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The gene Ry adg from S. tuberosum ssp. andigena provides extreme resistance to PVY. This gene has been genetically mapped to chromosome XI and linked PCRbased DNA markers have been identified. Advanced tetraploid russeted potato clones developed by the U.S. Pacific Northwest Potato Breeding ('Tri-State') Program with Ry adg PVY resistance were used in this study. The objective of this work was to assess the usefulness of molecular markers linked to Ry adg as a tool for selecting PVY resistance in a tetraploid potato breeding program. To achieve this, a full-sib tetraploid population segregating for Ry adg was screened with molecular markers linked to Ry adg , artificially inoculated with PVY O and evaluated in the greenhouse. A large percentage (96.4%) of the segregating lines showed coincidence between molecular markers and ELISA results at 40 days after inoculation. This justifies the use of molecular markers as an alternative to artificial inoculation followed by ELISA. Segregation (resistant vs. susceptible) based on ELISA and molecular marker results in the full-sib population indicated the presence of Ry adg as a simplex in the PVY resistant parent OR00030-1. Additional full-sib populations segregating for the Ry adg gene coming from OR00030-1 and from a related clone, AOR00628-3, were evaluated under field conditions. MAS can be used as a fast and efficient tool to select for PVY resistance, reducing the number of PVY susceptible lines retained for succeeding field evaluations, and thereby increasing the odds of generating PVY resistant potato varieties.Resumen El gen Ry adg de S. tuberosum ssp. andígena ofrece resistencia extrema contra el virus Y de la papa (PVY). Este gen ha sido genéticamente mapeado en el cromosoma XI y se han identificado marcadores ligados de ADN basado en PCR (reacción en cadena de la polimerasa). Clones avanzados tetraploides de papa rugosas, desarrollados por el Programa de Mejoramiento del Pacífico Noroeste de los Estados Unidos (`Tri-State´) con resistencia Ry adg al PVY fueron utilizados en este estudio. El objetivo de este trabajo fue evaluar la utilidad de los marcadores moleculares ligados a Ry adg , como una herramienta para seleccionar resistencia al PVY en un programa de mejoramiento de papa tetraploide. Para lograr esto, una población tetraploide de hermanos completos, segregantes para Ry adg fue tamizada mediante marcadores moleculares ligados al Ry adg , inoculada artificialmente con PVY o y Am. evaluada en invernadero. Un alto porcentaje (96.4%) de las líneas segregantes mostró coincidencia entre los marcadores moleculares y los resultados de ELISA 40 días después de la inoculación. Esto justifica el uso de marcadores moleculares como una alternativa a la inoculación artificial seguida por ELISA. La segregación (resistente vs. susceptible) basada en ELISA y los resultados de los marcadores moleculares en la población de hermanos completos, indicó la presencia de Ry adg como un simplex en el progenitor PVY resistente OR00030-1. Poblaciones adicionales de hermanos comp...

Ascorbic acid (vitamin C) is an essential nutrient in the human diet and potatoes are a valuable source. As a first step in breeding for potatoes (Solanum tuberosum L.) with higher levels of ascorbic acid, 75 clones from 12 North American potato-breeding programs were evaluated for concentration, and 10 of those for stability of expression. Trials were grown in Idaho, Oregon, and Washington in 1999 and 2000, tubers sampled, and ascorbic acid quantified. There were significant differences among clones and clone by environment interaction was also significant. Concentration of ascorbic acid of the clones was continuously distributed over a range of 11.5 to 29.8 mg/100 g. A subgroup of 10 clones was analyzed using an additive main effects and multiplicative interaction (AMMI) model, to diagnose interaction patterns and measure clone stability. The first two principal component axes accounted for over 80% of the variability. Bi-plot analysis showed `Ranger Russet' to be highly unstable across the environments tested. A plot of Tai's stability statistics found six of the 10 clones to be stable for ascorbic acid expression. Appropriate evaluation methods for ascorbic acid concentration must involve multi-year testing.

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