title: Discrimination against 15N among recombinant inbred lines of Phaseolus vulgaris L. contrasting in phosphorus use efficiency for nitrogen fixation.
abstract: Although isotopic discrimination processes during nitrogen (N) transformations influence the outcome of (15)N based quantification of N2 fixation in legumes, little attention has been given to the effects of genotypic variability and environmental constraints such as phosphorus (P) deficiency, on discrimination against (15)N during N2 fixation. In this study, six Phaseolus vulgaris recombinant inbred lines (RILs), i.e. RILs 115, 104, 34 (P deficiency tolerant) and 147, 83, 70 (P deficiency sensitive), were inoculated with Rhizobium tropici CIAT899, and hydroaeroponically grown with P-sufficient (250 μmol P plant(-1) week(-1)) versus P-deficient (75 μmol P plant(-1) week(-1)) supply. Two harvests were done at 15 (before nodule functioning) and 42 (flowering stage) days after transplanting. Nodulation, plant biomass, P and N contents, and the ratios of (15)N over total N content ((15)N/Nt) for shoots, roots and nodules were determined. The results showed lower (15)N/Nt in shoots than in roots, both being much lower than in nodules. P deficiency caused a larger decrease in (15)N/Nt in shoots (-0.18%) than in nodules (-0.11%) for all of the genotypes, and the decrease in shoots was greatest for RILs 34 (-0.33%) and 104 (-0.25%). Nodule (15)N/Nt was significantly related to both the quantity of N2 fixed (R(2)=0.96***) and the P content of nodules (R(2)=0.66*). We conclude that the discrimination against (15)N in the legume N2-fixing symbiosis of common bean with R. tropici CIAT899 is affected by P nutrition and plant genotype, and that the (15)N/Nt in nodules may be used to screen for genotypic variation in P use efficiency for N2 fixation.
authors.affiliation: Institut National de la Recherche Agronomique, UMR Ecologie Fonctionnelle & Biogéochimie des Sols et Agroécosystèmes, INRA-IRD-CIRAD-SupAgro, Place Pierre Viala 34060 Montpellier, France; Ecole Nationale Supérieure Agronomique (ENSA), Département de phytotechnie, Avenue Hassan Badi, El Harrach 16200 Alger, Algeria; Université de Khemis Miliana, Faculté des Sciences de la Nature et de la Vie & des Sciences de la Terre, Route Theniet El Had, Soufay 44225 Ain Defla, Algeria. Electronic address: m.lazali@yahoo.fr.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Lazali
authors.affiliation: Swedish University of Agricultural Sciences (SLU), Department of Biosystems and Technology, Box 103, SE-23053 Alnarp, Sweden.
authors.forename: Adnane
authors.initials: A
authors.lastname: Bargaz
authors.affiliation: Swedish University of Agricultural Sciences (SLU), Department of Biosystems and Technology, Box 103, SE-23053 Alnarp, Sweden.
authors.forename: Georg
authors.initials: G
authors.lastname: Carlsson
authors.affiliation: Ecole Nationale Supérieure Agronomique (ENSA), Département de phytotechnie, Avenue Hassan Badi, El Harrach 16200 Alger, Algeria.
authors.forename: Sidi Mohamed
authors.initials: SM
authors.lastname: Ounane
authors.affiliation: Institut National de la Recherche Agronomique, UMR Ecologie Fonctionnelle & Biogéochimie des Sols et Agroécosystèmes, INRA-IRD-CIRAD-SupAgro, Place Pierre Viala 34060 Montpellier, France. Electronic address: drevonjj@supagro.inra.fr.
authors.forename: Jean Jacques
authors.initials: JJ
authors.lastname: Drevon
mesh_terms: D009586:Nitrogen Fixation / Q000502:physiology*; D009587:Nitrogen Isotopes / Q000378:metabolism*; D027805:Phaseolus / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*
chemical_list: D009587:Nitrogen Isotopes; D010758:Phosphorus
keywords: (15)N; N(2) fixation; Phaseolus vulgaris; Phosphorus deficiency; Symbiosis