Jonathan L. Whitworth

Potato virus Y: An Evolving Concern for Potato Crops in the United States and Canada

North American potato production differs from other geographical regions such as Europe in that it is essentially a closed system, i.e., seed potatoes are not imported and production is dominated by only a few cultivars. The lack of significant seed imports provides a mechanism for seed certification to be extremely effective at minimizing virus levels in seed lots, especially if the changes in seed laws, postharvest testing, and tolerance limits discussed above are adopted. This is an opportunity to effectively manage PVY at levels that are at or below detection and well below economic significance. Aiding the seed certification programs in the adoption of the Canada/US-Management Plan for Potato Viruses that Cause Tuber Necrosis has and continues to build consensus and cooperation within the industry to reform and modernize seed certification practices and, as importantly, modernize best management practices that growers can implement so that their production meets or exceeds virus tolerances set within the seed certification standards. Seed inspectors could also benefit from continually updated information from the research community to help them better recognize the spectrum of symptoms caused by the various strains and variants of PVY in all the different cultivars now being grown in their states and provinces. They could also benefit from improved field diagnostics that will assist them and the growers in identifying problem plants that should be rogued. If PVY levels in seed can be minimized and on-farm management strategies can be optimized, then PVY incidence in the potato crop will be marginalized. The restricted distribution of the tuber necrotic strains also offers an opportunity to prevent these strains from becoming economically significant if appropriate testing of seed lots in those areas could prevent them from being planted. Shipping point inspections of tubers will also help in identifying and eliminating tuber necrotic viruses. The dominance of a few cultivars has been eroding in recent years. Russet Burbank, a cultivar introduced over 100 years ago, still accounts for 40 to 50% of the U.S. acreage, but acreage in the Northwestern United States has been declining steadily as other russet cultivars come on the market and gain acceptance. Potato cultivar has had a significant impact on the PVY problem, as with the release and widespread acceptance of Shepody, Russet Norkotah, and other asymptomatic carriers of PVY (http://oregonstate. edu/potatoes/latenttoPVYlist.htm), which in 2008 comprised more than 15 and 12% of the total U.S. and Canadian seed acreage, respectively. These cultivars have certainly contributed to the overall increase in PVY in the seed potato crop and by extension the commercial potato crop. The increased diversity of potato cultivars grown in both countries has also introduced a wider spectrum of PVY symptoms, most notably the milder symptoms that are characteristic of the PVYN/NTN and PVYN-Wi strains on many cultivars. Since the success of seed certification is dependent upon visual assessment of the crop, mild or absent symptoms means that many more infected plants go unnoticed. The more symptomatic PVYO strains are observed and removed, but the other strains remain in the crop and are passed along in the seed, contributing to an overall increase in PVY incidence and more importantly to a shift in PVY strain composition. The U.S. and Canadian potato industry stakeholders are increasingly aware of the PVY-associated challenges and have been moving rapidly to work with researchers and all aspects of the industry to implement plans to suppress PVY incidence. Continued education of growers, seed certification officials, and researchers alike, coupled with the development and adoption of new or revised best management practices and diagnostic tools, and the renewed inter est of breeders to develop virus resistant cultivars, will be the keys to success in bringing PVY incidence under control and in minimizing tuber necrotic strains.

Effect of Seedborne Potato virus Y on Performance of Russet Burbank, Russet Norkotah, and Shepody Potato

Potato virus Y (PVY) is one of the most important of the potato viruses, but little is known about the impact on yield of seedborne infection levels below 100%. Blending infected and healthy seed from different seed lots introduces the variable of performance differences between the seed lots, which may obscure the effect of virus alone. Seed lots containing various levels of seedborne PVY (0, 2, 10, 20, and 50% incidence of infected tubers) were created by combining in different proportions seed pieces from healthy and infected tubers from the same seed source. These seed lots were planted in replicated field plots at the University of Idaho Parma R & E Center in Parma, ID from 1995 to 1997. Regression analyses on data from the three consecutive seasons indicate that seedborne PVY has virtually the same negative impact on yield for all three cultivars.

Serological properties of ordinary and necrotic isolates of Potato virus Y: a case study of PVYN misidentification.

In the course of a multi-year survey of Potato virus Y (PVY) incidence and diversity in the U.S. seed potato crop, an unusual PVY variant was identified in low but significant levels in multiple states. This variant, PVYO-O5, was initially detected by a commercially available PVYN-specific monoclonal antibody, 1F5. This antibody is widely used by U.S. Seed Certification programs to test for PVYN and is one of two antibodies designated by the North American Plant Protection Organization (NAPPO) for pre-shipment testing of tuber lots that are to be transported between countries. Consequently, PVYN positives identified by the 1F5 antibody have triggered quarantine actions, prevented cross-border shipments and impacted trade. Here, we demonstrate by a variety of methods that the PVYO-O5 is a variant within the ordinary PVY strain (PVYO). Specifically, the PVYO-O5 variant likely arose due to a single amino acid substitution within the capsid protein. This variant does not induce vein necrosis in tobacco or tuber necrosis in susceptible varieties of potato. Furthermore, it is identified by RT-PCR based diagnostics as PVYO and it has a typical PVYO genome sequence. We demonstrate that another PVYN specific monoclonal antibody, SASA-N, recognizes an epitope distinct from that recognized by 1F5, and correctly identifies the PVYO-O5 variants as belonging to the PVYO serotype. Since the PVYO-O5 variant is present in many seed producing states and misidentification of PVYO-O5 as PVYN/NTN has clear quarantine implications for export shipments of potato, the limitations of the commercially available monoclonal antibodies should be considered in any certification or phytosanitary testing program.ResumenA lo largo del estudio de varios años sobre la incidencia y diversidad del virus Y de la papa (PVY) en los cultivos de papa para semilla en los Estados Unidos (EU), se identificó a una variante inusual a niveles bajos pero significativos en múltiples estados. Esta variante, PVYO-O5, se detectó inicialmente con un anticuerpo monoclonal comercialmente disponible específico para PVYN, el 1F5. Este anticuerpo es ampliamente usado por los Programas de Certificación de Semilla en los EU para PVYN, y es uno de los dos anticuerpos designados por la Organización Norteamericana de Protección de Plantas (NAPPO) para pruebas de pre-envío de lotes de tubérculos que serán transportados entre países. Consecuentemente, los PVYN positivos identificados con el anticuerpo 1F5 han disparado acciones cuarentenarias, evitando envíos trans-fronteras y han impactado al comercio. Aquí, nosotros demostramos con diversos métodos que PVYO-O5 es una variante del PVY ordinario (PVYO). Específicamente, la variante PVYO-O5 es probable que haya surgido debido a una substitución de un aminoácido dentro de la proteína de la cápside. Esta variante no induce necrosis de las venas en tabaco o necrosis del tubérculo en variedades susceptibles de papa. Aún mas, se le identifica como PVYO mediante RT-PCR y tiene la típica secuencia genómica del PVYO. Demostramos que otro anticuerpo monoclonal específico para PVYN, el SASA-N, reconoce un epítope distinto al reconocido por 1F5, e identifica correctamente a las variantes PVYO-O5 como pertenecientes al serotipo PVYO. Tomando en cuenta que la variante PVYO-O5 esta presente en muchos estados que producen semilla, y que la identificación equivocada de PVYO-O5 como PVYN/NTN tiene claras implicaciones cuarentenarias para envíos de exportación de papa, se deberían de considerar las limitaciones de los anticuerpos monoclonales disponibles comercialmente en cualquier programa de pruebas para certificación o fitosanidad.

Effect of Potato virus Y on Yield of Three Potato Cultivars Grown Under Different Nitrogen Levels

Previous studies have shown that Potato virus Y (PVY) reduces yield in many cultivars. Typical foliar symptoms can include veinal necrosis, leaf drop, and a mosaic pattern sometimes accompanied by leaf roughness. Infection by PVY in Russet Burbank produces identifiable PVY symptoms, whereas cv. Russet Norkotah expresses mild, almost latent symptoms. Yield also is influenced by nitrogen fertilizer levels. This research was conducted to determine whether increased nitrogen mitigates yield reduction caused by PVY. Russet Norkotah, CO80011-5, and Russet Burbank were used in replicated plots of non-PVY-infected and PVY-infected plants at three nitrogen levels in 1995 and 1996. There was a significant yield reduction between PVY-negative and PVY-positive plots in all cultivars, at most nitrogen levels. PVY yield reduction was similar (approximately 38%) in the mild symptom expression clones of Russet Norkotah and CO80011-5, whereas the yield reduction in Russet Burbank, which exhibits typical symptom expression, was 63.5%. We conclude that increased nitrogen can influence total yield, but does not significantly mitigate the yield reduction due to PVY infection.

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.

Characterization of Broad Spectrum Potato Virus Y Resistance in a Solanum tuberosum ssp. andigena-Derived Population and Select Breeding Clones Using Molecular Markers, Grafting, and Field Inoculations

PVY causes yield and quality loss in potato. The Ryadg gene from Solanum tuberosum ssp. andigena has been shown to provide extreme resistance to PVY; defined as resistance against all strains. However, Ryadg gene clones have not been screened against PVYN:O, a newly detected North America strain. Three Ryadg-diagnostic molecular markers were tested in tetraploid progeny of a PVY resistant x susceptible cross and in diverse clones/cultivars. Multiple isolates of PVY strains (PVYNTN, PVYN:O, PVYO) were used for mechanical inoculations of the progeny. In addition, PVYO, PVYN, and PVA were used for graft inoculation on a separate clone/cultivar set. Progeny segregated 1:1 for PVY resistance; fitting a gene model simplex for Ryadg. Marker positive progeny were resistant to all PVY strains, including PVYN:O. Marker presence was also in agreement with PVY resistance in the clones/cultivars. These findings show that these markers can identify resistance to all known PVY strains in North America.ResumenEl virus Y de la papa (PVY) causa reducción en la calidad y el rendimiento. Se ha demostrado que el gen Ryadg de Solanum tuberosum ssp. andigena provee resistencia extrema contra el PVY; definida como resistencia contra todas las cepas. Sin embargo, no se ha investigado la resistencia de los clones del gen Ryadg contra PVYN:O, una cepa de Norte América recientemente detectada. Tres marcadores moleculares de diagnostico del gen Ryadg fueron probados en progenie tetraploide de un cruce de PVY resistente x susceptible y en diversos clones/cultivares. Múltiples cepas aisladas de PVY (PVYNTN, PVYN:O, PVYO) fueron utilizadas para inoculaciones mecánicas de la progenie y PVYO, PVYN y PVA fueron usados para inoculación de injertos en un subconjunto de clones/cultivares. La progenie segregó 1:1 para resistencia contra PVY; encajando en un modelo genético simplex para Ryadg. Las progenies positivas a los marcadores fueron resistentes a todas las cepas de PVY, incluyendo PVYN:O. La presencia de marcadores tambien concordaba con la resistencia contra PVY en clones/cultivares. Estos hallazgos demuestran que estos marcadores pueden identificar la resistencia a todas las cepas de PVY conocidas en Norte América.

Identification of Potato virus Y Strains Associated with Tuber Damage During a Recent Virus Outbreak in Potato in Idaho

Potato virus Y (PVY) causes substantial losses in potato production by decreasing yields and affecting the quality of potato tubers. Management of PVY in potato is dependent primarily on potato seed certification programs to prevent or limit initial levels of virus inoculum. Prior to 1990, the ordinary strain of PVY (PVYO) was the predominant virus in North America. PVYO induces clear foliar symptoms in many potato cultivars, allowing successful management in seed potato through a combination of visual inspections and limited laboratory testing. In recent years, necrotic strains of PVY (PVYN, PVYNTN, and PVYN:O) have begun to spread in the United States, many of which induce mild symptoms in potato, making them more difficult to manage through visual inspections. In addition to reducing yield, necrotic isolates may also cause external and internal damage in tubers of susceptible cultivars, which is known as potato tuber necrotic ringspot disease (PTNRD). Tuber necrotic strains of PVY have been reported across the northern United States (1,2,4), although limited information is available on their incidence and spread in commercial potato production. During June and July of 2007, 38 random samples were collected from three different commercial fields displaying disease problems (cvs. Russet Ranger, Alturas, and Russet Burbank) in the vicinity of Idaho Falls, ID. Plants collected showed various degrees of mosaic and leaf yellowing. By using double-antibody sandwich (DAS)-ELISA and reverse transcription (RT)-PCR, 25 of these plants were identified as PVY positive. The mutiplex RT-PCR assay (3) confirmed that nine plants were infected with PVYNTN and 11 with PVYN:O. No RT-PCR products were amplified from five samples. During September and October of 2007, 25 tuber samples (cv. Russet Burbank) showing various degrees of unusual internal symptoms (e.g., brown spots) were collected near Idaho Falls, ID. Twenty-two tubers were found PVY positive by DAS-ELISA, and multiplex RT-PCR determined 13 of those were PVYNTN, three were PVYO, one was a PVYNTN/N:O mixture, and one was a PVYO/N:O mixture. No RT-PCR products were amplified from four samples. In October 2007, six tubers showing distinct external tuber damage characteristic of PTNRD (cv. Highland Russet) were collected near Twin Falls, ID. All six tubers were determined to be PVY positive by DAS-ELISA, and RT-PCR identified five as infected with PVYNTN and one with PVYN:O. All the mixtures were easily separated by inoculating tobacco plants followed by subsequent testing of individual plants. Asymptomatic tubers from the same lot not showing PTNRD damage were found PVY negative by DAS-ELISA and RT-PCR. All PVYNTN isolates collected during 2007 were inoculated into tobacco plants (Nicotiana tabacum L. cv. Xanthi) and confirmed to induce systemic vein necrosis. Limited sequencing of four of the PVYNTN isolates determined that they contained recombinant junctions 2 and 3, identifying them as being related to the European strain of PVYNTN (3). The data suggest an increase in distribution and incidence of necrotic strains of PVY in commercial, potato-production areas in Idaho during an outbreak in 2007 and the potential for an increase in PTNRD. References: (1) P. M. Baldauf et al. Plant Dis. 90:559, 2006. (2) J. M. Crosslin et al. Plant Dis. 90:1102, 2006. (3) J. H. Lorenzen et al. Plant Dis. 90:935, 2006. (4) L. M. Piche et al. Phytopathology 94:1368, 2004.

GemStar russet: A potato variety with high yield, good culinary quality, excellent fresh market appearance, and resistance to common scab

GemStar Russet, derived from the cross Gem Russet x A8341-5, was released in 2004 by the USDA/ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. The foliage of GemStar Russet is dark yellowish-green, spreading, with large leaves and abundant white flowers. The tubers are brown, medium to heavily russeted, oblong, with a slightly prominent eyebrow, white flesh, and indistinct pith. GemStar Russet was compared with Russet Burbank and Russet Norkotah in trials across the Pacific Northwest for yield, quality, and disease response. Except for locations in southern Idaho, in general, GemStar Russet produced slightly lower total yield than Russet Burbank, but much higher U.S. No. 1 yield. When compared with Russet Norkotah, GemStar Russet produced similar total and U.S. No. 1 yields in early harvest trials but higher total and U.S. No. 1 yields in late-harvest trials. When observed for defect problems, GemStar Russet exhibited resistance to second growth, growth cracks, and stemend discoloration, moderate resistance to blackspot and shatter bruising, but a high level of susceptibility to hollow heart. In product quality tests, GemStar Russet was rated superior to Russet Burbank for french fry quality and comparable for baked potato quality. GemStar Russet was found to be immune to PVX, resistant to common scab and powdery scab, moderately resistant to Verticillium wilt, tuber net necrosis caused by PLRV, and corky ringspot. It demonstrated susceptibility to late blight, PLRV, dry rot, soft rot, and ringrot and extreme susceptibility to PVYo. Biochemical analysis of GemStar Russet tubers showed them to be higher in protein and much higher in vitamin C than those of Russet Burbank or Russet Norkotah. Three-year average for tuber glycoalkaloid concentration was 1.5 mg 100 g−1.ResumenEn el ano 2004 el USDA/ARS y las Estaciones Experimentales Agrícolas de Idaho, Oregon y Washington liberaron la variedad GemStar Russet derivada del cruzamiento de Gem Russet x A8341-5. El follaje de GemStar Russet es amarillo verdoso oscuro, extendido, con hojas grandes y abundantes flores blancas. Los tubérculos son pardos, mediana a fuertemente rojizos, oblongos con prominencia del ojo ligeramente pronunciada, pulpa blanca y médula indistinguible. GemStar Russet ha sido comparada con Russet Burbank y Russet Norkotah en pruebas realizadas a lo largo del Pacífico nor-occidental para determinar rendimiento, calidad y respuesta a enfermedades. Con excepción de localidades del sur de Idaho, en general, GemStar Russet dio rendimientos totales ligeramente inferiores a Russet Burbank, pero mucho mayor rendimiento de US No 1. Comparado con Russet Norkotah, GemStar Russet produjo un rendimiento total similar y de US No 1 en pruebas de cosecha temprana, pero totales más altos y rendimiento de US No 1 en pruebas de cosecha tardía. Cuando se hicieron observaciones para determinar defectos, GemStar Russet exhibe resistencia a crecimiento secundario, rajaduras de crecimiento y decoloración de la base del tubérculo, resistencia moderada a mancha negra y magulladuras por golpe, pero un alto nivel de susceptibilidad al corazón vacío. En pruebas de calidad del producto GemStar Russet fue calificado como superior a Russet Burbank para papa frita y similar para papa horneada. Se encontró que GemStar Russet es inmune al virus PVX, resistente a la sarna común y sarna polvorienta, moderadamente resistente a la marchitez por Verticillium, necrosis reticulada del tubérculo causada por el virus PLRV y mancha corchosa anillada. Demostró susceptibilidad al tizón tardío, PLRV, pudrición seca, pudrición blanda y susceptibilidad extrema a PVYo. El análisis bioquímico de los tubérculos de GemStar Russet dio un alto contenido de proteína y mucho más alto de vitamina C que los de Russet Burbank o Russet Norkotah. El promedio de tres años sobre concentración de glicoalcaloides en el tubérculo fue de 1.5mg 100g-1.

Comparison of transmission efficiency of various isolates of Potato virus Y among three aphid vectors

Potato virus Y (PVY) strains are transmitted by different aphid species in a non‐persistent, non‐circulative manner. Green peach aphid (GPA), Myzus persicae Sulzer, is the most efficient vector in laboratory studies, but potato aphid (PA), Macrosiphum euphorbiae Thomas (both Hemiptera: Aphididae, Macrosiphini), and bird cherry‐oat aphid (BCOA), Rhopalosiphum padi L. (Hemiptera: Aphididae, Aphidini), also contribute to PVY transmission. Studies were conducted with GPA, PA, and BCOA to assess PVY transmission efficiency for various isolates of the same strain. Treatments included three PVY strains (PVYO, PVYN:O, PVYNTN) and two isolates of each strain (Oz and NY090031 for PVYO; Alt and NY090004 for PVYN:O; N4 and NY090029 for PVYNTN), using each of three aphid species as well as a sham inoculation. Virus‐free tissue‐cultured plantlets of potato cv. Russet Burbank were used as virus source and recipient plants. Five weeks post inoculation, recipient plants were tested with quantitative DAS‐ELISA to assess infection percentage and virus titer. ELISA‐positive recipient plants were assayed with RT‐PCR to confirm presence of the expected strains. Transmission efficiency (percentage infection of plants) was highest for GPA, intermediate for BCOA, and lowest for PA. For all aphid species, transmission efficiency did not differ significantly between isolates within each strain. No correlations were found among source plant titer, infection percentage, and recipient plant titer. For both GPA and BCOA, isolates of PVYNTN were transmitted with greatest efficiency followed by isolates of PVYO and PVYN:O, which might help explain the increasing prevalence of necrotic strains in potato‐growing regions. Bird cherry‐oat aphid transmitted PVY with higher efficiency than previously reported, suggesting that this species is more important to PVY epidemiology than has been considered.

Summit Russet: A new russet potato variety with good fresh market and frozen processing qualities

Summit Russet (A84118-3), the result of the cross A77236-6 x TND329-1Russ, was released in 2003 by the USDA/ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington. The vines of Summit Russet are erect, with very thick stems, large yellowish-green leaves and abundant white flowers. The tubers are tan, with medium russet skin, long-flattened shape, a slightly prominent eyebrow, white flesh, and moderately prominent pith. Tuber dormancy is very long. Summit Russet was compared with Russet Burbank in trials across the Pacific Northwest for yield, quality, and disease response. In general, Summit Russet produced similar or lower total yields than did Russet Burbank, but higher U.S. No. 1 yields. In Idaho variety trials, Summit Russet exhibited resistance to second growth, growth cracks, blackspot bruise, and stem-end discoloration, and moderate susceptibility to hollow heart and shatter bruise. In comprehensive product quality evaluations, Summit Russet was rated superior to Russet Burbank for french fry quality and similar for baked potato quality. French fry quality was retained after long-term storage. In replicated disease trials, Summit Russet was found to have good resistance to common scab, early blight tuber rot, and Verticillium wilt, and moderate resistance to Fusarium dry rot and tuber net necrosis caused by PLRV. It demonstrated susceptibility to late blight, foliar PLRV, PVX, PVYo, and bacterial soft rot. Biochemical analysis of Summit Russet tubers showed them to be higher in total solids and sucrose, and lower in dextrose than those of Russet Burbank. Tuber glycoalkaloid concentration as measured from tubers produced in 1994–1996 trials was 6.7 mg 100 g1.ResumenSummit Russet (A84118-3), es el resultado del cruzamiento de A77236-6 x TND329-1Russ, que fue liberada en el 2003 por el USDA/ARS y la Estación Experimental Agrícola de Idaho, Oregon y Washington. Las plantas de Russet Summit son erectas, con tallos gruesos, hojas grandes de color verde amarillento y abundantes flores blancas. Los tubérculos son bronceados, con piel rosada, achatados, largos, una ceja ligeramente prominente, pulpa blanca y médula moderadamente prominente. El estado de dormacia del tubérculo es largo. En pruebas a lo largo del noroeste del Pacífico se comparó Summit Russet con Russet Burbank, para rendimiento, calidad y respuesta a las enfermedades. En general, Summit Russet produjo rendimientos totales similares o más bajos que Russet Burbank pero un mayor número de tubérculos U.S. No 1. En Idaho, en ensayos varietales, Summit Russet mostró tubérculos con resistencia a crecimientos secundarios, rajaduras, manchas por magulladuras, decoloración del extremo del tallo y susceptibilidad moderada al corazón vacío y daños por golpe. En pruebas de calidad Summit Russet fue superior a Russet Burbank para papa frita y similar para calidad de horneado. La buena calidad para fritura se mantuvo por tiempo prolongado de almacenamiento. En repetidas pruebas para enfermedades se encontró que Summit Russet tiene buena resistencia a sarna común, pudrición del tubérculo por tizón temprano y marchitez por Verticillium, tiene resistencia moderada a pudrición seca por Fusarium y necrosis reticulada causada por PLRV. Demostró susceptibilidad a tizón tardío, PLRV, PVX, PVYo y pudrición bacteriana blanda. El análisis bioquímico de los tubérculos de Summit Russet mostró un alto contenido de sólidos totales y sacarosa y bajo contenido de dextrosa que los de Russet Burbank. La concentración de glicoalcaloides medida en tubérculos producidos en las pruebas de 1994 a 1996 fue de 6.7mg/100g1.