title: Using a physiological framework for improving the detection of quantitative trait loci related to nitrogen nutrition in Medicago truncatula.
abstract: Medicago truncatula is used as a model plant for exploring the genetic and molecular determinants of nitrogen (N) nutrition in legumes. In this study, our aim was to detect quantitative trait loci (QTL) controlling plant N nutrition using a simple framework of carbon/N plant functioning stemming from crop physiology. This framework was based on efficiency variables which delineated the plant's efficiency to take up and process carbon and N resources. A recombinant inbred line population (LR4) was grown in a glasshouse experiment under two contrasting nitrate concentrations. At low nitrate, symbiotic N(2) fixation was the main N source for plant growth and a QTL with a large effect located on linkage group (LG) 8 affected all the traits. Significantly, efficiency variables were necessary both to precisely localize a second QTL on LG5 and to detect a third QTL involved in epistatic interactions on LG2. At high nitrate, nitrate assimilation was the main N source and a larger number of QTL with weaker effects were identified compared to low nitrate. Only two QTL were common to both nitrate treatments: a QTL of belowground biomass located at the bottom of LG3 and another one on LG6 related to three different variables (leaf area, specific N uptake and aboveground:belowground biomass ratio). Possible functions of several candidate genes underlying QTL of efficiency variables could be proposed. Altogether, our results provided new insights into the genetic control of N nutrition in M. truncatula. For instance, a novel result for M. truncatula was identification of two epistatic interactions in controlling plant N(2) fixation. As such this study showed the value of a simple conceptual framework based on efficiency variables for studying genetic determinants of complex traits and particularly epistatic interactions.
authors: INRA, UMR 102 Génétique et Ecophysiologie des Légumineuses, 17 rue Sully, BP 86510, 21065, Dijon cedex, France. delphine.moreau@dijon.inra.fr
authors: Delphine
authors: D
authors: Moreau
authors: Judith
authors: J
authors: Burstin
authors: Grégoire
authors: G
authors: Aubert
authors: Thierry
authors: T
authors: Huguet
authors: Cécile
authors: C
authors: Ben
authors: Jean-Marie
authors: JM
authors: Prosperi
authors: Christophe
authors: C
authors: Salon
authors: Nathalie
authors: N
authors: Munier-Jolain
mesh_terms: D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D017343:Genes, Plant; D008040:Genetic Linkage; D046913:Medicago truncatula / Q000235:genetics* / Q000254:growth & development; D009584:Nitrogen / Q000378:metabolism*; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics*; D040641:Quantitative Trait Loci
chemical_list: D009584:Nitrogen