R. G. Novy

Genetic Resistances to Potato Leafroll Virus, Potato Virus Y, and Green Peach Aphid in Progeny ofSolanum etuberosum

Increasing prevalence of potato leafroll virus (PLRV) and potato virus Y (PVY) has been reported in seed and commercial potato production, resulting in the rejection of potatoes for certification and processing. Host plant resistance to PLRV and PVY and their primary vector, green peach aphid,Myzus persicae, could limit the spread of these viruses. Host plant resistance to PLRV, PVY, and green peach aphid has been identified in non-tuber-bearingSolanum etuberosum (PI 245939) and in its backcross 2 (BC2) progeny. Resistance to green peach aphid involved a reduction in fecundity and adult aphid size. In addition, one BC2 individual was identified as possessing a genetic factor that was detrimental to nymph survival. PVY resistance was identified in all five BC2 progenies evaluated in a field screening under intense virus pressure. PLRV resistance was identified in two of the five BC2 progeny. This resistance was stable in field and cage evaluations with large populations of viruliferous aphids. Based on the segregation of virus resistances in the BC2 , PVY and PLRV resistances appear to result from the action of independent genetic mechanisms that reduce the levels of primary and secondary virus infection. Two BC2 individuals, Etb 6-21-3 and Etb 6-21-5 were identified as having multiple resistances to PLRV, PVY, and green peach aphid derived fromS. etuberosum. This germplasm could prove useful to potato breeders in the development of virus-resistant cultivars.ResumenEI incremento en la prevalencia del virus del enrollamiento de la hoja de papa (PLRV) y del virus Y de la papa (PVY) ha sido reportado tanto en las semillas como en la producción comercial de papa, lo que conlleva al rechazo de las mismas durante las fases de certificación y procesamiento. La resistencia de la planta hospedante al PLRV y al PVY y su principal vector, el pulgón verde,Myzus persicae, podría limitar el esparcimiento de esos virus. Se ha identificado resistencia de la planta hospedante al PLRV, al PVY y al pulgón verde enSolanum etuberosum (PI 245939) no tuberizados y en su progenie 2 (BC2) de retrocruzamiento. La resistencia al pulgón verde implicó una reducción en la fecundidad y tamaño del pulgón adulto. Adicionalmente, se identificó un BC2 individual que posee un factor genético perjudicial para la sobrevivencia de las ninfas. La resistencia al PVY se identificó en las cinco progenies BC2 evaluadas en un campo de prueba bajo intensa presión del virus. Se identificó resistencia al PLRV en dos de las cinco progenies BC2. Esta resistencia fue estable en el campo y en evaluaciones en jaula con una alta población de pulgones virulentos. Basados en la segregación de resistencia a virus del BC2, las resistencias al PVY y al PLRV parecen ser resultado de la acción de mecanismos genéticos independientes que reducen los niveles primarios y secundarios de la infección viral. Se identificaron dos BC2 individuales, Etb 6-21-3 y Etb 6-21-5, con resistencia múltiple al PLRV, PVY y pulgón verde derivada deS. etuberosum. Este germoplasma podría ser útil para los mejoradores que desarrollan cultivares resistentes al virus.

Somatic hybrids between Solanum etuberosum and diploid, tuber bearing Solanum clones

Electrofusion was used to obtain somatic hybrids between Solanum etuberosum (2n=2x=24) and two diploid potato lines. These hybridizations were conducted to determine if haploidxwild species hybrids are better fusion partners than conventional S. tuberosumGp. Tuberosum haploids. Restriction fragment length polymerase (RFLP) analyses of the putative somatic hybrids confirmed that each parental genome was present. The somatic hybrids between S. etuberosum and a haploid S. tuberosum clone, US-W730, were stunted and had curled, purple leaves. In contrast, somatic hybrids between S. etuberosum and a haploidxwild species hybrid (US-W 730 haploidx S. berthaultii), were vigorous and generally tuberized under field conditions. These hybrids were designated as E+BT somatic hybrids. Analyses of 23 E+BT somatic hybrids revealed a statistically significant bias towards the retention of S. etuberosum chloroplasts. Stylar incompatibilities were observed when the E+BT somatic hybrids were used as pollen donors in crosses with S. tuberosum cultivars. Reciprocal crosses did not show this incompatibility. The progeny were vigorous and had improved tuber traits when compared to the maternal E+BT parent. RFLP analyses of three sexual progeny lines confirmed the presence of all 12 S. etuberosum chromosomes. In two of these lines, RFLPs that marked each of the 24 chromosome arms of S. etuberosum were present. However, RFLP markers specific for regions on chromosomes 2, 7, and 11 were missing from the third clone. Because other markers for these chromosomes were present in the progeny line, these results indicated the likelihood of pairing and recombination between S. etuberosum and S. tuberosum chromosomes.

Development and Evaluation of Potato Breeding Lines with Introgressed Resistance to Columbia Root-Knot Nematode (Meloidogyne chitwoodi )

Columbia root-knot nematode (Meloidogyne chitwoodi) (CRN) is a serious pest of potato in the Pacific Northwest of the USA. Because this nematode can reproduce rapidly within a single growing season, small initial populations are capable of causing crop loss in the Columbia Basin of Washington or Oregon. Presently, soil fumigation is the main treatment for controlling CRN on potato. Developing potato varieties with resistance to CRN is highly desirable to reduce the cost of control and to alleviate concerns about the effects of fumigants on the environment. Resistance to CRN race 1 was found in two wildSolanum species. Resistance fromS. bulbocastanum was introduced via protoplast fusion and fromS. hougasii via sexual hybridization. Subsequent breeding consisted of repeated backcrossing and selection. The dominant monogenic inheritance was expressed in undiminished fashion across several backcross generations. When tested in replicated trials in three locations, selected resistant clones from the BC4 and BC5 of theS. bulbocastanum introgression populations had total marketable yields and yields of >113-g (4 oz) tubers as good or better than standard potato varieties tested in replicated yield trials in three locations. Percentage of tubers weighing more than 113 g in the highest yielding clones was not significantly different from commercial standards. The resistance phenotype, typified by failure of the nematode to reproduce on the root systems, was sufficiently effective to prevent economic damage in a field exposure. All CRN-resistant clones are pollen sterile. Germplasm listed is available upon request.ResumenEl nematodo del nudo de Columbia (Meloidogyne chitwoodi) (CRN), es un parásito serio de la papa en la zona del Pacífico noroeste de los EUA. Poblaciones iniciales pequeñas son capaces de ocasionar la pérdida del cultivo, debido a la habilidad de este nematodo a reproducirse rápidamente dentro de un mismo periodo de cultivo en los valles de Columbia de Washington u Oregon. Actualmente, la fumigación del suelo es el principal método de control del CRN de la papa. El desarrollo de resistencia al CRN es muy deseable para reducir los costos de control y la preocupación que se tiene de los fumigantes sobre el medio ambiente. Se encontró resistencia a la traza 1 del CRN en dos especies silvestres deSolanum spp. La resistencia deS. bulbocastanum se introdujo por fusión de protoplastos y la deS. hougasii por hibridación sexual. Las siguientes pruebas de mejoramiento consistieron en retrocruzas repetidas y selección. La herencia monogénica dominante fue expresada a lo largo de varias generaciones de retrocruza. Cuando se hicieron pruebas múltiples en tres localidades, los clones resistentes seleccionados de BC4 y BC5 de la población de introgresión deS. bulbocastanum tuvo un rendimiento total comerciable de tubérculos por encima de los 113g (4 onzas), tan bueno o mejor que las variedades estándar de papa evaluadas en pruebas de rendimiento con repeticiones en tres localidades. El porcentaje de tubérculos con pesos mayores a los 113 gramos en el clon de mayor rendimiento, no mostró diferencia significativa en comparación con los estándares comerciales. La resistencia del fenotipo, tipificado por la falta de reproducción del nematodo en los sistemas de raíces, fue suficientemente efectiva para prevenir el daño económico en la exposición de campo. Todos los clones resistentes CRN son de polen estéril. El germoplasma incluido en la lista está disponible para quien lo solicite.

Resistance to potato virus Y in somatic hybrids between Solanum etuberosum and S. tuberosum x S. berthaultii hybrid

Somatic hybrids between a potato virus Y (PVY) resistant Solanum etuberosum clone and a susceptible diploid potato clone derived from a cross between S. tuberosum Gp. Tuberosum haploid US-W 730 and S. berthaultii were evaluated for resistance to PVY. All but one of the tested somatic hybrids were significantly more resistant than cultivars ‘Atlantic’ and ‘Katahdin’. However, none was as resistant as the S. etuberosum parent. One hexaploid somatic hybrid, possibly the product of a triple-cell fusion involving one S. etuberosum protoplast and two haploid x S. berthaultii protoplasts, was as susceptible to PVY infection as the cultivars. Tetraploid progeny of the somatic hybrids, obtained from crosses with Gp. Tuberosum cultivars, were neither as resistant as the maternal somatic hybrid parent, nor as susceptible as the paternal cultivar parent. It appears that the introgression of PVY resistance from (1EBN) S. etuberosum into (4EBN) S. tuberosum (EBN-endosperm balance number) will be successful through the use of somatic hybridization and subsequent crosses of the somatic hybrids back to S. tuberosum.

Characterization of the expression and inheritance of potato leafroll virus (PLRV) and potato virus Y (PVY) resistance in three generations of germplasm derived from Solanum etuberosum

Potato virus Y (PVY) and potato leafroll virus (PLRV) are two of the most important viral pathogens of potato. Infection of potato by these viruses results in losses of yield and quality in commercial production and in the rejection of seed in certification programs. Host plant resistance to these two viruses was identified in the backcross progeny of a Solanum etuberosum Lindl. somatic hybrid. Multiple years of field evaluations with high-virus inoculum and aphid populations have shown the PVY and PLRV resistances of S. etuberosum to be stably expressed in two generations of progeny. However, while PLRV resistance was transmitted and expressed in the third generation of backcrossing to cultivated potato (Solanum tuberosum L. subsp. tuberosum), PVY resistance was lost. PLRV resistance appears to be monogenic based on the inheritance of resistance in a BC3 population. Data from a previous evaluation of the BC2 progeny used in this study provides evidence that PLRV resistance was partly conferred by reduced PLRV accumulation in foliage. The field and grafting data presented in this study suggests that resistance to the systemic spread of PLRV from infected foliage to tubers also contributes to the observed resistance from S. etuberosum. The PLRV resistance contributed by S. etuberosum is stably transmitted and expressed through sexual generations and therefore would be useful to potato breeders for the development of PLRV resistant potato cultivars.

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 (solarium tuberosum L.) haploid x wild species hybrids with the capacity to cold-chip

Cold sweetening, the accumulation of reducing sugars in potatoes stored at low temperatures, results in dark chips unacceptable to the consumer. Developing potato cultivars that can chip directly from cooler temperatures (i.e., 3 to 4 C) requires the identification and use of new germplasm with cold-chipping resistance. Individuals from 16 haploid x wild species hybrid families were grown at two sites and their harvested tubers stored at 3 C for 15 wk. Following storage, individuals were evaluated for cold-chipping ability by (1) direct chipping, and (2) reconditioning for 2 wk at 18 C prior to chipping. At both sites, approximately 1% of progeny had good chip color (<2.0 rating using the Snack Food Association scale). Germplasm representing haploid x wild species hybrid families was evaluated for cold-chipping ability following storage of tubers at 3 C for 15 wk, and after storage at 18 C for 2 wk. The two cold-chipping clones identified with chip color means <2.0 were AH 66-1 and H 28-6, hybrids derived fromS. raphanifolium accessions 296126 and 310998, respectively.S. raphanifolium PI 296126 was exceptional in that chip color means of its progeny were 2.5 and 2.7 at McLeod (North Dakota) and Crookston (Minnesota), respectively. All clones with chip color means <2.6 involvedS. raphanifolium PIs 296126, 310998, and 458384 in their parentage. Following reconditioning, the number of progeny in the good and medium chipping categories improved from direct chipping with 14.1% of the progeny at McLeod and 3.8% at Crookston in the good chipping category.S. raphanifolium PIs 210048 and 310998 together accounted for 100% and 50% of the clones with chip scores <2.0 at McLeod and Crookston, respectively. Clones ranking high for chip color following direct chipping generally chipped well following reconditioning.

Resistance to phytophthora erythroseptica and pythium ultimum in a potato clone derived from s. berthaultii and s. etuberosum

Tubers of several potato clones and cultivars were screened for susceptibility to infection by zoospores of Phytophthora erythroseptica (causal agent of pink rot) and mycelia of Pythium ultimum (causal agent of leak) over a three-year period, from 2003-2005. Incidence of infected tubers (%) and penetration of rot (mm) were the parameters used to determine the susceptibility of each potato clone. Responses of each potato clone were compared to cultivars with known resistance or susceptibility to these pathogens. Tubers of cultivars Atlantic and Snowden have moderate resistance to infection and colonization by P. erythroseptica and P. ultimum, respectively, and were used as the resistant checks. Cultivars Russet Norkotah and Red Norland are susceptible to infection by both pathogens. A number of potato clones demonstrated resistance to pink rot equal to or greater than the control cultivar Atlantic, including Etb 6-5-2, ND5822C-7, ND6956b-13, ND7443Ab-44, ND7443Ab-181, ND7818-1Y and J101K6A22. In addition to demonstrating the highest resistance to pink rot, Etb 6-5-2 was the only clone that demonstrated resistance to leak greater than or equivalent to the resistant cultivar Snowden. Etb 6-5-2 is a backcross derivative from a somatic hybrid of Solanum etuberosum and Solanum berthaultii and will be investigated further as a potential source of resistance to these two storage rot diseases.ResumenLos tubérculos de varios clones y cultivares de papa fueron tamizados para susceptibilidad con zoosporas de Phytopthora erythroseptica (agente causal de pudricion rosada) y con micelio Pythium ultimum (agente causal de pudricion acuosa o gotera) en un periodo de tres aÑos, del 2003 al 2005. La incidencia de tubérculos infectados (%) y la profundidad de la pudriciön (mm) fueron los parámetros usados para determinar la susceptibilidad en cada clon de papa. Las respuestas de cada clon fueron comparadas con las de cultivares de conocida resistencia o susceptibilidad a estos patögenos. Tubérculos de los cultivares Atlantic y Snowden que tienen resistencia moderada a la infecciön y colonizacion por P. erythroseptica y P. ultimum respectivamente, fueron usados como testigo resistente. Los cultivares de Russet Norkotah y Red Norland son susceptibles a la infeccion de ambos patögenos. Varios clones de papa mostraron resistencia a la pudriciön rosada, igual o mayor que el testigo Atlantic, incluyendo, Etb 6-5-2, ND5822C-7, ND6956b-13, ND7443Ab-44, ND7443Ab-181, ND7818-1Y y J101K6A22. Además de demostrar muy alta resistencia, Etb 6-5-2 fue el único clon que demoströ resistencia a la gotera en mayor proporciön o equivalente al cultivar resistente Snowden. Etb 6-5-2 es producto de una retrocruza derivada de un híbrido somático de Solanum etuberosum y S. berthaultii y será investigada adicionalmente como fuente potencial de resistencia a estas dos pudriciones de tubérculos almacenados.

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.