Improving Nitrogen Use Efficiency of Winter Oilseed Rape (Brassica napus L.) by Determining the Genetic Control of Oil Yield Elaboration Under Nitrogen Constraint

Despite its high nitrogen (N) absorption capacity, oilseed rape (OSR) shows low values of N use efficiency (NUE), which makes its production dependent on N fertilization. Improving NUE in OSR is therefore a main target. The objectives of this work were to determine the genomic regions (QTL) associated with oil yield and to assess their stability under contrasted N conditions. Two mapping populations, AM and DK, were tested in two French locations (Md and LR) during three growing seasons (2011, 2012 and 2013), under two N levels (N2 optimal and N1 low). Eight yield-related traits were scored and N-responsive traits were calculated as N1/N2 and DN/N2. 191 QTL were detected: 77 N1-QTL, 96 N2-QTL and 18 N-responsive QTL. In LR station, very few genotype x N interactions were detected and a great stability of the QTL was assessed between the N conditions. Md station, determined as the most stressful environment, presented stronger genotype x N interactions. Most of the QTL found in Md were specific to a N condition and two N-responsive traits QTL zones were detected in the DK population. A particular dense zone of QTL stable across N conditions and crop sites (LR and Md) was found on the A05 linkage group (19 QTL) and could be a good candidate for a Maker Assisted Selection program. To confirm the presence of the QTL detected, precise their position and test a larger set of alleles, a GWAS on a set of 200 genotypes is in progress.