D. L. Corsini

Fusarium dry-rot resistant potato germplasm

The level ofFusarium dry-rot resistance found in important potato varieties has been improved with agronomically acceptableSolanum tuberosum genotypes. Three breeding selections, A74114-4, A76260-16, and BR6316-7 were highly resistant to the two commonFusarium dry-rot species (F. roseum Lk ex Fr. f. sp.sambucinum [Fs], andF. solani var.coeruleum (Sacc), Booth [Fc]). Resistance was determined separately for each of these species. Resistance to Fs was genetically distinct from resistance to Fc since there was no correlation between Fs and Fc reaction for 180 progeny clones from six crosses representing all combinations of resistance. Resistance to each of theseFusarium species was readily transmitted to progeny. Seventy-five percent of the progeny from resistant X resistant parents were also resistant to Fs, while 95% of the progeny from susceptible X susceptible parents were susceptible. Mixed infections withErwinia atroseptica and eitherFusarium species resulted in a qualitative change from a resistant reaction to a susceptible reaction. Bacterial interaction withFusarium spp. is, therefore, an important consideration in determining storage-rot resistance.ResumenEl nivel de resistencia a la pudrición seca porFusarium, econtrado en variedades importantes de papa, ha sido mejorado con genotipos agronomicamente aceptables deSolanum tuberosum. Tres selecciones de papa mejoradas, A74114-4, A76260-16, y BR6316-7 fueron altamente resistentes a las dos especies comunes deFusarium (F. roseum LK ex Fr. f. sp.sambucinum [Fs],y F. solani varcoeruleum (Sacc), Booth [Fc]. Se determinó, por separado, la resistencia para cada una de estas especies. La resistencia a Fs fue genéticamente distinta de la resistencia a Fc desde que no hubo correlación entre las reacciones a Fs y Fc de 180 clones de las progenies de seis cruzas que representaban todas las combinaciones de resistencia. La resistencia de cada una de las especies deFusarium fue transmitida fácilmente a las progenies. El 75% de la progenie de padres resistente X resistente fueron también resistentes a Fs, mientras que el 95% de la progenie de padres susceptible x susceptible fueron también susceptibles. Infecciones combinadas deErwinia atroseptica y cualquiera de las especies deFusarium, dieron por resultado un cambio cualitativo, pasando de una reacción resistente a una susceptible. Por lo tanto, la interacción resistente a una susceptible. Por lo tanto, la interacción bacteriana conFusarium spp., es una importante consideración para determinar la resistencia a la pudrición en el almacenamiento.

Differences in free and protein-bound tyrosine among potato genotypes and the relationship to internal blackspot resistance

Twelve potato clones were selected to represent the full range of internal blackspot response in order to determine the relationships between tuber protein, free tyrosine, and blackspot susceptibility. The blackspot reaction for each clone was consistent over five growing seasons, including tubers grown over a normal season (mature), and short season (immature) during one year. The blackspot index, determined by either an abrasive peel test or an impact bruise test, was highly correlated with the tyrosine content of the tubers (r = 0.90 p = 0.001 for the means of each clone over five location-years). Tubers with free tyrosine levels below 4 μmole/g dry weight consistently showed a resistant blackspot response. The relationship between tyrosine and blackspot susceptibility was also found in stolon and bud ends from five of the clones which represented the extremes of blackspot reaction and genetic diversity. Bud end samples of each of the clones had lower tyrosine content and a corresponding reduction in blackspot compared with stolon ends. Phenols, other than tyrosine, showed no consistent relationship to the blackspot reaction.There was a very high negative correlation between free tyrosine and estimated protein-bound tyrosine. R values ranged from −0.85 to −0.97 (p = 0.001) for mature tubers of the 12 clones over 4 growing seasons. Total tyrosine (free, plus protein-bound) remained relatively constant. There were no significant differences in mean total tyrosine content among the 12 clones over five location-years of testing; and there were no significant differences among the five growing seasons except for the short season (immature) tubers which were 14% lower in total tyrosine content. These results indicate a remarkably constant level of total tyrosine production in the twelve clones studied, that represented diverse genetic backgrounds. Mature tubers of all genotypes contained 26 ± 1 μmole/g dry weight total tyrosine. Partitioning of tyrosine between tuber protein and the free amino acid pool varied with genotype and appeared to be a major determinate of blackspot resistance.CompendioSe seleccionaron doce clones de papa para representar el rango completo de la respuesta de la mancha negra interna para determinar la relación entre la proteína, la tiroxina libre y la susceptibilidad a la mancha negra. La reacción a la mancha negra para cada clon fue consistente durante cinco temporadas, incluyendo tubérculos que crecieron en una temporada normal (maduros) y en una temporada corta (inmaduros) durante un año. El índice de mancha negra, determinado ya sea por una prueba de peladura con abrasivo o por una prueba de daño por impacto, estuvo ampliamente correlacionado con el contenido de tiroxina de los tubérculos (r=0, 90 p = 0,001 para los promedios de cada clon en cinco anos-localidad). Los tubérculos con niveles por debajo de 4 μmole/g de peso seco mostraron consistentemente una respuesta resistente a la mancha negra. La relación entre la tiroxina y la susceptibilidad a la mancha negra también fue encontrada en los estolones y puntas de las yemas de cinco de los clones que representaron los extremos de la rección a la mancha negra y diversidad genética. Muestras de las puntas de las yemas de cada uno de los clones tuvieron contenidos más bajos de tiroxina y la reducción correspondiente en mancha negra en comparación con las puntas de los estolones. Otros fenoles diferentes a la tiroxina no mostraron una relación consistente a la reacción a la mancha negra.Hubo una correlación negativa muy alta entre la tiroxina libre y el estimado de tiroxina ligada a proteína. Los valores de R variaron de −0,85 a −0.97 (p=0,001) para los tubérculos maduros de los 12 clones durante cuatro temporadas. La tiroxina total (libre, más ligada a proteína) permanecieron relativamente constantes. No hubieron diferencias significativas en el contenido promedio de tiroxina total entre los 12 clones durante cinco de los años-localidad y tampoco las hubo entre las cinco temporadas excepto para los tubérculos de la temporada corta (inmaduros) que tuvieron 14% menos de contenido total de tiroxina. Estos resultados indican un nivel constante notable de producción de tiroxina total en los doce clones estudiados y que representaban bases genéticas diversas. Los tubérculos maduros de todos los genotipos contuvieron 26 ± 1 μmole/g de peso seco de tiroxina total. La distribución de la tiroxina entre la proteína del tubérculo y el (pool) de amino ácidos libres varió con el genotipo y pareció ser un factor determinante de la resistencia a la mancha negra.

A rapid method for determining blackspot susceptibility of potato clones

Two methods of determining susceptibility of potato clones to blackspot were compared: (1) bruising by weight dropping and (2) bruising by abrasive peeling. A highly significant positive correlation was obtained between the intensity of enzymatic discoloration following abrasive peeling and the amount of blackspot that developed by weight dropping (r=0.93).Abrasive peeling was more rapid than the weight-dropping method. Tuber samples were abraded 30 sec and the amount of enzymatic discoloration evaluated after 24 hr. The need for individually bruising and hand peeling of tubers was eliminated with this method. Because of the rapidity of the abrasive peeling method, it can be used effectively in potato breeding programs to screen large numbers of clones for blackspot susceptibility.Results indicate that tuber maturity affects enzymatic discoloration and blackspot susceptibility. Immature tubers, dug while the vines are still green, are more resistant to blackspot than mature tubers. Tuber maturity therefore must be considered when screening clones for susceptibility to blackspot.ResumenSe compararon dos métodos para determinar la susceptibilidad de clones de papa a la mancha negra: (1) golpeando los tubérculos al dejar caer pesos sobre ellos, y (2) pelando los tubérculos mediante abrasivos. Se obtuvo una correlación positiva, altamente significativa, entre la intensidad de la decoloración enzimática que se presenta después del pelado con abrasivos y la cantidad de mancha negra que se desarrolló como consecuencia de los golpes (r = 0,93).El método de pelado con abrasivos fue más rápido que el método de golpes provocados. Las muestras de tubérculos fueron raspadas por 30 segundos y la cantidad de decoloración enzimática fue evaluada 24 horas después. La necesidad de provocar contusiones en cada tubérculo por separado y de pelarlos a mano, fue eliminada con este método. Debido a la rapidez del pelado con abrasivos, este método puede ser utilizado para evaluar la susceptibilidad a la mancha negra de un gran numéro de clones en programas de mejoramiento de papa.Los resultados indican que la madurez de los tubérculos influeye sobre la decoloración enzimática y sobre la susceptibilidad a la mancha negra. Los tubérculos inmaduros, extraídos cuando las plantas están aún verdes, son más resistentes a la mancha negra que los tubérculos maduros. Por lo tanto, la madurez de los tubérculos debe ser considerada cuando se evalúe la susceptibilidad de los clones a la mancha negra.

Defender: A High-Yielding, Processing Potato Cultivar with Foliar and Tuber Resistance to Late Blight

The potato cultivar Defender is high-yielding, white-skinned, and notable for having foliar and tuber resistance to late blight infection caused byPhytophthora infestans (Mont.) de Bary. It was released in 2004 by the USDA-ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. Defender is suitable for processing into french fries and other frozen potato products directly from the field or from storage. Defender also may be used for fresh markets in regions such as California, where cultivars with long tubers and white skin are traditionally grown. Resistances to late blight and other potato diseases make Defender an ideal candidate for organic potato production. Defender consistently produced greater total and U.S. No. 1 yields than ‘Russet Burbank’ in Idaho trials. In early harvest trials conducted in the western U.S., average total yields of Defender were 17% and 23% greater than yields for ‘Ranger Russet’ and ‘Shepody’, respectively. In full-season trials conducted in the western U.S., Defender averaged 10% and 15% higher yields than Ranger Russet and Russet Burbank, respectively. Specific gravity of Defender is consistently high, with values comparable to those of Ranger Russet; tuber ascorbic acid (Vitamin C) levels are also high. In addition to late blight, Defender also is resistant to tuber early blight (Alternaria solani, (Ellis & G. Martin), L.R. Jones & Grout), potato virus X, and net necrosis; it has moderate levels of resistance to Verticillium wilt (Verticillium dahliae, Kleb), pink rot, foliar early blight, corky ringspot, and Erwinia soft rot. Defender is susceptible to scab (common and powdery) and potato leafroll virus; it has moderate susceptibility to dry rot (Fusarium spp.) and potato virus Y. Susceptibilities to internal necrosis, tuber greening, and blackspot bruise also have been noted, but may be minimized through cultural and harvest practices.ResumenDefender es un cultivar de papa de alto rendimiento, piel blanca y excelente por su resistencia al tizón tardío causado porPhytophthora infestans (Mont.) de Bary, tanto a la infección foliar como a la de los tubérculos. Ha sido liberada el 2004 por USDA-ARS y las Estaciones Experimentales Agrícolas de Idaho, Oregon y Washington. Defender es apropiado para el procesamiento de papa frita y otros productos congelados de papa, directamente del campo o del almacén. Defender puede también ser usado en regiones como California, donde se cultivan tradicionalmente variedades de tubérculos alargados y piel blanca. La resistencia al tizón tardío y otras enfermedades de la papa hace de Defender un candidato ideal para la producción orgánica. Defender tuvo consistentemente un mayor rendimiento de tubérculos de grado “US No. 1” que Russet Burbank en pruebas en Idaho. En ensayos de cosecha temprana realizados en el oeste de EUA, el promedio de rendimiento total de Defender fue de 17 y 23% mayor que el de las variedades Ranger Russet y Shepody respectivamente. En ensayos de ciclo completo realizadas en el oeste, Defender tuvo rendimientos 10 y 15% mayores que Ranger Russet y Russet Burbank respectivamente. El peso específico de Defender es consistentemente alto, con valores comparables a los de Ranger Russet y los niveles de ácido ascórbico (Vitamina C) son también altos. Además de ser resistente al tizón tardío, Defender es también resistente al tizón temprano (Alternaria solani (Ellis & G. Martín) L. R. Jones & Grout), Virus X de la papa y necrosis en red. Tiene niveles moderados de resistencia a marchitez por Verticillium (Verticillium dahliae Kleb.), pudrición rosada, tizón foliar temprano, mancha corchosa en anillo y pudrición blanda causada por Erwinia. Defender es susceptible a la sarna (común y polvorienta) y al virus del enrollamiento; tiene moderada susceptibilidad a la pudrición seca (Fusarium spp.) y al virus Y de la papa. También se ha notado susceptibilidad a necrosis interna, verdeamiento del tubérculo y mancha negra, pero estas pueden minimizarse a través de prácticas culturales.

Potato germplasm resistant to corky ringspot disease

Potato germplasm was assessed for resistance to corky ringspot disease (CRS) incited by transmission of tobacco rattle virus (TRV). TRV is transmitted by the stubby root nematode,Paratrichodorus allius, in the Pacific Northwest, and characterized by necrotic areas in the tuber. Four tests were conducted at two different problem fields in Umatilla, OR and Pasco, WA. The fields differed in the virulence of the virus isolates. Some clones and named varieties showed resistance only in the field with the relatively mild Umatilla isolate, while others remained symptomless at both sites. The host suitability of test potatoes to threeP. allius populations from the region was determined in greenhouse pot tests, and expressed as reproductive values [Rf = (final population of nematode at 55 days) / (initial population)]. TheRf values for the nematodes were not correlated with resistance ratings based on visual scoring of CRS symptoms in field grown potatoes. Thus, it appears that CRS resistance is based on reaction of potato genotypes to virus and not the vector. The availability of resistant clones inin vitro form is indicated.

Field performance of transgenic Russet Burbank and Lemhi Russet potatoes

Transformed Russet Burbank and Lemhi Russet clones which contained three different transgene constructs were evaluated for performance under field conditions in Idaho. The transgenic lines were characterized over two growing seasons, using plants grown from both greenhouse produced minitubers (first year) and field grown seed (second year). Individual clones were evaluated for a variety of agronomic and quality properties. Many of the transformed clones showed reduced yield and increases in percent malformed and undersized tubers. Other characteristics, such as specific gravity and fry color, showed less variability. The variation observed in non-transgenic clones regenerated from tissue culture was less than that of the transformed lines. Out of an original population of 57 transgenic lines in tissue culture, maintenance of key agronomic and quality properties of the parental material was observed in only four clones. These results suggest that experiments designed to generate transgenic lines for the marketplace should be initiated with a large number of transgenic clones.CompendioClones transformados de Russet Burbank y Lemhi Russet, que contenían tres diferentes prototipos de transgenes fueron evaluados para comportamiento bajo condiciones de campo en Idaho. Las líneas transgénicas se caracterizaron en dos temporadas de cultivo, utilizando plantas obtenidas tanto de minituberculos producidos en invernadero (primer año) como semilla producida en el campo (segundo año). Se evaluaron clones individuales para diversas propiedades agronomicas y de calidad. Muchos de los clones transformados mostraron rendimientos reducidos y un incremento en el porcentaje de tubérculos deformesy de pequeño tamaño. Otras características, tales como la gravedad específica y el color a la fritura, mostraron una menor variabilidad. La variacíon observada en los clones no transgénicos regenerados de cultivo de tejidos fue menor que aquella de las líneas transformadas. De una población original de 57 líneas transgénicas en cultivo de tejidos, se observó que sólo cuatro de ellas mantenían las principales propiedades agronómicas y de calidad del material progenitor. Estos resultados sugieren que los experimentos diseñados para generar líneas transgenicas para el mercado deberán iniciarse con un gran número de clones transgenicos.

Reaction of potato clones and accessions of Solanum spp. to Verticillium dahliae Kleb. and its toxin.

SummaryThe reaction of 40 potato clones and six accessions ofSolanum spp. to wilt caused byVerticillium dahliae and to the acetone precipitate (AP) of the toxin produced by the pathogen in vitro was studied. There was a highly significant correlation between the wilt reaction of the clones in the glasshouse, the incidence and progress of wilt and severe wilt in the field, and the degree of colonization of stem apices byV. dahliae. Of the clones and accessions evaluated, NDA8694-3, Norgold Russet, BelRus, Superior, Russet Norkotah, Norland andS. demissum were the most susceptible, while A66107-51, A68113-4, Targhee, NDA843-3, Alpha, A7805-8, A7816-14, Russet Nugget,S. chacoense, S. sparsipilum, andS. tarijense were the most resistant to wilt. The reaction of genotypes to the AP ofV. dahliae toxin in an excised leaf bioassay was not correlated with their reaction to Verticillium wilt in the field or glasshouse.

Verticillium wilt resistant potato germplasm: A66107-51 and A68113-4

Potato breeding selections A66107-51 and A68113-4 (Solanum tuberosum gptuberosum) are being released as germplasm that is highly resistant to Verticillium wilt (Verticillium dahliae Kleb.) These selections have been extensively evaluated for resistance to Verticillium as measured by symptom severity and degree of colonization byV. dahliae. They combine outstanding wilt resistance with good tuber maturity characteristics, high yield, and french fry processing tuber type. A66107-51 has long-oblong, russeted tubers, with high yield and variable processing quality. A68113-4 has long-oblong, partially russeted tubers with high yield and good processing quality. Both selections are fertile as female parents, and A66107-51 is occasionally pollen fertile. The Verticillium resistance of these two clones has been transmitted to progeny. These selections were developed by USDA-ARS in cooperation with the Idaho Agricultural Experiment Station. Seed is available from USDA-ARS, Aberdeen, Idaho.CompendioLas selecciones mejoradas de papa A66170-51 y A68113-4 (Solanum tuberosum gptuberosum) están siendo liberadas como germoplasma altamente resistente a la marchitez porVerticillium (Verticillium dahliae Kleb.). Estas selecciones han sido evaluadas extensivamente para resistencia aVerticillium determinada por la severidad de los sintomas y el grado de colonización porV. dahliae. Ellas conbinan una gran resistencia a la marchitez, con buenas características de maduración, alto rendimiento y un tipo de tubérculo apto para el procesamiento como papa frita a la francesa. A66107-51 tiene tubérculos largos y oblangos, rojizos, con alto rendimiento y calidad variable de procesamiento. A68113-4 posee tubérculos largos y oblongos, parcialmente rojizos, con alto rendimiento y buena calidad de procesamiento. Ambas selecciones son fértiles como plantas madres y A66107-51 es ocasionalmente de polen fértil. La resistencia de estos dos clones aVerticillium ha sido transferida a la progenie. Estas selecciones fueron desarrolladas por el Servicio de Investigación Agrícola del Departamento de Agricultura de los Estados Unidos (USDA-ARS) en cooperación con la Estación Experimental Agrícola de Idaho. Los tubérculos-semillas se encuentran disponibles en el USDA-ARS, Aberdeen, Idaho.

Glucosylation as a mechanism of resistance to thaxtomin A in potatoes

Abstract Glucosylation of thaxtomin A by Streptomyces scabies occurs in vitro. The glucose conjugate of thaxtomin A (TA) from bacterial extracts was isolated and characterized as thaxtomin A-β-di- O -glucoside (TAG). On a specific activity basis, TAG was six times less toxic than TA in potato tuber slice tests. Evidence for glucosylation of TA in S. scabies includes electrospray mass spectroscopy, NMR spectroscopy, chromatographic data, and the unequivocal demonstration of the presence of glucose in the putative TAG after acid hydrolysis and GC-MS analysis. 14 C-thaxtomin A was produced by amending 6 day old cultures of S. scabies in oat meal broth with l -phenylalanine-UL- 14 C. The scab-resistant cultivar Nooksack and resistant selections of Ranger self-cross treated with 14 C-TA produced a higher amount of a radioactive metabolite with an R f value similar to TAG than the susceptible cultivar Ranger. Furthermore, there was almost twice as much glucose transferase on a specific activity basis in resistant than in susceptible potato cultivars and selections. Glucosylation appears to be a mechanism of TA detoxification in potato and is related to scab resistance and susceptibility in potato.

Factors contributing to the blackspot bruise potential of Idaho potato fields

Blackspot bruise is a major problem in the fresh market and frozen french fry industry. The blackspot bruise potential of Russet Burbank and Ranger Russet in Idaho potato fields was determined by surveying commercial fields during 1993 and 1994. Management factors were monitored to determine what practices were contributing to blackspot susceptibility in addition to mechanical damage. The survey included 17 Russet Burbank and 3 Ranger Russet fields in 1993, and 28 Russet Burbank and 8 Ranger Russet fields in 1994. The 1993 season was unusually cool and wet whereas 1994 was warmer than normal, resulting in a wide range of environmental conditions for the 2 year study. Blackspot bruise potential was determined at different stages of tuber physiological maturity by collecting samples several weeks prior to normal harvest, immediately before harvest, and after storing sub-samples for several months. The blackspot bruise potential was measured by both impact and abrasive peel tests.Field maturity was the factor most consistently related to blackspot potential both years. In 1994 a multiple regression of 3 independent variables — field maturity index, specific gravity, and percent available soil water at tuber sampling, compared with the blackspot potential as the dependent variable gave a correlation coefficient of r = 0.73 (p = 0.001). Due to the cool, wet growing season in 1993, there was not enough variability in specific gravity and available soil water among the fields sampled for these factors to correlate with the blackspot potential. The available fertility data, although not complete for all fields, indicated no direct relationship between N, P, or K fertilization and blackspot potential. Preharvest samples in late August had lower blackspot potential than harvest samples in mid September, and storage samples in February had the highest susceptibility. There was a consistent increase in blackspot severity when tubers were equilibrated at 4 C compared with 10 C prior to bruising.