Résumé
Key message: QTL mapping and GWAS detected resistance QTL to Aphanomyces euteiches in faba bean, lentil, and Medicago truncatula. Weak genomic conservation between resistance QTL was identified between these legumes and pea.Abstract: QTL mapping and GWAS detected resistance QTL to Aphanomyces euteiches in faba bean, lentil, and Medicago truncatula. Weak genomic conservation between resistance QTL was identified between these legumes and pea. Aphanomyces root rot, caused by Aphanomyces euteiches, is a damaging disease affecting various legume species. Quantitative trait loci (QTL) for partial resistance have been mainly identified in pea, and to a lesser extent in lentil and Medicago truncatula. This study aimed to identify novel resistance loci from available lentil and faba bean populations, and examine genomic conservation of resistance QTL across legume host species. QTL mapping in the Pop2 faba bean recombinant inbred line (RIL) population and genome-wide association study (GWAS) in the AGILE lentil diversity panel were performed for resistance to A. euteiches under controlled conditions, using genotyping data previously reported. A previous QTL mapping in the LR3 M. truncatula RIL population was updated using 1,536 new SNPs (single-nucleotide polymorphisms). Synteny between resistance QTL to A. euteiches was analyzed based on gene orthology in QTL regions projected onto genomes, using the OrthoLegKB graph database. Four loci, including a major-effect QTL on chromosome 3, Ae-Vf3.1, were associated with resistance in faba bean. In lentil, six minor-effect GWAS-SNPs and two favorable haplotypes at Ae-Lc1.1 and Ae-Lc2.1 loci were identified. Updated analyses in M. truncatula narrowed to 8 Kb the interval of the major-effect locus AER1 and revealed three candidate genes. No synteny between major-effect QTL, detected in this study or previously reported in the literature, was identified across grain legume genomes. These results pave the way for translational genomics approaches facilitating resistance gene discovery and for resistance QTL deployment strategies in legume rotations to preserve their durability.