Selection and utilization of solanum phureja clones with high resistance to different strains of pseudomonas solanacearum

Abstract

Over 250 accessions ofSolanum phureja from Colombia and 300S. phureja—S. tuberosum hybrids were screened in the greenhouse for resistance toPseudomonas solanacearum (isolate K-60). Each plant was inoculated by stem puncture at the pre-bud stage and then held at a constant 28 C for 15 days. Seventeen clones with different levels of resistance to K-60 were inoculated with nine additional isolates representing all three races of the bacterium. The reactions of individual clones varied from resistance to almost all isolates, resistance to only one isolate, or complete susceptibility. Crosses amongS. phureja clones and betweenS. phureja and 24-chromosomeS. tuberosum stocks gave progeny with various percentages of resistant plants. Clones with resistance equal to that inS. phureja were found in theS. phureja × S. tuberosum crosses. Tests conducted in growth chambers showed that resistance was expressed more frequently at high light intensity (2000 ft-c) than at low intensities (1300 ft-c) at 24 C and 28 C. Resistance appears to be relatively simply inherited and the prospects for transferring a high level of resistance into cultivated forms are promising.

Resumen

Más de 500 accesiones deSolanum phureja introducidas de Colombia fueron probadas en el invernadero con respecto a resistencia aPseudomonas solanacearum (cepa K-60). Cada planta fue inoculada por medio de punción del tallo antes de la floración y se mantuvo a una temperatura constante de 28 C por 15 días. Diecisiete clones con diferentes niveles de resistencia a K-60 fueron inoculados con 9 cepas adicionales que incluían las 3 razas de la bacteria. Las reacciones de clones individuales variaron desde resistencia a casi todas las cepas de la bacteria, resistencia a una cepa solamente, o susceptibilidad completa. Cruzamientos entre clones deS. phureja, y entreS. phureja y clones deS. tuberosum de 24 cromosomas dieron progenies con varios porcentajes de resistencia. Es significativo que clones derivados de las cruzamientos deS. phureja × S. tuberosum demostraron resistencia igual a la deS. phureja. Experimentos en fitotrones indicaron que la resistencia aP. solanacearum se expresa con más frecuencia en condiciones de alta intensidad de la luz (2000 bujía-pies) que a baja intensidad (1300 bujía-pies) a 24 y 28 C. La resistencia parece ser heredada en forma simple y la posibilidad de transferir esta resistencia a variedades de papa cultivables es prometedora.