Efficacy of Seed Aging and Gibberellin Treatments for Manipulating Apical Dominance,Tuber Set and Size Distribution of cv. Shepody

The cultivar Shepody has excellent early processing qualities and produces above average tuber yields but sets relatively few tubers that often become excessively large relative to market demand. Optimizing tuber set and size of Shepody for seed and frozen processing markets currently entails adjusting in-row spacing and vine kill date. However, arresting tuber growth by vine killing for size control sacrifices yield potential. Aging seed by storing at 12, 22, and 32°C for 80-, 450-, and 900-degree days, or gibberellin (GA) treatments, were evaluated as more direct approaches for modulating stem number (apical dominance), tuber set, and size distribution relationships. Shepody proved to be inherently resistant to high temperature-induced age-priming treatments. In contrast to other cultivars studied previously, age-priming Shepody seed during storage had no effect on plant emergence and the resulting increases in stem number, tuber set, and associated decreases in average tuber weight were marginal. By contrast, GA applied as seed dip or spray effectively hastened plant emergence, reduced apical dominance, increased tuber set, and decreased average tuber size. The magnitude of these GA-induced effects depended on concentration and application technique (seed dip versus spray). For frozen processing, GA applied as a seed dip at 1 mg L^-1 added an additional tuber per plant and decreased average tuber size by 15% without affecting U.S. No. 1 tuber yields and gross returns; however, 2 and 3 mg L^-1 GA decreased U.S. No. 1 tuber yields and crop value by an average of 16 and 14%, respectively. Spray applications of 2–6 mg L^-1 GA also reduced U.S. No. 1 tuber yield and frozen processing value. Conversely, the increase in tuber set (1.5 tubers plant^-1) and associated 25% reduction in average tuber weight induced by 2 mg L^-1 GA applied as either dip or spray increased gross crop values on a seed contract by 25 and 38%, respectively. The differential efficacies of dip versus spray applications of GA on tuber set and size distribution were likely attributable to differences in GA deposition on the seed. Applying low concentrations of GA to cut seed of Shepody as either a dip (1–2 mg L^-1) or spray (2 mg L^-1) effectively modulated tuber set and size to significantly increase gross returns for seed, and to better satisfy the needs of processors for more moderate size tubers.     

TerraRossa: A Mid-Season Specialty Potato with Red Flesh and Skin and Resistance to Common Scab and Golden Cyst Nematode

TerraRossa (POR01PG20–12) is a mid-season specialty potato, released by Oregon State University, and is a product of the Northwest Potato Variety (Tri-State) Development Program. This cultivar is unique among commercially available potato cultivars in that plants produce small- to medium-sized smooth, oblong- to long-shaped tubers with red skin and red flesh. Total tuber yields of TerraRossa are similar to Dark Red Norland and less than Red La Soda. Average tuber size (136 g) is less than both of the comparison cultivars, reflecting inherent differences in tuber size distribution. TerraRossa tubers have total antioxidant levels higher than traditional white fresh varieties and comparable to the All Blue purple potato, known for its high antioxidant levels. Sensory evaluations of TerraRossa tubers indicated that it has good culinary attributes following boiling, baking, and microwaving. Potato chips made from TerraRossa tubers retained their unique red color, which represents a novelty in the chipping industry. TerraRossa could be a good candidate for the organic sector due to its tolerance to common scab (Streptomyces scabies) and tuber late blight (Phytophthora infestans) and its resistance to golden cyst nematode (Globodera rostochiensis). Due to its high yields, high chipping quality, good culinary properties, high antioxidant content and disease resistance, TerraRossa is a good candidate for opening new specialty type markets, adding diversity to the marketplace.     

Influence of Growth Regulators on Plant Growth, Yield, and Skin Color of Specialty Potatoes

2,4-D has been used since the 1950’s to enhance color in red-skinned potatoes, but there is little research on the potential use of other plant growth regulators to improve tuber skin color in the wide range of specialty potatoes now available on the market. Field trials conducted at Parma, ID in 2009 and 2010 evaluated the effect of foliar applications of 2,4-D, NAA, and LPE on plant height, foliar injury, tuber yield, size distribution, and skin color of six specialty potato cultivars. Skin color was rated visually and via HunterLab colorimeter at harvest, and again after storage (132 days in 2009 and 93 days in 2010) at 4 °C and 95 % R.H. 2,4-D caused slight foliar injury and reduced tuber size in all cultivars. It also increased visual skin color rating in the red-skinned cultivars ‘Red LaSoda’ and ‘TerraRosa’ at harvest and after storage, and influenced incidence of pink coloration around the eyes of ‘Yukon Gem’ tubers, but did not affect color of blue/purple-skinned cultivars. NAA and LPE did not consistently influence plant growth, yield, tuber size or visual skin color in any cultivar. Colorimetric evaluations mostly agreed with the visual ratings, and indicated that storage significantly altered skin color in all cultivars, regardless of growth regulator treatment.     

Auxin Modulates Gibberellin-Induced Effects on Growth,Yield, and Raw Product Recovery for Frozen Processing in Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.)

Tuber shape phenotype is an important determinant of raw product (≥7.6-cm-long French fries) recovery for frozen processing. Tuber length-to-width (L/W) ratios ≥1.8 translate to maximum yield of raw product; however, some cultivars produce tubers with much lower L/W ratios. While gibberellin (GA) can be used to elongate tubers, it also decreases tuber size and can thereby attenuate raw product recovery. We investigated the utility of GA and naphthaleneacetic acid (NAA) combination treatments for modifying tuber set, size, and shape to increase yield of raw product from ‘Payette Russet’ and ‘Alturas’; two late-season frozen-processing cultivars that often produce tubers with undesirably low L/W ratios. Models describing L/W ratio and fry yield by tuber size class were developed to translate total U.S. No. 1 tuber yields (>113 g) into yield of raw product. Increases in the L/W ratios of 113–284-g tubers had a greater effect on recovery of French fries (% fresh wt) than for tubers >284 g. Undersize (<113 g) and oversize (>340 g) tubers yielded 0 and 96% fries, respectively, regardless of L/W ratio. GA applied as a seed treatment effectively hastened emergence and altered tuber shape by increasing the L/W ratios of ‘Alturas’ and ‘Payette Russet’ tubers, enhancing total fry yield for the 113–340-g tubers by 24–46%, depending on concentration and application technique (dip, spray, in-furrow). However, GA also decreased apical dominance and shifted tuber size distribution away from >284-g tubers toward higher yields of <170-g tubers, erasing the gains in fry yield when all size classes (>113 g) were considered. When combined with GA, NAA maintained apical dominance, attenuated the shift in tuber size distribution, had no effect on the GA-induced increase in tuber L/W ratio, and only partly moderated the GA-induced stimulation of plant emergence. Raw product yield from ‘Payette Russet’ increased 12–39% in spray application trials by using NAA to confine the effect of GA to tuber shape and limit the loss of U.S. No. 1 tubers to undersize. Increases in tuber L/W ratio with GA/NAA seed treatments translated to increased yield of fries only when the relative concentrations were adjusted to minimize loss of >284-g tubers and gain in undersize tubers, as dictated by cultivar sensitivity to GA. ‘Alturas’ was less sensitive to GA than ‘Payette Russet’ for shifts in tuber size distribution but not shape, resulting in 17% increase in raw product with GA alone in pre-plant seed spray application studies. GA/NAA combination treatments provide an effective approach to manipulate tuber size distribution and enhance the yield of raw product for frozen processing in cultivars with a rounder tuber shape phenotype.     

Red Gold: A yellow-fleshed,red-skinned potato cultivar with short dormancy and high tuber set

Red Gold is a midseason maturity potato with pink-red skin and a bright yellow flesh. It is characterized by having a high set per plant of medium-small sized tubers. Marketable yields in Ontario, Canada are similar to or slightly less than Conestoga, Yukon Gold, and Superior. Boiling, baking, and field chip quality are acceptable with medium specific gravities (1.070–1.080). Short tuber dormancy makes this variety well adapted for whole seed tuber production for fall export markets. Red Gold has performed well in trials in Uruguay. Red Gold is moderately resistant to scab, field resistant to virus Y and leafroll, and susceptible to mild mosaic.     

Huckleberry Gold: A Specialty Market Potato Cultivar with Purple-Skin,Yellow-Flesh,High Tuber Antioxidants,and Resistance to Potato Cyst Nematode (H1) and Potato virus X (Nb and Rx1)

Huckleberry Gold is a purple-skin, yellow-flesh fresh market cultivar with similar culinary qualities to the market standard Yukon Gold. It has lower specific gravity, sucrose and vitamin C content, but a significantly higher level of tuber antioxidants than Yukon Gold. Notable disease resistant characteristics are Potato virus X resistance based on the presence of molecular markers for the PVX resistance genes, Nb and Rx1. In addition it also has the H1 gene present which confers resistance to the potato cyst nematode, Globodera rostochiensis, which has been confirmed by bioassay to pathotype Ro1. The size profile of Huckleberry Gold is smaller than Yukon Gold, allowing a better fit into specialty markets that are geared to smaller size for fresh use. Huckleberry Gold represents the first purple-skin, yellow-flesh cultivar to come from the Northwest (Tri-State) Potato Variety Development program.     

Potato Crop Response to Genotype and Environment in a Subtropical Highland Agro-ecology

Potato response to environment, planting date and genotype was studied for different agro-ecological zones in Lesotho. Field experiments were conducted at four different sites with altitudes ranging from 1,655 to 2,250 m above sea level during the 2010/2011 and 2011/2012 summer growing seasons. Treatments consisted of three cultivars that varied in maturity type, two planting dates and four sites differing in altitude and weather patterns. Various plant parts were measured periodically. To understand and quantify the influence of abiotic factors that determine and limit yields, the LINTUL crop growth model was employed which simulated potential yields for the different agro-ecological zones using weather data collected per site during the study period. Observed actual crop yields were compared with model simulations to determine the yield gap. Model simulations helped to improve our understanding of yield limitations to further expand potato production in subtropical highlands, with emphasis on increasing production through increased yields rather than increased area. Substantial variation in yield between planting date, cultivar and site were observed. Average tuber dry matter (DM) yields for the highest yielding season were above 7.5 t DM ha^?1 or over 37.5 t ha^?1 fresh tuber yield. The lowest yield obtained was 2.39 t DM ha^?1 or 12 t ha^?1 fresh tuber yield for cultivar Vanderplank in the 2011/2012 growing season at the site with the lowest altitude. Modelled potential tuber yields were 9–14 t DM ha^?1 or 45–70 t ha^?1 fresh yield. Drought stress frequently resulted in lower radiation use efficiencies and to a lesser degree harvest indices, which reduced tuber yield. The site with the lowest altitude and highest temperatures had the lowest yields, while the site with the highest altitude had the highest yields. Later maturing cultivars yielded more than earlier maturing ones at all sites. It is concluded that the risk of low yields in rain-fed subtropical highlands can be minimised by planting late cultivars at the highest areas possible as early as the risks of late frosts permit.     

Rose Gold: A yellow fleshed,pink-red skinned,tablestock cultivar with short dormancy and full season maturity

Rose Gold is a pink-red skinned, bright yellow fleshed, tablestock potato cultivar. In Ontario trials, Rose Gold is later maturing than its half sibling Red Gold and is characterized by producing larger and fewer tubers per plant than Red Gold. Rose Gold rarely develops symptoms of virus diseases when grown for repeated generations under high virus disease pressure (PVY, PLRV, PVX). Tubers have a very short dormancy. Yields are similar to Yukon Gold on mineral soil and generally higher than Red Gold. Rose Gold has produced high marketable yields on muck soil.     

Economic Optimum Nitrogen Fertilization Rates and Nitrogen Fertilization Rate Effects on Tuber Characteristics of Potato Cultivars

The objective of the research was to determine the economic optimum nitrogen (N) fertilization rates and to determine the effects of N fertilization rates on tuber characteristics and fresh mass loss after storage under cold and ambient conditions of four potato cultivars, Ágata, Asterix, Atlantic, and Monalisa. The experiments were, simultaneously, conducted in the same area and similar experimental conditions during the fall/winter period in Viçosa, Minas Gerais State, Brazil. In each experiment, five N fertilization rates (0, 50, 100, 200, 300 kg ha^?1) were evaluated in a randomized complete block design. For all cultivars, increasing N fertilization rate increased total and marketable yields and tuber dry matter yield up to a maximum following a quadratic model. Increasing N fertilization rate linearly increased the tuber protein concentration of Atlantic and Monalisa and had no effect on tuber pH. N fertilization rate effects on tuber mass, tuber titratable acidity, and fresh mass loss during storage were cultivar-dependent. N use efficiency (tuber yield divided by N fertilization rate) decreased with increase in N fertilization rate. The economic optimum N fertilization rates ranged from 147 to 201 kg ha^?1 depending upon cultivar and relative prices of N and potato tubers. Depending on the cultivar, under favorable price conditions (low N price and high tuber price), the economic optimum N fertilization rates to be applied by potato growers were 92–95% of the estimated N fertilization rate for obtaining the maximum potato yield, whereas under unfavorable conditions (high N price and low potato tuber price) the economic optimum N fertilization rates to be applied should be decreased to 86–92% of the rates for maximum yield.     

Anatomy and compositional variations within potatoes. IV. Total solids distribution in different cultivars

Distribution of cortical, perimedullary, and pith tissues and total solids content were determined on both a fresh and a dry weight basis for six potato cultivars grown concurrently in three locations in California. At one location, tubers harvested 80 days from planting were 1.0 to 2.5% lower in total solids than tubers harvested at later dates. The high solids cortical tissues ranged from 39 to 51% of whole tubers on a dry basis, and the amount appeared to be related to tuber shape. White Rose and Red LaSoda showed greater difference in per cent total solids between cortical and perimedullary tissues than did Kennebec, Lenape,³ Norchip, and Russet Burbank. The high total solids of the cortical tissues is particularly significant to processing losses. Any method of peeling that removes one half the linear depth of the cortical tissues can result in a loss of 25% or more of total tuber solids, depending upon cultivar and tuber shape. Tuber development and distribution of total solids and other components were previously described for Red Pontiac, Russet Burbank, and White Rose tubers obtained from the retail market (6,9,10,11). It was particularly noted that the high-solids cortical tissues, although averaging only about 6mm in depth, comprised between 40 and 50% of both fresh and dry tuber weights (6,11). Because this sort of distribution of solids is especially significant to peeling loss, possible differences in solids among cultivars and at different harvest dates were investigated.     

Arsenic-prone rice cultivars: a study in endemic region

Rice is prone to arsenic accumulation compared to other cereals as typically grown up under waterlogged situation favoring arsenic mobility. Arsenic in rice depends on arsenic availability to plants from irrigation water, even differs among cultivars and their plant parts. Present study was concentrated on arsenic accumulation in various plant parts of five common rice cultivars grown using irrigation water from different water sources in various fields in arsenic-endemic region. Additionally, dose response experiment under laboratory net house was conducted on the same cultivars excluding open environmental factors. The common cultivars were categorized according to high to low arsenic accumulator in rice grain, straw and root parts. The cultivar Shatabdi has shown highest arsenic accumulation in rice grain compared to other rice cultivars in fields and when grown at various soil arsenic doses. In field samples, a highest grain arsenic concentration ranged between 0.69 ± 0.04 and 0.78 ± 0.12 mg kg^?1 for Shatabdi, whereas lowest grain arsenic concentration ranged between 0.37 ± 0.07 and 0.41 ± 0.07 mg kg^?1 for the cultivars GB3 and Lalat. Speciation study detected more inorganic arsenic than organoarsenicals with a trend of arsenite > arsenate > DMA > MMA, which would be problem for consumers. The concluding remark is the characterization of common rice cultivars according to arsenic concentration to highlight an important remediation strand by changing to low arsenic cultivar.     

TX1523-1Ru/Y a.k.a Sierra Gold™: An early maturing, yellow-fleshed ruseet cultivar for the specialty/gourmet market

TX1523-1Ru/Y, a unique specialty cultivar with deep-yellow flesh color and an attractive russet skin, was released in 2003 by the Texas Agricultural Experiment Station. The smaller, immature tubers are round, but take on an oval shape as they mature. Eyes are shallow and the tuber surface is smooth. Tuber size tends to be medium (113.4–283.5 g; 4–10 oz). Total and marketable yield varies with year and location, but tends to be comparable to ‘Yukon Gold’, with percent marketable yield slightly higher. Vines are semi-prostrate, with medium vigor and size, and relatively early maturity. Specific gravity is about the same or slightly less than Yukon Gold, but generally greater than ‘Russet Norkotah’. TX1523-1Ru/Y has good culinary qualities, with resistance to after-cooking-darkening, and can be chipped, boiled, baked, or microwaved. It has been reported to be excellent to superior as a microwave product. Unlike Yukon Gold, TX1523-1Ru/Y is resistant to hollow heart, brown centers, and internal discoloration. It tends to be less susceptible to tuber infection by late blight (Phytopthora infestans) than Yukon Gold, has greater resistance to common scab (Streptomyces scabies), and is less susceptible to black scurf (Rhizoctonia solani). TX1523-1Ru/Y is believed to be the first yellow-fleshed resset-skin cultivar released in the United States.     

Management of nitrogen and phosphorus rates does not suppress verticillium wilt in yukon gold

Effect of nitrogen and phosphorus fertilization rates on the incidence of Verticillium wilt caused byVerticillium albo-atrum orV. dahliae and tuber yield in potato cv Yukon Gold was evaluated in field plots. In three years of study,V. albo-atrum caused a higher incidence of wilt symptoms (74%–100%) thanV. dahliae (5%–81%) resulting in lower marketable tuber yield. In plots infested withV. albo-atrum, tuber yield ranged from 12.3-22.8 T ha1 compared to 18.1– 31.5 T ha^-1 in plots infested withV. dahliae. Application of nitrogen above (280 kg ha^-1) or below (70 kg ha^-1) the recommended rate of 140 kg ha^-1 at planting did not suppress foliar symptoms or protect against yield loss caused by eitherV. albo-atrum orV. dahliae. Similarly, phosphorus rate adjustments did not consistently affect disease incidence regardless of the pathogen. Management of nitrogen or phosphorus fertility rates at planting does not appear to be a viable approach for suppressing Verticillium wilt in the determinant, wiltsusceptible cultivar Yukon Gold.     

Potato Plants Grown from Minitubers are Delayed in Maturity and Lower in Yield,but are not at a Higher Risk of <Emphasis Type="Italic">Potato virus Y</Emphasis> Infection than Plants Grown from Conventional Seed

Potato virus Y (PVY) is the most important virus in North American seed potato (Solanum tuberosum L.) production. Planting virus-free minitubers in place of field-grown seed, which usually has a low PVY incidence, reduces initial PVY inoculum in the field. However, plants grown from minitubers are smaller and emerge later than those grown from conventional seed, which could make them more likely to become infected with PVY. We tested the effects of seed type of three potato cultivars (Dark Red Norland, Goldrush, and Red La Soda) on PVY incidence, tuber yield, and flowering time. The incidence of PVY in plants grown from minitubers did not differ from that of plants grown from conventional seed. Minituber-grown plants produced lower tuber yields than plants grown from conventional seed. Plants from minitubers also emerged and flowered later, but this did not increase their incidence of PVY. Cultivar-specific differences were observed in tuber yield and flowering times, suggesting that this variation may influence PVY incidence more than seed type.     

Determination of yield stability in advanced potato cultivars as affected by water deficit and potassium humate in Ardabil region, Iran

This experiment was done on the three potato cultivars [Agria (susceptible), Satina (semi-tolerant) and Ceaser (tolerant to water deficit)] and three irrigation treatments (after 30 mm evaporation from basin class A, after 60 mm evaporation + spraying by Potassium Humate, and after 60 mm evaporation from basin class A) for two locations in 2007. Experimental design was Split Plot with three replications. Potassium Humate spraying (250 mL ha(-1)) were done in three stages of emergence, before tuberization and during tuberization period. Combined analysis of variance showed that there were significant differences between locations, cultivars, irrigation treatments and location x cultivars interaction as effect on tuber yield. Comparison of means for irrigation treatments showed that spraying by Potassium Humate in stress condition induced increasing of tuber yield. Spraying by Potassium Humate in water deficit condition increased tuber yield up to 11.01 ton ha(-1). Ceaser had the highest tuber yield. It had higher tolerance to water deficit as well. Ceaser had a high potential in control and severe stress. Decrease in yield of Ceaser after 60 mm evaporation + spraying by Potassium Humate and after 60 mm evaporation from basin class A, relative to control (after 30 mm evaporation from basin class A) was 1.03 and 13.08 ton ha(-1) but for Satina was 7.83 and 16.61 ton ha(-1), respectively. Satina had the lowest Environmental Variance, Environmental Variance Coefficient, Finlay and Wilkinson's and Eberhart and Russell's model and was the most stable cultivar. Lin and Binns parameter showed that Ceaser and Satina were the most stable cultivars. Results of GMP, STI and MSTI were very considerable and Ceaser and Satina had a high yield in water stress and control conditions.     

Potato composition: III. Tissue selection and its effects on total nitrogen,free amino acid nitrogen and enzyme activity (polyphenolase,monophenolase, peroxidase and catalase)

Russet Burbank, Norchip, Kennebec, White Rose, Red La Soda and Lenape tubers were sampled at harvest, after storage for 2 and 4 mo at 7 C, and after 3 wk at 20 C following each storage treatment. Freeze-dried tissue from the bud-end, stem-end and core was analyzed for total, and free amino acid nitrogen, and for monophenolase, polyphenolase, peroxidase, and catalase activities. Significant differences among cultivars and among different parts of the tuber were found for all nitrogen fractions and all enzyme activities. Storage treatments significantly changed the total and free amino acid nitrogen contents and polyphenolase, peroxidase, and catalase activities. When compared for total nitrogen content and catalase activity, differences among different parts of the tuber which were statistically significant were similar in all cultivars. However, when compared for free amino acid content, and monophenolase, polyphenolase and peroxidase activities, differences among different parts of the tuber which were statistically significant were dependent upon which cultivar was examined. The differences among cultivars which were statistically significant for all nitrogen fractions and all enzyme activities, except peroxidase, were not significantly changed by storage treatment. The differences among different parts of the tuber which were statistically significant for quantity of both nitrogen fractions and for all enzyme activities were not significantly changed by storage.     

Changes in color and sugar content of yellow-fleshed potatoes stored at three different temperatures

Yellow-fleshed potatoes, Yukon Gold, Red Gold, Sag-maw Gold, Augsberg Gold, and AO82283.1 were compared to white-fleshed cultivars, Russet Burbank and Norchip, in relation to flesh color and sugar content during long-term storage. Yellow-fleshed cultivars had higher hue angles (h°) and chroma values (C*) compared to the white-fleshed potatoes. These values were consistently higher at all storage temperatures. Chroma values were maximum for most yellow-fleshed tubers when stored at 8.3 C for 84 days. As expected, lower concentrations of sucrose, glucose, and fructose were observed in tubers stored at 10 C compared to those stored at 3.3 and 8.3 C. After storage at either 3.3 or 8.3 C, Saginaw Gold, Augs-berg Gold, and AO82283.1 accumulated lower amounts of glucose or fructose compared to Norchip, Russet Burbank, Yukon Gold, and Red Gold. Although the yellow-fleshed clones accumulated up to 7.4 mg/g glucose or fructose when stored at 3.3 C, Saginaw Gold and Augsberg Gold responded well to reconditioning.     

Relationships Among Antioxidant Activity, Total Phenolic Content and Specific Gravity in Several Potato (Solanum tuberosum L.) Cultivars Grown in Different Environments

Environmental conditions influence crop productivity and quality, making breeding for improvement of a particular trait challenging. Similarly, relationships among traits may make trait improvement difficult, especially if selection for high levels of one trait results in low levels of the other(s). Therefore, understanding the influence of environment and relationships among traits is necessary in trait selection and crop improvement. The objective of this study was to investigate the variability and correlations among antioxidant activity (AOA), total phenolic content (TP), and specific gravity (SPG) in potato cultivars and advanced breeding selections. This research included investigation of genotype x environment (GxE), using four cultivars (Atlantic, Red LaSoda, Russet Norkotah, and Yukon Gold) grown for 3 years (2005, 2006, and 2007) in nine states (CA, ID, MI, MN, NJ, NC, OR, TX, and WI), and two broader genotype studies using 15 advanced breeding selections grown in Texas in 2005 and 60 advanced selections and five cultivars grown in Texas in 2009. Two methods, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), were used to evaluate AOA, and total phenolic (TP) content was determined using the Folin-Ciocalteau method. Significant effects of cultivar, year, location and their interactions on AOA, TP, and SPG were observed, as well as significant trait differences among cultivars within and between locations. The correlations between AOA and TP were significantly positive, while between AOA and SPG, and between TP and SPG were weak and negative in the GxE study. Correlations between AOA and SPG, and between TP and SPG in the two genotype studies were not significant. The weak relationships observed in the GxE study between AOA and SPG, and between TP and SPG may have been due to the small sample size and/or the cultivar Atlantic consistently exhibiting the lowest values of AOA and TP, and highest SPG in all locations. Results from the genotype studies suggest that breeding for high AOA and TP to increase the nutritional value of potato cultivars can be done without compromising tuber quality in terms of specific gravity.     

The Effect of Long Term Storage on Bacterial Soft Rot Resistance in Potato

Bacterial soft rot is a serious disease in potato (Solanum tuberosum L.), causing rapid tuber tissue maceration and, consequently, marketable yield loss. Soft rot bacteria, including Pectobacterium carotovorum subsp. carotovorum (Pbc), are favored by moist conditions, which are prevalent in large potato storage facilities. However, although most potatoes in North America are stored before use, there are no published surveys of soft rot resistance in cultivars exposed to long-term storage conditions. Thus, we tested 65 cultivars and 13 breeding lines for soft rot resistance after 6 months of storage. There was a significant effect of cultivar and production environment on soft rot resistance score. During 6 months of storage, tuber soft rot resistance in resistant clones did not change, while it changed in susceptible clones. The three most resistant cultivars to soft rot were Freedom Russet, Anett, and Alaska Red Eye.     

Potato composition: I. Tissue selection and its effects on solids content and amylose/amylopectin ratios

Solids content and amylose/amylopectin ratios were determined in different parts of tubers of White Rose, Red La Soda, Kennebec, Russet Burbank, Norchip and Lenape at harvest, after storage at 7 C for 2 and 4 mo, and after reconditioning at 20 C for 3 wk following each storage period. In all cultivars, solids content was greatest in stem-end, lower in bud-end and lowest in core tissue. The relationships for distribution of solids among the different parts of the tubers was not changed by storage treatments in any of the cultivars. Amylose/amylopectin ratios were similar in all parts of the tuber. Both the solids content and amylose/amylopectin ratio were changed by storage, but not uniformly in all cultivars.