RESUMEN
Diazotrophic nodule isolates are acknowledged promoters of plant growth and rhizospheric community. Consequently, in the lentil agroecosystem, inoculation of atypical rhizobial isolates could be a viable alternative to chemical fertilizers for fallow land usage optimization. The aim of this study is to evaluate and select the rhizobial isolates of lentil nodules with plant-growth-promoting (PGP) attributes and to elucidate their application in rice-fallow soil for determining the growth of lentils and its impact on the rhizospheric bacterial community. Lentil's nodule isolates were identified and screened for their PGP attributes, biofilm, exopolysaccharide (EPS) formation, and early plant growth promotion. The pot experiment with the selected atypical rhizobial isolates Pararhizobium giardinii (P1) and Ochrobactrum sp. (42S) significantly enhanced germination, vigour index, nodule formation (P1 60%, 42S 42% increase), nodule fresh weight, shoot length (65% P1 & 35% 42S), and chlorophyll content as compared to the uninoculated control treatment. The genes for nitrogen fixation nifH and nifK were detected in both isolates. Scanning Electron Microscopy (SEM) revealed successful root and nodule colonization by both isolates, while Transmission Electron Microscopy (TEM) displayed nitrogen-fixing zones within root nodules. Proteobacteria predominated in the lentil rhizosphere of all the treatments. Whereas, application of either P1 or 42S increased Rhizobium, Mesorhizobium, and Bradyrhizobium genra, thus positively modulating rhizospheric community structure. The correlation network analysis revealed an abundance of some interdependent bacterial genera with a possible role in overall plant growth. Functional genes for siderophore biosynthesis and ABC transporter were positively modulated by application of either P1 or 42S. This study showed the significant effect of P. giardinii P1 and Ochrobactrum sp. 42S of L. culinaris on lentil growth, improving fallowsoil health for optimum usage, and modulated rhizospheric community structure which strongly manifest prospects of low-cost, eco-friendly and sustainable biofertilizers.