Evaluación de la diversidad genética y fenotípica retenida en colecciones nucleares de manzano formadas a partir de caracterizaciones agro-morfológicas o moleculares

Las colecciones nucleares de plantas pueden formarse a partir de la información obtenida en caracterizaciones morfológicas, agronómicas o eco-geográficas, así como a partir de caracterizaciones bioquímicas o moleculares. Un aspecto poco estudiado de la formación y validación de colecciones nucleares es la capacidad de éstas para conservar la estructura y diversidad de la colección global en aquellos caracteres que no han sido empleados para formar la colección nuclear. En el presente estudio se determinaron tres colecciones nucleares para el Banco de Germoplasma de Manzano de la Universidad Pública de Navarra: para el primero se emplearon los datos de caracterización de 10 marcadores SSR, la segunda fue formada a partir de la caracterización hecha con 12 loci de isoenzimas, y la tercera se construyó a partir de la información proporcionada por 23 caracteres morfo-agronómicos. Se comparó la estructura y diversidad genotípica y fenotípica de las tres colecciones, entre sí y respecto de la colección original, para determinar el impacto que sobre dicha estructura y diversidad tenía el tipo de dato con que se formó la colección nuclear. Las tres colecciones conservaron una diversidad similar y no difirieron de la original en sus índices de Nei y Shannon-Weaver, y siempre se mantuvieron las frecuencias de las clases alélicas o fenotípicas. En conjunto, el tipo de caracterización empleada en la formación de la colección nuclear tuvo escasa influencia sobre la diversidad retenida, de lo que se concluye que en el manzano los microsatélites son especialmente adecuados para formar dichas colecciones.Various types of data have been used for sampling plant core collections, including morphological, agronomic and eco-geographical traits, and molecular and biochemical markers. However, little is known about the ability of woody perennial core collections to retain the diversity and structure of the whole collection for characters that were not considered in the selection, especially when molecular markers are used. In this study, three core subsets were established for the apple germplasm bank curated at the Public University of Navarre (UPNa, Spain): based upon the diversity found with 10 SSR markers, another based upon the diversity assessed with 12 isozyme loci; and a third based upon morpho-agronomic diversity evaluated by 23 morpho-agronomic traits. Comparisons between these three subsets and to the whole collection were assessed to determine the impact of the data used in the selection on phenotypic and genetic diversity and on their population structure. The three subsets had a similar diversity and they did not differ from the original collection, according to Nei and Shannon-Weaver indices. The allelic/class frequencies were also always maintained in the three subsets. Overall, the kind of data used to constitute a core collection had little influence on the phenotypic and genetic diversity retained, so in the case of apple collections the use of molecular markers is preferable for this task because they allow a rapid and reliable characterization.This study was funded by the Spanish Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) grants Nº RF200400008-C03-00 and Nº RFP2004-00003-00-00

Genetic diversity of the Spanish apple genetic resources using SSRs

The Spanish Program of Plant Genetic Resources integrates, among others, the collections located at Public University of Navarre, Centro de Investigaciones Agrarias de Mabegondo, Cabildos (Tenerife, La Palma and Gran Canaria), University of Lleida, Estación Experimental de Aula Dei-CSIC and CITA of Aragon. Those collections include mainly local cultivars from their respective regions, covering most of the Spanish apple-growing areas. Though some previous studies about the genetic variability of apple genetics resources from Spain were already performed, a complete analysis is needed in order to evaluate the complete diversity of Malus spp. in Spain. For doing that, the Spanish Government funded the project ¿Harmonization of the methodology of characterization, assessment of genetic diversity and definition of the core collection of the apple germplasm conserved in Spanish genebanks¿. In total, we have evaluated 1206 accessions using standardized methodologies, with SSR markers and morphological descriptors. SSR fingerprinting was performed with 13 SSR markers. SSR profiles were obtained independently and allele sizes were compared using a common set of cultivars selected as references. Results showed 601 genotypes for 1206 accessions. Most of the genotypes (438) were identified only in one accession. The other 163 genotypes were repeated in two to 81 accessions (involving 767 accessions in total). The harmonization of morphological descriptors will allow us to determine if the accessions with the same genotype are synonymies or closely related individuals. Results of this study highlight the interest of coordinated actions in order to optimize the management of germplasm collections and to evaluate the complete genetic diversity of Malus spp. in Spain.Peer Reviewe

Genetic diversity of the Spanish apple genetic resources using SSRs: abstract

PublishedPoster number 6