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Nitrogen fixation resulting from mutual symbiosis of rhizobia and cultivated legume plants is therefore critical to food security as it directly affects agricultural production. Biological Nitrogen Fixation (BNF) can be an important factor in sustainable agriculture. A collection of 20 isolates from fresh Nodules of the legume plant Vicia faba was isolated from five soil of Algeria. The soil from each region has undergone physical-chemical analysis : (granulometry, total carbon, organic matter, pH, and electrical conductivity, determination of available phosphorus and determination of total nitrogen). A media viz., Glucose-Peptone Agar (GPA), Congo red, Yeast Mannitol Agar (YMA) containing 2% NaCl were employed to make presumptive decisions on the recognition and classification of the isolated bacterial strains. All the isolates were found with poor absorption of dye Congo red and little or no growth on the media of GPA and without altering the pH. Almost all of the isolates exhibit good growth on 2% NaCl, poor growth on GPA, thus confirming the rhizobia. After biochemical tests like catalase test and citrate utilization test isolates were confirmed. The presence of rhizobia on root nodules of leguminous plant.

Low availability of phosphorus (P) is a major constraint to legume production, and efforts are being made to identify legume genotypes with tolerance to low P and greater P use efficiency (PUE). Cowpea (Vigna unguiculata L.) genotypes vary in their adaptation to low-P soils. In order to investigate to what extent this variation may be related to PUE for symbiotic nitrogen fixation (SNF), five genotypes, Adrar, El Kala, Djenet, Tizi Ouzou and Bejaia, were grown in semihydroponic culture with sufficient versus deficient P supply. At the flowering stage, the biomass of plants and nodules and their P contents was determined after measuring the quantity of N2 fixed. The results showed that nodule and shoot biomass were less when P was deficient. The genotypes that presented the maximum growth during the experiment presented a high efficiency in use of the rhizobial symbiosis calculated as the slope of plant biomass regression as a function of nodulation. Under P-deficiency, efficiency in use of P for SNF was significantly increased in the genotypes El Kala, Djenet and Adrar and accompanied with an increase of the efficiency in use of the rhizobial symbiosis. Hence the large differences show that traits for more P uptake-efficient plants exist in the tested cowpea genotypes. This opens the possibility to breed for more P uptakeefficient varieties as a way to bring more sparingly soluble soil P into cycling in crop production and obtain capitalisation of soil P reserves.

Symbiotic nitrogen fixation (SNF) by legumes may provide an ecologically acceptable complement or substitute for mineral nitrogen fertilizers that farmers try to minimize for economic limitation and environment sake. However, phosphorus (P) deficiency is a major limiting factor for legume–rhizobia symbioses, particularly in acidic and calcareous soils. Nevertheless, the expression of legume SNF potential under P deficiency may be improved. Indeed genotypes contrasting in P use efficiency (PUE) for SNF could be found for such legumes spp. as Phaseolus vulgaris, Vigna unguiculata, or Medicago truncatula in hydroaeroponic culture under glasshouse conditions after inoculation with specific reference rhizobia. In order to assess the contribution of phosphatase activity to PUE for SNF, an in situ RT-PCR methodology was used to localize and quantify the mRNA of candidate genes in nodules of common bean grown under deficient versus sufficient P supply. The transcript localization of phytase, phosphoenolpyruvate phosphatase, and trehalose 6 phosphate phosphatase was found to be tissue specific and differ among any phosphatase APase genes, P treatments, and legume genotypes. In order to assess whether the genotypic difference in PUE for SNF may contribute to adaptation of the rhizobial symbiosis to low-P soils, the nodulation and growth of contrasting common-bean recombinant lines from the cross of BAT477 and DOR364 were assessed in fields of farmers in reference agroecosystems of the Mediterranean basin following a participatory approach. The most efficient genotype, namely RIL115, was superior in most fields where nodulation was above the threshold for significant contribution to legume nutrition. From those fields with low-P soils where adaptation was observed for low-efficiency genotypes, bacteria were isolated from nodules and rhizosphere in order to search for rhizobia or rhizobacteria that could increase the P efficiency for the legume symbiosis. Since mycorrhizae may contribute to the PUE, the tripartite symbiosis was tested in hydroaeroponic culture, showing that some species may limit nodulation by contrast with Glomus intradices that increased it under P deficiency. It is concluded that (i) phosphatases contribute to the use of organic P for N2 fixation and to the increase in nodule permeability to O2 under P deficiency; (ii) nodulation in agroecosystems varies considerably in space and time; (iii) high PUE for SNF may increase the N2-dependent growth of common bean in low-P soils and the overall P bioavailability; and (iv) some local rhizobia may contribute to the PUE for SNF.

Legume-cereal intercropping, is a productive and sustainable system by its nutrients facilitation, and its effect to increase N uptake for intercropped cereal; via symbiotic nitrogen (N2) fixation. The aim of this work was to test effect of maize-common bean intercropping system on the growth, nodulation, yield and N uptake. This field study was conducted in Setif region, North of Algeria. The study was carried out using intercropping system with one Cvs of common bean and one maize CV which were cultivated locally by the farmers of the region. The results showed a positive correlation between the nodule and shoot dry weight, this correlation is more significant in the intercropping than sole crop. However intercropping increase maize yield by more than 12.5%, the N concentration in shoot (20.8%) and seed (33.5%); as consequence N concentration in rhizosphere soil was significantly enhanced for intercropped common bean. Intercropping advantage was observed especially; at low concentration of nitrogen in indigenous soil. We conclude that nitrogen symbiotic fixation was contributes to facilitate N uptake for intercropped maize.

In order to assess the relation between symbiotic nitrogen fixation and soil phosphorus, a multi-local test was proposed to producers of Tizi Ouzou area in Algeria, without modification of their cultivation practises. The nodulation and growth of the cultivar traditionally used by farmers, was studied with seven potentially interesting recombinant inbred lines selected among the crossing of BAT 477 and DOR 364 in addition. The sampling was performed at the flowering stage. The major finding in this work is that nodule biomasss were positively correlated with Olsen-P. Although, the curvilinear regressions of nodule biomass and shoot biomass as a function of Olsen-P suggest the existence of 2 ranges of Olsen-P among studied sites that are separated by critical P values. It is concluded that the low nodulation of the RILs was partly compensated by increasing the efficiency in use of the rhizobial symbiosis.

Background: In order to investigate environmental and genotypic variability of common bean effects on discrimination against natural atmospheric 15N, six Recombinant Inbred Lines, namely RILs 147, 115, 104, 83, 70 and 34 of common bean (Phaseolus vulgaris L.) were inoculated with Rhizobium tropici CIAT 899,and grown in hydroaeroponic culture under P sufficiency (250 μmol P plant−1 week−1) versus P deficiency (75 μmol P plant−1 week−1) conditions.[br/]Methods: At the 15 and 42 days after transplanting, plants and nodules biomasses, P and 15N contents were determined after measuring O2 uptake by nodulated roots and nodule conductance to O2 diffusion.[br/] Results: The analysis of natural abundance in 15N determined from different plant parts showed a depletion of the 15N/Nt ratio in the following order: shoots > roots > nodules. Additionally, 15N/Nt ratio was less when P wasdeficient, with differences between bean genotypes. Under P deficiency, 15N/Nt ratio decreased more in shoots (31%) than in nodules (8%). Furthermore, a significant decrease of 15N/Nt ratio was observed under P deficiency in nodules of the RILs 104 (26%) and 34 (18%) and in shoots of the RILs 147 (64%) and 104 (63%). These decreases were associated with significant variation in nodule O2 conductance among bean genotypes and P level. Moreover, positive correlations were found between nodule 15N/Nt ratio and both N2 fixed and P content innodules (r = 0.98** and r = 0.53* respectively). [br/]Conclusion: We concluded that the discrimination against 15N during N2 fixation is affected under environmental constraint such as P deficiency and varied according genotypic variability.