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Titre : Diversidad genética en el patosistema maíz-fusarium en el Altiplano de México

Auteur : Briones Reyes, Dolores.

Etablissement de soutenance : Colegio de Postgraduados (COLPOS) Consejo Nacional de Ciencia y Tecnología (CONACYT)

Grade : Doctorado en Ciencias, especialista en Genética 2013

Résumé
The native (creole) varieties of maize (Zea mays L. ) preserved by farmers through generations, constitute more than 80% of the area planted with maize in Mexico ; the Fusarium spp. ear rot could cause yield losses up to 30 %. The study of maize populations and their pathogens as pathosystem makes sense, because in the genetic variation of native maize can be found resistance/tolerance to such disease ; the knowledge of the maize and the pathogen structure populations could help to solve the rot problem, increase the grain production and preserve the genetic diversity. In 2010, 56 native maize populations were collected, with and without symptoms of ear rot from five states in Mexico at altitudes between 1498 and 2520 m. In 2010 and 2011, under rainfed conditions and natural infection by Fusarium, the response of maize populations was evaluated in three locations (Montecillo and Ayapango, Edo. de Mex., and Huamelulpan, Oax.). In 2012, the virulence of the pathogen and the susceptibility/tolerance of maize populations to Fusarium spp. of different geographical origin were assessed in seedling stage. In 2013 an isoenzymatic analysis for maize populations and Fusarium populations were required in order to know the genetic diversity in the pathosystem. The field response, showed significant differences between maize populations, between locations and interaction environment x population, was evident that local maize populations in the evaluation environment tend to have less damage by Fusarium spp., and higher grain yield ; by geographical origin, maize from Oaxaca should less damage than those from the states of Mexico, Puebla, Tlaxcala and Guerrero. The seedling test showed variation in virulence between sources of inoculum ; the most virulent was from the state of Mexico, while the on from Guerrero caused minor damages. Maize populations responded differently, expressing different degree of damage through various sources of inoculum. The maize and Fusarium spp. populations showed a pattern of grouping according to their geographical origin. The variation observed in the maize-Fusarium spp. pathosystem through isoenzyme analysis, may be related to ecological variation in the exploration area, located between 1490 and 2720 m, which provides wide environmental variation, generating diversity in both populations. Experimental evidences were obtained about patterns of Fusarium virulence and maize populations responses that seems correspond with geographical origin (ecological conditions) that may suggest the need of research in order to better insight on coevolution processes.Tesis (Doctorado en Ciencias, especialista en Genética).- Colegio de Postgraduados, 2013.Consejo Nacional de Ciencia y Tecnología (CONACYT)..

Mots clés : Diversidad. Patosistema. Fusarium spp.. Maíz nativo. Pudrición de mazorca. Virulencia. Diversity. Pathosystem. Native maize. Ear rot. Virulence. Genética

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