Chickpea is the most cultivated grain legume in the world and it shares the first rank with faba bean in Tunisia. However, the yield remains low, mainly due to the limited availability of N and P, and to the severe bioclimatic conditions. No inoculation trials had been conducted on chickpea in the Tunisian soils. This paper reports the yield response to inoculation by two different strains of Mesorhizobium ciceri, an exogenous type strain (UPMCa7 T ) and a selected local strain (CMG6). Field experiments were conducted in different sites in the north of Tunisia using three chickpea cultivars (cvs. Amdoun I, Chetoui and Kasseb). Rhizobia occupying field nodules were isolated and identified using 16S rDNA typing for both inoculated and non-inoculated plots. In contrast to the exogenous strain, the local strain gave a significant increase in nodule number and shoot dry yield in all the experimental fields for the three cultivars used. Monitoring of the nodule occupancy showed that the local strain competed well the native populations of rhizobia. The usefulness and the persistence of this strain in the different soils where it was introduced will be assessed further during the next years.

This study compared the response of common bean (Phaseolus vulgaris L.) to arbuscular mycorrhizal fungi (AMF) and rhizobia strain inoculation. Two common bean genotypes i.e. CocoT and Flamingo varying in their effectiveness for nitrogen fixation were inoculated with Glomus intraradices and Rhizobium tropici CIAT899, and grown for 50 days in soil-sand substrate in glasshouse conditions. Inoculation of common bean plants with the AM fungi resulted in a significant increase in nodulation compared to plants without inoculation. The combined inoculation of AM fungi and rhizobia significantly increased various plant growth parameters compared to simple inoculated plants. In addition, the combined inoculation of AM fungi and rhizobia resulted in significantly higher nitrogen and phosphorus accumulation in the shoots of common bean plants and improved phosphorus use efficiency compared with their controls, which were not dually inoculated. It is concluded that inoculation with rhizobia and arbuscular mycorrhizal fungi could improve the efficiency in phosphorus use for symbiotic nitrogen fixation especially under phosphorus deficiency.

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Inoculation of grain legumes with rhizobia may improve biological N2 fixation and crop yield. However, drought, high temperature and soil salinity constrain legume root‐nodule formation and function. Here, two rhizobial strains nodulating Tunisian chickpea, Mesorhizobium ciceri strain CMG 6 and Mesorhizobium mediterraneum strain CTM 226 originating from semi‐arid regions, were selected for their symbiotic performance and their salt stress tolerance (3 % NaCl). Both strains were then examined as inoculants in different soils and field conditions. Field experiments were conducted in four sites using four chickpea cultivars. Rhizobia occupying nodules in non‐inoculated plots were isolated and characterized using 16S rDNA typing; to examine nodule occupancy by the inoculant strains we used polymerase chain reaction (PCR)‐restriction fragment length polymorphism of 16S rDNA gene and repetitive extragenic palindromic PCR. The inoculant strains gave a significant increase in nodule number, shoot dry weight and grain yield in all the experimented fields for the four cultivars used, even in the non‐irrigated soils. The improvement in plant production was equal to or better than nitrogen fertilization. Moreover, the monitoring of the nodule occupancy showed that inoculant strains competed well in the native populations of rhizobia. These results suggest that nodulation and yield of chickpea can be improved by inoculation with competitive and salt‐tolerant rhizobia and is economically promising to increase chickpea production in water‐limited regions.

Common bean (Phaseolus vulgaris L.) genotypes CocoT and Flamingo were inoculated with Rhizobium tropici CIAT899 and Glomus intraradices (Schenck & Smith) and grown under sufficient versus deficient phosphorus supply for comparing the effects of double inoculation on growth, nodulation, mycorrhization of the roots, phosphorus use efficiency and total nitrogen. Although the double inoculation induced a significant increase in all parameters whatever the phosphorus supply in comparison to control, significant differences were found among genotypes and treatments. Nevertheless, the highest phosphorus use efficiency and plant total nitrogen were found under P deficiency in combination with arbuscular mycorrhizal fungi. It is concluded that inoculation with rhizobia and arbuscular mycorrhizal fungi could improve symbiotic nitrogen fixation even under phosphorus deficiency.