Endophytic passenger bacteria associated with Genista cinerea nodules growing in North African drylands

Elsevier, Rhizosphere, Volume 14, June 2020, 100205
Ahmed Dekak, Taha Menasria, Yacine Benhizia, Haroun Chenchouni

This study aimed to characterize endophytic bacteria associated with root-nodules of a wild legume (Genista cinerea: Fabaceae) growing in arid soils of Algeria. A total of ten non-symbiotic endophytic bacterial strains were isolated and identified using a combination of conventional and molecular approaches based on 16S rRNA gene sequencing. Moreover, growth variations of the isolates under different environmental conditions were examined using advanced statistical modeling techniques (Markov Chain Monte Carlo sampler for multivariate generalized linear mixed models-MCMCglmm). The results revealed the existence of a large physiological diversity among the endophyte isolates, which formed two distinct groups. Group 1, included fast-growing and salt-tolerant isolates and Group 2 covered acid-sensitive isolates. The bacterial isolates showed capabilities to assimilate different carbonaceous and nitrogenous substances, with consistent and large tolerances to pH [4–10], temperature [4–55 °C], and salinity [NaCl = 2–10%]. In addition, The MCMCglmm indicated that scored growth rate increased with pH and decreases at high level of salinity. The endophytic strains were classified as fast-growing bacteria belonged to the β and γ-Proteobacteria including Achromobacter, Klebsiella, Luteibacter, Pantoea and Pseudomonas. The present findings may support the idea that these isolates are passenger bacteria able to colonize nodules of Genista cinerea. Furthermore, the salt and temperature tolerant patterns found among the isolates reflect the environmental stresses pressure and the importance of using efficient indigenous endophytic strains for successful plant inoculation in arid agriculture.