Búsqueda de portainjertos de aguacate tolerantes resistentes a Phytophthora cinnamomi Rands

Abstract

México se considera el centro de origen del aguacate y mantiene diversidad genética en materiales criollos. En este estudio, se realizaron colectas de semilla para detectar tolerancia o resistencia a Phytophthora cinnamomi Rands, principal patógeno de la raíz del aguacate. El material se colectó en los estados de Querétaro, Puebla y Estado de México, seleccionando árboles que no mostraban síntomas (árboles “escape”) aún cuando los huertos están infestados con el patógeno. Además, se incluyeron en la investigación semillas de 22 accesiones del Banco de Germoplasma (BG) de la Fundación Salvador Sánchez Colín CICTAMEX S.C. y planta clonal del portainjerto Duke-7 resistente a P. cinnamomi y utilizado como testigo. Se inocularon 5,200 plántulas con micelio de P. cinnamomi para hacer una selección masal recurrente; treinta y ocho plantas mostraron potencial para utilizarse como portainjerto. Para evaluar el polimorfismo entre genotipos, caracterizarlos y detectar la cercanía entre individuos, de los 38 materiales seleccionados, se extrajo el ADN y se caracterizó molecularmente con RAPD e ISSR; se incluyeron también los materiales: Topa-topa (susceptible), Duke-7 (resistente) y Day resistente a P. cinnamomi y salinidad, provenientes del BG y utilizados como referencia. Los dendogramas se elaboraron con el programa FreeTree, versión 0.9.1.50, aplicando un método de remuestreo con 1,000 repeticiones. La similitud genética se estimó con el coeficiente Nei and Li, y para los agrupamientos se utilizó el método UPGMA. Trece de los 25 iniciadores presentaron polimorfismo; el promedio del contenido de información polimórfica (PIC) para RAPD e ISSR fue de 0.9052 y 0.9054, respectivamente, con un total de 3,057 bandas. De forma independiente se caracterizaron 16 accesiones de aguacate provenientes del BG, 14 de ellas con resistencia o tolerancia en campo a P. cinnamomi y dos con susceptibilidad al patógeno. El análisis detectó un alto grado de polimorfismo entre los materiales evaluados.________México is considered as the origin center of the avocado and maintain genetic diversity in wild materials. Seed collections were carried out to find tolerance or resistance to Phytophthora cinnamomi Rands, main pathogen of the avocado root. The collection sites were the states of Queretaro, Puebla and state of Mexico, where “escape” trees were selected in orchards infested whit the pathogen, likewise, in this research there were included seeds of 22 accessions from the Germplasm Bank (GB) located in Coatepec Harinas, state of Mexico, y clone plant Duke-7 as standard. After five years from the beginning of the collection, the outcome was 5,200 seedlings that were inoculated with P. cinnamomi through recurrent mass selection. From this selection, 38 plants survived and are considered as potential of rootstock. Likewise, there were materials selected to water with salty water with concentrations up to 14.2 meq/L of Na+ and 4.52 meq/L of Cl-. From these 38 materials, the DNA was extracted and characterized molecularly with RAPD and ISSR, which includes three materials from the Germoplasm Bank used as reference: Topa-topa (susceptible), Duke-7 (resistant) and Day resistant to P. cinnamomi and salinity as well. The objective was to evaluate the polymorphism among genotypes, characterize them and detect a close relationship among individuals. The Dendograms (trees) were constructed with the software FreeTree, version 0.9.1.50 considering a re-sampling method with 1 000 replications. The close genetic relationship was estimated by Nei and Li coefficient, and the cluster analysis was analyzed by the UPGMA method. Only 13 of 25 primers showed polymorphism; the average of the polymorphic information content for RAPD and ISSR was 0.9052 and 0.9054, respectively, with a total of 3,057 bands. Other study was by vegetal culture of 16 accessions from the GB, 14 resistant to P. cinnamomi in field, this analysis detected a high degree of polymorphism among materials assessed.