The Legume–Rhizobia Symbiosis
2015
Drevon, Jean-Jacques | Alkama, Nora | Bargaz, Adnane | Rodiño, A. Paula | Sungthongwises, Kiriya | Zaman-Allah, Mainassara | Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro) | Department des Sciences Agronomiques ; Université Mouloud Mammeri [Tizi Ouzou] = Mouloud Mammeri University of Tizi-Ouzou (UMMTO) | Biosystems and Technology ; Swedish University of Agricultural Sciences = Sveriges lantbruksuniversitet (SLU) | Biology of Agrosystems, Misión Biológica de Galicia (MBG) ; Consejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain] (CSIC) | Faculty of Agriculture ; Khon Kaen University [Thailand] (KKU) | Southern Africa Regional Office ; International Maize and Wheat Improvement Center (CIMMYT) ; Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR) | De Ron, Antonio M.
The symbiotic nitrogen fixation (SNF) with legumes is the primary source of biologically fixed nitrogen for agricultural system. It is performed by a group of bacteria commonly called rhizobia. It is characterized by a host preference, and the differences among symbioses between rhizobial strains and legume genotypes are related to infection, nodule development and effectiveness in N2 fixation. The interaction between a rhizobia and the legume is mediated by a lipochitin oligosaccharide secreted by the rhizobia, and called “Nod factor”. It is recognized by transmembrane receptors on the root-hair cells of the legume. It can regulate the nodule organogenesis by inducing changes in the cytokinin balance of the root, during nodule initiation. N2 fixation in legume nodules is catalyzed by the nitrogenase enzyme depending upon the photosynthate supply, the O2 concentration, and the fixed-N export. Among environmental factors that influence the SNF, the temperature is essential for nodule formation; the salinity and drought decrease the nodule permeability to O2 and the photosynthate supply to the nodule, the phosphorus deficiency inhibits the nodule development and the total N2 fixation. Rhizobia strains differ in their efficiency in N2 fixation with host legume. There is evidence of genotypic variability for SNF at different levels of available P which show a possibility of selecting cultivars able to support biological N2 fixation under low P soils.
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