potato Commission research reviews. Refereed journal articles have been published (see below). What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project focuses heavily on advanced agronomic trials to further develop cultivars released by the Pacific Northwest Potato Variety Development Program (NWPVD). Additionally, germplasm from the NWPVD program offers a unique opportunity for fundamental research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses in potato. From 2009 through 2014, the NWPVD program released the following cultivars: Classic Russet (2009), Alpine Russet (2009), Clearwater Russet (2009), Owyhee Russet (2009), Red Sunset (2009), Crimson Red (2009), Purple Pelisse (2009), Sage Russet (2010), AmaRosa (2010), Teton Russet (2011), Palisade Russet (2011), Huckleberry Gold (2011), Yukon Nugget (2013). All varieties developed by the NWPVD Program have been licensed to the Potato Variety Management Institute (PVMI), a non-profit organization working on behalf of the program to promote and market varieties since 2005. Detailed information about these and other NWPVD varieties can be found at www.pvmi.org. Major goals of the research were to identify clones that are more efficient in producing yield and higher economic returns than the mainstay cultivar, Russet Burbank, and to develop best management practices (BMP) and ‘sustainability indices’ for the most productive and newest releases from the NWVDP. Research-based sustainability indices (e.g., N, P, and land and water use efficiencies) and BMP recommendations for the selected newly released cultivars are an improvement for WA growers over existing recommendations, which were based solely on management of Russet Burbank. The following studies were completed during the reporting period: (1) Defined the growth and yield responses of Sage and Alpine Russet to in-season N; modeled the attainment of tuber physiological maturity and determined subsequent effects on retention of nutritional and process qualities during storage. (2) Evaluated the effects of soil temperature on tuber quality, postharvest physiology and storability of processing potatoes (Premier & Ranger Russet). (3) Tested the hypothesis that respiration is the ‘pacemaker’ of tuber aging and that inherent- and management-induced differences in tuber respiration are significant determinants of the ability to retain quality of seed and processing potatoes. Identified production factors that affect tuber metabolic rate & quality retention. Determined how the sensitivity of seed to temp-induced accelerated aging changes from vine kill through storage to planting. (4) Completed land use efficiency plant population trials for Premier Russet; Alturas, Umatilla Russet, Russet Burbank, Russet Norkotah, Chieftain, and Ranger Russet. (5) Established comparative N and P use efficiencies and management recommendations for Russet Burbank, Ranger, Umatilla, Classic Russet, Owyhee Russet, Teton Russet, Alpine Russet, Alturas, and Sage in the Columbia Basin. (6) Completed water use efficiency trials for a range of NWPVD program varieties.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Zommick, D.H., L.O. Knowles, M.J. Pavek and N.R. Knowles. 2014. In-season heat stress compromises postharvest quality and low temperature sweetening resistance in potato (Solanum tuberosum L.). Planta 239:1243-1263. DOI 10.1007/s00425-014-2048-8
• Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Zommick, Daniel. 2013. Postharvest physiological responses of potato (Solanum tuberosum L.) to temperature stress during production and storage. PhD dissertation, WSU, Dept. of Horticulture, Pullman, WA
• Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Jacob M. Blauer. 2013. Factors affecting tuber ascorbate content, physiological age, tuber set and size distribution in potato (Solanum tuberosum L.). Program in Molecular Plant Sciences, Dept. of Horticulture, WSU. JMB is currently Research & Development Scientist and Agronomist  Whole Plant Team Manager at J.R. Simplot Co., Boise, ID.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Zommick, D.H., L.O. Knowles and N.R. Knowles. 2014. Tuber respiratory profiles during low temperature sweetening (LTS) and reconditioning of LTS-resistant and susceptible potato (Solanum tuberosum L.) cultivars. Postharvest Biol Tech 92:128-138.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Whitworth JL, Novy RG, Stark JC, Love SL, Thornton MK, Charlton BA, Yilma S, Knowles NR, Pavek MJ, and X Wang. 2014. Huckleberry Gold: a high antioxidant purple-skin yellow-flesh specialty market cultivar with potato cyst nematode resistance (H1) and Potato virus X resistance (Nb and Rx1). Am J Pot Res 91:447-458.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Novy RG, Whitworth JL, Stark JC, Charlton BA, Yilma S, Knowles NR, Pavek MJ, Spear RR, Brandt TL, Olsen N, Thornton M, Brown CR, James SR, and DC Hane. 2014. Teton Russet: an early-maturing, dual-purpose potato cultivar having high protein and vitamin C content, low asparagine, and resistances to common scab and Fusarium dry rot. Am J Pot Res 91:380-393
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Zommick D.H., Kumar, G.N.M., Knowles, L.O. and N.R. Knowles. 2013. Translucent tissue defect in potato (Solanum tuberosum L.) tubers is associated with oxidative stress accompanying an accelerated aging phenotype. Planta 238:1125-1145
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Mooney, S, Chen, L, Kuhn, C., Navarre, D.A., Knowles, N.R. and H. Hellmann. 2013. Genotype specific changes in vitamin B6 content and the PDX family in potato. BioMed Research International http://dx.doi.org/10.1155/2013/389723
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Blauer, J.M., Knowles, L.O. and N.R. Knowles. 2013. Manipulating stem number, tuber set and size distribution in specialty potato cultivars. Am J Pot Res 90:470-496.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Blauer, J.M., Knowles, L.O. and N.R. Knowles. 2013. Evidence that tuber respiration is the pacemaker of physiological aging in seed potatoes (Solanum tuberosum L.). J Plant Growth Regul 32:708-720.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Navarre, D.A,, Payyavula, R.S., Shakya, R., Knowles, N.R., and S.S. Pillai. 2013. Changes in potato phenylpropanoid metabolism during tuber development. Plant Physiol Biochem 65:89-101
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Blauer, J.M., Kumar, G.N.M., Knowles, L.O., Dhingra, A. and N.R. Knowles. 2013. Changes in ascorbate and associated gene expression during development and storage of potato tubers (Solanum tuberosum L.). Postharvest Biol Tech 78:76-91.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2014 Citation: Novy, R., J. Whitworth, J. Stark, B. Charlton, S. Yilma, V. Sathuvalli, N.R. Knowles, M. Pavek, R. Spear, T. Brandt, N. Olsen, M. Thornton, C. Brown, and J. Debons. 2014. A02507-2LB and A03158-2TE: Promising breeding clones from the Northwest (Tri-State) Potato Variety Development Program. Am. J. Pot. Res (in press).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2014 Citation: Dolezal, C., Z. Holden, N.R. Knowles, L.O. Knowles and M.J. Pavek. 2014. The effects of phosphorus fertilizer on the commercial production and postharvest quality of nine potato cultivars. Proceedings of the 98th Annual Meeting of the Potato Association of America. Am. J. Pot. Res (in press).
• Type: Other Status: Published Year Published: 2014 Citation: Pavek, M.J. and N.R. Knowles. 2014. WSU potato cultivar yield and postharvest quality evaluations for 2013. Washington State University Special Report. 135 pp
• Type: Other Status: Accepted Year Published: 2014 Citation: Pavek, M.J., N.R. Knowles, Z. Holden, L.O. Knowles and R. Spear. 2014. Water stress research on ten varieties via variable rate irrigation (VRI). WSU Annual Potato Field Day, IAERC, Othello, WA, June 26.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Knowles, N.R., L.O. Knowles and M.J. Pavek. 2013. In-season management and postharvest quality  lessons learned from Alpine Russet, Sage Russet and other cultivars. Proceedings of the 2013 Washington and Oregon Potato Conference. pp. 34-47.v
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Pavek, M.J., N.R. Knowles and Z.J. Holden. 2013. Definition and application of potato harvest index and source-sink relationships. Proceedings of the 2013 Washington and Oregon Potato Conference. pp. 52-57.
• Type: Other Status: Accepted Year Published: 2014 Citation: Knowles, N.R., M.J. Pavek, L.O. Knowles, D.H. Zommick and D. Herman. 2014. Crop development, morphology and stress tolerance. WSU Annual Potato Field Day, IAERC, Othello, WA, June 26.

Progress 01/01/13 to 09/30/13

Outputs
Target Audience: The target audience includes: potato growers, including seed and commercial growers of fresh pack and frozen processing potatoes; processors; consultants; fertilizer, chemical and equipment manufacturers Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The overall program provides continuing opportunities for training personnel in the science of breeding and genetics, variety development, agronomic management, and postharvest handling, storage and processing quality evaluation of a diverse array of germplasm. On average, the multi-state project engages two to four graduate students, three postdoctoral, five technical, and numerous undergraduate students in the project annually. Extension personnel and industry stakeholders also participate in efforts to grow and evaluate the clonal entries on an annual basis. In 2013, there were 6 graduate students working under the supervision of the PIs MJ Pavek and NR Knowles. How have the results been disseminated to communities of interest? Results from the program are disseminated through field days conducted at all sites (Washington, Idaho and Oregon) and reports to the potato industry during the annual meetings of the WA/OR Potato industry (including a focused half-day session on potato variety development and the annual results from this program) and the ID potato industry. Stakeholders and personnel from major processing companies also attend the annual meetings of the Tri-State and Western Regional potato variety development committees where they receive a summary of the results, provide input into performance and participate in selecting entries to be included in the following year. Additionally, results from agronomic and physiology based studies are reported in formal presentations given by the PIs and graduate students at national/international meetings (e.g., Potato Association of America, Montreal, Canada August 2013). What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project focuses heavily on advanced agronomic trials to further develop cultivars released by the Pacific Northwest Potato Variety Development Program (NWPVD). The germplasm from this program offers a unique opportunity for fundamental research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses in potato. From 2009 through 2013, the following potato varieties were officially released by the NWPVD Program (also known regionally as the Tri-State Program): Classic Russet (2009), Alpine Russet (2009), Clearwater Russet (2009), Owyhee Russet (2009), Red Sunset (2009), Crimson Red (2009), Purple Pelisse (2009), Sage Russet (2010), AmaRosa (2010), Teton Russet (2011), Palisade Russet (2011), Huckleberry Gold (2011) and Yukon Nugget (2013). All varieties have been licensed to the Potato Variety Management Institute (PVMI), a non-profit organization working on behalf of the program to promote and market varieties since 2005. Detailed information about these and other NWPVD varieties can be found at www.pvmi.org. Research to identify clones that are more efficient in producing yield and higher economic returns than the mainstay cultivar, Russet Burbank (RB), and to develop best management practices (BMP) and sustainability information for the most productive and newest releases from the NWVDP was accomplished. Research-based sustainability indices (e.g., N and P use efficiencies) and BMP recommendations for the selected newly released cultivars are an improvement for WA growers over the existing recommendations, which are based solely on management of the mainstay cultivar, Russet Burbank. Management recommendations and resource utilization efficiencies based on this work were and are being formulated for cultivars Premier Russet, Alpine Russet, Sage Russet, Alturas, Umatilla Russet, Classic Russet, Owyhee Russet, and Teton Russet. Measurable outcomes and impacts are the identification and ultimately the adoption by industry of cultivars that are more efficient in their use of agronomic inputs than standard cultivars, along with the BMP recommendations needed to maximize production efficiency and retention of postharvest quality of each cultivar. Potential reductions in use of fertilizer, water, and fossil fuel as a result of growing these cultivars is being quantified and reported to industry. Additional studies were completed to: (1) understand how vitamin C accumulates during growth and development and is lost during storage in relation to expression of genes in the biosynthetic and recycling pathways; (2) test the hypothesis that tuber respiration is the pacemaker of physiological aging in seed-potatoes; and (3) evaluate the efficacy of seed-tuber age and gibberellins (GA) to alter apical dominance, tuber set, and size distribution of five red/specialty cultivars to better meet the requirements of various markets. AsA concentration increased rapidly in tubers during the early stages of tuberization and through bulking, reaching a maximum just prior to the attainment of physiological maturity, then fell during the maturation period as vines began to senesce. AsA was lost rapidly from tubers following harvest and the rate of loss was affected by genotype, tuber age, wounding, oxygen concentration, and sprouting; preventing this loss has the potential of greatly increasing the contribution of potatoes to vitamin C in our diet. Research to understand the role of respiration in dictating the physiological age (PAGE) and productive potential of seed demonstrated that seed-tubers given high-temperature age-priming treatments at the beginning of storage maintained higher respiration rates throughout storage until planting. Lowering the respiration rate of age-primed seed during storage resulted in younger tubers. Respiration appears to be the pacemaker of PAGE and production and storage conditions that affect respiration may ‘set the clock speed’ that will ultimately determine the PAGE at planting. Methods for manipulating apical dominance, tuber set and size distribution of specialty cultivars of potatoes were developed. While aging treatments were ineffective, pre-plant applications of GA to cut seed substantially increased crop values, due to combined effects on apical dominance, tuber set, total yields and shifts in tuber size distribution toward smaller size tubers with higher value. Additional work was completed on the mechanism of translucent tissue defect (TTD) development in storage. The newly released, low temperature sweetening (LTS)-resistant cultivar Premier Russet can develop TTD within 5-6 months of storage (9°C), which manifests as random pockets of translucent tissue that fry dark during processing due to RS buildup. Physiologically, TTD is similar to the irreversible senescent-sweetening that occurs during long-term storage of potatoes. Time-course studies and tissue specific analyses demonstrated that TTD is a consequence of oxidative stress associated with an accelerated aging phenotype. Carbohydrate metabolism was characterized in relation to temperature-induced changes in tuber respiration rate during LTS and reconditioning for four cultivars with disparate resistances to reversible LTS: Premier Russet (highly resistant), GemStar Russet (moderately resistant), Russet Burbank (susceptible) and Defender (highly susceptible). RS accumulation in these cultivars corresponded to sucrose forming potential in relation to activities of invertase and endogenous invertase inhibitors. Exposure to 4°C induced a predictable respiratory acclimation response that correlated with the extent of sweetening and likely reflected the metabolic energy required to catabolize starch to sucrose and RS. Soil temperature was increased during the tuber bulking and maturation phases of crop development to evaluate the effects of in-season heat on subsequent retention of postharvest quality in LTS resistant and susceptible cultivars. High heat ( 13°C above ambient) during bulking virtually eliminated tuber yield while moderate heat ( 7°C above ambient) compromised process quality at harvest. Higher soil temperatures during maturation under dead vines reduced dormancy length and modified the basal respiration rates of tubers consistent with over-maturation and advanced physiological age. Heat stress during bulking, maturation or early storage exacerbated sweetening in ‘Ranger Russet’ tubers and abolished the LTS-resistant phenotype of ‘Premier Russet’ tubers. AO02183-2 was more tolerant of heat stress for retention of process quality. Breeding for retention of postharvest quality and LTS resistance should consider strategies for incorporating more robust tolerance to in-season heat stress.

Publications

• Type: Journal Articles Status: Accepted Year Published: 2013 Citation: Novy RG, Whitworth JL, Stark JC, Charlton BA, Yilma S, Knowles NR, Pavek MJ, Spear RR, Brandt TL, Olsen N, Thornton M, Brown CR, James SR, and DC Hane. 2013. Teton Russet: an early-maturing, dual-purpose potato cultivar having high protein and vitamin C content, low asparagine, and resistances to common scab and Fusarium dry rot. Am J Pot Res (in press, accepted 11-25-13).
• Type: Journal Articles Status: Under Review Year Published: 2013 Citation: JL, Novy RG, Stark JC, Love SL, Thornton MK, Charlton BA, Yilma S, Knowles NR, Pavek MJ, and X Wang. 2013. Whitworth Huckleberry Gold: a high antioxidant purple-skin yellow-flesh specialty market cultivar with potato cyst nematode resistance (H1) and Potato virus X resistance (Nb and Rx1). Am J Pot Res (in review).
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Zommick D.H., Kumar, G.N.M., Knowles, L.O. and N.R. Knowles. 2013. Translucent tissue defect in potato (Solanum tuberosum L.) tubers is associated with oxidative stress accompanying an accelerated aging phenotype. Planta 238:1125-1145.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Blauer, J.M., Knowles, L.O. and N.R. Knowles. 2013. Manipulating stem number, tuber set and size distribution in specialty potato cultivars. Am J Pot Res 90:470-496. (DOI 10.1007/s12230-013-9317-0).
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Blauer, J.M., Knowles, L.O. and N.R. Knowles. 2013. Evidence that tuber respiration is the pacemaker of physiological aging in seed potatoes (Solanum tuberosum L.). J Plant Growth Regul 90:470-496. (DOI 10.1007/s00344-013-9338-4).
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Navarre, D.A,, Payyavula, R.S., Shakya, R., Knowles, N.R., and S.S. Pillai. 2013. Changes in potato phenylpropanoid metabolism during tuber development. Plant Physiol Biochem 65:89-101.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Blauer, J.M., Kumar, G.N.M., Knowles, L.O., Dhingra, A. and N.R. Knowles. 2013. Changes in ascorbate and associated gene expression during development and storage of potato tubers (Solanum tuberosum L.). Postharvest Biol Tech 78:76-91.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Zommick, DH. 2013. Postharvest physiological responses of potato (Solanum tuberosum L.) to temperature stress during production and storage. PhD Dissertation, Washington State University, 181 pp.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2013 Citation: Kumar, G.N.M. and N.R. Knowles. 2013. Wound response is activated in tubers infected with zebra chip. Proceedings of the 97th Annual Meeting of the Potato Association of America. Am. J. Pot. Res (in press).
• Type: Other Status: Published Year Published: 2013 Citation: Knowles, N.R. and M.J. Pavek. 2013. WSU potato cultivar yield and postharvest quality evaluations for 2012. Washington State University Special Project Annual Report. 122 pp.
• Type: Websites Status: Published Year Published: 2013 Citation: Product: Pavek, MJ and NR Knowles. WSU potato research and extension website. http://potatoes.wsu.edu/

Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: This project focuses heavily on advanced agronomic trials to further develop cultivars released by the Pacific Northwest Potato Variety Development Program (PNWPVDP)also known regionally as the Tri-State Program. The germplasm from this program offers a unique opportunity for fundamental research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses in potato. Direct outputs from the PNWPVDP from 2009 through 2012 include: Classic Russet (2009), Alpine Russet (2009), Clearwater Russet (2009), Owyhee Russet (2009), Red Sunset (2009), Crimson Red (2009), Purple Pelisse (2009), Sage Russet (2010), AmaRosa (2010), Teton Russet (2011), Palisade Russet (2011), Huckleberry Gold (2011), and Yukon Nugget (2012). All varieties developed by the NWPVD Program have been licensed to the Potato Variety Management Institute (PVMI), a non-profit organization working on behalf of the program to promote and market varieties since 2005. Detailed information about these and other NWPVD varieties can be found at www.pvmi.org. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Potato growers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Seed Productivity Studies:
Results from seed productivity studies are enabling seed growers to manage seed lots to produce tuber size distributions that have maximum yield and economic return potential. The work has resulted in recommendations for managing heat-unit accumulation by seed during maturation and storage, and for grouping compatible cultivars in seed storage in relation to the degree days needed to produce target stem numbers. Basic studies have revealed how temperature during seed production modulates tuber age to affect productive potential the following year. Methods for rejuvenating older seed lots to optimize tuber size distribution have broadened management options for growers.

Regulation of Postharvest Quality & Nutritional Attributes of Processing Potatoes:
Defining the attainment of physiological maturity for new cultivars has led to management recommendations for optimizing at-harvest and out-of-storage quality and thus profitability for growers. Elucidation of the biochemical/molecular bases for cultivar-dependent differences in low temperature sweetening (LTS) and mottling disorder is identifying genetic markers for selection of cold tolerance for use in the PNWPVDP breeding program. Other studies are revealing how agronomic and environmental variables during production interact to affect retention of postharvest processing and nutritional qualities. Ongoing research on the mechanism(s) of ascorbate accumulation and loss in tubers following harvest are facilitating the selection of high ascorbate-retaining genotypes and may lead to the development of handling and storage protocols to reduce ascorbate loss. Genotypes that produce low asparagine and reducing sugars during production and storage are being selected to reduce acrylamide in the nation's food supply. Ongoing studies of agronomic and environmental factors affecting accumulation of these precursors are revealing management techniques for production of low acrylamide forming potential in existing and newly released varieties.

Potato Variety Development and Seed Lot Evaluation Studies:
The effect of the Tri-State Potato Variety Development Program on the Northwest potato industry has been substantial. The fresh market industry, French fry processors and chippers have incorporated many varieties developed through the Tri-State variety development program into their businesses. Ranger Russet, Umatilla Russet, Alturas, Premier Russet, Bannock Russet, Ivory Crisp, Western Russet, and Alpine Russet ranked 3rd, 4th, 7th, 13th, 14th, 16th, 21st, and 22nd most widely grown cultivars in the United States in 2012, respectively. Tri-State varieties represent over 21%, or 200,000 acres, of the fall crop nationally. (NASS, Crop Production, November, 2012). Varieties released by the Tri-State program are now produced on 137,000 acres in the Pacific Northwest with value to growers estimated at ca. $495M. Compared with 2010, the 2012 US farm-gate value of Tri-State varieties increased by ca. $80 million. Many of these varieties are more efficient in use of agronomic inputs (N, P, water, pesticides) and have resistance to major potato diseases.

Publications

• Yilma S., M.I.Vales, B.A.Charlton, D.C.Hane, S.R.James, C.C.Shock, A.R.Mosley, D.Culp, E.Feibert, L.Leroux, E.Karaagac, N.R.Knowles, M.J.Pavek, J.C.Stark, R.Novy, J.Whitworth, J.J.Pavek, D.L.Corsini, T.L.Brandt, N.Olsen, C.R.Brown 2012. Owyhee Russet: A variety with high yields of U.S. No. 1 tubers, excellent processing quality, and moderate resistance to Fusarium dry rot (Fusarium solani var. coeruleum). American Journal of Potato Research: An Official Publication of the Potato Association of America. 89:175-183.
• Knowles L., N.R.Knowles 2012. Toxicity and metabolism of exogenous a,Beta-unsaturated carbonyls in potato (Solanum tuberosum L.) tubers.. Journal of Agricultural and Food Chemistry. 60:11173-11181.
• Brown C.R., M.I.Vales, S.Yilma, S.R.James, D.C.Hane, C.C.Shock, E.Feibert, B.A.Charlton, D.Culp, M.J.Pavek, N.R.Knowles, R.Novy, J.Whitworth, J.C.Stark, C.Miller, D.Holm, D.Navarre 2012. "AmaRosa," a red skinned, red fleshed fingerling with high phytonutrient value. American Journal of Potato Research : An Official Publication of the Potato Association of America. 89:249-254.
• Vales M.I., C.R.Brown, S.Yilma, D.C.Hane, S.R.James, C.C.Shock, B.A.Charlton, E.Karaagac, A.R.Mosley, D.Culp, E.Feibert, J.C.Stark, M.J.Pavek, N.R.Knowles, R.Novy, J.Whitworth 2012. Purple Pelisse: A specialty fingerling potato with purple skin and purple flesh.. American Journal of Potato Research : An Official Publication of the Potato Association of America. 89:306-314.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: This project focuses heavily on advanced agronomic trials to further develop cultivars released by the Pacific Northwest Potato Variety Development Program (PNWPVDP). The germplasm from this program offers a unique opportunity for fundamental research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses in potato. Direct outputs from the PNWPVDP from 2007 through 2011 include the following potato cultivars: Premier Russet (2007), Highland Russet (2007), Yukon Gem (2007), Gallatin Russet (2009), A84180-8 (2008), Classic Russet (2009), Alpine Russet (2009), Clearwater Russet (2009), Owyhee Russet (2009), Red Sunset (2009), Crimson Red (2009), Purple Pelisse (2009), Sage Russet (2010), TerraRosa (2010), AmaRosa (2010), Teton Russet (2011), Palisade Russet (2011), and Huckleberry Gold (2011). All varieties developed by the PNWPVDP have been licensed to the Potato Variety Management Institute (PVMI, www.pvmi.org), a non-profit organization working on behalf of the program since 2005, with the goal of enhancing promotion and marketing efforts. Detailed information about these potato varieties can be found at www.pvmi.org. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Seed Productivity Studies: Results from seed productivity studies are enabling seed growers to manage seed lots to produce tuber size distributions that have maximum yield and economic return potential. The work has resulted in recommendations for managing heat-unit accumulation by seed during maturation and storage, and for grouping compatible cultivars in seed storage in relation to the degree days needed to produce target stem numbers. Basic studies have revealed how temperature during seed production modulates tuber age to affect productive potential the following year. Methods for rejuvenating older seed lots to optimize tuber size distribution have broadened management options for growers. Regulation of Postharvest Quality & Nutritional Attributes of Processing Potatoes: Defining the attainment of physiological maturity for new cultivars has led to management recommendations for optimizing at-harvest and out-of-storage quality and thus profitability for growers. Elucidation of the biochemical/molecular bases for cultivar-dependent differences in low temperature sweetening (LTS) and mottling disorder is identifying genetic markers for selection of cold tolerance for use in the PNWPVDP breeding program. Other studies are revealing how agronomic and environmental variables during production interact to affect retention of postharvest processing and nutritional qualities. Ongoing research on the mechanism(s) of ascorbate accumulation and loss in tubers following harvest are facilitating the selection of high ascorbate-retaining genotypes and may lead to the development of handling and storage protocols to reduce ascorbate loss. Genotypes that produce low asparagine and reducing sugars during production and storage are being selected to reduce acrylamide in the nations food supply. Ongoing studies of agronomic and environmental factors affecting accumulation of these precursors are revealing management techniques for production of low acrylamide forming potential in existing and newly released varieties. Potato Variety Development and Seed Lot Evaluation Studies: The impact of the PNWPVDP on the Washington potato industry is demonstrated by the change in acreage planted to Russet Burbank vs. new cultivars and numbered clones during recent years. Varieties recently released by the Tri-State program (see Outputs) are now produced on over 130,000 acres in the Pacific Northwest with value to growers estimated at approximately $470 million in 2011. Compared with 2010, the 2011 US farm-gate value of Tri-State varieties increased by approximately $55 million. Ranger Russet, Umatilla Russet, Alturas, Premier Russet, Bannock Russet, Western Russet, and Alpine Russet are examples of Tri-State varieties that have greatly benefited the United States and Northwest potato industry, being the 3rd, 4th, 7th, 11th, 14th, 21st, and 24th most widely grown cultivars in the United States in 2011, respectively. Tri-State varieties represented over 20%, or 194,000 acres, of the fall crop nationally in 2011. Many of these varieties are more efficient in use of agronomic inputs (N, P, water, pesticides, etc.) and have resistance to major potato disease.

Publications

• Whitworth, J., R.Novy, J.C.Stark, J.J.Pavek, D.L.Corsini, S.L.Love, N.Olsen, S.Gupta, T.L.Brandt, M.I.Vales, A.R.Mosley, S.Yilma, S.R.James, D.C.Hane, B.A.Charlton, C.C.Shock, N.R.Knowles, M.J.Pavek, J.S.Miller, and C.R.Brown. 2011. Alpine Russet: A potato cultivar having long term tuber dormancy making it suitable for processing from long-term storage. American Journal of Potato Research : An Official Publication of the Potato Association of America. 88:256-268.
• Weeda, S.M., M.G.Kumar, and N.R.Knowles. 2011. Protein mobilization from potato tubers during long-term storage and daughter tuber formation. International Journal of Plant Sciences. 172:459-470.
• Novy, R., J.Whitworth, J.C.Stark, B.A.Charlton, S.Yilma, N.R.Knowles, M.J.Pavek, T.L.Brandt, S.Gupta, N.Olsen, R.K.Thornton, C.R.Brown, D.L.Corsini, J.J.Pavek, S.R.James, D.C.Hane, H.Lozoya-Saldana, and M.I.Vales. 2011. Palisade Russet: A late blight resistant potato cultivar having a low incidence of sugar ends and high specific gravity. American Journal of Potato Research : An Official Publication of the Potato Association of America. 10.1007/s12230-011-9224-1.

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: From 2006 through 2010, the following potato varieties were officially released by the Northwest Potato Variety Development (NWPVD) Program (also known regionally as the Tri-State Program): Premier Russet (2007), Highland Russet (2007), Yukon Gem (2007), Gallatin Russet (2009), A84180-8 (2008), Classic Russet (2009), Alpine Russet (2009), Clearwater Russet (2009), Owyhee Russet (2009), Red Sunset (2009), Crimson Red (2009), Purple Pelisse (2009), Sage Russet (2010), TerraRosa (2010), and AmaRosa (2010). All varieties developed by the NWPVD Program have been licensed to the Potato Variety Management Institute (PVMI, www.pvmi.org), a non-profit organization working on behalf of the program since 2005, with the goal of enhancing promotion and marketing efforts. Detailed information about these potato varieties can be found at www.pvmi.org. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Seed Productivity Studies: Results from seed productivity studies are enabling seed growers to manage seed lots to produce tuber size distributions that have maximum yield and economic return potential. The work has resulted in recommendations for managing heat-unit accumulation by seed during maturation and storage, and for grouping compatible cultivars in seed storage in relation to the degree days needed to produce target stem numbers. Methods for handling Summit seed to overcome delayed emergence and low yield have been developed and are being implemented commercially. Methods for rejuvenating older seed lots to optimize tuber size distribution have broadened management options for growers. Regulation of Postharvest Quality & Nutritional Attributes of Processing Potatoes: Defining the sensitivities of new cultivars to end-of-season tuber maturity for retention of processing quality has led to management recommendations for optimizing at-harvest and out-of-storage quality and thus profitability for growers. Elucidation of the biochemical/molecular bases for cultivar-dependent differences in LTS and mottling disorder is identifying genetic markers for selection of cold tolerance for use in the breeding program. Studies on the effects of tuber maturity on wound-healing ability and resistance to desiccation and pathogens have led to recommendations for end-of-season crop management (vine desiccation, storage temperature and vapor pressure deficit) to optimize wound-healing and minimize shrink for these cultivars. Understanding the mechanism(s) by which ascorbate declines in tubers following harvest will facilitate the selection of high ascorbate-retaining genotypes and may lead to the development of handling and storage protocols to reduce ascorbate loss. Potato Variety Development and Seed Lot Evaluation Studies: The impact of the Pacific Northwest Potato Variety Development program on the Washington potato industry is demonstrated by the change in acreage planted to Russet Burbank vs. new cultivars and numbered clones during recent years. Varieties recently released by the Tri-State program are now produced on over 110,000 acres with value to growers estimated at approximately $150 million. This impact is expected to increase. A recent economic analysis of the program revealed that every dollar invested in the program results in a $39 return. As improved varieties are adopted, quality and production efficiency will improve, fertilizer and pesticide inputs will decrease, and environmental impact will be lessened. The overall impact will be to maintain or improve the competitiveness of the Northwest potato industry, assist farmers to retain their way of life, and improve the safety and quality of the work environment for all involved in potato production. Two Tri-State releases, Ranger Russet and Alturas, are the 3rd and 7th most widely grown potato varieties in the United States. In 2002, the Tri-State variety development program released the cultivar 'Alturas', which produces yields similar to or greater than the mainstay cultivar, 'Russet Burbank', while using 50% less nitrogen.

Publications

• Novy, R., J.Whitworth, J.C.Stark, S.L.Love, D.L.Corsini, J.J.Pavek, M.I.Vales, S.R.James, D.C.Hane, C.C.Shock, B.A.Charlton, C.R.Brown, N.R.Knowles, M.J.Pavek, T.L.Brandt, S.Gupta, and N.Olsen. 2010. Clearwater Russet: A dual-purpose potato cultivar with cold sweetening resistance, high protein content, and a low incidence of external defects and sugar ends. American Journal of Potato Research: An Official Publication of the Potato Association of America. 87:458-471.
• Stark, J.C., R.Novy, J.Whitworth, N.R.Knowles, M.J.Pavek, S.L.Love, M.I.Vales, S.R.James, D.C.Hane, C.R.Brown, B.A.Charlton, D.L.Corsini, J.J.Pavek, T.L.Brandt, and N.Olsen. 2010. Classic Russet: An Early Season Potato Variety with High Yields of U.S. No. 1 Tubers and Excellent Fresh Market Characteristics. American Journal of Potato Research: An Official Publication of the Potato Association of America. 87:360-373.
• Kumar, M.G., E.Lulai, J.Suttle, and N.R.Knowles. 2010. Age-induced loss of wound-healing ability in potato tubers is partly regulated by ABA. Planta. 232:1433-1445.
• Whitworth, J., R.Novy, J.C.Stark, J.J.Pavek, D.L.Corsini, S.L.Love, J.S.Miller, M.I.Vales, A.R.Mosley, S.Yilma, S.R.James, D.C.Hane, B.A.Charlton, C.R.Brown, N.R.Knowles, and M.J.Pavek. 2010. Yukon Gem: A yellow-fleshed potato cultivar suitable for fresh-pack and processing with resistances to PVYo and late blight. American Journal of Potato Research: An Official Publication of the Potato Association of America. 87:327-336.
• Weeda, S.M., M.G.Kumar, and N.R.Knowles. 2010. Correlative changes in proteases and protease inhibitors during mobilization of protein from potato (Solanum tuberosum L.) seed-tubers. Functional Plant Biology. 37:32-42.

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: The way in which seed-tubers are handled can significantly affect physiological age and thus productive potential. Seed-tuber age is affected by time and temperature, especially during the period from vine kill to planting. The respiration rate of tubers increases with temperature, which in turn accelerates the rate of aging. One way to estimate physiological age is to track the number of degree-days (heat-units) from vine kill through storage and handling to planting. This can be calculated in degrees centigrade or Fahrenheit by subtracting a base temperature of 4oC (39oF) from the average tuber pulp temperature on a particular day and summing the daily values over an extended period (e.g. from vine kill through storage to planting) to arrive at the total accumulated degree-days for a particular seed lot. The number of stems per seedpiece increases with increasing degree-days (age). Tuber set per hill increases with stem number, resulting in a decrease in average tuber size. At particular in-row spacing, the tuber set and final size distribution are largely dictated by the average stem number per seedpiece. Hence, there is an opportunity to control tuber size distribution and potentially add value to seed, processing, and fresh market crops by managing seed-tuber age and stem numbers. Toward this goal, we have modeled these relationships for Umatilla Russet, Russet Burbank, Ranger Russet, three Norkotah selections, and Shepody. Biochemical markers of seed age for these cultivars were identified and we have further demonstrated that crop value can be enhanced substantially by manipulating age. Stem number and tuber set relationships for Premier Russet, Summit Russet, GemStar Russet, and A95109 are now being modeled. PARTICIPANTS: Seed potato growers. TARGET AUDIENCES: Researchers and the potato industry. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Based on the results from our studies, seed growers are altering the way in which they manage seed at the end of the growing season and throughout storage to maximize productive and economic value to commercial growers.

Publications

• Weeda, S., M.G.Kumar, and N.R.Knowles. 2009. Developmentally linked changes in proteases and protease inhibitors suggest a role for potato multicystatin in regulating protein content of potato tubers. Planta. 230:73-84.
• Stark, J.C., R.Novy, J.Whitworth, S.L.Love, D.L.Corsini, J.J.Pavek, M.I.Vales, S.R.James, D.C.Hane, B.A.Charlton, C.R.Brown, N.R.Knowles, M.J.Pavek, T.L.Brandt, and N.Olsen. 2009. Highland Russet: A Full Season, Processing Variety with High Yields of Uniform U.S. No. 1 Tubers. American Journal of Potato Research : An Official Publication of the Potato Association of America. 86:171-182.
• Knowles, N.R., E.Driskill, and L.Knowles. 2009. Sweetening responses of potato tubers of different maturity to conventional and non-conventional storage temperature regimes. Postharvest Biology and Technology. 52:49-61.
• Nissen, M.S., M.G.Kumar, B.Youn, D.Knowles, K.Lam, N.R.Knowles, and C.Kang. 2009. Characterization of Solanum tuberosum Multicystatin and its Structural comparison with other Cystatins. The Plant Cell. 21:861-875.

Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: The way in which seed-tubers are handled can significantly affect physiological age and thus productive potential. Seed-tuber age is affected by time and temperature, especially during the period from vine kill to planting. The respiration rate of tubers increases with temperature, which in turn accelerates the rate of aging. One way to estimate physiological age is to track the number of degree-days (heat-units) from vine kill through storage and handling to planting. This can be calculated in degrees centigrade or Fahrenheit by subtracting a base temperature of 4oC (39oF) from the average tuber pulp temperature on a particular day and summing the daily values over an extended period (e.g. from vine kill through storage to planting) to arrive at the total accumulated degree-days for a particular seed lot. The number of stems per seedpiece increases with increasing degree-days (age). Tuber set per hill increases with stem number, resulting in a decrease in average tuber size. At particular in-row spacing, the tuber set and final size distribution are largely dictated by the average stem number per seedpiece. Hence, there is an opportunity to control tuber size distribution and potentially add value to seed, processing, and fresh market crops by managing seed-tuber age and stem numbers. Toward this goal, we have modeled these relationships for Umatilla Russet, Russet Burbank, Ranger Russet, three Norkotah selections, and Shepody. Biochemical markers of seed age for these cultivars were identified and we have further demonstrated that crop value can be enhanced substantially by manipulating age. Stem number and tuber set relationships for Premier Russet, Summit Russet, GemStar Russet, and A95109 are now being modeled. Knowles, N.R., and L.Knowles. 2008. Use of C3 to C14 aliphatic aldehydes, ketones, and primary and secondary C3 to C7 alcohols to inhibit sprouting of potato tubers. Full patent application filed in USPTO Aug. 6, 2008, serial no. 12/186,861. Patent 60/955,156. PARTICIPANTS: L.O. Knowles; M. Martin, J.R. Simplot; G. Harris, RDO; Philip Gross, Spokane Hutterian Bretheren TARGET AUDIENCES: Potato Scientific Community; Potato Industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Based on the results from our studies, seed growers are altering the way in which they manage seed at the end of the growing season and throughout storage to maximize productive and economic value to commercial growers.

Publications

• Mosley, A.R., S.Yilma, D.C.Hane, S.R.James, K.A.Rykbost, C.C.Shock, S.L.Love, D.L.Corsini, J.J.Pavek, R.K.Thornton, B.A.Charlton, E.P.Eldredge, R.Novy, M.J.Pavek, N.R.Knowles, J.Whitworth, C.R.Brown, J.C.Stark, and M.I.Vales. 2008. Willamette: A chipping cultivar with high yield and specific gravity, low incidence of hollow heart and brown center, and suitability for fresh-market usage. American Journal of Potato Research : An Official Publication of the Potato Association of America. 85(1):85-92.
• Novy, R., J.Whitworth, J.C.Stark, S.L.Love, D.L.Corsini, J.J.Pavek, M.I.Vales, S.R.James, D.C.Hane, C.C.Shock, B.A.Charlton, C.R.Brown, N.R.Knowles, M.J.Pavek, T.L.Brandt, and N.Olsen. 2008. Premier Russet: A dual-purpose potato cultivar with significant resistance to low temperature sweetening during long-term storage. (selected as cover feature article). American Journal of Potato Research : An Official Publication of the Potato Association of America. 85(3):198-209.
• Knowles, N.R., E.Driskill, and L.Knowles. 2008. Sweetening responses of potato tubers of different maturity to conventional and non-conventional storage temperature regimes. http://dx.doi.org/10.1016/j.postharvbio.2008.08.015. Postharvest Biology and Technology. published online first.

Progress 01/01/07 to 12/31/07

Outputs
The way in which seed-tubers are handled can significantly affect physiological age and thus productive potential. Seed-tuber age is affected by time and temperature, especially during the period from vine kill to planting. The respiration rate of tubers increases with temperature, which in turn accelerates the rate of aging. One way to estimate physiological age is to track the number of degree-days (heat-units) from vine kill through storage and handling to planting. This can be calculated in degrees centigrade or Fahrenheit by subtracting a base temperature of 4oC (39oF) from the average tuber pulp temperature on a particular day and summing the daily values over an extended period (e.g. from vine kill through storage to planting) to arrive at the total accumulated degree-days for a particular seed lot. The number of stems per seedpiece increases with increasing degree-days (age). Tuber set per hill increases with stem number, resulting in a decrease in average tuber size. At a particular in-row spacing, the tuber set and final size distribution are largely dictated by the average stem number per seedpiece. Hence, there is an opportunity to control tuber size distribution and potentially add value to seed, processing, and fresh market crops by managing seed-tuber age and stem numbers. Toward this goal, we have modeled these relationships for Umatilla Russet, Russet Burbank, Ranger Russet, three Norkotah selections, and Shepody. Biochemical markers of seed age for these cultivars were identified and we have further demonstrated that crop value can be enhanced substantially by manipulating age. Stem number and tuber set relationships for Premier Russet, Summit Russet, GemStar Russet, and A95109 are now being modeled.

Impacts
Since contracts for processing, fresh market, and seed potatoes favor certain size classes, the value of a crop can be altered substantially by manipulating age and thus average stem numbers produced by a particular seed lot. Therefore, variation in accumulated degree-days among seed lots can translate into variable economic returns from the corresponding commercial crops. Developing practical methods for controlling this variation presents both a challenge and an opportunity for seed and commercial growers to increase crop value. Based on our studies, seed growers are altering the way in which they manage seed at the end of the growing season and throughout storage to maximize productive and economic value to commercial growers.

Publications

• Kumar, M.G., S.P.Iyer, and N.R.Knowles. 2007. Strboh A homologue of NADPH oxidase regulates wound-induced oxidative burst and facilitates wound-healing in potato tubers. Planta. 227(1):25-36.
• Knowles, N.R., and E.S.Plissey. 2007. Maintaining tuber health during harvest, storage, and post-storage handling. In Potato Health Management, D. Johnson ed. 2nd ed. APS Press. 79-99 (ch 10, invited).
• Kumar, M.G., S.P.Iyer, and N.R.Knowles. 2007. Extraction of RNA from fresh, frozen, and lyophilized tuber and root tissues. Journal of Agricultural and Food Chemistry. 55:1674-1678.
• Driskill, E., L.Knowles, and N.R.Knowles. 2007. Temperature-induced changes in potato processing quality during storage are modulated by tuber maturity. American Journal of Potato Research: An Official Publication of the Potato Association of America. 84:367-383 (journal cover feature article).
• Stark, J.C., R.Novy, S.L.Love, J.Whitworth, D.L.Corsini, J.J.Pavek, A.R.Mosley, M.J.Pavek, N.R.Knowles, R.K.Thornton, S.R.James, D.C.Hane, N.Olsen, M.I.Vales, and D.Hammond. 2007. Blazer Russet: an early to mid-season potato cultivar with high U.S. No. 1 Yields and good processing qualities. American Journal of Potato Research : An Official Publication of the Potato Association of America. 84(6):467-477.
• Knowles, N.R. 2007. Stages of physiological age of seed tubers. In Potato Health Management, D. Johnson ed., 2nd ed. p. 48 ch 7., APS Press.

Progress 01/01/06 to 12/31/06

Outputs
The goal of this research is to develop and commercialize new potato varieties to benefit the Northwest potato industry. During the past 3 years, 4 new potato varieties have been released - Western Russet, GemStar Russet, Defender and Blazer Russet. In addition, 3 new cultivars are being prepared for release - Premier Russet, Highland Russet and Yukon Gem. Western Russet is the result of an Aberdeen USDA/ARS cross and produces high yields of long, russeted tubers that have excellent quality for both the fresh market and processing uses. GemStar Russet resulted from an Aberdeen USDA/ARS cross and is a medium maturing variety with outstanding yield potential, excellent tuber appearance, and resistance to cold sweetening, giving it potential for both fresh market and processing uses. Defender, an Aberdeen USDA/ARS cross, is the first product of breeding efforts in the Northwest to develop late blight resistant varieties with processing quality, and is the first potato released in the U.S. that combines French fry processing quality with a high level of resistance to late blight. It has been tested under heavy disease pressure and shows potential to provide a four- to five-fold reduction in fungicide application. Blazer Russet is an early to mid-season variety notable for its high yield of oblong-long, medium-russeted tubers and resistances to sugar ends, tuber malformations and most internal and external defects. It shows good potential for both processing and fresh markets, with the processing industry viewing Blazer Russet as a replacement for Shepody, an early harvest variety widely grown in the U.S. Premier Russet is a mid- to late-season variety notable for its high yield, high percentage of U.S. No. 1's, attractive tuber appearance, high specific gravity, excellent fry color from cold storage and resistances to sugar ends, tuber malformations and most internal and external defects. Premier Russet is highly resistant to the accumulation of reducing sugars following long-term storage at 40-45 degrees F. This characteristic allows storage at colder temperatures, thereby prolonging tuber dormancy and quality for processing or fresh pack use. Premier Russet should be useful in both tablestock and processing markets. It also has a high level of resistance to PVY and good resistance to Verticillium wilt. Highland Russet is a mid- to late-season variety notable for its high yield of large, uniform tubers, moderately high specific gravity and resistance to tuber malformations and most internal and external defects. It also has reasonably good resistance to Verticillium wilt and PVY. Highland Russet has been successfully grown and processed in commercial trials. Fry recovery from the field and storage has been high and it shows good potential for the processing market. Yukon Gem is an advanced selection with light-yellow flesh and higher yield potential than Yukon Gold (its paternal parent). Total yield across all western regional sites was 36, 82, and 118 cwt greater than Yukon Gold in 2002, 2003, and 2004, respectively. Merit for fresh pack was comparable to Yukon Gold in all three years.

Impacts
The fresh market industry, French fry processors and chippers have incorporated varieties developed through the Tri-State variety development program into their businesses. Two Tri-State releases, Ranger Russet and Alturas, are the 3rd and 7th most widely grown potato varieties in the United States. In 2002, the Tri-State variety development program released the cultivar 'Alturas', which produces yields similar to or greater than the mainstay cultivar 'Russet Burbank' while using 50% less nitrogen. Production of Alturas in ID, OR, and WA jumped to over 18,000 acres in just 2 years, potentially reducing the amount of nitrogen applied to the soil by 2.7 million lbs compared with the same acreage planted to Russet Burbank. The reduced use of nitrogen may translate into less nitrate-contaminated ground water. The potential economic savings to NW growers was $1.3 million or $72 per acre. Varieties recently released by the Tri-State program are now produced on over 110,000 acres with value to growers estimated at approximately $150 million. This impact is expected to increase. A recent economic analysis of the program revealed that every dollar invested in the program results in a $39 return (Araji and Love, 2002). As improved varieties are adopted, quality and production efficiency will improve, fertilizer and pesticide inputs will decrease, and environmental impact will be lessened. The overall impact will be to maintain or improve the competitiveness of the Northwest potato industry.

Publications

• Knowles, N.R., and L. Knowles. 2006. Manipulating stem number, tuber set, and yield relationships for northern- and southern-grown potato seed lots. Crop Science. 46:284-296.
• Grunenfelder, L., L. Knowles, L.K. Hiller, and N.R. Knowles. 2006. Glycoalkaloid development during greening of fresh market potatoes (Solanum tuberosum L.). Journal of Agricultural and Food Chemistry. 54:5847-5854.
• Grunenfelder, L., L.K. Hiller, and N.R. Knowles. 2006. Color indices for the assessment of chlorophyll development and greening of fresh market potatoes. Postharvest Biology and Technology. 40:73-81.
• Love, S.L., R. Novy, J. Whitworth, D.L. Corsini, J.J. Pavek, A.R. Mosley, R.K. Thornton, N.R. Knowles, S.R. James, and D.C. Hane. 2006. Summit Russet: A long russet potato variety with good fresh market and frozen processing quality and resistance to internal and external tuber defect. American Journal of Potato Research: An Official Publication of the Potato Association of America. 82:425-432.
• Novy, R., S.L. Love, D.L. Corsini, J.J. Pavek, J. Whitworth, A.R. Mosley, S.R. James, D.C. Hane, C.C. Shock, K.A. Rykbost, C.R. Brown, R.K. Thornton, N.R. Knowles, M.J. Pavek, N. Olsen, and D.A. Inglis. 2006. Defender: A high-yielding, processing potato cultivar with foliar and tuber resistance to late blight. American Journal of Potato Research: An Official Publication of the Potato Association of America. 83:9-19.
• Love, S.L., R. Novy, J. Whitworth, D.L. Corsini, J.J. Pavek, A.R. Mosley, M.J. Pavek, N.R. Knowles, C.R. Brown, S.R. James, and D.C. Hane. 2006. GemStar Russet: A new russet potato variety with high yield, good culinary quality, excellent fresh market appearance, and resistance to common scab. American Journal of Potato Research: An Official Publication of the Potato Association of America. 83:171-180.
• Love, S.L., R. Novy, J. Whitworth, D.L. Corsini, J.J. Pavek, A.R. Mosley, M.J. Pavek, N.R. Knowles, C.R. Brown, S.R. James, and D.C. Hane. 2006. Western Russet: A new potato variety with excellent fresh market and frozen-fried processing quality and field resistance to common scab and PVY. American Journal of Potato Research: An Official Publication of the Potato Association of America. 83:161-169.

Progress 01/01/05 to 12/31/05

Outputs
A potential marker of tuber age and productivity may be 2-methyl-1-butanol. The level of this compound was higher in seed aged at higher temperatures during storage, and correlated well with stem numbers (and thus tuber set and yield) from different ages of Ranger and Russet Burbank seed. Hence, seed butanol content predicts the average stem number per seedpiece prior to planting, from which the potential yield profile for a particular seedlot can be estimated. This marker shows promise in enabling prediction of stem numbers and thus yield potential of seed prior to planting. Our research at the Othello Field Station is currently focusing on modeling stem number/tuber set relationships for Russet Norkotah strains, so that tuber size profiles can be controlled with greater precision for the fresh market. We are also extending our seed productivity studies on Ranger and Russet Burbank to determine how at-harvest seed maturity interacts with storage and handling of seed prior to planting, to affect yield potential. Studies to determine the extent to which predicted yields (based on stem counts after planting and seed butanol content before planting) can be altered through adjusting management practices, such as in-row spacing, are also underway. Our research has demonstrated that: (1) Aging seed in storage affects the productivity of Russet Burbank, Ranger Russet and Umatilla Russet seed-tubers primarily by altering stem number/tuber set relationships, resulting in substantial shifts in tuber size distribution. (2) Within limits, manipulating seed storage temperature can effectively change tuber size distribution to meet market requirements without affecting total, U.S. #1 or marketable yields. (3) Umatilla was the most sensitive to aging treatments for a shift in tuber size distribution and a decline in productivity, followed by Ranger and Russet Burbank. This underscores the need for good temperature management of Umatilla seed after harvest. (4) 'Northern vigor' was nonexistent in Russet Burbank and Ranger seed (total, U.S. No. 1 and marketable yields were equivalent for northern and southern seed). However, the size distribution of U.S. No. 1 and marketable tubers was affected by seed source; northern seed produced more oversize (>14 oz) tubers than southern seed. (5) Tuber set and size development can be predicted from early-season stem counts for Russet Burbank, Ranger and Umatilla Russet potatoes, providing an opportunity to adjust management practices to optimize yield for a particular market. (6) Seed butanol concentration can predict stem numbers in Ranger Russet and Russet Burbank seed, providing a potential marker of the relative productivity of different ages of seed-tubers prior to planting.

Impacts
This research has had a positive impact on seed and commercial potato growers. Both segments of the industry now recognize that there is an opportunity to add value to both seed and commercial crops by controlling the physiological age of potato seed-tubers. Seed growers are beginning to keep track of the heat-units accumulated by their crops from vine kill to planting the following season. This information can be used as a marketing tool to enhance the value of a particular seed crop. Seed growers recognize that providing a crop that consistently produces the same stem numbers year after year will allow commercial growers to adjust management practices to optimize tuber size distribution profiles for maximum value. Our research has identified optimal spacing in relation to stem numbers for maximizing yield of the most desirable tuber size classes for seed, fresh, and processing markets for the main fresh and processing cultivars produced in the Pacific Northwest.

Publications

• Knowles, N.R. and L.O. Knowles. 2005. Seed productivity research: precision control of tuber size distribution. In: Proceedings of the 44th Annual Washington State Potato Conference, Moses Lake, WA. pp. 45-56.
• Knowles, N.R., L.O. Knowles and M.M. Haines. 2005. 1,4-Dimethylnapthalene treatment of seed potatoes affects tuber size distribution. Am. J. Pot. Res. 82:179-190.

Progress 01/01/04 to 12/31/04

Outputs
The main goals of this project are to identify biochemical/physiological markers of potato seed-tuber age and determine their efficacy for predicting the relative productivity of different lots of seed-tubers. The project has accomplished the following: 1.) Comparative evaluation of newly released cultivars (Ranger and Umatilla Russet) for responses to factors (growing environment, storage) that affect physiological age of seed, and elucidation of the postharvest handling procedures that may be useful for manipulating seed age to optimize yield and grade for various markets. The relative sensitivity to yield modification, induced by variation in seed storage temperature, was characterized for each cultivar. 2.) Characterization of the growth and yield responses from northern- and southern-grown seed in the Columbia Basin. This knowledge will provide growers the opportunity to adjust management practices to achieve maximum productivity (yield & grade) for a particular market, when using seed from these areas. 3.) Basic relationships among stem numbers, tuber set, yield, and tuber size distribution were established and modeled for Ranger Russet, Umatilla Russet and Russet Burbank cultivars. The resulting models provided the basis for development of relative 'Crop Productivity Estimator' calculators for northern- and southern-produced seed for use by the WA potato industry. 4.) 2-methyl butanol was identified as a metabolic marker of relative seed productivity and was incorporated into the 'Crop Productivity Estimator'. When assayed at the end of the storage season, this marker accurately predicted the productive potential of our RB seed over three seasons. Pending further research, this marker and related compounds may provide the industry with an effective means by which to evaluate the relative productivity of seed prior to planting.

Impacts
The butanol content of seed-tubers at the end of the storage season (i.e. prior to planting) was a good indicator of the number of aboveground mainstems produced from both northern- and southern-grown Russet Burbank seed-tubers planted in the Columbia Basin. Since tuber set and size distribution could be predicted from stem numbers, the concentration of 2-m-butanol in seed can be used as a relative indicator of seed productivity. Productivity, however, can be defined in many ways. For example, productivity could simply refer to the total, U.S. #1 or marketable yields. Such a narrow definition is not adequate, however, since it is possible for these yields to be equal among different ages of seed-tubers, while the yield profile (e.g. tuber size distribution) varies greatly, as demonstrated for different seed sources and/or selected physiological ages. To encompass the widest possible use of butanol as a marker, I have defined productivity in terms of relative tuber size distribution and marketable yield. The butanol content of RB seed-tubers can thus be used to estimate stem number, tuber set, tuber size profile and marketable yields from northern- and southern-grown seed planted in the Columbia Basin (due to high correlation with stem numbers and thus tuber set and % yields of various size classes making up marketable yield). The research has led to the development of seed and crop productivity estimators for the Columbia Basin of WA state.

Publications

• Knowles, N.R. 2004. Potato Crop Productivity Estimator for the Columbia Basin. www.ionophore.com/seed. This interactive website was constructed to illustrate stem number/tuber set relationships for the major processing potato cultivars produced in the Columbia Basin. The website incorporates four years of field research data. Based on early season stem counts, growers can predict and manipulate tuber size distribution to match market requirements.
• Knowles, N.R., L.O. Knowles and G.N.M. Kumar. 2004. Predicting the yield potentials of northern and southern seed lots in the Columbia Basin. Proceedings of the 87th Annual Meeting of the Potato Association of America, American Journal of Potato Research 81:70.
• Kumar, G.N.M., L.O. Knowles and N.R. Knowles. 2004. Physiological basis for the loss of wound-healing ability with advancing tuber age. Proceedings of the 87th Annual Meeting of the Potato Association of America, American Journal of Potato Research 81:70-71.
• Ozga, J.A., D.M. Reinecke and N.R. Knowles. 2004. Characterization of the loss of seedling vigor in pea (Pisum sativum L.). Canadian Journal of Plant Science 84:443-451.

Progress 01/01/03 to 12/31/03

Outputs
The main goals of this project are to identify biochemical/physiological markers of potato seed-tuber age and determine their efficacy for predicting the relative productivity of different lots of seed-tubers. The project has accomplished the following: 1.) Comparative evaluation of newly released cultivars (Ranger and Umatilla Russet) for responses to factors (growing environment, storage) that affect physiological age of seed, and elucidation of the postharvest handling procedures that may be useful for manipulating seed age to optimize yield and grade for various markets. The relative sensitivity to yield modification, induced by variation in seed storage temperature, was characterized for each cultivar. 2.) Characterization of the growth and yield responses from northern- and southern-grown seed in the Columbia Basin. This knowledge will provide growers the opportunity to adjust management practices to achieve maximum productivity (yield & grade) for a particular market, when using seed from these areas. 3.) Basic relationships among stem numbers, tuber set, yield, and tuber size distribution were established and modeled for Ranger Russet, Umatilla Russet and Russet Burbank cultivars. The resulting models provided the basis for development of relative "Crop Productivity Estimator" calculators for northern- and southern-produced seed for use by the WA potato industry. 4.) 2-methyl butanol was identified as a metabolic marker of relative seed productivity and was incorporated into the "Crop Productivity Estimator". When assayed at the end of the storage season, this marker accurately predicted the productive potential of our RB seed over three seasons. Pending further research, this marker and related compounds may provide the industry with an effective means by which to evaluate the relative productivity of seed prior to planting.

Impacts
The butanol content of seed-tubers at the end of the storage season (i.e. prior to planting) was a good indicator of the number of aboveground mainstems produced from both northern- and southern-grown Russet Burbank seed-tubers planted in the Columbia Basin. Since tuber set and size distribution could be predicted from stem numbers, the concentration of 2-m-butanol in seed can be used as a relative indicator of seed productivity. Productivity, however, can be defined in many ways. For example, productivity could simply refer to the total, U.S. #1 or marketable yields. Such a narrow definition is not adequate, however, since it is possible for these yields to be equal among different ages of seed-tubers, while the yield profile (e.g. tuber size distribution) varies greatly, as demonstrated for different seed sources and/or selected physiological ages. To encompass the widest possible use of butanol as a marker, I have defined productivity in terms of relative tuber size distribution and marketable yield. The butanol content of RB seed-tubers can thus be used to estimate stem number, tuber set, tuber size profile and marketable yields from northern- and southern-grown seed planted in the Columbia Basin (due to high correlation with stem numbers and thus tuber set and % yields of various size classes making up marketable yield). The research has led to the development of seed and crop productivity estimators for the Columbia Basin of WA state.

Publications

• Al-Saad, K.A., V. Zabrouskov, W.F. Siems, N.R. Knowles and H.H. Hill Jr. 2003. Structural analysis of phosphatidylcholine by post-source decay matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Journal American Society of Mass Spectrometry 14:373-382.
• Al-Saad, K.A., V. Zabrouskov, W.F. Siems, N.R. Knowles, R.M. Hannan and H.H. Hill Jr. 2003. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry of lipids: Ionization and prompt fragmentation patterns. Rapid Communications in Mass Spectrometry 17:87-96.
• Knowles, N.R., D.B. Knowles and L.O. Knowles. 2003. Potato crop productivity estimator for the Columbia Basin. calculator-based computer program launched on the web for use by the WA potato industry. (www.ionophore.com/seed)
• Knowles, N.R., Kumar, G.N.M., Knowles, L.O. and N. Fuller. 2003. Physiological and biochemical markers of potato seed-tuber age and their relevance to production. Washington State Potato Commission Progress Reports for the year 2002 (final report). pp. 71-109.
• Knowles, N.R., L.O. Knowles and G.N.M. Kumar. 2003. Stem number and tuber set relationships for Russet Burbank, Ranger and Umatilla Russet potatoes in the Columbia Basin. Potato Progress 3(13):1-4.
• Kumar, G.N.M. and N.R. Knowles. 2003. Wound-induced superoxide production and PAL activity decline with potato tuber age and wound healing ability. Physiologia Plantarum 117:108-117.