ARS | Publication request: QUANTITATIVE TRAIT LOCI ANALYSIS OF GROWTH RESPONSE TO VARYING NITROGEN SOURCES IN ARABIDOPSIS THALIANA.

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 2001
Publication Date: N/A

Interpretive Summary: Nitrogen is generally the limiting nutrient for plant growth. Hence, sixty-five billion kilograms of nitrogen are applied annually to the world's crops, which provides huge agricultural benefits; however, up to 66% of applied nitrogen runs off fields having detrimental consequences for the environment. We examined the response of the model plant Arabidopsis to a range of fertilizers in an attempt to find mechanisms for more efficient use of nitrogen. Genetic background was found to be extremely important in determining how these plants responded to each fertilizer. We then determined some of the important regions of the genome for nitrogen response. This work provides the basis for identifying and manipulating specific genes that will improve the use of nitrogen fertilizer. In addition, these results suggest that crops may need to be bred for specific nitrogen fertilizers in order to create the greatest use efficiency and lowest runoff.

Technical Abstract: The efficiency of nitrogen absorption and assimilation is variable among plants due to two factors: the type of nitrogen available and the genetic variation among species within the resulting nitrogen pathways. Several genes involved in nitrogen uptake and assimilation have been identified, yet little is known about the genes that control quantitative responses to different nitrogen sources. First, we identified significant interaction between the aerial mass of 56 Arabidopsis ecotypes and 99 recombinant inbred genotypes with nitrogen sources. With quantitative trait loci (QTL) mapping in 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 environments. A total of 16 QTL (p < 0.01) were identified among the nitrogen environments. Most of the QTL were specific to a single environment. The percent 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 environments suggesting that there is no optimal genotype for all nitrogen sources; rather plants may need to be designed for the specific nitrogen source provided.