Abstract
Soft rot resistance in potato (Solanum tuberosum L.) tubers can be determined by inoculating tuber slices with soft rotErwinia species. Questions have been raised in the literature concerning the reliability of the tuber slice method. The objectives of this study were to 1) examine the statistical assumptions underlying the analysis of variance for different response variables as measures of soft rot resistance using the tuber slice method of evaluation; 2) estimate the sample sizes necessary to detect specified differences with power 0.83; and, 3) choose the “best” variable for measuring resistance to soft rot based on valid statistical analysis and minimal sample size. Slices from fifteen tubers from each of three cultivars (Atlantic, Norchip, Superior) were inoculated withErwinia carotovora subsp.atroseptica, E. carotovora subsp.carotovora orE. chrysanthemi and incubated at two different temperatures (20 C and 30 C) for 48 hrs. The test was conducted on two dates. Tuber samples were sliced and weighed prior to inoculation and after the macerated tissue was removed following a 48 hr incubation period. The maximum diameter of macerated tissue, actual weight loss, four measures of proportional weight loss, and various transformations of these variables were analyzed. The “best” response variables for measuring resistance to soft rot by the tuber slice method were the diameter of the macerated tissue and the square root transformation of one of the measures of proportional weight loss. No differences were found among the cultivars nor theErwinia subsp. for either of these response variables, and the cultivar ×Erwinia subsp., cultivar × temperature and cultivar ×Erwinia subsp. × temperature interactions were not significant. However, there were significant differences between the incubation temperatures, and theErwinia subsp. × temperature interaction was significant for both response variables. Estimates of sample sizes necessary to find a 20% difference in main effect and interaction effect means were calculated.
Resumen
Se puede determinar la resistencia a la pudrición blanda en tubérculos de papa (Solanum tuberosum L.) mediante la inoculación de rodajas de tubérculo con especies deErwinia causantes de esta enfermedad. Han surgido interrogantes en la literatura en cuanto a la confíabilidad de este método. Los objetivos de este estudio fueron: 1) examinar los supuestos estadísticos que subyacen el análisis de la variancia para las diferentes variables como medidas de la resistencia a la pudrición blanda empleando el método de evaluación en las rodajas del tubérculo de papa; 2) estimar los tamaños de muestras necesarios para detectar diferencias específicas con poder 0.83; y 3) escoger la variable “mejor” para medir la resistencia a la pudrición blanda basándose en los análisis estadísticos válidos y en el tamaño mínimo de la muestra. Las rodajas de quince tubérculos de cada uno de los tres cultivares analizados (Atlantic, Norchip, Superior) fueron inoculadas conErwinia carotovora subsp.atroseptica,E. carotovora subsp.carotovora o E. chrysanthemi e incubados a dos temperatures (20 C y 30 C) durante 48 horas en dos fechas diferentes. Los tubérculos fueron rebanados y pesados antes de la inoculación y luego de que el tejido macerado fuera extraído después de un período de incubación de 48 horas. Se analizaron el máximo diámetro del tejido macerado, la pérdida real de peso, las cuatro medidos de la pérdida proporcional de peso y diversas transformaciones de estas variables. Las “mejores” variables para la medición de la resistencia a la pudrición blanda mediante el método de rodajas de tubérculo fueron el diámetro del tejido macerado y la transformación de la raíz cuadrada de una de las medidas de la pérdida proporcional de peso. No se encontraron diferencias entre los cultivares o subespecies deErwinia para ninguna de estas variables y las interacciones de cultivar ×Erwinia subsp., cultivar × temperatura y cultivar ×Erwinia subsp. × temperatura no fueron significativas. Sin embargo, hubo diferencias significativas entre las temperaturas de incubación, y la interacciónErwinia subsp. × temperatura fue significativa para ambas variables. Se calcularon estimados de los tamaños de muestras necesarios para hallar un 20% de diferencia en el efecto principal y el medio del efecto de interacción.
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Haynes, K.G., Potts, W.J.E. & Goth, R.W. Evaluation of the reliability of determining soft rot resistance in potatoes by the tuber slice method. American Potato Journal 74, 265–275 (1997). https://doi.org/10.1007/BF02851725
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DOI: https://doi.org/10.1007/BF02851725