[Aplicación de Thaxtomin A para la identificación de resistencia a enfermedades en papa y conjugación de glucosa como mecanismo de resistencia]

Autor:Acuña B., Ivette

Institución:Montana State University

Potato scab is one of the most important diseases worldwide affecting market quality and increasing processor peel losses. Resistant varieties have been one of the best solutions to this disease; however, traditional potato breeding programs do not have good screening techniques that allow for early generation selection for scab resistance. The discovery of thaxtomin A (TA), produced by pathogenic Streptomyces scabies, and its important role in bacterial pathogenicity suggested new approaches in scab resistance screening techniques and the mechanism of resistance to thaxtomin A in potato tubers. This research investigated the correlation between an optimized true potato seed (TPS) - TA resistance assay with common scab resistance of potato tubers as determined by tuber TA sensitivity and scab symptoms in field tests; and tested the hypothesis that glucosylation of TA is related to potato plant resistance to pathogenic S. scabies. The TA seedling-screening assay was a useful tool for identifying scab resistant germplasm under homogeneous standard conditions. Doses of 1Mu of TA and an exposure time of 7 days allowed distinguishing between seedling progenies from cultivars that vary in resistance to scab. TA did not strictly select 100% resistant individuals, but it allowed approximately 30% a decrease in the size of the population to be tested under field conditions. Significant correlations were determined between a seedling index of damage by TA and tuber scab symptoms (R = 0.63, P = 0.0001; R = 0.49, P = 0.0001) and between tuber TA sensitivity and tuber scab symptoms (R = 0.64, P = 0.0001; R = 0.75, P0.01). Scab resistant individuals were identified, which can be tested directly for commercial purposes, can serve as parents in breeding programs or as a source of resistance genes. Glucosylation of TA by S. scabies occurs in vitro. The glucose conjugate of thaxtomin A from bacterial extracts was described as Thaxtomin A-Beta-di-O-gluosides (TAG). TAG was 6 times less toxic than TA in potato tubers. This research suggests a similar mechanism of TA detoxification in potato tubers. Resistant plants inoculated with 14 C - TA were able to produce a higher amount of a radioactive metabolite with an Rf similar to TAG than susceptible ones. We found almost twice as much glucose transferase specific activity in resistant than in susceptible individuals. Glucose conjugation may be a mechanism of TA detoxification in potato and it appears to be related to scab resistance and susceptibility in potato plants


Citar esta publicación:
Acuña B., Ivette (2000) [Aplicación de Thaxtomin A para la identificación de resistencia a enfermedades en papa y conjugación de glucosa como mecanismo de resistencia] [en línea]. Montana, USA: Disponible en: https://biblioteca.inia.cl/handle/123456789/56400 (Consultado: ).