NE1231: Collaborative Potato Breeding and Variety Development Activities to Enhance Farm Sustainability in the Eastern US
(Multistate Research Project)
NE1231: Collaborative Potato Breeding and Variety Development Activities to Enhance Farm Sustainability in the Eastern US
Duration: 10/01/2012 to 09/30/2017
Statement of Issues and Justification
Importance of work - Consumer demographics and food preferences present new challenges for farmers who seek to supply high quality, highly nutritional products to consumers, while maintaining economically and environmentally sustainable production practices. This multidisciplinary regional research project helps farmers address these needs. Specifically, we propose to provide farmers new potato varieties to solve production problems and meet consumers changing needs. These varieties will have improved yields, enhanced fresh market, processing or value-added traits, and better pest resistance resulting in reduced chemical inputs. As evidenced in Appendix 1, we have a solid track record in producing new potato varieties that have been commercially accepted. For example, the varieties Reba, Keuka Gold, Pike, Andover, Harley Blackwell and Marcy have all enjoyed success in the marketplace and occupy significant acreage in the east. We propose to continue our regional collaborative efforts to breed, select, and develop improved potato varieties to enhance marketing opportunities and reduce farm dependence on costly agricultural chemicals (e.g., fertilizers, insecticides, nematicides, fungicides, herbicides, vine desiccants, sprout inhibitors, and disinfection agents). Success in our research efforts will benefit growers and the public because it will result in reduced chemical usage and provide new potato varieties with expanded marketing opportunities. This will lead to a more economically and environmentally sustainable potato production system.
Importance of potato production to the Eastern US - Potato ranks amongst the top three vegetable crops produced in FL, ME, NC, NY, OH, PA and VA (USDA NASS 2009). Potato is also a significant portion of the diversified vegetable industries in many other Eastern states. Cash farm receipts for Eastern potatoes during 2008 were approximately $490 million (USDA NASS, 2009). Multiplier effects in the state and regional economies are many times this amount. For example, the Maine potato industry's total impact on the ME economy was estimated at $540 million sales, $230 million income, and 6,100 jobs earlier in this decade (Planning Decisions, Inc, 2003) and remains at a similar level today. Potato production in the Eastern US occurs under an extremely wide range of production and marketing conditions, ranging from the winter crop in southern FL to the fall storage crops of ME, NY and PA. Markets range from high value, direct sales of specialty varieties to contracting with large, international processing companies. This span of conditions creates a tremendous diversity in variety needs. Due in part to the large population base in the East, fresh market production remains a significant aspect of the potato industry of most Eastern states (e.g., 15% of MEs and 60% of PAs 2010 crop); however, many potato chip plants are located in the Eastern or Southeastern US, accounting for 43 percent of all chips produced nationwide (National Potato Council Potato Statistical Yearbook, 2009). Processing for French fries and chips accounted for 67% of ME's utilization during 2010. Also, ME and NY maintain large, high quality seed potato industries which service most of the Easts seed potato markets. Thus, research aiding the Eastern potato industry impacts markets associated with over half of the US population. Consumers benefit from the release of new potato varieties that provide new, high quality products, facilitate efficient production for fresh market, chipping, and other processing markets in the East, and provide improved pest resistance resulting in less pesticide use.
Needs as indicated by stakeholders - Grower and industry stakeholders need high quality improved varieties for the fresh and processing market segments. Stakeholders want new varieties suited to the demanding quality needs of each market segment. New varieties are needed which are also resistant to diseases and insects. In this long-term project, stakeholders have always had a key role in our potato breeding, evaluation, and variety development efforts. Variety adoption is impossible without active interaction between researchers, extension, growers, and industry. All Eastern potato breeding programs utilize direct input from growers, processors, and industry groups (e.g., National Potato Council executive board, state grower associations, processors, and individual growers, etc.) to provide input on needs and establish priorities for their breeding efforts. The breeding efforts described in this project proposal (e.g., disease resistance, quality attributes, yield, etc.) are a direct result of this input process.
New red-skinned varieties, in particular, are in high demand. A premium-priced market exists for red-skinned and novelty varieties. For reds, the skin color needs to be bright and stable in storage. Resistance to skinning, netting, and silver scurf are especially important. Novelty varieties (e.g., fingerlings, purple-skinned, blue-skinned, and multi-colored-flesh types) are growing in popularity in the high-value, direct-sale market. Better-adapted novelty varieties would offer new marketing opportunities to many Eastern growers. The organic sector is also a very rapidly increasing production and marketing segment that would benefit greatly from varieties developed by this project. New varieties containing multiple resistances to insects, pathogens and stress factors would provide better performance without chemical inputs in this growing market segment.
For the processing types, two distinct marketing opportunities exist for chip potatoes in the Eastern region. Potato producers from the southern areas (FL, NC, VA, NJ, OH) sell their potatoes for processing directly following harvest. The variety requirements for these regions stress earliness, chip quality from the field, and tolerance to high temperatures during bulking. Atlantic currently predominates in these areas; however, it is very susceptible to internal heat necrosis (IHN), a serious quality defect throughout many of the Eastern-coastal and Southeastern states (Henninger et al., 1979; Yencho et al., 2008). Harley Blackwell, released in 2003 by the USDA ARS is resistant to IHN, but when commercial quantities of this clone were grown it was observed that under stress this variety developed a physiological defect called star cracking. Because of this defect, and because its specific gravity is not as high as Atlantic, its utilization has been limited. Thus, the southeastern US still needs new varieties that are free of IHN and produce high quality chips within seven days of harvest, while still maintaining the high yields and high specific gravity of Atlantic.
Contrasted with the south, processing growers from the northern states (PA, NY, and ME) sell most of their crop following storage. These growers need high yielding, high specific gravity varieties with low defect levels and the ability to process into chips or fries from long-term cold storage. Most of the russet- and French fry-type varieties developed in the western and mid-western states are poorly adapted to the East, as is the standard variety, Russet Burbank. A major goal is to develop russet varieties with high yield, improved disease resistance, uniform long tuber shape, high specific gravity, low internal and external defects, and acceptable fry color under Eastern growing conditions. This is critical for Maine's French fry markets and could allow expansion of French fry processing into other Eastern states.
In all market sectors, disease- and insect-resistant varieties are also needed for the Eastern potato production system. Commercially produced potato, Solanum tuberosum spp. tuberosum, in North America lacks sufficient resistance to many important pests. While significant progress has been made addressing these needs, much work remains. Foliar fungicide applications for control of late blight (Phytophthora infestans) and early blight (Alternaria solani) account for approximately 80% of the pesticide active ingredient applied to Eastern potatoes during a typical growing season. These applications are costly to growers and may result in chronic environmental degradation and/or health problems for agricultural workers. Disease and insect resistant varieties provide an economical and environmentally sound alternative to pesticide use.
Concerted efforts are needed to identify new genetic sources of resistance and incorporate them into productive S. tuberosum clones. In addition to late blight, early blight, white mold (Sclerotinia sclerotiorum) and verticillium wilt (Verticillium dahliae and V. albo-atrum), which are visibly present in foliage and destroy the crop or reduce yield and quality, numerous other pests and diseases hamper potato production in the region. Colorado potato beetle (CPB, Leptinotarsa decemlineata), aphids (e.g., Myzus persicae and Macrosiphum euphorbae), and leaf hoppers (Empoasca fabae) are commonly encountered insect pests in the Eastern United States. Cosmetic diseases of the potato tuber such as scab (Streptomyces spp.), silver scurf (Helminthosporium solani), black scurf (Rhizoctonia solani), and powdery scab (Spongospora subterranea), can result in a crop that is unmarketable for seed or table use. Wart (Synchytrium endobioticum Schilb.) and golden nematode (Globodera rostochiensis) are so destructive to the potato crop that their spread is controlled by quarantine regulations. Other nematodes (e.g., Pratylenchus spp.) are widespread and are controlled by chemical fumigation and crop rotation. Virus diseases (e.g., potato viruses A, M, S, X, Y; potato leafroll virus, potato spindle tuber viroid, tobacco rattle virus) that impact potato productivity and quality are controlled by eliminating insect vectors that spread several of the diseases, sanitation, and propagation of virus-free seed. Similarly, bacterial ring rot (Clavibacter michiganense subsp. sepedonicus) is a destructive potato pest that is controlled by sanitation, careful inspection, and strict seed production regulations. Once the crop is in storage, storage decay caused by a range of pathogenic organisms (e.g., Erwinia carotovora, Phytophthora erythroseptica, Pythium spp, Fusarium spp., P. infestans, and A. solani) can cause complete and devastating losses to growers.
Advantages of a collaborative, multistate research project - This project addresses the needs of the Eastern potato industry through a collaborative process of potato breeding, selection, evaluation, and variety release (see Appendix 2 for a flow chart of this system). This project is a highly collaborative project involving eight states and five breeding programs in the Eastern US. Our project encourages pooling of regional resources and promotes collaboration and communication among researchers and stakeholders - all with the aim of enhancing farmer's ability to provide a safe and nutritious supply of potatoes to consumers in an environmentally sustainable manner that enhances profits and rural America. Our overall goal is to develop an array of attractive, high yielding, disease- and insect-resistant, tablestock, processing and/or specialty-type potato varieties that can be produced by potato farmers in the Eastern US for a diverse consumer base. Within this context, it is important to recognize that the Eastern US region is not only linked geographically, but is also closely linked through potato seed sales and product marketing. Thus, regional communication among scientists, farmers and industry members is a critical aspect of the variety development process.
Potatoes grown in the East are exposed to a wide range of day length, day and/or night temperatures, soils, humidity, and moisture conditions. Environmental conditions have dramatic effects on the performance and acceptability of potato breeding lines and varieties (Tai et al., 1993). Genotype by environment interactions must be evaluated to select new varieties with improved adaptation to production sites and cultural practices (Hill, 1975; Souza et al., 1993; Zobel et al., 1988). In addition to breeding, this project conducts collaborative selection and performance trials under diverse environmental conditions and a wide array of disease and pest pressures so that new potato varieties can be selected that are adapted to varying conditions of the Eastern region.
Related, Current and Previous Work
The NE-1031 Project and its predecessors have played a central role in Eastern potato variety development for many years. Appendix 1 summarizes the thirteen (seven fresh market, five chipping and one dual-purpose fresh/processing russet) potato varieties released through this program during 2002-2012.
By way of example - two new chipping cultivars (Waneta and Lamoka) were released by the NY program in February 2011. Both have been extensively tested by the NE-1031 network, and both were found to have chip color comparable to or better than the current industry standard, Snowden, as well as moderate to good resistance to common scab (Snowden is susceptible). Both are also resistant to golden nematode race Ro1 (Snowden is susceptible). Because Waneta and Lamoka have performed well in many environments, and because growers have heard many NE-1031 evaluators speak favorably about their experience with these clones, industry interest in these two varieties has been remarkably high, to the extent that commercial seed growers have not yet been able to meet demand.
Indeed, adoption and seed multiplication inevitably takes considerable time in the potato industry, in part because vegetative multiplication is slow, and in part because it growers need several years before they can determine whether a promising new variety will indeed work for them (many agronomic practices need to be tweaked for any new variety to achieve optimal production). Thus impacts occur over a long time period. Recent eastern releases since 2002 (e.g. Marcy, Monticello, Harley Blackwell, Red Maria, Lehigh, Waneta, Lamoka and Peter Wilcox) were grown on 726 seed acres nationwide during 2011 with a seed value of $1,900,000. The resulting seed crop has the potential to plant 7200 acres in 2012 with a ware value conservatively estimated at $14.5M. Over a longer time frame, 20 varieties released by the Eastern programs since 1990 represented 3270 seed acres nationwide with a seed value of $8.6M. This seed crop has the potential to plant 33,800 acres in 2012 with a conservatively projected value of $66,000,000.
NE-1031 productivity extends to research as well: over the past five years NE-1031 scientists have published 29 peer-reviewed articles. Each year the NE-1031 team also leverages regional funding to attract additional funding from the federal government and potato industry. In 2011, NE-1031 scientists shared $254,609 in funding via the potato special grant (administered by USDA), and attracted an additional $281,600 from industry stakeholders.
Currently, the NE-1031 project serves to coordinate potato breeding and genetics research across eight states, three Canadian Provinces, and two federal agencies (two USDA-ARS laboratories and the AAFC research center in Fredericton, NB, Canada). The regional potato variety development projects have allowed potato breeders to share breeding materials and test results. Importantly, the NE-1031 project has developed a uniform potato germplasm evaluation and selection system, which takes advantage of the diverse environmental and pest incidence conditions of the Eastern region. All seed is produced at a single site in Maine, to eliminate the substantial impact of seed source on clone performance, and evaluation methods are standardized across the trial network. Each year the project evaluates about 30 potato clones across the Northeast and compares performance to 11 existing varieties. The 30 clones tested each year represent the very best of the 100,000-plus seedlings that the Northeast potato breeding programs sow each year. The project also provides a mechanism for screening regional selections for specific characteristics at a single location (e.g., early blight, late blight, and powdery scab resistance in PA; golden nematode resistance in NY) and multiple locations (e.g., chip quality in ME, NY, PA, NC, FL). This collaborative evaluation system makes efficient use of scientific expertise available in the region, and results in more efficient release and adoption of new potato varieties than would occur without the project. We have a robust project website and have developed a user-friendly web-based variety database that has become a model for the rest of the U.S. potato variety development programs (http://potatoes.ncsu.edu/NE.html).
The objectives and activities of related projects, such as NRSP-6 (introduction, preservation, distribution, and evaluation of Solanum species), NCCCR-84 (potato genetics), and WRCC-27 (potato variety development) are complementary to this project. NE-1031 interacts with these projects through exchange of promising germplasm, seedling tubers for selection under conditions not available to individual breeding program, and published results. There is a need for good communication between regions to take advantage of widely-adapted germplasm. Occasionally a selection from the Western or North Central region will perform well in the East; however, this is quite unusual. In order to obtain selections that are well adapted to the Eastern U.S., clones usually must be selected in the East. When a clone looks like it might grow well outside of its region of origin it is sent to other regions for evaluation. The NE region tests a few clones developed outside the Northeast each year. Several NE breeders routinely attend the annual NCCCR-84 meeting in Chicago each December, and one NCCCR-84 breeder recently began attending the annual NE-1031 meeting.
The National Coordinated Chip (NCPT) and National Fry Processing (NFPT) Trials are new, industry-driven, nationwide initiatives to coordinate the development of new chip and french fry varieties. Both started in 2010 when industry became concerned that a variety developed in one region might be discarded before it was established whether it also grew well in other regions, i.e., we might be dropping good clones. Thus for the past two years industry has provided funding to evaluate chip and french fry clones at multiple sites nationwide. NE breeders contribute clones to these trials and host trial sites in NY, NC, ME and FL. The resulting data from these national trials is hosted by NC, using the same platform initially developed to host data generated by our NE regional project (see above). NCPT and NFPT have proven useful in two important respects. First, they allow originating breeders to identify broadly-adapted clones much earlier than was possible before. Second, they provide free publicity to the best clones - when a good clone is identified, the entire processing industry knows about it, not just the scientists in the region that developed it.
The incorporation of disease resistance into varieties with desirable horticultural characteristics is of immense importance. In New York, golden nematode control would be impossible without resistant varieties. The number of fungicide applications normally used to control late blight on susceptible varieties can be substantially reduced when resistant varieties are grown. In the absence of resistant varieties, common scab, pink rot, and other tuber diseases can severely reduce marketable yield. The breeders in the NE-1031 Project have succeeded in incorporating these and other important resistance factors into many of the recently released varieties and clones now being tested. All selections in the NE-1031 Project are now being screened for the development of internal necrosis, bacterial ring rot symptom expression, and total glycoalkaloid content to insure that these undesirable attributes are not discovered after naming and release of a new variety. Breeding, selection and evaluation of disease- and pest-resistant clones continues to be a priority for NE-1031.
The USDA-ARS program in Beltsville currently oversees national trials that evaluate clones for resistance to late blight and common scab. When a NE breeder wants more information about a clone's reaction to these diseases than can be obtained in our regional network - it is submitted to the national trials for further evaluation.
Although progress has been made in developing and introducing new varieties with combined disease resistance, favorable horticultural traits and desirable processing qualities, large-scale commercial adoption is hampered by marketing and seed production constraints. Our project intends to continue its focus on enhancing disease/pest resistance of potato while continuing to meet the diverse marketing needs of the Eastern fresh market (e.g., whites, reds, russets, organic and specialty varieties, etc.) and processing (French fries and chipping from field and/or storage) industries. We are also developing additional information and programs to enhance commercialization of new varieties (e.g., web-based information, variety profiles, licensing procedures, etc.).
Fresh Market and Specialty Varieties. Excellent appearance and cooking quality are essential for fresh market varieties. White- and russet-skinned varieties must have a bright, clean appearance when washed as well as uniform tuber size and shape. Resistance to common scab and other diseases which cause external blemishes is extremely important. Resistance to mechanical damage during handling is critical. Unique tuber skin color (e.g., red, purple, yellow, etc.) can enhance appeal and marketing opportunities. Heavy tuber netting and susceptibility to tuber skinning limits the marketability of many white-, purple- and red-skinned varieties in the East, so elimination of these traits is important in our breeding and selection efforts. Yellow-fleshed potatoes are becoming increasingly popular in U.S. markets. Methods for breeding for improved yellow-flesh characteristics have been developed (Haynes et al., 1994; Haynes et al., 1996). Yellow-flesh intensity is highly heritable in the diploid hybrid phu-stn population, indicating that the development of intense yellow-flesh in this population will be relatively easy (Haynes, 2000). However, when utilized in 4x-2x crosses, the carotenoid content of the resultant tetraploid progeny, although higher than what is currently available, did not reach the same levels as in their diploid parents (Haynes et al. 2011). Cooking and internal quality are also critical for fresh market. Our project provides an excellent, collaborative system for selecting varieties with good external appearance and resistance to the most common internal defects (e.g., hollow heart, blackspot bruise, and internal heat necrosis). Flavor and sensory components of cooked potato can be compared with various analytical methods (e.g., Oruna-Concha et al., 2001; Jensen et al., 1999; Ulrich, et al., 2000; Vainionopaa et al., 2000); however, these methods have not effectively substituted for sensory evaluation. Our project routinely conducts sensory evaluation of advanced potato selections to assure that new releases meet the markets rigorous quality demands. Potatoes are naturally nutritious and rich in vitamin C; however, introgression of yellow-fleshed diploid phu-stn hybrids into S. tubersosum will increase tuber concentrations of carotenoids, and other phytonutrients that would be highly beneficial to human health. Improving the nutritional quality of potato is a long-term goal of the project. Over the past 10 years, eight fresh market and specialty varieties have been released by this project (Appendix 1). Continued improvement is needed in the quality and pest resistance of potato varieties available to Eastern growers so that marketing opportunities can be expanded and production can be more profitable, while minimizing negative environment impacts.
Chipping and French Fry Processing. Selection of clones that maintain processing quality during cool temperature storage is a high priority of the project and is a viable approach towards reducing sprout inhibitor and energy use. Diploid potato species which have long-term cold storage chipping ability [S. phureja and S. raphanifolium (Hanneman, 1993)] and other germplasm with resistance to sugar accumulation in cold storage are being used to improve the genetic base of chipping potatoes adapted to Eastern conditions. Adapted French fry processing clones are being selected from crosses conducted in ME and other states. New chipping varieties with high yields, high tuber dry matter, reduced susceptibility to bruising, and resistance to IHN are being developed by all Eastern breeding programs. Our research has shown that there is no significant correlation between susceptibility to IHN and either total yield or specific gravity in commercial potato germplasm (Henninger et al., 2000) and that diploid hybrid population of S. phureja x S. stenotomum (phu-stn) can be used to expand the genetic base for chipping potatoes and reduce IHN problems for growers (Haynes et al., 1995; Sterrett et al., 2002). Over the past 10 years, six chipping and/or French fry processing varieties have been released by this project (Appendix 1). The varieties Pike, Andover, Harley Blackwell and Marcy have been particularly successful in the processing marketplace, and early indications suggest that Waneta and Lamoka will do likewise. However, continued improvements in the yield, quality, and pest resistance of new chipping and processing varieties available to Eastern potato growers are needed.
Potato Diseases Constraining Eastern Production. Bacterial and fungal diseases such as late blight, early blight, scab (common, acid, and powdery), verticillium wilt, rhizoctonia (stem canker and black scurf), silver scurf, pink rot, soft rot, dry rot (Fusarium spp.) and virus diseases (leafroll, potato viruses X and Y, corky ring spot) reduce the yield and quality of the Eastern potato crop. All currently available potato varieties are susceptible to one or more of these diseases. Resistance to fungicides previously used for disease control [e.g., mefenoxam resistance to pink rot (Fitzpatrtick and Lambert, 2006); changes in late blight populations and resistance levels since 1990] makes development of improved genetic resistance particularly important. Breeding and selection for improved disease resistance is a major focal area for the Eastern potato breeding programs and NE-1031. The impacts provided by successful development of high yielding, high quality and pest-resistant potato varieties are tremendous for Eastern growers (e.g., reduced costs, fewer losses, lower risk, etc.) and the public (e.g., less pesticide use, higher quality, etc.).
Insect Pests and Variety Resistance. Colorado potato beetle (CPB) continues to be the most serious insect threat to Eastern potato production because of the severe damage that it causes and because this insect has developed resistance to all insecticides deployed against it (Weber and Ferro 1994). Aphids, leafhoppers, fleabeetles, and other insect pests also cause significant losses to the profitability of Eastern potato production. Research to develop potatoes resistant to CPB and other insects will contribute to the development of more sustainable approaches to insect control. Resistance to insect pests in the East is focused on the incorporation of two complementary sources of resistance, trichome-mediated resistance from S. berthaultii (Bonierbale et al., 1992, 1994) and leptine-based resistance from S. chacoense (Sanford et al., 1997; Yencho et al., 2000). Considerable progress has been made in the NY program to incorporate glandular trichomes (e.g., NY released NYL235-4 as an insect resistant clone for use in germplasm improvement (Plaisted et al., 1992) and has released two insect resistant varieties for organic production (Prince Hairy and King Harry)). Leptines, which are foliage-specific glycoalkaloids, also provide resistance against CPB. Leptines are coded by only a few genes (Sinden et al., 1986) and research to combine trichome-mediated and leptine-based resistance to provide even more effective and durable insect control has been conducted in NC (Yencho et al., 2000).
Regional Evaluation and Modeling Efforts. Performance data obtained from collaborative trials in the NE-1031 project have provided a rich information source to carry out research on genotype x environment interactions in the East. The project has developed two sets of baseline data: one consisting of five industry standards that are grown at all sites; the other being "breeders choices" where each of the participating breeders indicates one to three advanced selections that are tested at all sites for that year. The analytical results provide considerable information on the interplay between genotype and environment. Tai et al. (1993) showed that linear regression was useful for evaluating the performance and adaptability of selections over a range of environments. AMMI (additive main effect and multiplicative interaction model)[Gauch, 1992]; BLUP (best linear unbiased predictor); and REML (residual maximum likelihood)[Genstat, 1993; Horgan, 1992] have been used to further analyze NE1031 trial data with the goal of better understanding genotype x environment interactions and helping us develop better selection tools for potato variety development in the region.
Conduct multidisciplinary conventional and molecular marker-assisted breeding, germplasm enhancement, and early-generation selection research to improve potato productivity and quality for important Eastern U.S. markets.
Use novel and improved potato germplasm to reduce the impact of economically important potato pests in the Eastern US.
Evaluate yield, quality, and pest resistance of preliminary and advanced potato breeding lines in experimental- and commercial-scale trials at multiple Eastern locations to aid industry adoption of new varieties.
Provide timely and relevant information to stakeholders through various means including the maintenance of a project website and a web-based potato variety performance database for use by researchers, extension, potato growers, and allied industry members.
MethodsFor a list of cooperators by objective see Appendix 3 Objective 1: Conduct multidisciplinary conventional and molecular marker-assisted breeding, germplasm enhancement, and early-generation selection research to improve potato productivity and quality for important Eastern US markets. 1a. Development of a Collaborative Approach to Potato Breeding, Selection, and Variety Development in the Eastern US. Initial crossing and germplasm improvement will be conducted within the ME, NY, NC, VA and USDA-ARS potato breeding programs using the approach outlined in Appendix 2. Parents are selected for desirable yield, quality, and pest resistance traits, as well as pollen and flower fertility. Wild or cultivated diploid germplasm (e.g., S. phureja and S. stenotomum, S. albicans, S. microdontum, S. iopetulum and S. gourlyii in the USDA-ARS program; S. chacoense for insect resistance in the USDA-ARS and NC programs; and S. berthaultii for insect resistance in the NY program) is also used to introduce novel traits for pest resistance or improved quality. VA will assist in breeding efforts by developing self-pollinating, true breeding inbred lines of diploid potato that can be used in genetic studies. Initial selection is usually done by each breeding program at their field sites. However, the diverse environments provided by regional cooperators are increasingly being used to supplement the early-selection process and improve the adaptation of plant materials across Eastern environments. For example, 2nd-year material from the ME program is screened in NC for adaptation to the warm, southeast environment. Lines will be field tested within each breeding program for 5 to 8 years and at multiple eastern sites to evaluate yield, quality (size distribution, external appearance, tuber glycoalkaloid levels, processing quality, etc.), disease resistance (e.g., scab, late blight, early blight, verticillium wilt, etc.), and other characteristics (e.g., tuber greening, bruise susceptibility, vine maturity, cooking quality, etc.). The most promising clones will be entered into the Eastern regional potato variety trials (NE-1031 Regional Project) to use the diverse NE-1031 environmental conditions for further screening and selection. Promising chipping and French-fry clones will also be submitted to the National Coordinated Chip and French Fry Processing trial networks. 1b. Quantitative, molecular genetic and biochemical studies to improve resistance to internal heat necrosis. Germplasm from the four breeding programs will continue to be screened for IHN resistance in FL and NC. The methods used in these studies have been outlined by Henninger et al. (2000), Sterrett et al. (2003), and Sterrett and Henninger (1997). To better understand the genetic basis of IHN during our last project period we developed two medium density molecular genetic maps in cultivated tetraploid potato using AFLP and SSR markers (McCord et al. 2011a,b). To date, we have identified QTL for increased resistance to IHN on chromosomes IV, V, and groups VII and X of Atlantic, and on group VII of B1829 that account for 5 - 29% of the variation for mean IHN severity, and from 4 to 15% of the variation for percent IHN incidence. Most QTL detected were dominant, and associated with decreased IHN symptoms. Thirteen AFLP markers that were linked to IHN in one population were tested on a second population but only one marker was associated with decreased symptoms in both populations. One of our populations has been genotyped with the SolCAP SNP chip (http://solcap.msu.edu) and 8303 single nucleotide polymorphism markers scored. We plan to expand upon the work described above using our existing populations, if we can secure additional funding. 1c. Further develop and capitalize on the improved genetic base for long-term cold storage processing ability. Tetraploid lines with the ability to chip directly from long-term cold storage at 4C have previously been developed by R. Hanneman and S. Jansky of the USDA in Madison, WI and C. Thill of the Univ. of MN. This cold-processing ability results primarily from crosses with the wild species S. raphanifolium. Crosses among lines that chip directly from long-term cold storage and S. tuberosum will be made and evaluated for adaptation (USDA, ME, NY). Those with the best agronomic performance will then be crossed with regionally adapted chipping varieties. Progeny from these crosses will be selected based on their ability to produce light colored chips or fries after prolonged cold storage. Recent molecular genetic analyses have shown that some alleles of vacuolar and apoplastic invertases are associated with improved cold-chipping ability in European germplasm (Draffehn et al. 2010). Moreover, RNAi-mediated silencing of vacuolar invertase dramatically improves fry color (Bhaskar et al. 2010), suggesting that natural alleles with low expression levels are key to good fry color. Consistent with this, vacuolar invertase expression is very low in S. raphanifolium (Bhaskar et al. 2010). NY will characterize allelic variation of invertase genes in Cornell germplasm to determine if any alleles, including those previously introgressed from S. raphanifolium, are associated with good fry color. If any are -- as seems likely -- assays to simplify the tracking of desirable alleles will be developed, to facilitate the development of improved processing clones in future years. An elite tetraploid cross (NY121 x NY115) that segregates for chip color and starch content has recently been genotyped with 8303 SNP markers (NY), and is currently being phenotyped for a second year for both these processing traits. If any QTL of large effect are identified, simple markers diagnostic for desirable alleles will be developed. 1d. Improve the genetic base of specialty potatoes, such as yellow-fleshed and red-skinned types. Yellow-Fleshed Potatoes - Total carotenoid content of yellow-fleshed diploid PHU-STN clones ranged from 3 to 13 times of that found in the yellow-fleshed variety Yukon Gold (Lu et al., 2001). Three diploid yellow-fleshed clones (with 14x, 6-8x, and 2x the carotenoid content of Yukon Gold) were crossed to a light yellow-fleshed tetraploid selection from TBR. Tubers of the resultant progeny were small and low yielding. Carotenoid content in orange-flesh potatoes is primarily due to high levels of zeaxanthin (Brown et al. 2008; Haynes, personal communication). A recent European patent application identified a recessive allele of zeaxanthin epoxidase (designated zep allele 1) responsible for increased levels of zeaxanthin. Orange-flesh potatoes have been identified in PHU-STN and 4x-2x crosses are being made to transfer the orange-flesh trait to the tetraploid level. Red-, Purple-Skinned, and Other High-Value Novel-Colored Potatoes - Crosses and backcrosses will be made between tetraploid TBR and diploid PHU-STN lines with solid or patterned red or purple skin to increase color variation in regionally adapted clones. The PHU-STN population contains red- and purple-fleshed segregants and together with colored-fleshed selections from other breeding programs (CO, ARS-WI) these will be used to develop red- and purple-fleshed progeny for eastern growing conditions. Red and purple skinned clones will also be intercrossed with yellow-flesh clones to develop a population of colored-skin, yellow-flesh lines (USDA, ME, NY, NC). Objective 2: Use novel and improved potato germplasm to reduce the impact of economically important potato pests in the Eastern US 2a. Improve potato resistance to significant pests in the East. Late Blight - A diploid PHU-STN late blight resistant population has been developed by USDA and PSU. After one cycle of recurrent maternal half-sib selection late blight was reduced by 1/6th, and after two cycles of selection, late blight was reduced by one-half. Another reduction in late blight severity is predicted for the next cycle of selection currently underway (USDA, PSU). 4x-2x crosses were made to incorporate late blight resistance from these diploids into the tetraploid population. This material is being crossed with TBR to enhance the levels of late blight resistance in TBR germplasm (USDA, PSU). USDA, ME and NY all conduct field screening for late blight resistance; however, PA provides a centralized screening site for materials from all of the eastern programs. The goal is to identify stable late blight resistant clones for developing late blight resistant varieties. Early Blight - Resistance to early blight in a diploid PHU-STN population was found to be highly heritable. Based on the high heritability, early blight resistance was predicted to decrease by about 40% in the second cycle of selection. However, after one cycle of selection for resistance to early blight, the resultant population was more susceptible and later in maturity (Santa-Cruz et al. 2009). Two of the QTL for resistance to early blight identified in the diploid PHU-STN population were found in an area associated with late maturity (Zhang 2004). Other QTL associated with early blight resistance were found to be independent of maturity (Zhang 2004). Remnant seed from five families with early blight resistance that were earlier maturing than the rest of the population were selected. Of the approximately 5000 clones harvested, only 150 matured early. These are presently being evaluated for early blight resistance. Scab - To develop molecular markers for resistance to common scab, individuals in a population must be accurately phenotyped. Field trials have been too variable for accurate assessments. True seed from diploid PHU-STN families with resistance or susceptibility to common scab will be grown in a controlled environment. Known quantities of inoculum will be introduced into sterilized potting mix and seedlings from these diploid families will be grown to maturity. These same clones will be planted in scab infested field trials at USDA and PA and evaluated for their reaction to common scab. If sufficient segregation is observed in one of these families, molecular markers will be developed. Golden Nematode - Virtually all crosses in the NY breeding program include at least one golden nematode resistant parent. Segregating populations from the breeding program will be evaluated for resistance to both races of the golden nematode and for superior horticultural characteristics. Mapping studies will continue to map the gene(s) conferring resistance to race Ro2 of the golden nematode (NY). Golden nematode resistant parents are also used in the NC, ME, and USDA breeding programs. Screening for resistance in the progeny is conducted in NY by collaborator X. Wang (USDA-ARS). Marker-assisted selection for golden nematode resistance (H1 marker; Galek et al. 2011) will be used to supplement traditional screening methods and provide earlier detection of resistant clones within selected breeding families (NY, ME). Virus - Potato virus Y has become a significant challenge for the US potato industry in recent years. Virus resistant parents (e.g., NY121, Eva, and European varieties) are being used with increased frequency in our crossing programs (ME, NC, NY, USDA) with the goal of increasing the availability of varieties with PVY resistance in the future. Marker-assisted selection for potato virus Y resistance (RYSC3; Kasai et al, 2000) will be used to supplement traditional screening methods and provide earlier detection of resistant clones with selected breeding families (NY, ME). Colorado Potato Beetle and Potato Leafhopper - Two complementary approaches will be adopted for this work. The first approach will focus on the introgression of genes for resistance to CPB and PLH from S. berthaultii (NY). The second will focus on introgressing genes for leptine biosynthesis, a potent class of glycoakaloids from S. chacoense that impart resistance to CPB and are present only in potato foliage (NCSU). Progeny from these crosses will be grown in CPB and/or leafhopper-infested fields each year in NY and NC. The most resistant selections will then be utilized as parents in the next crossing cycle. When the trichome-based and leptine based resistance work has progressed sufficiently we will attempt to pyramid these valuable genes into a common background. Objective 3. Evaluate yield, quality, and pest resistance of preliminary and advanced potato breeding lines in experimental- and commercial-scale trials at multiple Eastern locations to aid industry adoption of new varieties. 3a. Evaluate Promising Selections in Standardized Trials for Early Maturity, Quality, and Storage Potential. Seed Increase for Standardized Regional Variety Trials - Advanced selections from the breeding programs will be placed in the NE-1031 Project seed nursery at the University of Maine Aroostook Research Farm in Presque Isle, ME. This nursery will serve as a source of uniform plant material for use by project cooperators. The seed will be tested according to Maine seed certification regulations. This common seed source is a vital component for valid research and modeling of environmental characteristics, since performance of any given clone varies widely according to the growing conditions and storage environments to which the seed stocks are exposed. Regional Variety Trial Procedures - All tablestock, processing and specialty market selections will be evaluated in replicated field trials in multiple locations (FL, ME, NY, NC, OH, PA, MD) using standardized NE-1031 evaluation techniques and descriptors. These techniques include observations on plant traits to identify selections that mature early with minimal need for chemical desiccation, external tuber appearance, total and marketable yield, tuber size distribution, and internal tuber defects incidence. Bruise susceptibility (Hunter and Reeves 1983; Pavek et al. 1985), storage weight loss, and sprouting characteristics will also be measured (ME, NY). Processing from Storage - Samples of varieties and selections entered into the NE-1031 project from the breeding programs will be stored at a minimum of two temperatures. Weight loss will be measured to help select clones that do not require the use of plant growth regulators for sprout suppression. Chip or fry color will be measured with an Agtron instrument or with USDA Chip or Fry Color Charts following storage for two to six months at temperatures ranging from 4 to 10C (ME, NY, PA, USDA). 3b. Evaluate Promising Selections for Resistance to Potato Pests. Early, Late Blight, and Scab - All selections undergoing evaluation for possible release as a new variety will be evaluated for their reaction to late blight, scab, and early blight in replicated field trials (PA). Varieties with known reaction to each pathogen will be included each year of the test as a basis for comparison. Viruses - Advanced potato breeding selections in the NE-1031 project will be planted in replicated field trials and inoculated with potato virus Y using infected spreader plants and by placing 2-4 aphids that have fed on infected potato plant onto each test plant (ME). Ten tubers per plot will be harvested and replanted during the subsequent year. Visual symptoms of virus infection will be recorded as well as virus titers using ELISA. 3c. Evaluate promising selections for sensory and nutritional quality. Six to ten advanced selections will be grown each year in ME. Through collaboration with the Department of Food Science and Human Nutrition at the Universty of Maine, each line will be evaluated for boiling and baking quality after four months of storage at 7oC. Test lines will be compared to appropriate industry standards (e.g., Superior, Katahdin, or Russet Burbank). Only lines with acceptable total gylcoalkaloid (TGA) content (<20 mg per 100g) will be evaluated for sensory quality (Asano et al. 1996; Baker et al. 1991; Friedman and McDonald 1997). A consumer panel will evaluate the samples in comparison to the appropriate standard variety. A nine point hedonic scale will be used for each of the baked attributes (cooked color, texture, flavor, and overall acceptability); 50 consumers will rate the sample. A panel of 10-12 persons will be trained to objectively evaluate color, after-cooking darkening, sloughing texture and other appearance attributes using 15-point scales based on the Spectrum descriptive analysis method (Meilgaard et al., 2007). Another consumer panel will evaluate peeled, boiled potatoes for color, flavor, after cooking darkening, sloughing, and overall acceptability. Chlorogenic acid content (Banjongsiniri 1999) as well as the rate of browning (Sapers and Miller 1993) will be evaluated at the time of the sensory evaluations. Correlations between chemical and sensory data will be explored. Sensory quality of promising French fry lines will be evaluated in ME. Tubers from each French fry line will be stored at 10oC for two months and then evaluated versus Russet Burbank as a standard. Fries will then be served to panelists for color, texture, flavor and overall quality evaluation. Advanced potato breeding lines will be assayed for phytonutrient quality and quantity (ME). Extracted ascorbic acid will be quantified by the microfluorometric method (AOAC, 2000). Tuber carotenoids (lutein, and other provitamin A carotenoids) will be determined by reverse phase HPLC according to Bushway (1986) and Simonne et al. (1993; 1997b; 2001). Antioxidant capacity will be measured following the Oxygen Radical Absorbance Capacity (ORAC) methods of Cao et al. (1996). Protein (Simonne et al., 1997a), moisture, ash, and total lipid content of the tubers will be analyzed by AOAC Intl. methods (AOAC, 2005). Information obtained will be used to direct breeding and selection efforts to improve potato nutritional quality. 3d. Study cultural practices that optimize the performance of new potato clones and develop more sustainable agricultural systems. Optimized cultural practices need to be developed for new potato clones to increase the likelihood of success in commercial production. Some important environmental factors may be mitigated by cultural practices such as irrigation, appropriate fertilization or timely harvest. Cultural practice experiments will be performed with new clones to determine optimal input levels (ME, NY, PA, FL, NC, MD). These studies typically include optimizing fertilization, harvest date, irrigation, plant spacing, response to the herbicide metribuzin, and other cultural practices. A subset of these sites will conduct cultural studies with a range of genotypes to help develop selection tools for specific cultural practices. For example, several sites will evaluate performance of selected pest-resistant lines under organic or low chemical production systems. Objective 4. Provide timely and relevant information to stakeholders through various means including the maintenance of a project website and a web-based potato variety performance database for use by researchers, extension, potato growers, and allied industry members. Project cooperators will present project information to stakeholders through oral presentations, printed media, and websites to inform them of promising selections and new variety releases. A long-term database for NE-1031 trials has been established to facilitate the data analysis and encourage collaboration among NE-1031 participants. Web interfaces to this database have been created to allow access for all project participants and they are continually updated and improved as the need and new ideas emerge. The website also provides up-to-date potato production information and project results and an interactive, searchable potato variety trial database designed to provide easy and rapid access to the results of the trials coordinated through the Eastern potato variety development project, as well at the National Chip Processing Trials supported by the U.S. Potato Board and the Snack Food Association.
Measurement of Progress and Results
- Potato breeders and allied scientists will design improved regional breeding and selection strategies to more efficiently develop varieties for wide geographic areas.
- The germplasm pool of high specific gravity, disease-resistant, insect-resistant and/or nutritionally enhanced clones available for breeding purposes in the US will be broadened.
- New potato varieties with improved disease and/or insect resistance, resistance to IHN, improved processing or fresh market characteristics, and enhanced nutritional quality will be released.
- Several genetic maps of important potato breeding progenies will be developed enabling the identification of genes and/or QTL associated with traits such as yield, cold-chipping ability, specific gravity, and resistance to diseases.
- Communication and interactions among potato scientists located in Eastern US and elsewhere will be maintained and strengthened.
- Output 6: A project website and a web-based potato variety performance database for use by researchers, Extension, potato growers, and allied industry members will be developed and maintained to facilitate communication, information exchange and data analysis.
Outcomes or Projected Impacts
- New potato varieties with improved disease and insect resistance, resistance to IHN, improved processing or fresh market characteristics, and enhanced nutritional quality will be released, providing growers with better marketing opportunities and/or improved resistance to pests.
- Adoption of new, high quality, pest resistant varieties will be more rapid, leading to increased profitability, greater worker safety, and reduced pesticide load in the environment and human diet.
- Web-based and traditional conduits for the distribution of timely and readily available potato variety production information to growers, allied industry members and consumers will be further developed and strengthened.
- Rural communities dependent upon Eastern potato production will be better stabilized resulting in improved economic and environmental sustainability of Eastern potato industries.
Milestones(2013): Incorporate disease and insect resistances, abiotic stress resistances, improved processing characteristics, and enhanced nutritional quality, from diverse diploid and tetraploid potato species into high quality, adapted germplasm (S. tuberosum) (on-going activity)
(2013): Molecular genetic studies to understand basis of processing quality commenced (on-going activity)
(2013): Improvements to our interactive and searchable potato variety trial database implemented in response to (ever-increasing) user feedback (on-going activity)
(2014): Crosses and backcrosses made between tetraploid TBR and diploid PHU-STN lines with solid or patterned red or purple skin to increase color variation in regionally adapted clones and selections made (on-going activity)
(2015): Improved nematode and insect resistant germplasm identified, and crosses made with advanced S. tuberosum breeding lines to develop varieties with improved resistance to GN and/or CPB and PLH (ongoing activity)
Projected ParticipationView Appendix E: Participation
The NE-1031 Regional Potato Variety Development Project currently conducts extensive outreach activities in all participating states using numerous techniques ranging from face-to-face presentations at grower and scientific meetings to providing web-based content for industry members and consumers. Typical outreach activities include:
- Publication of project results in the NE-1031 annual publication, scientific journals, and other outlets.
- Development of applied publications and Extension materials targeted to growers in each participating state or province.
- Multiple formal and informal presentations, demonstrations, and field days targeted to growers and industry in each participating state or province.
- Providing web-based project information via the NE-1031 project website to enhance access to research results, variety profiles, and photographs (http://potatoes.ncsu.edu/NE.html).
The regional technical committee is composed of all participating cooperators (see Appendix E), an administrative advisor (Dr. Kirby Stafford) appointed by the Northeast Agricultural Experiment Station Directors, and a NIFA Representative (Dr. Ann Marie Thro). The technical committee meets at least once each year to discuss progress of the research, review procedures, coordinate research and plan future research activities. Voting privileges are restricted to one member from each participating unit.
The regional technical committee will elect an executive committee composed of a chair, vice-chair, and secretary. A succession of officers will be maintained so that the vice-chair becomes chair, the secretary becomes vice-chair, and a new secretary is elected each year. The responsibilities of the executive committee members are as outlined in the Guidelines for Multistate Research Activities. The chair will preside at all meetings of the technical committee and is responsible for organizing the agenda of the annual meeting. The vice-chair will prepare the annual report for the project. The secretary will prepare the minutes of the annual meeting and any special meetings. The administrative advisor is responsible for distributing the minutes and submitting the annual report and minutes to the NIFA representative and other interested parties. Participation by Agriculture Canada, the Provinces of Quebec and Prince Edward Island, Maine Department of Agriculture, Cooperative Extension, and Industry representatives is at the invitation of the Technical Committee with the approval of the Administrative Advisor.
AOAC International. 2000. Official Methods of Analysis, 17th ed.
AOAC International. 2005. Official methods of analysis of AOAC International. W. Horwitz, editor; G.W. Latimer, assistant editor. Gaithersburg, MD.
Asano, M., N. Goto, and K. Isshiki. 1996. J. Jpn. Soc. Food Sci. Technol. 43:593-597.
Baker, D.C., R.F. Keeler, and W. Gaffield. 1991. Toxicosis from steroidal alkaloids of Solanum species. In: Handbook of Natural Toxins, Keeler, R.F., Ed., Marcel Dekker, New York, Vol 6., 71-82.
Banjongsinsiri, P. 1999. The influence of potato cultivar and chemical treatment on the development of a pre-peeled, refrigerated product. M.S. Thesis, University of Maine, 104 pp.
Bhaskar, P.B, L. Wu, J.S. Busse, B.R. Whitty, A.J. Hamernik, S.H. Jansky, C.R. Buell, P.C. Bethke, and J. Jiang. 2010. Suppression of the vacuolar invertase gene prevents cold-induced sweetening in potato. Plant Physiology 154, 939-948.
Bonierbale, M.W., R.L. Plaisted and S. Tanksley. 1992. Genetic mapping and utilization of quantitative trichome-mediated insect resistance in potato. Neth. J. Pl. Path. 98 Supplement 2:211-214.
Bonierbale, M.W., R.L. Plaisted, O. Pineda and S.D. Tanksley. 1994. QTL analysis of trichome-mediated insect resistance in potato. Theor. Appl. Genet. 87:973-987.
Brown C.R., R.W. Durst, R. Wrolstad, and W. De Jong (2008) Variability of Phytonutrient Content of Potato In Relation to Growing Location and Cooking Method. Potato Research 51: 259-270
Bushway, R.J. 1986. Determination of a- and P-carotene in some raw fruits and vegetables by
high-performance chromatography. J. Agr. Food Chem. 34:409-412.
Cao, G. E. Sofic, and R.L. Prior. 1996. Antioxidant capacity of tea and common vegetables. J. Agr. Food Chem. 44:3426-3431.
Draffehn, A.M., S. Meller, L. Li, and C. Gebhardt. 2010. Natural diversity of potato (Solanum tuberosum) invertases. BMC Plant Biology 10:271
Friedman, M., and G.M. McDonald. 1997. Potato glycoalkaloids: Chemistry, analysis, safety and plant physiology. Crit. Rev. Plant Sci. 16:55-132.
Galek, R. M. Rurek, W.S. De Jong, G. Pietkiewicz, and H. Augustyniak. 2011. Application of DNA markers linked to the potato H1 gene conferring resistance to pathotype Ro1 of Globodera rostochiensis. J. Applied Genetics 52:407-411.
Gauch, H.G. Jr. 2006. Statistical Analysis of Yield Trials by AMMI and GGE. Crop Sci. 46:1488-1500.
Genstat 5 release 3 Reference Manual. 1993. Chapter 10: REML estimation of variance components and analysis of unbalanced designs. Pp. 539-584.
Hanneman, R.E., Jr. 1993. Ability of wild and cultivated potato species to chip directly from 2C storage. Am. Potato J. 70:814.
Haynes, K.G. 2000. Inheritance of yellow-flesh intensity in diploid potatoes. J. Amer. Soc. Hort. Sci. 125:63-65.
Haynes, K.G., W.E. Potts, J.L. Chittams and D.L. Fleck. 1994. Determining yellow-flesh intensity in potatoes. J. Am. Soc. Hort. Sci. 119:1057-1059.
Haynes, K.G., B.A. Clevidence, D.D. Rao, and B.T. Vinyard. 2011. Inheritance of Carotenoid Content in Tetraploid and Diploid Potato clones. Journal of the American Society for Horticultural Science. 136:265-272.
Haynes, K.G., J.B. Sieczka, M.R. Henninger and D.L. Flock. 1996. Clone x environment interactions for yellow-flesh intensity in tetraploid potatoes. J Am Soc Hort Sci
Haynes, K.G., D.R. Wilson and M.S. Kang. 1995. Genotype x environment interactions for specific gravity in diploid potatoes. Crop Sci 35:977-981.
Henninger, M. R., J. W. Patterson, and R.E. Webb. 1979. Tuber necrosis in Atlantic. Amer. Potato J. 56:464.
Henninger, M.R., S.B. Sterrett and K.G. Haynes. 2000. Broad-sense heritability and stability of internal heat necrosis and specific gravity in tetraploid potatoes. Crop Science. 40:977-984.
Hill, J. 1975. Genotype-environment interactions -- a challenge for plant breeding. J. Agr. Sci. 85:477-493.
Horgan, G.W. and E.A. Hunter. 1992. Introduction to REML for scientists. 59pp. Univ. of Edinburgh.
Hunter, J.H. and A.F. Reeves. 1983. Respiration increase as an objective measurement of relative susceptibility to bruise damage in breeding clones. Am Potato J 60:811(abst.).
Jensen, K., M.A. Peterson, L. Poll, and P.B. Brockhoff. 1999. Influence of cultivar and growing location on the development of flavor in precooked vacuum-packed potatoes. J. Agric. Food Chem. 47:1145-1149.
Kasai, K. Y., V.A. Morikawa, J.P.T. Valkonen, C. Gebhardt, and K.N. Watanabe. 2000. Development of SCAR markers to the PVY resistance gene RYadg based on a common feature of plant disease resistance genes. Genome 43:1-8.
Lu, W., K. Haynes, E. Wiley, and B. Clevidence. 2001. Carotenoid content and color in diploid potatoes. J. Amer. Soc. Hort Sci. 126:722-726.
McCord, P.H., B.R. Sosinski, K.G. Haynes, M.E. Clough, and G.C. Yencho. 2011. Linkage mapping and QTL analysis of agronomic traits in tetraploid potato (Solanum tuberosum L. subsp. tuberosum). Crop Science. 51: 771-785.
McCord, P.H., B.R. Sosinski, K.G. Haynes, M.E. Clough, and G.C. Yencho. 2011. QTL mapping of internal heat necrosis (IHN) in tetraploid potato. Theoretical and Applied Genetics. Theor Appl Genet 122:129142.
Meilgaard, M.C., G.V. Civille, and B.T. Carr. 2007. Sensory Evaluation Techniques. Taylor & Francis, Boca Raton, FL.
National Potato Council. 2009. Potato statistical yearbook, 2009. NPC, Washington, DC, 80pp.
Oruna-Concha, M.J., S. C. Duckham, and J. M. Ames. 2001. Comparison of volatile compounds isolated from the skin and flesh of four potato cultivars after baking. J. Agric. Food Chem. 49:2414-2421.
Pavek, J., D. Corsini, and F. Nissley. 1985. A rapid method for determining blackspot susceptibility of potato clones. Am Potato J 62:511-517.
Plaisted, R.L., W.M Tingey and J.C. Steffens. 1992. The germplasm release of NYL235-4, a clone with resistance to the Colorado potato beetle. Am. Potato J. 69:843-846.
Planning Decisions, Inc. 2003. A study of the Maine Potato Industry, its economic impact. S. Portland, ME, 36 pp.
Sanford, R.S. Kobayashi, K.L. Deahl, and S.L. Sinden. 1997. Diploid and tetraploid Solanum chacoense genotypes that synthesize leptine glycoalkaloids and deter feeding by Colorado potato beetle. Am Pot J 74:15 21.
Santa Cruz, J., K.G. Haynes, and B.J. Christ. 2009. Effects of one cycle of recurrent selection for early blight resistance in a diploid hybrid solanum phureja-S. stenotomum population. American Journal of Potato Research. 86:490-498.
Sapers, G.M and R.L. Miller. 1993. Control of enzymatic browning in pre-peeled potatoes by surface digestion. J. Food Sci. 58:1076.
Simonne, A.H., S.J. Kays, P.E. Koehler, and R.R. Eitenmiller. 1993. Assessment of beta-carotene content in sweetpotato (Ipomoea batatas Lam.) breeding lines in relation to dietary requirements. J. Food Compos. Anal. 6:336-345.
Simonne, A.H., E.H. Simonne, R.R. Eitenmiller, H.A. Mills and C.P. Cresman, III. 1997a. Could the Dumas method replace the kjeldahl digestion for nitrogen and crude protein determination in foods?. J. Sci. Food Agr.73:39-45.
Simonne, A. H., E. H. Simonne, R.R. Eitenmiller, H.A. Mills, and N.R. Green. 1997b. Ascorbic acid and provitamin A contents of unusual colored bell peppers (Capsicum annuum L.). J. Food Comp. Anal. 10:299-311.
Simonne, A.H., T.-S. Huang, and C.I. Wei. 2001. Cooking time unequally affects carotenoids in different vegetables. Paper presented at the 2001 Annual IFT meeting, NewOrleans, LA.
Sinden, S.L., L.L. Sanford, and K.L. Deahl. 1986. Segregation of leptine glycoalkaloids in Solanum chacoense Bitter. J Agric Food Chem 34:372-377.
Souza, E., J.R. Myers and B.T.Scully. 1993. Genotype by environment interaction in crop improvement. In: Crop Improvement for Sustainable Agriculture. Edited by M.B. Callaway and C.A. Francis. University of Nebraska Press. pp. 192-233.
Sterrett S.B. and M.R. Henninger. 1997. Internal heat necrosis in the mid-Atlantic regioninfluence of environment and cultural management. Am Potato J 74:233-243.
Sterrett, S.B., M.R. Henninger, G.C. Yencho, W. Lu, B.T. Vinyard, and K.G. Haynes. 2003. Stability of internal heat necrosis in tetraploid x diploid potatoes. Crop Science43: 790-796.
Tai, G.C.C., T.R. Tarn, G.A. Porter and S.B. Sterrett. 1993. Performance evaluations of varieties and selections in the Northeastern regions of North America. Amer. Potato J. 70:685-698.
Ulrich, D., E. Hoberg, W. Neugebauer, H. Tiemann, and U. Darsow. 2000. Investigation of the boiled potato flavor by human sensory and instrumental methods. Am. J. Potato Res. 77:111-117.
USDA National Agricultural Statistics Service. 2009. Potato Production Statistics.
Vainionopaa, J., R. Kervinen, M. de Pardo, E. Laurila, M. Kari, L. Mustonen, and R. Ahvenainen. 2000. Exploration of storage and process tolerance of different potato cultivars using principal component and canonical correlation analyses. J. Food Eng. 44:47-61.
Weber, D.C. and D.N. Ferro. 1994. Colorado potato beetle: diverse life history poses challenge to management. In: G.W. Zehnder, R.K. Jansson, M.L. Powelson, and K.V. Raman (eds.). Advances in Potato Pest Biology and Management. APS Press, St. Paul, MN.
Yencho, G.C., Kowalski, S.P., Kennedy, G.G., and Sanford, L.L. 2000. Inheritance of leptine glycoalkaloids and resistance to Colorado potato beetle (Leptinotarsa decemlineata Say) in F2 Solanum tuberosum (4x) X S. chacoense (4x) potato progenies. Am. J. Potato Res. 77: 167 178.
Yencho, G.C., P.H. McCord, K.G. Haynes, and S.B. Sterrett. 2008. Internal heat necrosis of potato a review. Am. J. Potato Research. 85:6976.
Zobel, R.W., M.J. Wright and H.G. Gauch, Jr. 1988. Statistical analysis of a yield trial. Agron. J. 80:388-393.