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Titre : Search for new QTL of resistance to powdery mildew (Blumeria graminis f.sp. hordei) in a Spanish barley landrace

Auteur : Dhif Hichem

Etablissement de soutenance : Instituto Agronómico Mediterráneo de Zaragoza (IAMZ) - Centre international de hautes études agronomiques méditerranéennes (CIHEAM)

Diplôme : Master of Plant Breeding / Amélioration Génétique Végétale / Mejora Genetica Vegetal (2008)

Résumé
The aim of this study was to investigate the location and effect of quantitative trait loci for resistance against powdery mildew (caused by Blumeria graminis f.sp. hordei) in a Spanish barley line derived from a landrace, CNE97. For this purpose, a RIL population of 262 lines was constructed (CNE97 x French cultivar Plaisant), susceptible to most races of powdery mildew. Phenotyping was carried out at a collaborating laboratory (IRRST-JKI), with artificial inoculations at seedling stage. Genotyping was carried out with a total of 111 markers, comprising mostly microsatellites and some resistance gene analogs (RGA), in a sequential manner : First, 75 lines at the F6 stage were assayed with all the markers. Then, only 20 markers were assayed in the rest of the population, focusing on regions most likely to carry QTL, according to the analysis of the F6. Two QTL of large effect were both localized on chromosome 7H at both steps of the process. Between both, they explain 34 to 45 per cent of the phenotypic variance for resistance. One locus was localized on chromosome arm 7HS, in the region flanked by the RGA S9020 and the microsatellite GBM1060, which is consistent with the mapped mlt gene, which confers resistance to powdery mildew. The second QTL was in tight linkage with the microsatellite EBmac0755, on chromosome arm 7HL. Due to this location, it is possible that it co-locates with another powdery mildew resistance gene, Mlf.

Mots Clés : Erysiphe graminis microsatellites genetic maps Disease resistance Fungal diseases Mildews Blumeria plant genetics Plant breeding Barley

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