Genetic regions determine tolerance to nitrogen deficiency in European elite bread wheats grown under contrasting nitrogen stress scenarios
Abstract
Increasing the nitrogen use efciency of wheat varieties is an important goal for breeding. However, most genetic studies of wheat grown at diferent nitrogen levels in the feld report signifcant interactions with the genotype. The chromo somal regions possibly involved in these interactions are largely unknown. The objective of this study was to quantify the response of elite bread wheat cultivars to diferent nitrogen feld stress scenarios and identify genomic regions involved in this response. For this purpose, 212 elite bread wheat varieties were grown in a multi-environment trial at diferent nitrogen levels. Genomic regions associated with grain yield, protein concentration and grain protein deviation responses to nitrogen defciency were identifed. Environments were clustered according to adjusted means for grain yield, yield components and grain protein concentration. Four nitrogen availability scenarios were identifed: optimal condition, moderate early defciency, severe late defciency, and severe continuous defciency. A large range of tolerance to nitrogen defciency was observed among varieties, which were ranked diferently in diferent nitrogen defciency scenarios. The well-known nega tive correlation between grain yield and grain protein concentration also existed between their respective tolerance indices. Interestingly, the tolerance indices for grain yield and grain protein deviation were either null or weakly positive meaning that breeding for the two traits should be less difcult than expected. Twenty-two QTL regions were identifed for the tolerance indices. By selecting associated markers, these regions may be selected separately or combined to improve the tolerance to N defciency within a breeding programme.