American Potato Journal

, Volume 69, Issue 7, pp 423–435 | Cite as

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

  • Dennis L. Corsini
  • Joseph J. Pavek
  • Bill Dean


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.

Additional Key Words

Potato protein potato amino acids Solanum tuberosum 


Se 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.


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Copyright information

© Springer 1992

Authors and Affiliations

  • Dennis L. Corsini
    • 1
  • Joseph J. Pavek
    • 1
  • Bill Dean
    • 2
  1. 1.USDA-ARSAberdeen
  2. 2.Washington State UniversityProsser, Washington

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