QTL mapping of seedling root traits associated with nitrogen and water use efficiency in maize

The dramatically increased use of nitrogen fertilizers and global warming raise concerns about environmental pollutions, crop production and future food security. The urgent need for new crops with higher nitrogen and water use efficiency in agricultural practices has been recognized. Root architecture is crucial for acquisition of water and nutrients from the soil; and the selection for specific root traits might be advantageous. In this study seedlings of seven maize inbred lines from a Southern-European breeding genepool were analysed for root morphological characteristics and response to nitrate. As all the lines revealed a similar adaptive reaction to altered nitrate concentrations, we focused our efforts on analysis of two lines, NUEC2 and NUEC4, with the most contrasting differences in constitutive root traits. Investigation of early plant growth under greenhouse conditions revealed inter-genotype differences in NUE and response to drought that might be associated with divergent root architecture of the two lines. We performed a quantitative trait locus mapping of seedling root traits in the populations of 60 double haploid lines derived from the cross NUEC2 × NUEC4. Thirty QTL were detected for seven root traits. Some of the QTL were clustered together, and, in total, 8 loci in the maize genome were found to influence multiple root traits. Interestingly, the positions of QTL for root traits located on chromosomes 3 and 8 overlap with the QTL for grain yield identified in the same population. Further research is needed to validate the QTL and examine their possible causal relationships with corn yield.