The compatibility between rhizobia and legumes for nitrogen-fixing nodules and the stages of root hair curling, formation of infection thread, and nodulation initiation have been vitally studied, but the factors for the sustainable root surface colonization and efficient symbiosis within chickpea and rhizobia have been poorly investigated. Hence, we aimed to analyze phenotypic properties and phylogenetic relationships of root-nodule bacteria associated with chickpea (Cicer arietinum) in the north-west Indo Gangetic Plains (NW-IGP) region of Uttar Pradesh, India. In this study, 54 isolates were recovered from five agricultural locations. Strains exhibited high exopolysaccharide production and were capable of survival at 15–42 °C. Assays for phosphate solubilization, catalase, oxidase, Indole acetic acid (IAA) production, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity revealed that all the tested isolates possessed plant growth-promoting potential. Metabolic profiling using Biolog plates indicated that patterns of substrate utilization differed considerably among isolates. A biofilm formation assay showed that isolates displayed a nearly four-fold range in their capacity for biofilm development. Inoculation experiments indicated that all isolates formed nodules on chickpea, but they exhibited more than a two-fold range in symbiotic efficiency. No nodules were observed on four other legumes (Phaseolus vulgaris, Pisum sativum, Lens culinaris, and Vigna mungo). Concatenated sequences from six loci (gap, edD, glnD, gnD, rpoB, and nodC) supported the assignment of all isolates to the species Mesorhizobium ciceri, with strain M. ciceri Ca181 as their closest relative.

Salinity is a global challenge to agriculture production. Cicer arientinum L. grows under wide range of climatic conditions and is highly sensitive to salt stress. Salt stress causes osmotic, ionic and secondary stress, impairing various metabolic processes in plants and eventually results in a decline in the plant yield. The aim of the present study was to study the effect of salinity on morphological, anatomical and ionic responses of chickpea seedlings of the genotype PBG-7. Three NaCl concentrations (40 mM, 60 mM and 80 mM) with three replicates were investigated by conducting the experiments in petriplates and growth pouches. For the first 7 days, experiments were carried out in petriplates. Thereafter, the seedlings were transferred to the growth pouches of respective treatment and were maintained subsequently for 21 days. The results collectively suggest that salt stress negatively affected the xylem and phloem width along with the total biomass production. Further, the results indicated that salinity leads to an increase in the sodium ion content in the plants and was accompanied by a decline in K⁺/Na⁺ as well as Ca²⁺/Na⁺ ratio. Sodium ion content was found to be negatively correlated with all the measured parameters.

Rhizobia and plant legumes have been potentially associated by an essential process symbiosis for biological nitrogen fixation (BNF). However, compatibility and responsible factors for symbiosis are poorly understood. The present study revealed the 55 indigenous rhizobacterial isolates from root nodules of Crotalaria juncea from three different agricultural regions/locations in North-east Indo Gangetic Plains (NE-IGP) Uttar Pradesh and Uttarakhand. Amongst them, strain NCR5, was screened as a resilient antagonistic isolate against Macrophomina phaseolina. Based on 16S rRNA gene sequencing, it was identified as Rhizobium leguminosarum. Amplification of Nod gene proved it to be a nodulating strain. Phenotypically, NCR5 grew well within the temperature range 10-40 ºC and pH 5.5-9.0 as well as survived with 3.0% salt stress. Plant growth promotion characteristics were confirmed it as the best-performing PGP strain. The characteristics included phosphate solubilization, IAA production, siderophore production, HCN productions. This study underwrote the Rhizobium leguminosarum NCR5 as a potential applicant for bioformulation to apply in the soil for promoting the PGP traits and. It can also be employed as fungicides against Macrophomina phaseolina in adverse soil types and environments.