R. E. Webb

Genetic and environmental control of potato glycoalkaloids

Genetic and environmental factors that can cause potato tubers and processed products to have excessive glycoalkaloid levels (> 20 mg/100 g fresh wt) are reviewed and discussed. Measures that breeders, growers, processors, and distributors might take to maintain glycoalkaloid levels at their present low levels are suggested.ResumenSe revisan y se discuten los factures genéticos y ambientales que pueden producir niveles excesivos de glicoalcaloides (> 20 mg/100 g de peso fresco) en los tubérculos de papa y los productos procesados. Se sugieren medidas que puedan tomar los fitomejoradores, agricultores, técnicos en procesamiento y distribuidores para mantener bajos los niveles de glicoalcaloides.

Atlantic: A new potato variety with high solids, good processing quality, and resistance to pests

Atlantic is a medium late maturing var. which has been shown to have the following characteristics: tolerance to scab and Verticillium wilt; high yields of attractive tubers; resistance to the bacterial disease pink eye; high solids content; excellent chip and French fry quality and acceptable fresh market quality. It is low in total glycoalkaloids. It was evaluated for yield, sp. gr., and chipping quality from 1973 through 1975 in replicated trials with locally adapted var. Compared with locally adapted var. grown in Florida, Virginia, New Jersey and Maine, Atlantic excelled in TS content. It contained 24.4% more TS than Sebago in Florida, 14.8% more than Pungo in Virginia, 14.9% more than Superior in New Jersey and 18.1% more than Superior and Katahdin in Maine. Mean chip colour scores were better for Atlantic than for locally adapted var. grown in Florida, New Jersey, and Maine. It produced excellent chips when either processed within 2 wk of harvest and then held at ambient air temp. for 6 wk or held in 4°C temp. storage and then reconditioned at 21°C for 14 days. The baking quality of Atlantic was rated acceptable.

Effect of variety and location on the glycoalkaloid content of potatoes

Significant differences in tuber glycoalkaloid (TGA) content were found among five commercial varieties and B5141-6 grown at 39 different locations in 28 states. Line B5141-6 had the highest average TGA content, 29.3 mg/100 g in 1970 and 28.1 mg/100 g in 1971. Average TGA contents in 1970 of Kennebec, Russet Burbank, Katahdin, Irish Cobbler, and Red Pontiac were 9.7, 7.9, 7.9, 6.2, and 4.3 mg/100g, respectively. There were also significant location effects. Possible causes of high TGA levels are discussed.

Canopy photosynthesis, stomatal conductance and yield ofSolanum tuberosum grown in a warm climate

Selected potato (Solanum tuberosum L.) genotypes were grown in the field from May to September during 1984 and 1985, to study their growth and gas exchange responses in a warm climate. The parameters measured were leaf area index (LAI), canopy photosynthesis on ground area basis (CPn-Ga), stomatal conductance, dry matter partitioning and yield. The LAI ranged from 1.40 for Dakchip to 6.60 for Pungo during August 1984. The LAI also differed significantly among the potato genotypes for the three samplings during 1985. Atlantic, Chipbelle and DTO-33 showed no decline in their LAI up to 73 days after planting (DAP), indicating a better heat-stress tolerance response than the other genotypes. During both years, CPn-Ga differed significantly among the genotypes and Pungo had higher CPn-Ga than all the other genotypes. Mean CPn-Ga rates were 1.72 and 4.34 g CO2 m−2hr−1 during 1984 and 1985, respectively. Mean adaxial and abaxial stomatal conductances were 0.86 and 1.46 cm sec−1, during 1984, and stomatal conductances were similar for both years. Stomatal conductance did not appear to limit gas exchange in potato leaves. Dry matter partitioning to tubers ranged from 8.9% for Pungo to 55.5% for Atlantic 67 DAP during 1984. At final harvest, July 19, 1985, dry matter partitioning to tubers varied from 47.5% for Pungo to 69.9% for Chipbelle. The tuber yield ranged from 9.6 to 27.8 MT/ha. This study indicated that Atlantic and La Chipper have potential for growing in a warm climate.CompendioDe mayo a setiembre, durante 1984 y 1985, se cultivaron genotipos selectos de papa (Solanum tuberosum L.), para estudiar su crecimiento y la respuesta al intercambio de gases en clima cálido. Los parámetros medidos fueron el índice de área de hoja (LAI), la fotosíntesis del follaje expuesto en base al área de terreno (CPn-Ga), la conductión estomática, la repartición de la materia seca, y el rendimiento. Durante agosto de 1984, la LAI varió de 1,40 para “Dakchip” a 6,60 para “Pungo.” Durante 1985, la LAI también fue significativamente diferente entre los genotipos de papa para las tres muestras estudiadas. “Atlantic,” “Chipbelle” y DTO-33 no mostraron declinatión en su LAI hasta los 73 días después de la siembra (DAP), indicando una respuesta mejor para la tolerancia al estrés al calor en comparación con los otros genotipos. Durante ambos años, la CPn-Ga difirió significativamente entre los genotipos y “Pungo” tuvo una CPn-Ga más alta que todos los otros genotipos. Durante 1984 y 1985, las tasas de CPn-Ga fueron l,72 y 4,34 g CO2 m-2hr-1,respectivamente. La conductión estomática media para las caras superior e inferior de las hojas, durante 1984, fue 0,86 y 1,46 cm sec-1, respectivamente, y fue similar para ambos años. La conductión estomática aparentemente no limitó el intercambio gaseoso en las hojas de papa. La repartición de materia seca a los tubérculos varió de 8,9% para “Pungo” a 55,5% para “Atlantic” 67 DAP, durante 1984. A la cosecha final, julio 19, 1985, la repartición de materia seca a los tubérculos varió de 47,5% para “Pungo” a 69,9% para “Chipbelle.” El rendimiento en tubérculos varió de 9,6 a 27,8 t/ha. Este estudio indicó que “Atlantic” y “La Chipper” tienen potential para ser cultivadas en clima cálido.

LOSS OF YIELD IN POTATO SELECTIONS INFESTED WITH POTATO LEAFHOPPERS

The loss of yield resulting from infestation with potato leafhoppers,Empoasca fabae (Harris), was measured in a group of potato selections (Solatium tuberosum subsp.tuberosum). For 6 years in which 300 different clones were tested, the average loss of yield was 39%. The correlation over clones between level of infestation and percent hopperburn equaled 0.56; between level of infestation and loss of yield 0.36; and between percent hopperburn and loss of yield 0.41. Each coefficient is significant at P=0.01.Significant differences were found in levels of infestation and in percent hopperburn among the selections, but even those selections with the most resistant foliage had greatly reduced yields when infested. No selections were found that consistently produced a normal yield when infested with leafhoppers. The low level of infestation on the more resistant clones, however, may make chemical control at lower rates more effective.ResumenLas pérdidas en la cosecha causadas por el saltahojas de la papa,Empoasca fabae (Harris), fueron medidas en un grupo de selecciones de papa (Solarium tuberosum sub sp.tuberosum). Durante seis años en los cuales se probaron 300 clones diferentes, el promedio de perdida en la cosecha fue de 39%. La correlación de los clones entre niveles de infestación y porcentaje del daño de los saltahojas fue igual a 0.56; entre niveles de infestación y pérdidas en la cosecha fue 0.41. Cada uno de los coeficientes es significativo al nivel de P = 0.01.Se encontraron diferencias significativas en los niveles de infestación y en el porcentaje de daño entre las selecciones pero, aquellas selecciones que tuvieron el follaje más resistente, tuvieron también las más grandes reducciones en la cosecha cuando fueron infestadas. No se encontró ninguna selección que produjera una cosecha normal cuando estuvo infestada con saltahojas. Los niveles bajos de infestación encontrados en los clones más resistentes, sin embargo, pueden reducir la frecuancia en la aplicación del control químico con mejores resultados.

Resistance of solanum species to potato viruses A, X, and Y

SummarySome selections ofS. tuberosum (S. andigenum) were found to possess a high level of resistance to mechanical and graft inoculation with viruses A and X. Nine of the selections proved highly resistant to inoculation with both viruses; graft inoculated plants developed no symptoms nor could either virus be recovered from them. Apparent immunity to graft inoculation with virus X was found in selections ofS. acaule, S. sucrense and 1 species hybrid. Four selections ofS. tuberosum and 1 selection ofS. maglia developed symptoms of virus X infection but were poor hosts for the virus as indicated by low titer upon subinoculating to indicator hosts. One selection ofS. cardiophyllum, 4 ofS. chacoense, 3 ofS. demissum, 2 ofS. hougasii, 1 ofS. phureja, 1 ofS. tuberosum, 8 ofS. stoloniferum and 2 species hybrids were apparently immune from mechanical inoculation with virus Y. Nine of these selections were apparently immune from graft inoculation with virus Y. Apparent immunity to graft inoculation with virus A was found in selections ofS. chacoense, S. demissum, S. hougasii, S. maglia, S. phureja, S. stoloniferum and 8 species hybrids. About half of the selections developed symptoms of virus A infection but the virus could not be recovered from them. No selection was found to be highly resistant to all three viruses.

The correlation of yield and specific gravity in the USDA potato breeding program

Every year potato (Solarium tuberosum L.) clones which remain in the USDA potato breeding program after six or more years of selection are entered into yield trials in Maine. Specific gravity and yield data were analyzed for six years (1972, 1975, 1978, 1981, 1984, and 1987) to determine the relationship between specific gravity and yield for populations of white and russet potatoes. In these trials, marketable yields of white-skinned potatoes were significantly greater than those of russet potatoes. Average specific gravity was significantly greater in the white than in the russet potatoes in three of the six years. A slight, but usually not significant, negative correlation of marketable yield with specific gravity was found for russet potatoes. A significant negative correlation of marketable yield with specific gravity was found in three of the six years for white potatoes. Regression analyses of marketable yield on specific gravity showed a great dispersion of values. Since only one or two advanced lines are potential variety releases, the present breeding approach is sufficient to continue to release potato varieties of acceptable yield and specific gravity.CompendioCada año, los clones de papa (Solarium tuberosum L.) que permanecen en el programa de mejoramiento de papa después de seis o más años de selectión son incorporados en ensayos de rendimiento en Maine. Los datos sobre la gravedad específica y rendimiento fueron analizados por seis años (1972, 1975, 1978, 1981, 1984 y 1987) para determinar la relatión existente entre la gravedad específica y el rendimiento para poblaciones de papa de piel blanca y piel roja. En estos ensayos, los rendimientos comerciables de la papa de piel blanca fueron significativamente mayores que aquellos de la papa roja. En tres de los seis afios la gravedad específica promedio fue significativamente mayor en la papa blanca que en la papa roja. Una pequefñia, pero generalmente no significativa correlatión negativa de rendimiento comerciable con la gravedad específica fue encontrada para la papa roja. En tres de los seis años se encontró una correlation negativa significativa del rendimiento comerciable con la gravedad específica para la papa blanca. El análisis de regresión del rendimiento comerciable sobre la gravedad específica mostró una gran dispersión de valores. Desde que solo una o dos líneas avanzadas son variedades potenciales a liberarse, el presente enfoque de mejoramiento es suficiente para continuar liberando variedades de papa de rendimiento y gravedad específica aceptables.

Red la soda—A mutation of la soda

SummaryRed LaSoda produces a very attractively colored tuber and several growers are anxious to obtain seed tubers. It has proven its adaptability in the seed-producing areas of the North and also its superior yielding ability over Triumph in the southern potato-producing areas. The Red LaSoda variety will yield equally as well as LaSoda and the tubers do not require added coloring to make an attractive product. The quality of the tubers is equally as good as most potato varieties grown in the southern states.The authors feel that this potato variety has a definite place in the potato trade. There is always a heavy market demand for attractive red-colored tubers from most of the potato-growing areas of the United States.

Belrus: A new russet skin potato variety, combining high quality, pest resistance, and adaptation to the Northeastern United States and Florida

BelRus, a new russet potato variety, is medium late in maturity and adapted primarily for the Northeastern United States and northern Florida. Tubers are long, smooth and moderately flat with a heavy russet skin. Eyes are shallow and immediately adjacent skin is, for the most part, nonrussetted in the Northeastern U.S. Industry speaks of the BelRus there as the “white eyed russet.” BelRus is slightly higher in specific gravity than ‘Russet Burbank’, has a superior flavor when baked, and yields excellent french fries and flakes. Glycoalkaloid content of BelRus is quite low, being about 2 mg/100 g fresh tissue. BelRus is immune to virus A and tuber net necrosis; highly resistant to tuber heat necrosis, northern root knot nematode (Meloidogyne hapla), and the pinkeye bacterial disease; moderately resistant to scab, Verticillium wilt, leaf roll and potato virus Y. It is not resistant to either late blight or early blight, or viruses M, S, and X. Necrotic spotting of the foliage occurs following periods of high temperature and extended drought. BelRus has demonstrated high tolerance to bruising and storage rots incurred during harvest and handling. Shrinkage in bulk storage has been minimal. BelRus is recommended to be planted at about 25 cm (10 inches) in-the-row on 90 cm (36) rows with about 215 kg (180–200 lbs/acre), N2/ha in-the-row.ResumenBelRus, una nueva variedad de papa de piel “russet”, es de maduración intermedia y adaptada al nororiente de los Estados Unidos y el norte de Florida. Los tubérculos son largos, lisos y moderadamente aplanados con una piel del tipo “russet”; de ojos superficiales con la piel adyacente inmediata al ojo, del tipo no “russet”, mayormente de ocurrencia en el noreste de los Estados Unidos. La industria la llama “russet” ojo bianco. BelRus tiene ligeramente más peso específico que “Russet Burbank”, tiene un sabor superior cuando es horneada y rinde papas fritas y hojuelas de excelente calidad. Su contenido de Glycoalcaloides es bajo (2 mg/100 g. tejido fresco). Es inmune a virus A y necrosis en net del tubérculo; altamente resisente a necrosis de tubérculo por calor, nematodo del nudo del norte (Meloidogyne hapla) y enfermedad bacteriana del ojo rosado; moderadamente resistente a la sarna (Streptomyces scabies), marchitez por Verticillium, enrollamiento de las hojas y virus Y. Es susceptible al tizón tardío y temprano, virus M, S y X. Punteado necrótico sobre el follaje ocurre luego de períodos de alta temperatura y largas sequías. Esta variedad ha demostrado alta tolerancia al daño y pudrición incurrido durante la cosecha y manipuleo de los tubérculos. Arrugamiento del tubérculo durante almacenamiento a granel es mínimo. Se recomienda sembrar esta variedad a 25 cm. (10 pulgadas) entre plantas y 90 cm. (36 pulgadas entre surcos y aplicando al surco alrededor de 215 kg (180–200 lbs/acre) de N2/ha.

Naturally occurring strains of the potato leaf roll virus

SummaryResults of these studies of isolates of the potato leaf roll virus from 56 various seed potato areas of the United States and Canada, covering a wide geographical range, substantiate the existence of distinct strains of the virus. In addition to the 3 strains from Wisconsin previously reported, one additional very severe strain, designated as strain 4, exists in at least one area in South Dakota. The strains are distinguished most readily by the initial symptom type and relative disease severity onP. floridana. The response ofP. floridana infected with strain 4 at 24° and 28° C, is directly opposite to that of the other 3 strains at the same temperatures.The four strains produced a wide range of symptoms onP. floridana, varying from severe defoliation and death of plants with strain 4, to moderate initial symptoms and subsequently rapid recovery with strain 1.A temperature of 24° C. was found to be optimum for symptom expression and development. Distinct strain differences, however, are shown at 16° and 28° C.Strains 1, 2 and 3 seem to be coexistent in most potato growing areas of the United States and Canada.Further experiments are being conducted to study the 4 leaf roll strains under controlled conditions on a number of potato varieties.