Abad, Jorge A, James W Moyer, George G Kennedy, Gerald A Holmes and Marc A Cubeta. 2005. Tomato spotted wilt virus on Potato in Eastern North Carolina. Am J of Potato Res 82:255-261. [Short Communication]

Leaf, stem, and tuber samples collected from diseased potato plants exhibiting tospovirus-like symptoms in eastern North Carolina (NC) were assayed for the presence of Tomato spotted wilt virus (TSWV) by serology (ImmunoStrips) and reverse transcription-polymerase chain reaction (RT-PCR) methods. All symptomatic samples tested positive for TSWV with serology and RT-PCR. Mechanical inoculation of the indicator host Nicotiana benthamiana with symptomatic leaf, stem, and tuber tissue resulted in plants with symptoms of systemic virus infection. The presence of TSWV in infected tissue of N. benthamiana was confirmed with serology, RT-PCR, and sequence analysis of the nucleocapsid (N) protein gene. Phylogenetic analysis of the predicted N protein of three isolates of TSWV from potato in NC and 11 isolates obtained from peanut, pepper, and tomato in Georgia and NC suggested that the isolates were related. One isolate of TSWV from potato in NC was selected for vector transmission tests, and the virus was transmitted to potato with tobacco thrips (Frankliniella fusca), but no vertical transmission from infected seed tubers to actively developing potato sprouts, stems or leaves was observed. This is the first documentation of the occurrence, isolation and characterization of TSWV from field grown potato in North America.

Bamberg, JB, JP Palta and SE Vega. 2005. Solanum commersonii Cytoplasm Does Not Improve Freezing Tolerance in Substitution Backcross Hybrids with Frost-sensitive Potato Species.  Am J Potato Res 82:251-254. (Short Communication)

Solanum commersonii Dun. (cmm) is the most frost hardy wild potato species known, being able to tolerate an acute freezing episode to about -5 C and further acclimate to tolerate -10 C after being exposed to chilling temperature for several days. Breeding with this species to incorporate its frost-hardiness traits can be accomplished by standard sexual hybridization or protoplast fusion. These methods can result in hybrids that vary in contribution of the cmm plastome. To test the effect of cmm cytoplasm, cytoplasmic substitution backcross hybrids were made with three very frost-sensitive specifies, S. brachistotrichum, S. cardiophyllum, and S. pinnatisectum, by using S. commersonii as the female to make an F1, then performing repeated backcross (BC) using the sensitive species as males. Relative freezing tolerance (RFT) of all genotypes was assessed by measurement of ion leakage of excised terminal leaflets subjected to a controlled ice nucleation and simulated free0thaw stress. Even against the background of these very sensitive species' genomes, the cmm cytoplasm of substitution hybrids promoted insignificant improvement in frost hardiness or ability to acclimate. We conclude that either (1) cmm cytoplasm does not contribute to frost hardiness, or (2) if cmm cytoplasmic frost hardiness genes do exist, they must be epistatic to (depend on the presence of) nuclear hardiness genes for expression.

Brown, CR. 2005. Antioxidants in Potato. Am J Potato Res 82:163-172 [Invited Review]

The content of compounds in potato that may act as antioxidants in the human diet is not widely appreciated. Carotenoids are present in the flesh of all potatoes. The contents mentioned in the literature range from 50 to 100 µg per 100 g fresh weight (FW) in white-fleshed varieties to 2000 µg per 100 g FW in deeply yellow to orange-fleshed cultivars. The carotenoids in potato is not a source of pro-vitamin A carotenes. In potatoes with total carotenoids ranging from 35 to 795 µg per 100 g FW, the lipophilic extract of potato flesh presented oxygen radical absorbance capacity (ORAC) values ranging from 3.6 to 15.3 nmoles (a-tocopherol) equivalents per 100 g FW. Potatoes contain phenolic compounds and the predominant one is chlorogenic acid, which constitutes about 80% of the total phenolic acids. Up to 30 µg per 100 g FW of flavonoids are present in the flesh of white-fleshed potatoes with roughly twice the amount present in red- and purple-fleshed potatoes. The predominant flavonoids are catechin and epicatechin. Red and purple potatoes derive their color from anthocyanins. The skin alone may be pigmented, or the flesh may be partially or entirely pigmented. Whole unpeeled with complete pigmentation in the flesh may have up to 40 mg per 100 g FW or total anthocyanins. Red-fleshed potatoes have acylated glucosides of pelargonidin while purple potatoes have, in addition, acylated glucosides of malvidein, petunidin, peonidin, and delphinidin. The hydrophilic antioxidant activity of solidly pigmented red or purple potatoes is comparable to brussels sprouts or spinach. In red and purple potatoes with solidly pigmented flesh with levels of total anthocyanin ranging from 9 to 38 mg per 100 g FW, ORAC ranged from 7.6 and 14.2 umole per g FW or Trolox equivalents. Potato contains on average 20 mg per 100 g FW of vitamin C, which may account for up to 13% of the total antioxidant capacity. Potatoes should be considered vegetables that may have high antioxidant capacity depending on the flesh composition.

Crosslin, JM*, PM Hamm, PJ Shiel, DC Hane, CR Brown and PH Berger.  2005. Serological and Molecular Detection of Tobacco Veinal Necrosis Isolates of Potato virus Y (PVYn) from Potatoes Grown in the Western United States. Am J Potato Res 82:263-269.

Isolates of Potato virus Y polyvirus that induced system veinal necrosis in tobacco (PVY^N) were transmitted from potatoes grown in Washington, Oregon, California, and Idaho. The detection of these viruses by serological and molecular methods was evaluated. In addition to PVY^N-like isolates, putative recombinant isolates (PVY^N:O) were detected. ELISA tests using monoclonal antibodies specific for ordinary (PVY^O) or necrosis-inducing (PVYN) serotypes of the virus indicated that both O and N serotypes were represented among the PVYN isolates. All of the necrosis-inducing PVY^N and PVY^N:O isolates were rapidly detected and differentiated from the ordinary strain using a novel coupled, one-tube, duplex reverse transcription-polymerase chain reaction (cRT-PCR) assay.

Curless, Meghan A, Keith A Kelling* and Phillip E Speth. 2005.  Nitrogen and Phosphorus Availability from Liquid Dairy Manure to Potatoes.  Am J Potato Res 82:287-297.

The effective use of manure nutrients requires an accurate assessment of their availability to the specific crops being grown. A fertilizer equivalence approach was used to evaluate the availability of nitrogen (N) and phosphorus (P) from liquid dairy manure to potatoes in field experiments conducted in northeast Wisconsin in 2000, 2001, and 2002. Crop responses to moderate and high rates of liquid dairy manure (93,500 and 187,000 L ha^-1) were compared to results obtained from N or P fertilizer applied at five rates (0 to 269 kg ha^-1). Availability estimates were made using the fertilizer eqivalence method based on tuber yield, harvested tuber N or P concentration and uptake, petiole nitrate or total P concentration, and soil nitrate or extractable P phosphate levels. Results showed an apparent availability of manurial N from 10% to 40%, with an overall average across all 3 years and all parameters of 28.6% for the high rate. These values are slightly less than average availability measured where corn has been used as the test crop. Although all parameters did not show responses to P fertilizer additions in these trials, where estimates were possible, P availability ranged from 20% to 90% with an overall average across all 3 years of 55.4% for the low and 50.5% for the high manure rates. Despite potato being more shallow-rooted and somewhat less efficient in N and P use compared to corn, it appears that only minor adjustments to manurial nutrient availability estimates are warranted when potatoes are grown.

Davenport, Joan R, Paul H Milburn, Carl J Rosen and Robert E Thornton. 2005. Environmental Impacts of Potato Nutrient Management. Am J Potato Res 82:231-328. [Part of the '98 Symposium Presented at the 82nd Annual Meeting]

Use of soluble chemical fertilizers for crop production, particularly to supply nitrogen, phosphorus, and potassium, has increased potato yields and quality for several decades. Over the past 10 years, however, there has been an increased concern over the environmental impact of agricultural fertilizers, particularly as non-point sources of water pollution. Currently, nitrogen is a target for improved use efficiencies in potato to reduce potential nitrate contamination of groundwater. Phosphorus management is increasingly being examined as a potential non-point source contaminant of surface waters. Potato researchers throughout North America are conducting studies that focus on maintaining or enhancing crop production while reducing the potential of negative environmental impacts. Precision agriculture, cover crops, slow-release fertilizers, and genetic manipulation are key strategies being studied. Concurrently, new challenges are arising, such as concerns over phosphorus leaching and heavy metal contamination in fertilizers. These have the potential to restrict nutrient use in agricultural systems, requiring both potato producers and scientists to seek additional alternatives to improve nutrient-use efficiency.

Davis, Jeffrey A, Edward B. Radcliffe and David W. Ragsdale. 2005. Soybean Aphid, Aphis glycines Matsumura, a New Vector of Potato Virus Y in Potato.  Am J Potato Res 82:197-201.

Soybean aphid (Aphis glycines Matsumura), an exotic species first discovered in the North Central region of the United States in 2000, is a competent vector of several Potyviridae. Soybean aphid has high fecundity and produces alatae (winged morphs) readily, characteristics typical of proficient virus vectors. When soybean aphids were exposed to Potato virus Y (PVY)-infected potato plants and then clip-caged on healthy potato plants in groups of five or as single aphids, PVY transmission ranged from 14% to 75% across all experiments. PVYO, PVYN, and PVYNTN strains were transmitted by soybean aphid.

Durham, Catherine A and Qingyue Ling. 2005. Impact of French Fry Length on the Number of Servings Produced Per Case for Quick Service Restaurants.  Am J Potato Res 82:241-249.

The contribution of different fry length categories short (<2 in.), medium (2 to3 in.), and long (3 to 4 in.) and extra long (>4 in.) to serving (individual portions) production in a “quick service restaurant” (QSR) was estimated using regression analysis with serving data developed for the purpose. The analysis provides coefficient estimates to measure serving production as a function of the number of short, medium, long, and extra long fries. The results showed significant differences between the numbers of servings produced from different length distributions. Higher proportions of longer fries produced a larger number of servings and thus produced higher serving yield per case. This study indicates greater serving production per case and potentially greater profitability for quick service restaurants that serve french fries in bags or boxes if they use fry grades with longer fry lengths.

Groza, HI, BD Bowen, D Kichefski, SJ Peloquin, WR Stevenson, AJ Bussan and J Jiang. 2005. Millennium Russet: A Dual Purpose Russet Potato Variety. Am J Potato Res 82:211-219.

Millennium Russet is a medium-late variety with long tubers having light russet skin and white flesh. It has potential as a fresh market and processing (french fries) variety. The tuber type of Millennium Russet is similar to Russet Burbank, but with better external and internal quality. The marketable yield, tuber set, and specific gravity are higher than Russet Burbank. Tubers show good fry color when processed from cold storage (7.2 C). Millennium Russet has a bland flavor and is less mealy and discolored than Russet Burbank. Chemical maturity of Millennium Russet occurs at approximately the same time as Russet Burbank, but it has lower sucrose levels in the bud and stem end. The glucose levels of Millennium Russet were 50% less than Russet Burbank throughout the first 4 months of storage at 10 C. Low glucose levels in the stem end of Millennium Russet when processed out of storage suggest tolerance to stress and low vulnerability to sugar end. Millennium Russet is resistant to common scab and corky ring spot, moderately resistant to dry rot, pink rot, and black scurf, and moderately susceptible to Verticillium wilt, bacterial wilt and brown rot. Millennium Russet is more sensitive to blackspot bruise than Russet Burbank, but more resistant to shatter bruise. Tuber yield of Millennium Russet was less responsive to nitrogen rates when compared with Russet Burbank, but tuber size distribution was more responsive to increases in in-row spacing.

Habib, Ahsan and Danielle J Donnelly. 2005. Stimulation of Ca²⁺ Uptake into Micropropagated Potato Plantlets by UV light and Vitamin D₃.  Am J Potato Res 82:191-196.

Micropropagated potato plantlets (Solanum tuberosum cvs Acadia Russet, Red Gold, Red Pontiac, and Russet Burbank) were used to test the effects of exposure to ultra violet rays (UV) or inclusion of vitamin D₃ (cholecalciferol) in the test solution on plantlet calcium (Ca) uptake. Ca uptake was determined by measuring shoot tissue ⁴⁵ Ca²⁺ concentration in ex vitro plantlets placed into test solutions containing radiolabelled calcium ⁴⁵CaCl₂. Shoot tissue ⁴⁵Ca²⁺ concentration was very significantly increased in all cultivars exposed for 24 h to UV treatment compared with control plantlets. This increase in shoot ⁴⁵Ca2+ concentration was similar (three cultivars) or greater (one cultivar) than that caused by 10 mg L^-1 vitamin D₃ in the test solution. When plantlets were exposed to UV, then placed for 24 h in the dark, significantly greater shoot ⁴⁵ Ca²⁺ concentrations occurred compared with plantlets tested immediately following treatment. This suggests that a change in the UV-elicited cellular product occurred during the dark interval that promoted more Ca uptake into plantlets.

Halloran, JN, TS Griffin and CW Honeycutt. 2005. An Economic Analysis of Potential Rotation Crops for Maine Potato Cropping Systems.  Am J Potato Res 82:155-162.

Potato cropping systems in Maine include both continuous potatoes and short-term potato rotations with small grains. Producers recognize the genefits of increased rotations, but the economics of producing a high-valued crop such as potatoes (Solanum tuberosum L.) create incentives for continuous potato production. Research at the USDA-ARS research site in Newport, ME, is evaluating the agronomic and economic impacts of five crops in two-year rotations on potato production and whole-farm profitability. The rotation crops are barley (Hordeum vulgare L.) sweet corn (Zea mays L.), green beam (Phaseolus vulgares L.), soybean (Glycine max L., Merc.), and canola (Brassica napus L.). Enterprise budgets for five crops were developed. The budgets and historical prices and yields were used as inputs to a Monte Carlo simulation. The simulation was conducted to determine the impact of rotation crops on whole-farm profitability and income risk, as measured by income variability. The net incomes of the five rotation sequences were compared against continuous potatoes. Two rotation crops, sweet corn and green beans, resulted in an increase in net income relative to continuous potatoes. All of the rotation crops were found to greatly reduce income risk and chance of economic losses. In the case of green beans and sweet corn, the analysis was rerun using data from the research trials on the following potato crop yields. Depending on whether the rotation effect was negative or positive, net income either fell or rose when compared to fist analysis. However, even when the rotation crop led to decreased yields in the following potato crop, income variability and likelihood of economic loss was still superior to the continuous potato rotation. These findings provide support for including rotation crops as a method to improve potato production and sustainability, increase whole-farm profitability, and reduce income risk.

Hiller, Larry K., Organizing Committee Co-Chair. 2005. 1998 Symposium Introduction. Symposium Presentation of PAA Production and Management Section at the 82nd Annual Meeting [Future Challenges for Potato Nutrient Management] Am J Potato Res 82:299-338.

This symposium was the first major session of the 82^nd Annual Meeting of The Potato Association of America. Sponsored by the Production and Management Section, the symposium explored the topic “Future Challenges for Potato Nutrient Management.” Dramatic changes have occurred in the nutrient management of potato crops during the past decade. There has been increased emphasis on reducing non-target/environmental impacts and movement towards definable, sustainable production systems. Good agricultural and management practices are necessary for environmental concerns, crop yields and quality, and food safety awareness. Nutrient management is needed to help prevent losses from potato diseases that are responsive to soil nutrient availability. New technologies and site-specific management are being introduced that selectively apply fertilizers based on soil nutrient availability. The Symposium topics provided an informative review of the present situation in these areas and a thoughtful look into the future challenges that will be considerations in managing the nutritional needs of potato crops.

Dr. Dale Westermann (USDA Soil Scientist, Kimberly, Idaho) presented a general review of the nutrient requirements of potato crops, uptake and mobility of the nutrients, and the soil-nutrient relationships important in achieving high yield and quality in potato production. Dr. David Lambert (University of Maine) reviewed important diseases affected by soil nutrient availability and how nutrient relationships influence the development and expression of these potato diseases. Dr. Joan Davenport (Washington State University, Prosser) discussed current management practices such as water systems and fertility interactions in nutrient management that may contribute to environmental concerns. Dr. Jeff Stark (University of Idaho, Aberdeen) presented research and insight into how crop rotations and cropping systems may be used to improve nutrient availability and recycling while minimizing adverse environmental effects. All of the topics related to the recent advances in site-specific management, also known as precision agriculture or precision farming in potato-cropping systems. This approach is based on the identification of variability within a field or area and then modifying inputs or management strategies accordingly. The symposium reported on research efforts as well as applications by growers and industry toward the comparison and adoption of this new and evolving tec.

Kim-Lee, H-Y, J-S Moon, Y-J Hong & M-S Kim. 2005. Bacterial Wilt Resistance in the Progenies of the Fusion hybrids between Haploid of Potato and Solanum commersonii. Am J Potato Res 82:129-137.

Bacterial wilt of potatoes, which used to be a widespread disease in tropics and subtropics, has become a threat to potato production in temperate region. The diploid species Solanum commersonii has several desirable characteristics including cold tolerance and resistance to several diseases. Selected somatic hybrids between S. tuberosum dihaploid and bacterial-wilt-resistant S. commersonii clones were cross pollinated with S. tuberosum cultivars for further selection of bacterial wilt resistance. The chromosome numbers of the fusion parents were confirmed as 24, and the three fusion hybrids crossed were all tetraploids. The chromosome number of 11 backcross 1 progenies (BC1) was 48 and that of the other six was close to the tetraploid number. Backcross 2 progenies (BC2) were obtained from only three of the 44 BC1 clones crossed. The S. commersonii parent clone, LZ3.2, was the most resistant to bacterial wilt among wild species clones tested. The first sexual progenies segregated for resistance, with one clone highly susceptible and four clones highly resistant. Three highly resistant BC1 clones, CT02-4, CT08-4, and CT10b-4, were backcrossed to cultivars. Two cross combinations produced mostly susceptible BC2 progenies; however seven clones were resistant or highly resistant for both race 1 and race 3. The highly resistant three clones, CT204-3, CT206-9 and CT206-10, were selected for the further testing as cultivars or breeding materials.

Knowles, N Richard, Lisa O Knowles and Margo M Haines. 2005. 1,4-Dimethylnaphthalene treatment of seed potatoes affects tuber size distribution. Am J Potato Res 82:179-190.

1,4-DMN is a relatively new sprout inhibitor for use on main crop and seed potatoes. Despite its registration as a “dormancy enhancer” for seed, relatively little is known about its effects on plant establishment and productivity. The main objective of this study was to evaluate the effects of 1,4-DMN on the productivity of seed potatoes. ‘Umatilla Russet’ (UR), ‘Ranger Russet’ (RR), and ‘Russet Burbank’ (RB) seed tubers were stored at 4, 7, and 9 C over three seasons to create 80-, 554- and 642-degree-day seed, and 1,4-DMN was applied to maintain dormancy several times during each season. 1,4-DMN residue levels at the end of storage were lower in seed aged at higher temperatures. Multiple applications of 1,4-DMN at higher-than-label rates were necessary to effectively inhibit sprouting of seed of all cultivars stored above 4 C. In field trials, depending on cultivar and year, 1,4-DMN either delayed plant emergence slightly or had no effect. 1,4-DMN increased stem numbers from RB and UR seed, but not from RR seed. 1,4-DMN reduced total tuber yields by 3.2 to 5.6 t ha^-1 (5% to 9%), and U.S. No. 1 tuber yields by 4.8 to 7.8 t ha^-1 (8% to 15%) in all cultivars, regardless of seed tuber age. 1,4-DMN also reduced the average tuber weight for all three cultivars and shifted the size distribution from larger (284 g) to smaller tubers. 1,4-DMN reduced the respective yields of >397-g, 340- to 397-g, and 284- to 340-g tubers by 43%, 19%, and 18% for RR seed, 31%, 14%, and 11% for RB seed, and 40%, 47%, and 27% for UR seed. Conversely, depending on cultivar, yields of smaller tubers (170 g) were 11% to 38% higher from 1,4-DMN-treated seed. The shift in tuber size distribution for RR was accompanied by a 1,4-DMN-induced increase in tuber number per plant and per hectare. However, no such effects on tuber set occurred in RB and UR. Moreover, in most cases, the 1,4-DMN effects on yield and tuber size distribution were independent of seed age. Since the 1,4-DMN-induced shifts in tuber size distribution were greater than the reductions in total and U.S. No. 1 yields, 1,4-DMN may be a suitable treatment to reduce average tuber size and increase yield and uniformity of specific size classes of tubers to more closely match market requirements.

Lambert, DH, ML Powelson and WR Stevenson.  2005. Nutritional Interactions Influencing Diseases of Potato.  (Part of '98 Symposium Presented at 82nd Annual Meeting).  Am J Potato Res 82:309-319.

Nutrient management can decrease the severity of a number of important potato diseases, and certain practices, such as maintaining a low pH for scab control, have been followed for that single objective. More commonly, growers have incorporated fertility modifications into their particular disease and farming situations. Unfortunately, disease minimization may or may not be consistent with optimal fertilization for yield, quality, and profitability. Optimization for one disease may not match that for another, and the exact mechanisms involved are often complex and poorly understood. Potato growers will continue to experience conflicting production constraints. These constraints include price-driven needs for yield improvement and expense reduction; customer-driven demands for quality improvement; varietal shifts driven by the above considerations rather than by disease reduction; increasing pressure to justify, shift and reduce pesticide use; continuing concerns about nitrogen and phosphorus movement in groundwater and runoff; and increased attention to management of rotation crops.

On the positive side, nutrient management strategies for highly specific situations continue to improve and practices addressing nutrient and disease variability within fields are becoming more sophisticated. In this context, there are opportunities for cultural management practices that reduce disease pressure and reliance on chemical controls. To be effectively integrated into such specialized management systems, the mechanisms of these control measures and the conditions under which they are practical will need to be better understood. Likewise, disease responses to these tactics need to be better quantified to allow an adequate cost-benefit analysis. With mounting concerns about the effects of agricultural pesticides on food safety, farm workers, and the environment, management of plant-available nutrients may become practical approaches for disease suppression in the future.

Lebecka, R, E Zimnoch-Guzowska and Z Kaczmarek. 2005. Resistance to Soft Rot (Erwinia carotovora subsp. atroseptica) in tetraploid potato families obtained from after 4X-2X crosses. Am J Potato Res 82:203-210.

Diploid potato clones, interspecific hybrids of Solanum species, having in their origin S. tuberosum, S. chacoense, S. yungasense, S. phureja, S. gourlayi, and S. demissum, with resistance to soft rot, were crossed to tetraploid potato clones in 4x-2x crosses. The 24 tetraploid families obtained in a North Carolina II design were examined for tuber resistance to soft rot in a laboratory test and for basic agronomic traits in field trials conducted for two consecutive years. In addition, one family originating from a 4x-2x cross of two susceptible parents was tested. Statistical analysis of the data revealed significant general (GCA) and specific combining ability (SCA) effects, year, GCA(female) x year, GCA(male) x year, and SCA x year upon the inheritance of resistance to soft rot. About 35% of the progeny was selected as resistant to tuber soft rot, and of these 11% showed high resistance combined with good tuber yield, tuber weight, and tuber appearance. The relationships between resistance to soft rot and chosen agronomic traits were not noted or were weakly significant and sporadic. The resistance to tuber soft rot found in diploid potato hybrids can be transferred to the cultivated tetraploid pool through 4x-2x crosses, and a high frequency of offspring posses resistance.

Lopez-Delgado, H,* HA Zavaleta-Mancera, ME Mora-Herrera, M Vaz-Rivera, FX Flores-Gutierrez and IM Scott. 2005. Hydrogen Peroxide Increases Potato Tuber and Stem Starch Content, Stem Diameter, and Stem Lignin Content. Am J Potato Res 82-279-285.

Field-grown potato plants were sprayed twice weekly, from 21-90 days after planting, with 5 to 50 mM hydrogen peroxide (H₂O₂) solutions. Relative to water-sprayed controls, the H₂O₂ treatments significantly enhanced tuber starch accumulation by between 6.7% and 30%, as determined by specific gravity or the anthrone spectrophotometric method. Pronounced effects of similar H₂O₂ treatments on aerial stem anatomy and starch content were also found in glasshouse experiments. H₂O₂ treated stems were up to 27% thicker than controls. mainly due to enlarged medullar parenchyma cells. Histochemical observations indicated that there were more starch grains in cortex and pith tissue of H₂O₂-treated stems. H₂O₂ also increased the number and size of xylem tracheary elements in the vascular bundles and the number of interfascicular fibers. Quantification using image analysis confirmed that stems of H₂O₂ treated plants contained up to 3.4-fold more starch and 62% more lignin. This new chemical treatment to promote starch accumulation has potential utility in potato crop production and research.

Love, SL, JC Stark and T Salaiz. 2005. Response of Four Potato Cultivars to Rate and Timing of Nitrogen Fertilizer.  Am J Potato Res 82:21-30.

The release of three new potato (Solanum tuberosum L.) cultivars, Bannock Russet, Gem Russet, and Summit Russet, with unique plant growth characteristics, necessitates the development of appropriate N fertilizer recommendations. These three new cultivars, along with the standard cultivar, Russet Burbank, were treated with four N rates (0, 100, 200, and 300 kg N ha^-1) using two different application timing procedures (“early,” with two-thirds N applied preplant, and “late,” with one-third applied preplant). Measurements included total and U.S. No. 1 yields, petiole NO ₃-N concentrations, and net returns derived from economic analysis using a processing-based contract. Each of the four cultivars showed a unique response to N application treatments. Bannock Russet achieved maximum yield and net returns with relatively small amounts of N fertilizer. It also showed no response to N application timing and had moderate NO₃-N sufficiency concentrations early in the season, that decreased markedly late in the season. Gem Russet N requirement for maximum yield was similar to that of Russet Burbank, but required a higher amount of N for maximum net returns. Gem Russet also showed no response to application timing and had NO₃-N sufficiency concentrations similar to or slightly higher than those of Russet Burbank. Summit Russet showed a strong trend for improved N use-efficiency when most of the N was applied early. On the other hand, analysis of net returns revealed a trend for greater profitability for Summit Russet when the majority of N was applied during tuber bulking. Petiole NO₃-N sufficiency concentrations for Summit Russet were generally higher than those for the other three cultivars. In comparison with some earlier studies with Russet Burbank, this research suggested lower optimal N rates and petiole NO₃-N sufficiency concentrations.

Lui, LH, A Vikram, Y Abu-Nada, AC KushaJappal*, GSV Raghavan and K A1-Mughrabi. 2005.  Volatile Metabolic Profiling for Discrimination of Potato Tubers Inoculated with Dry and Soft Rot Pathogens.  Am J Potato Res 82:1-8.

Volatile metabolites from ‘Russet Burbank’ potatoes inoculated with Erwinia carotovora ssp. carotovora (ECC), Erwinia carotovora ssp. atroseptica (ECA), and Fusarium sambucinum (FSA) were analyzed by sampling the headspace at 3 and 6 days after inoculation and then using a gas chromatograph/mass spectrometer (GC/MS) to identify the compounds. Non-wounded non-inoculated and wounded non-inoculated tubers served as checks. Compounds with an abundance of ≥5 and with frequency of ≥3 out of 20 replicates (10 replicates x 2 incubation times) were subjected to further analysis. A total of 81 volatile metabolites were detected, of which 58 were specific to one or common to a few, but not to all inoculations/diseases. Acetic acid ethenyl ester was unique to ECA, while cyclohexene, diazene, and methoxy(l,1-dimethyl-2-dihydroxy-ethyl)-amine were unique to ECC, and 2,5-norbornadiene and styrene were unique to FSA. Several metabolites were common only to tubers inoculated with ECC and ECA and were not detected in fungus-inoculated or in control tubers. High abundances of acetone and butane were detected in ECC- and ECA inoculated tubers, respectively. The possible use of differences in volatile metabolic profiles to discriminate diseases of potato tubers in storage is discussed.

McKenzie, Marian J, Joseph R Sowokinos, Irene M Shea, Sanjay K Gupta, Rebecca R Lindlauf and John AD Anderson. 2005. Investigations on the Role of Acid Invertase and UDP-glucose Pyrophosphorylase in Potato Clones with Varying Resistance to Cold-Induced Sweetening. Am J Potato Res 82:231-239.

Fifteen potato (Solanum tuberosum L.) clones with varying resistance to cold-induced sweetening were analyzed for vacuolar acid invertase (AcInv, EC 3.2.1.26) and UDP-Gle pyrophosphorylase (UGPase; EC 2.7.7.9) activities related to their ability to accumulate sugars following cold storage (4 C). The UGPase isozyme profiles for each clone were also determine. Immunoblot analysis demonstrated a 55 kD protein, in seven of the 15 clones, that reacted with UGPase antisera in addition to the 53 kD UGPase subunit previously reported. The UGPase activity of these closes was significantly lower than that of the "single submit" cones. Basal AcInv activity showed a positive correlation to the Glc:Suc ratio across the clones that was moderately significant before and after cold temperature storage. The activity before and after cold temperature storage. The activity of UGPase, which limits the rate of Suc formation, was of secondary importance in limiting the rate of hexogenesis when vacuolar AcInv activity was excessive. It is suggested that with the potato clones from this breeding program that AcInv (and its inhibitor) plays a dominant role in the hexogenic pathway by regulating the hexose:Suc ratio. The finding of a new protein that is reactive with UGPase antisera may prove to play an important function in the regulation of Suc formation in potatoes.

Oyarzún, Pedro J, Carla D. Garzón, Diego Leon, Irene Andrade and Gregory A Forbes. 2005. Incidence of Potato Tuber Blight in Ecuador.  Am J Potato Res 82:117-122.

Potato late blight, caused by Phytophthora infestans (Mont.) de Bary, is the most important biotic constraint to potato yield and productivity in Ecuador. Yields are severely reduced by foliage blight, but tuber blight has never been quantified in this country. To address this issue, three independent surveys were carried out in Ecuador to estimate the incidence of tuber infection by P. infestans. The first two (1998-1999) involved the collection and assessment of more than 8,000 tubers from the four provinces that produce the most potatoes: Carchi, Chimborazo, Pichincha, and Tungurahua. In the third survey (1999-2001), approximately 10,000 tubers were sampled from the two provinces producing the most potatoes, Carchi and Chimborazo, and from Cañar and Bolivar, two provinces that produce relatively small amounts. In spite of confirmed foliage infection in most fields sampled, very few infected tubers were found. In 1999, an extremely low incidence of tuber blight (less than 0.1%) was detected in three samples (each of more than 1,000 tubers) from the province of Pichincha. In a separate survey in 1999, tuber blight was also found in three fields in the province of Carchi, but with very low incidence. Our data indicate that tuber blight does occur in Ecuador, but the incidence of the disease is extremely low. Factors that might suppress tuber blight in Ecuador are discussed.

Pavlista, Alexander D and Dillon M Feuz. 2005. Potato Prices as Affected by Demand and Yearly Production. Am J Potato Res 339-343. {Short Communication}

With increased potato production in the past decade, actual price for potatoes given to growers has changed little, which means that inflation-adjusted price has decreased. Since production is the result of acres harvested and yield per acre, these two parameters to price are key to understanding price fluctuation. To quantify the relation between potato price and production, acreage and yield, NASS data from 1980 to 2002 were analyzed using linear regressions. Pricing and production showed an inverse, linear relationship, which is divided into two periods. Between 1980 and 1988, the price of potatoes (US$/cwt) increased by $1.00 with a decrease in production of 15.6 million cwt, and between 1993 and 2002 with a decrease in production of 35.7 million cwt. Prices have become less responsive to changes in production. Harvested acres account for about one-third of the annual variation in prices, while yield per acre accounts for about one-half of the variability in prices. It appears that there was an increase in demand for potatoes from 1989 to 1992 that divides the two periods. There also was an increase in the percentage of the crop being used in the frozen and fry market, and a decrease in the percentage of the crop being used in the table or fresh market during this time period. This market change could explain the difference between 1980-1988 and 1993-2002 relationships.

Peters, RD, HW (Bud) Platt and CA Levesque. 2005. First Report of Phythium sylvaticum causing Potato tuber Rot. Am J Potato Res 82:173-177 [Short Communication]

Leak is a post-harvest disease of potato tubers manifested by a wet, spongy rot that can quickly lead to complete tuber decay. In North America, leak is most commonly caused by Phythium ultimum var. ultimum Trow, although a number of other Phythium spp. have been found to be pathogenic to potato tubers. We report that an isolate identified by DNA sequencing as P. sylvaticum Campbell & Hendrix was pathogenic to potato tubers. The organism produced a dark, hollow cavity in tubers that was much drier in texture than typical symptoms of leak. Symptomology was similar in tubers of the cultivars Yukon Gold, Green Mountain, and Russet Burbank. Studied to complete Koch's postulates confirmed that P. sylvaticum could be reisolated from diseased tissue and produced the same disease symptoms when isolates were subsequently re-inoculated into healthy tubers. This is the first report of P. sylvaticum causing rot in potato tubers.

Prange, Robert K, Barbara J Daniels-Lake, Jin-Cheol Jeong and Michael Binns. 2005. Effects of Ethylene and 1-Methylcyclopropene on Potato Tuber Sprout Control and Fry Color. Am J Potato Res 82:123-128.

The study examined the efficacy of 1-methylcyclopropene (1-MCP), an anti-ethylene compound, as a preventative treatment for ethylene-induced fry color darkening in potato (Solanum tuberosum L.) tubers, without reducing the effectiveness of ethylene as a tuber sprouting control agent. The experiment was conducted for three years with ‘Shepody’ and two years with ‘Russet Burbank’ Tubers of each cultivar from four separate growers received one of the following treatments: Air (control), Air +1-MCP (1 µL.L^-1 for 48 h), isopropyl N -(3-chlorophenyl) carbamate (chloropropham; CIPC; 1% a.i. [v/v]); continuous ethylene (4 µL·L^-1 in air; continuous ethylene pre-treated with 1-MCP once; continuous ethylene pre-treated with 1-MCP and repeated monthly; and continuous ethylene pre-treated with 1-MCP and repeated bi-monthly. Treatment started after suberization and cooling to 9 C, and samples were evaluated at 3-wk (year 1) or 4-wk (years 2 and 3) intervals thereafter until April (Shepody) or June (Russet Burbank). Sprout growth (sprout fresh weight per tuber), fry color (Agtron reflectance units), tuber weight loss, incidence of disease infection and internal disorders were evaluated. Weight loss, tuber infection, and the occurrence of disorders were not affected by any of the treatments. Sprout growth was controlled by the continuous ethylene supply in both cultivars, and single or multiple additions of 1-MCP to the ethylene treatment did not affect the ethylene control of sprouting. As expected, ethylene treatment alone enhanced fry color darkening in both cultivars. In Russet Burbank tubers, fry color was not darkened in any of the ethylene + 1-MCP (once, monthly, or bimonthly) treatments. In Shepody, fry color was not darkened in the ethylene + 1-MCP monthly or bi-monthly treatments, but started darkening 4 wk after exposure in the single ethylene + 1-MCP treatment. It is concluded that 1-MCP can be used to control fry color darkening induced by ethylene without blocking ethylene control of tuber sprouting. However, the number of 1-MCP applications required may vary with the cultivar, e.g., one application was sufficient in Russet Burbank but not in Shepody.

Reyes, LF, JC Miller Jr. and L Cisneros-Zevallos. 2005. Antioxidant Capacity, Anthocyanins and Total Phenolics in Purple- and Red-Fleshed Potato (Solanum tuberosum L.) Genotypes. Am J Potato Res 82:271-277.

Purple- and red-fleshed potatoes (Solanum tuberosum L.) were evaluated for their total anthocyanin (ACY), total phenolic (PHEN), and antioxidant capacity. The ACY and PHEN compounds were distributed throughout the tubers; however, a higher concentration was found at the stem-end than the bud-end. Although ACY and PHEN concentrations in potato peel were 0.9- 1o 1.6-fold higher than in potato flesh, overall contribution of the peel to ACY and PHEN contents of a potato slice was -20%. These observations differ from the widespread idea that phytonutrients are mostly accumulated in the peel of tubers. The ACY and PHEN contents of different purple- and red-fleshed potato genotypes ranged from 11 to 174 mg cyanidin-3-glucoside/100 a fresh weight, respectively, and were genotype and location dependent. High positive correlations between antioxidant capacity and ACY and PHEN suggest that these compounds are mainly responsibility for the antioxidant capacity. These results provide useful and important information for potato breeders and researchers in order to increase the antioxidant capacity and functional value of purple- and red-fleshed potatoes for the food and nutraceutical industries.

Rubio-Covarrubias, OA, DS Douches, R Hammerschmidt, A daRocha and WW Kirk. 2005. Effect of Temperature and Photoperiod on Symptoms Associated with Resistance to Phytophthora infestans After Leaf Penetration in Susceptible and Resistant Potato Cultivars. Am J Potato Res 82:139-146.

The effect of temperature and photoperiod on the expression of resistance against Phytophthora infestans in five potato cultivars with and without resistance (R) genes was investigated. Four experiments were carried out under controlled conditions in growth chambers. Two cultivars (393295.236 and 391046.22) without known R genes from the International Potato Center (CIP) in Lima, Peru, two Mexican cultivars with major R genes (Tollocan and Malinche), and a susceptible cultivar (Atlantic) were used in this study. Plants were grown for 32 days in growth chambers at two temperatures (16 and 24 C) and two photoperiods (12 and 16 h day length), then inoculated with a compatible isolate of P. infestans and incubated in a mist chamber at 18 C. The inoculation efficiency, the percentage of lesions that did not grow beyond the inoculation spot, the sporangia density, and the AUDPC were recorded. The percentage of arrested lesions increased with the temperature in the two most resistant cultivars (393295.236 and Malinche), and the AUDPC was lower at 16 than at 24 C in four of the five cultivars. The inoculation efficiency and the sporangia density were not affected by change in temperature. Sporangia density increased at 16 h photoperiod; however, the final infected leaf area was not affected. Our results demonstrate that the expression of horizontal and vertical resistance was affected by temperature; however, the relative resistance ranking among cultivars was the same in the four experiments with different temperatures and photoperiods. It is assumed that the resistance in the Mexican cultivars may be conferred by minor resistance genes and by the residual effect of defeated R genes. These results emphasize the difficulty in differentiating between horizontal and vertical resistance.

Salaiz, Thomas A,* Stephen L Love, Paul E Patterson and Joseph F Guenthner. 2005. Economic Performance of Two New Potato Varieties Using a Fresh Market Consignment- Packing Model. Am J Potato Res 82:147-153.

New potato varieties may provide economic advantages in traditional potato markets. An economic analysis was conducted to determine potential advantages of two new varieties, 'Gem Russet' and 'Summit Russet.' when compared with 'Russet Burbank' in the fresh market. Yield and grade data from 15 location/years were used to calculate net returns for each variety using a price based on a fresh market consignment packing model. Gem Russet and Summit Russet had slightly higher total yield than Russet Burbank when averaged over all locations/years. In only six of the 15 location/years for Gem Russet and four of the 15 for Summit Russet was total yield statistically higher than Russet Burbank. Gem Russet and Summit Russet had numerically higher % US No. 1 yield in all of the locations/years and statistically higher in 12 and 13, respectively. Both varieties were equal to or higher than Russet Burbank in all location/years for % cartons, consignment sale net value and net returns. The higher net return for Gem Russet and Summit Russet over Russet Burbank make these varieties economically advantageous to grow. This type of analysis is important in assessing the value of a new variety to growers based on existing markets.

Shuman, Joel L and Christ, Barbara. 2005. Integrating a Host-Resistance Factor into the FAST System to Forecast Early Blight of Potato. Am J Potota Res 82:9-19.

A host resistance factor was integrated into the FAST (Forecaster of Alternaria solani on Tomatoes) system to initiate and to schedule fungicide applications for three levels of potato cultivar susceptibility while maintaining disease control and yield. Four cultivars ranging from susceptible to moderately resistant were each treated with the fungicide chlorothalonil during two field seasons. The five fungicide treatments were a 7-day schedule initiated after 50% flowering; a non-sprayed control; and three FAST application schedules based on combinations of critical levels of cumulative severity (CS, the disease severity values as a function of leaf wetness and temperature) and cumulative rating (CR, the disease rating values as a function of average temperature and hours of relative humidity greater than 90%) values. The FAST system predicted the onset of early blight and subsequent periods conducive for disease development in 1993 and 1994. There were cultivar-by-spray-schedule interactions for both disease severity and yield, suggesting that differences in early blight susceptibility exist between cultivars. Use of the recommended schedules for the cultivar’s targeted level of susceptibility reduced early blight severity and minimized fungicide use while maintaining yield. These results indicate that a host-resistance factor can be incorporated into the FAST system.

Stark, JC and GA Porter. 2005. Potato Nutrient Management in Sustainable Cropping Systems. Am J Potato Res 82:329-338. [Part of '98 Symposium Presented at 82nd Annual Meeting]

Sustainable nutrient management involves a set of management practices designed to conserve soil resources, to maintain or enhance productivity, and to help reduce growers’ reliance on chemical fertilizers. Sustainable nutrient management systems will most certainly rely heavily on the use of legume rotation crops and/or organic soil amendments. To realize the full benefit to the crop ecosystem, sustainable nutrient management programs will also likely require longer crop rotations with less frequent potato production. There is considerable research evidence indicating that these systems can maintain or increase productivity while having positive impacts on nutrient supply, soil physical properties, and soil conservation. However, their successful adoption and continued use on a large scale will require resolution of uncertainties related to economic risk associated with inconsistent nutrient availability in alternative nutrient management systems, potential environmental risks associated with excessive P applications in animal manures, and the potential for increased potato pest incidence resulting from manure application.

Wang, Aixia and George Lazarovits. 2005. Role of Seed Tubers in the Spread of Plant Pathogenic Streptomyces and Initiating Potato Common Scab Disease. Am J Potato Res 82:221-230.

The influence of tuber-borne pathogenic Streptomyces on potato common scab incidence in daughter tubers was examined under micro-plot conditions. Visually healthy tubers, surfaced-disinfested healthy tubers, and tubers with 25% scab coverage were planted in pasteurized soil. At 30, 57, and 93 days after planting, soil and below ground plant parts were sampled from various zones around the mother tuber. The total population of actinomyctes was determined by plating on a semi-selective medium, and colonies of pathogenic Streptomyces were identified using polymerase chain reaction (PCR) targeting the txtA gene. At day 30, pathogenic Streptomyces populations were below detectable levels, whereas by day 93, measurable levels were present on the below ground plant parts and in soild adjacent to scab mother tubers at 10⁴ to 10⁵ CFU g01 soil. Incidence of scab in the progeny tubers was 89% at harvest. Progeny tubers produced by visually healthy seed tubers had an incidence of 60% scab and substantial populations of pathogenic Streptomyces were present in the zone near the mother tuber (10⁴ CFU g^-1 soil). Plots planted with suface disinfested seed tubers had a very low Streptomyces populations in the tuber zone and yield 100% marketable tubers. A perfect correlation (r = 1.00) was found between the population densities of pathogenic Streptomyces in the root zone and daughter tuber disease incidence indicating that measurement of such populations in the field can serve as an excellent predictor of scab disease. After harvest, populations of pathogenic Streptomyces (10⁶ to 10⁷ CFU g^-1 lesion tissue) remained high on the mother tubers.

Westermann, DT.  2005. Solanum tuberosum, essential elements, fertilization, tissue tests, research opportunities.  Am J Potato Res 82:301-307. [Part of Symposium '98 Presented at 82nd Annual Meeting]

Plant nutrition is the practice of providing to the plant the right nutrient, in the right amount, in the right place, at the right time. This paper gives an overview of the roles that each of the 16 essential nutrients have in plant nutrition, their relative mobility as related to deficiency symptom expression, and what is generally known about nutrient responses to field applications on potatoes (Solanum tuberosum L.) in the USA and Canada. Maintaining high crop yields with minimum nutrient losses to the environment is and will continue to be a significant challenge to the potato producer. Additional nutritional research efforts in genetically modified plants, precision agriculture, food quality and safety, fertilizer impurities, and other management concerns should significantly help the producer in this effort.