Quantitative trait loci analysis of growth response to varying nitrogen sources in Arabidopsis thaliana

Nitrogen absorption and assimilation is variable among plants as a result of two factors: the source of nitrogen available and the genetic variation among species within the resulting nitrogen pathways. Several genes involved in nitrogen cycling have been identified, yet little is known about the genes that control quantitative responses to different nitrogen sources. With quantitative trait loci (QTL) mapping in Arabidopsis thaliana recombinant inbred lines (Columbia x Landsberg erecta) we have identified chromosomal regions controlling aerial mass, root mass, and root length when plants are grown in nitrate, ammonium, ammonium nitrate, or low nitrogen treatments. A total of 16 QTL (P < 0.01) were identified among the nitrogen treatments. Most of the QTL were specific to a single treatment. The percentage additive genetic effects of significant QTL were as high as 17%. Five significant QTL corresponded to the locations of candidate genes associated with nitrogen assimilation, while a few QTL corresponded with candidate genes in the developmental pathways. Most QTL were not shared across treatments, suggesting that there is no optimal genotype for all nitrogen sources.