Multi-year linkage and association mapping confirm the high number of genomic regions involved in oilseed rape quantitative resistance to blackleg
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A repertoire of the genomic regions involved in quantitative resistance to Leptosphaeria maculans in winter oilseed rape was established from combined linkage-based QTL and genome-wide association (GWA) mapping.
Linkage-based mapping of quantitative trait loci (QTL) and genome-wide association studies are complementary approaches for deciphering the genomic architecture of complex agronomical traits. In oilseed rape, quantitative resistance to blackleg disease, caused by L. maculans, is highly polygenic and is greatly influenced by the environment. In this study, we took advantage of multi-year data available on three segregating populations derived from the resistant cv Darmor and multi-year data available on oilseed rape panels to obtain a wide overview of the genomic regions involved in quantitative resistance to this pathogen in oilseed rape. Sixteen QTL regions were common to at least two biparental populations, of which nine were the same as previously detected regions in a multi-parental design derived from different resistant parents. Eight regions were significantly associated with quantitative resistance, of which five on A06, A08, A09, C01 and C04 were located within QTL support intervals. Homoeologous Brassica napus genes were found in eight homoeologous QTL regions, which corresponded to 657 pairs of homoeologous genes. Potential candidate genes underlying this quantitative resistance were identified. Genomic predictions and breeding are also discussed, taking into account the highly polygenic nature of this resistance.
We would like to acknowledge Gilles Lassalle and Anne Laperche for the script that was used to choose the markers for QTL analysis and Mathieu Rousseau-Gueutin, Jérôme Morice for Circos representation of homoeologous relationships between the QTL regions. The authors are grateful to Claude Domin and the INRA Experimental Unit (UE La Motte, Le Rheu) for field experimentations. The authors would like to thank the BrACySol biological resource center (INRA Ploudaniel, France) for providing the seeds used in this study. This work was supported by the French ‘Institut National de la Recherche Agronomique’—Department of ‘Biologie et Amélioration des Plantes’, Terres Inovia and PROMOSOL. VK was funded through the European PLANT-KBBE-IV research program in the French-German Project GEWIDIS (Exploiting genome-wide diversity for disease resistance improvement in oilseed rape; ANR13-KBBE-0004-01).
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Conflict of interest
The authors declare that they have no conflict of interest.
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