Matching Brassica Root Architecture to Optimize Nitrogen Acquisition in Time and Space

Nitrogen fertilization has been used for decades to increase crop yield but excessive concentrations of nitrate are detrimental to people and the environment (nitrate leaching and greenhouse gas emission). One way to reduce nitrogen fertilizer input is to breed for crops with better Nitrogen Use Efficiency (NUE). Our goal is to increase the degree of lateral root branching for exploring a larger soil volume in search of the mobile nitrogen resource. We study Brassica napus (oilseed rape) because it has relatively poor NUE and its small recovery of applied N involves risks of soil leaching. We screened 57 cultivars from the Belgian Catalogue of Agricultural Plant Varieties upon in vitro culture at low and moderate nitrate supplies. Cultivars with high root length also had high shoot biomass production at two nitrate supplies. This suggests that high root branching can be a positive NUE indicator. In order to identify the genetic determinism of such root traits, we screened a panel of 150 double haploïd lines, which represents the diversity across the crop gene pool. After our initial screen, we pursue (i) root transcriptome sequencing for detecting homologous gene copies differentially expressed between genotypes with contrasting root morphologies. (ii) genome wide-association study with the root traits from all lines. Finally, delineation of genomic regions that control root traits will be helped with the aligning syntenic chromosomic regions of the model species Arabidopsis thaliana, a close parent of Brassica crops.