Eric P. Eldredge

The effect of timed water stress on quality, total solids and reducing sugar content of potatoes

Potato (Solanum tuberosum L.) solids and reducing sugars were examined before, just after, and two weeks after transient water stress to gain an understanding of tuber changes that occur directly associated with water stress. Russet Burbank and A082260-8 potatoes were grown on Owyhee silt loam at the Malheur Experiment Station, Ontario, Oregon. Potatoes were subjected to a single episode of transient water stress by omitting furrow irrigation in either late June, July, or in early August of 1988 and 1989 to examine variety differences in the short term effects of water stress on changes in solids and reducing sugars in tuber stem ends. Irrigation was managed to maintain soil water potential above -65 kPa at 20 cm depth during tuber initiation through bulking except during transient stress when the soil water potential reached -82 to -110 kPa. Tuber samples were taken from plots and minimally stressed check treatments before stress, at the peak of stress, two weeks after the transient stress period, and after harvest. Tubers were sectioned longitudinally and the percent solids and reducing sugars were determined for samples from the tuber stem end, center, and apical end. Longitudinal tuber strips were fried after harvest to determine fry color. Tuber stem-end fry color did not darken in A082260-8 potatoes subjected to water stress. The line A082260-8 had higher stem-end solids and lower stem-end reducing sugars than Russet Burbank. Neither variety responded to transient water stress or recovery from transient stress with an immediate increase in reducing sugars in any tuber part. Reducing sugars were elevated in harvested tubers, particularly in the stem-ends of Russet Burbank potatoes subjected to water stress. Increases in tuber reducing sugars related to transient water stress were not found during the stress period or immediately after stress, but were present in harvested tubers.CompendioSe examinaron los sólidos y los azúcares reductores de la papa (Solanum tuberosum L.), antes, inmediatamente después y dos semanas después de un breve estrés al agua para determinar los cambios que ocurren en los tubérculos, directamente asociados con el estrés al agua. Papas Russet Burbank y A082260-8 se cultivaron en suelo franco-limoso de Owyhee en la Estación Experimental Malheur, Ontario, Oregón. Las papas fueron expuestas a un solo periodo de breve estrés al agua, omitiendo el riego por surco ya fuese al final de junio, julio o a comienzos de agosto de 1988 y 1989, para determinar las diferencias varietales en los efectos del corto periodo de estrés al agua sobre los sólidos y azúcares reductores en el extremo basal del tubérculo. La irrigación fué suministrada para mantener el potencial de agua del suelo por encima de -65 kPa a 20 cm de profundidad durante el inicio de la tuberización y durante todo el periodo de desarrollo de los tubérculos, excepto durante el breve estrés, en que el potencial de agua del suelo alcanzó de -82 a -100 kPa.Se tomaron de las parcelas, y de los tratamientos testigo con estrés mínimo, muestras de tubérculos antes del estrés, al momento de máximo estrés, dos semanas después del breve periodo de estrés y después de la cosecha.Los tubérculos fueron seccionados longitudinalmente y se determinó el porcentaje de sólidos y de azúcares reductores en muestras tomadas del extremo basal, centro y extremo apical de los mismos. Se frieron rebanadas longitudinales de papas después de la cosecha para determinar el color de la fritura. El color de las porciones basales, después de fritas, no se oscureció en las papas A082260-8 expuestas al estrés al agua. La línea A0822608 tuvo en el extremo basal más sólidos y menos azúcares reductores que Russet Burbank. Ninguna de las variedades respondió al breve estrés al agua o se recobraron del mismo con un aumento inmediato de azúcares reductores en alguna parte del tubérculo. Los azúcares reductores fueron abundantes en los tubérculos cosechados, particularmente en los extremos basales de las papas Russet Burbank expuestas al estrés al agua. Durante el periodo de estrés, o inmediatamente después, no se encontraron incrementos de azúcares reductores en los tubérculos en relation con el breve estrés al agua, pero sí se observaron en los tubérculos cosechados.

Effects of transitory water stress on potato tuber stem-end reducing sugar and fry color

Potatoes grown for processing in irrigated regions of the Pacific North-west sometimes develop undesirably high concentrations of reducing sugars in tuber stem ends due to hot weather and water stress during tuber development. Such tubers usually produce french fries with dark stem ends or sugar ends. In order to better quantify the relationship between water stress and stem-end sugar levels for Russet Burbank, single episodes of transitory water stress were established by delaying irrigations until soil water potentials ranging from -32 to -107 kPa were reached during early tuber bulking. To determine when the increase in reducing sugars occurred, tubers were sampled before transitory stress, at maximum stress, after stress was relieved with sprinkler irrigation, and post harvest. Reducing sugar concentrations did not increase in tuber stem ends until two weeks or longer after the plant water stress was relieved. Increased reducing sugar concentrations were positively associated with decreased soil water potential (drier soil). Tubers were sliced and fried at harvest and six weeks post-harvest. Decreasing soil water potential (drier soil) was associated with progressively darker fry colors at harvest and post harvest. Significant darkening in the average stem-end fry color light reflectance of tubers at harvest as observed at -80 kPa in 1988 and -69 kPa in 1989. The effect of imposed water stress on tuber stem-end reducing sugar concentrations was most pronounced post harvest.

Irrigation best management practices for potato

Application of the principle of best management practices (BMPs) for potato irrigation maximizes economic use of resources while minimizing environmental disturbances. Potato is a shallow-rooted crop that responds negatively to variations in water supply. Reported research confirms the detrimental effects of small errors in irrigation management on potato production profitability. Potato water use has been thoroughly documented in the literature. Newer irrigation application and control technology is available to growers. Irrigation BMPs for scheduling irrigation by crop evapotranspiration (ETc) and soil water tension (SWT) are presented and discussed. In most cases only refinements of existing potato irrigation systems are needed; growers need to acquire some way to measure ETc or soil water, or preferably both, along with record keeping to track irrigation, ETc, and soil water. An increased increment of management applied to potato irrigation can return greater profits to potato growers while enhancing the sustainability of production by avoiding environmental degradation.ResumenLa aplicación de prácticas de un mejor manejo (BMPs) del riego para el cultivo de papa, maximiza el uso económico de recursos mientras que minimiza las alteraciones del medio ambiente. La papa es un cultivo de raíices poco profundas que responde negativamente a la variación en el abastecimiento de agua. Informes de investigación confirman el efecto nocivo de pequeños errores en el manejo del riego sobre la producción de papa. El uso de agua por el cultivo de papa ha sido ampliamente documentado en la literatura. La más reciente tecnología de aplicación y control del riego está disponible para los que cultivan papa. Se presentan y discuten las BMPs para programar el riego por evapotranspiración del cultivo (ETc) y tensión de agua del suelo (SWT). En la mayoría de los casos sólo se necesita un afinamiento de los sistemas de riego ya existentes; los que cultivan papa necesitan tener la forma de medir la ETc o el agua del suelo o preferiblemente ambos, junto con los registros para rastrear el agua de riego, ETc y agua del suelo. Un mayor incremento en el manejo del riego en la papa puede rendir mayores beneficios, a la vez que la sostenibilidad de la producción mejora evitando la degradación del medio ambiente.

Compositional and enzymatic changes associated with the sugar-end defect in Russet Burbank potatoes.

This study was initiated to determine the starchsugar composition and the activities of relevant enzymes of carbohydrate metabolism in Russet Burbank (cv.) potatoes exhibiting the sugar-end defect. The frequency of sugar-end tubers was increased by applying a single, transient, moisture-deficit stress period following tuberization. The following properties were unique to sugar-end tubers compared to normal tuber tissue. (1) Starch and total solids decreased markedly while glucose content increased 15-fold, (2) The concentration of Suc was markedly lower, (3) Pi was slightly but significantly increased, (4) The activities of UGPase and Susy decreased nearly 3 and 2-fold, respectively, (5) The activity of AGPase decreased 50%, (6) The ratio of STPLase to AGPase shifted over 3-fold in favor of starch mobilization, (7) Basal AcInv activity (assayed in the presence of inhibitor) increased 7-fold during storage, (8) Tuber Glc concentration showed a better correlation to basal Aclnv activity than to total Aclnv activity (inhibitor destroyed), (9) Kinetic analysis suggested that the level and/or effectiveness of the Aclnv inhibitor was decreased in the sugar-end tuber tissue. These results are discussed in relation to metabolic changes which occur in converting a starch storing tuber to one primarily involved with starch mobilization.

Automation of Subsurface Drip Irrigation for Crop Research

Automatic feedback control of precision irrigation scheduling allows the determination of optimum soil water potential for crops, close determination of N fertilizer requirements, and other measures of crop development and yield responses. Soil water potential (SWP) was measured with granular matrix sensors (GMS; Watermark Soil Moisture Sensors Model 200SS, Irrometer Co., Riverside, Calif., USA) at 0.2-m depth below onion and potato rows. Sensors were calibrated to SWP. The GMS were connected to a datalogger (CR10X datalogger, Campbell Scientific, Logan, Utah, USA) via five multiplexers (AM416 multiplexer, Campbell Scientific). The datalogger was programmed to read the GMS in each irrigation treatment zone 4 to 8 times a day and irrigate each zone individually as necessary. Irrigations were controlled by the datalogger signaling a controller (SDM-CD16AC controller, Campbell Scientific) connected to solenoid valves for each zone. The pressure in the drip lines was maintained at 69 kPa by a pressure regulator in each zone. The amount of water applied in each zone was recorded by a water meter installed between the solenoid valve and the drip tape. The irrigation criteria for onion (Allium cepa) and potato (Solanum tuberosum) were determined for subsurface drip irrigation (SDI). N fertilizer requirements may be reduced due to reduced N leaching under SDI.

Relationship of Beet Curly Top Foliar Ratings to Sugar Beet Yield

Sugar beet (Beta vulgaris) varieties were evaluated for disease resistance to curly top to establish if disease ratings made in inoculated nurseries correlated with disease ratings and yield in sugar beet crops exposed to natural disease outbreaks. Cultivars were planted both in inoculated curly top nurseries in Kimberly, ID, and in commercial cultivar trials in irrigated fields near Ontario, OR and Nampa, ID. Plants were evaluated for curly top using a rating scale of 0 (no symptoms) to 9 (dead). Moderate disease pressure in the Ontario (mean rating = 3.8) and Nampa (mean rating = 4.1) fields resulted in significant differences for disease rating, root yield, sugar content, and estimated recoverable sugar among cultivars. Disease ratings from both commercial fields were positively correlated (r = 0.91 and 0.82, P < 0.0001) with ratings from the inoculated nurseries. In commercial fields, root yield was negatively related to disease rating (r2 = 0.47 and 0.39, P ≤ 0.0004). For each unit increase in disease rating (increasing susceptibility), root yield decreased 5.76 to 6.93 t/ha. Thus, curly top nurseries reliably predict curly top resistant cultivars for commercial cultivation.

Potato tuber stem-end fry color determination

Precise measurement of tuber stem-end fry color is necessary to determine the fry quality of potatoes (Solanum tuberosum L.). Changes in fry color as influenced by small variations in measurement location, delays between slicing and frying, and delays between frying and measuring were examined. Variations in time between frying and measurement, and variations in the location of measurement contributed more to changes in observed color than delays between slicing and frying. The standard visual method for determining stem-end fry color was compared to objective methods using a Photovolt reflectance meter. Photovolt reflectance readings of two types of transverse stem-end tuber slices were compared with those from longitudinal strips. All methods produced closely related re-sults. Optimum sample size and applications for each method are discussed.

Wallowa Russet: A full season long Russet for processing and fresh market

The Agricultural Experiment Stations of Oregon, Idaho, and Washington and the U.S. Department of Agriculture jointly released Wallowa Russet in 2002. This late maturing variety is most suitable for frozen french fry use, but may find limited fresh market potential because of outstanding flavor and texture when baked. Wallowa Russet was evaluated as AO87277-6 in Oregon irrigated trials from 1993 through 1999, and in western regional trials from 1997 through 1999. Averaged over 13 locations in seven states, Wallowa Russet produced total yields of 55.6 mt/ha compared to 53.5 and 45.7 mt/ha for Russet Burbank and Russet Norkotah, respectively, and U.S. No.1 yields of 44.4 mt/ha compared to 30.7 and 36.0 mt/ha for Russet Burbank and Russet Norkotah. Specific gravity is consistently higher for Walowa Russet than for Russet Burbank and fry color is as light or lighter; sugar end development is less than that observed in Russet Burbank. Wallowa Russet is similar to Russet Burbank in susceptibility toVerticillium wilt, foliar early blight (Alternaria solani), and potato leafroll virus (PLRV). However, Wallowa Russet develops less net necrosis than Russet Burbank from PLRV infection. Wallowa Russet is more susceptible to common scab (Streptomyces scabies) than Russet Burbank. It has moderate resistance to potato virus Y (PVY). Tubers of Wallowa Russet are less susceptible to tuber infection and decay caused by potato late blight (Phytophthora infestans) than Russet Norkotah and Ranger Russet. Wallowa Russet has less hollow heart, brown center, blackspot bruise, and fewer growth cracks than Russet Burbank but is more susceptible to shatter bruise. Vitamin C is higher for Wallowa Russet (30.4 mg/100 g fresh weight) than for Russet Burbank (21.9) or Russet Norkotah (22.0), and protein content averaged 5.6% compared to 4.7% and 4.9% for Russet Burbank and Russet Norkotah, respectively.ResumenLas Estaciones Experimentales de Oregon, Idaho y Washington, y el Departamento de Agricultura de los Estados Unidos han liberado conjuntamente en el 2002 la variedad Wallowa Russet. Esta variedad de maduración tardía es más apropiada para su uso como papa frita congelada, pero además puede encontrar un mercado potencial limitado para su consumo fresco debido a su excelente sabor y textura cocido al horno. Wallowa Russet fue evaluada como AO87277-6 en pruebas bajo riego realizadas en Oregon desde 1993 hasta 1999 y en pruebas regionales de 1997 a 1999. En un promedio de 13 localidades en siete estados, Wallowa Russet dio rendimientos totales de 55.5 t/ha en comparación con 53.5 y 45.7 t/ha de Russet Burbank y Russet Norkotah. La gravedad específica es consistentemente más alta para Wallowa Russet que para Russet Burbank y el color de la fritura es tanto o más claro; el contenido de azúcares reductores es menor que el observado en Russet Burbank. Wallowa Russet y Russet Burbank son similares en susceptibilidad a la marchitez causada porVerticillium, al tizón temprano del follaje (Alternaria solani) y al virus del enrollamiento (PLRV). Sin embargo, Wallowa Russet desarrolla menos necrosis reticulada originada por la infección de PLRV que Russet Burbank. Wallowa Russet es más susceptible a la sarna común (Streptomyces scabies) que Russet Burbank. Tiene resistencia moderada al virus Y de la papa (PVY). Los tubérculos de Wallowa Russet son menos susceptibles a la infección y pudrición causados por el tizón tardío (Phytophthora infestans) que los de Russet Norkotah y Ranger Russet. Wallowa Russet presenta menos corazón vacío, corazón negro, magulladuras en forma de puntos y menor cantidad de grietas de crecimiento que Russet Burbank, pero es más susceptible a las lesiones con fisuras del tejido. El contenido de Vitamina C es mayor en Wallowa Russet (30.4 mg/100g de peso fresco) que en Russet Burbank (21.9) o Russet Norkotah (22.0), y un promedio de 5.6% de contenido de proteína comparado con 4.7% y 4.9% de Russet Burbank y Russet Norkotah respectivamente.

Comparison of hydraulic press and pressure chamber estimates of potato leaf water potential1

The leaf water potential of field-grown Russet Burbank potato plants (Solarium tuberosum L.) was estimated with a pressure chamber and a leaf press to assess the usefulness of the leaf press for evaluation of potato leaf water status.Paired leaflets were used for leaf water potential estimation with both instruments. Leaflets were taken from potato plants exposed to excessive soil moisture and high relative humidity, from plants with adequate soil moisture, and from plants under severe water stress.Over the range from -0.28 to -1.61 MPa, for 124 leaflet pairs, the leaf press estimates of leaf water potential were exponentially related (r2 = 0.85) to pressure chamber estimates. The leaf press compared well with the pressure chamber in the range from -0.6 to -1.2 MPa.

Modoc: A potato variety with bright red skin and early maturity for fresh market

Modoc is an early maturing, red-skinned, whitefleshed potato cultivar for fresh market use. The Agricultural Experiment Stations of Oregon, North Dakota, California, Idaho, and Washington jointly released Modoc in 2003. Modoc was derived from a 1989 cross of ND1196-2R and ND2225-1R performed at North Dakota State University. Modoc retains bright skin color in storage and is suited for marketing directly from the field or storage. It produces slightly lower total yield than Red LaSoda or Dark Red Norland, but higher marketable yield and more desirable tuber size and shape. Modoc tubers seldom exhibit growth cracks, secondary growth, hollow heart or other external or internal defects. Dry matter content of Modoc tubers is similar to Dark Red Norland and Red LaSoda (18.9% compared to 18.8% and 17.7%, respectively). Culinary quality of Modoc was rated equal to Dark Red Norland and Red LaSoda for boiling and microwaving preparation methods. Modoc tubers are similar to standard varieties in sugar, vitamin C, and glycoalkaloid (4.5 mg/100 g) concentration. Modoc foliage clearly expresses PVY symptoms and has not demonstrated high susceptibility to viral or fungal diseases during a decade of seed production and evaluation.ResumenModoc es un cultivar de papa de madurez precoz, piel roja y de uso en fresco. Las Estaciónes Experimentales de Oregon, North Dakota, California, Idaho y Washington han liberado conjuntamente el cultivar Modoc en el 2003. Modoc deriva de un cruzamiento de ND1196-2R y ND2225-1R realizado en la Universidad del Estado de North Dakota en 1989. Modoc retiene el color rojo brillante de la piel en almacenamiento y es apropiada para su comercialización directa a partir del campo o del almacén. Tiene rendimientos totales ligeramente menores que la Red LaSoda o la Dark Red Norland, pero mayor cantidad de tubérculos comercializables y de forma y tamaño preferidos. Los tubérculos de Modoc raramente exhiben rajaduras de crecimiento, crecimiento secundario, corazón vacío u otros defectos internos y externos. El contenido de materia seca de Modoc es similar al de Dark Red Norland y Red LaSoda (18.9 comparado con 18.8 y 17.7 por ciento, respectivamente). Las cualidades culinarias de Modoc son iguales a las de Dark Red Norland y Red LaSoda para hervido y métodos de preparación en microondas. Los tubérculos de Modoc son similares a los de las variedades estándar en la concentración de azúcares, vitamina C y glicoalcaloides (4.5 mg/100 g). El follaje de Modoc muestra claramente síntomas de PVY pero no ha demostrado alta susceptibilidad a enfermedades virales o fungosas durante la década de producción y evaluación de semilla.