Caracterización de ADN de clones de papa e identificación de fitoplasmas asociados al síndrome de la punta morada

espanolEn muchas areas sembradas con papa en Mexico se manifiesta el sindrome de la punta morada, que reduce el rendimiento y la calidad del tuberculo. Un factor principal de este sindrome es la presencia de fitoplasmas y el inadecuado manejo de su insecto vector. Una opcion para controlar esta enfermedad es generar genotipos de papa resistentes y un diagnostico oportuno para evitar su diseminacion. Por ello los objetivos de este trabajo fueron detectar fitoplasmas asociados a la punta morada presentes en clones de papa asintomaticos, pero que estuvieron expuestos a la misma por cuatro ciclos, e identificar la relacion hospedero-patogeno. Al final del ciclo de cultivo del 2005, fueron recolectadas hojas de 18 clones de papa sin sintomas, en Toluca, Estado de Mexico, originarios de dos programas de mejoramiento genetico del Departamento de Agricultura de EE.UU. (USDA/ARS). Ademas fueron incluidos el cultivar Alpha con sintomas de la enfermedad como testigo positivo y plantas libres del fitoplasma. La deteccion del patogeno se hizo con PCR directa, PCR anidada y marcadores RFLP, usando las enzimas Alu 1, Hinf 1, Kpn 1, Eco R1, Tru 9, Taq 1, e identificando la presencia de tres grupos de fitoplasma en todos los clones. Los clones fueron agrupados en tres grupos relacionados con el testigo positivo, usando cinco iniciadores de marcadores RAPDs. Fue detectada una limitada relacion especifica hospedero-patogeno en funcion de las huellas de ADN de ambos. EnglishIn many potato growing areas in Mexico, there is presence of purple top syndrome, which reduces the yield and quality of this tuber. A main factor of this syndrome is the presence of phytoplasms and inadequate management of its insect vector. One option for controlling this disease is to generate resistant potato genotypes and early diagnosis to prevent its disemination. Therefore, the objectives of the present study were to detect phytoplasms associated with purple top present in asymptomatic potato clones, but which were exposed to the disease for four seasons, and to identify the host-pathogen relationship. At the end of the 2005 growing season, leaves of 18 asymptomatic potato clones, in Toluca, State of Mexico, were collected, originating from two breeding programs of the United States Department of Agriculture (USDA/ARS). Also included were the Alpha cultivar with symptoms of the disease as positive control and plants free of phytoplasm. The detection of the pathogen was made with direct PCR, nested PCR and RFLP markers, using the enzymes Alu 1, Hinf 1, Kpn 1, Eco R1, Tru 9, Taq 1, and identifying the presence of three groups of phytoplasm in all of the clones. The clones were clustered in three groups related to the positive control, using five primers of RAPDs markers. A limited specific host-pathogen relationship was detected as a function of the DNA fingerprints of both host and pathogen.