Diversité des populations françaises d' Aphanomyces euteiches Drechs., agent de la pourriture racinaire du pois: variabilité pathogène et moléculaire

Abstract : The common root rot of pea recently appeared in France, causing big damages in the major pea-producing areas. For a better understanding of the origin of this epidemic, and to search for breeding and cultural solutions, the pathogenic and molecular variability of the french populations of A.euteiches had to be investigated. The host specificity of a french collection of isolates, as well as some reference isolates from foreign countries, was estimated by their pathogenicity on pea, common vetch, alfalfa, faba bean and snap bean. It appeared that the french isolates were preferentially pathogenic on pea, but not specialised on this species, most of them attacking also vetch, alfalfa and faba bean. 10% of the isolates exhibited a broad-host range. The foreign isolates from other legume species were much more specialized to their host. To investigate the variability in virulence on pea of the A.euteiches french populations, a new set of differential genotypes was set up. Eleven virulence types were characterised, but a type highly predominated, virulent on the whole set and aggressive. The french isolates appeared to be more aggressive than the foreign isolates, and were virulent on some lines found resistant to foreign isolates. AFLP markers revealed a very high genotypical diversity within the french isolates, suggesting the endemic origin of the A.euteiches inoculum and a great amount of outcrossing. The French populations were found to be structured neither by their host specificity, nor by geography. However, the population structure of this soilborne fungus was found to be strongly homothallic. Hypotheses to explain this paradox are proposed. This study was the first one to investigate the population diversity of this fungus at this scale of study. It has many agronomical repercussions, regarding cultural control methods, and breeding strategies for A.euteiches resistance in pea.
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Submitted on : Friday, February 5, 2016 - 5:12:02 PM
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Emmanuel Wicker. Diversité des populations françaises d' Aphanomyces euteiches Drechs., agent de la pourriture racinaire du pois: variabilité pathogène et moléculaire. Génétique des populations [q-bio.PE]. Ecole Nationale Superieure Agronomique de Rennes, 2001. Français. ⟨tel-01269995⟩

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