Nodulation and Growth Promotion of Chickpea by Mesorhizobium Isolates from Diverse Sources

The cultivation of chickpea (Cicer arietinum L.) in South Africa is dependent on the application of suitable Mesorhizobium inoculants. Therefore, we evaluated the symbiotic effectiveness of several Mesorhizobium strains with different chickpea genotypes under controlled conditions. The tested parameters included shoot dry weight (SDW), nodule fresh weight (NFW), plant height, relative symbiotic effectiveness (RSE) on the plant as well as indole acetic acid (IAA) production and phosphate solubilization on the rhizobia. Twenty-one Mesorhizobium strains and six desi chickpea genotypes were laid out in a completely randomized design (CRD) with three replicates in a glasshouse pot experiment. The factors, chickpea genotype and Mesorhizobium strain, had significant effects on the measured parameters (p < 0.001) but lacked significant interactions based on the analysis of variance (ANOVA). The light variety desi genotype outperformed the other chickpea genotypes on all tested parameters. In general, inoculation with strains LMG15046, CC1192, XAP4, XAP10, and LMG14989 performed best for all the tested parameters. All the strains were able to produce IAA and solubilize phosphate except the South African field isolates, which could not solubilize phosphate. Taken together, inoculation with compatible Mesorhizobium promoted chickpea growth. This is the first study to report on chickpea-compatible Mesorhizobium strains isolated from uninoculated South African soils with no history of chickpea production; although, their plant growth promotion ability was poorer compared to some of the globally sourced strains. Since this study was conducted under controlled conditions, we recommend field studies to assess the performance of the five highlighted strains under environmental conditions in South Africa.