Characterization of Bradyrhizobium spp. Nodulating Lupinus cosentinii and L. luteus Microsymbionts in Morocco

Abstract

In this work, we analyzed the diversity of the nodule-forming bacteria associated with Lupinus luteus and Lupinus cosentinii grown in the Maamora Cork oak forest acidic soils in Morocco. The phenotypic analysis showed the high diversity of the strains nodulating the two lupine's species. The strains were not tolerant to acidity or high alkalinity. They do not tolerate salinity or high temperatures either. The strains isolated from L. luteus were more tolerant to antibiotics and salinity than those isolated from L. cosentinii. The plant growth promoting (PGP) activities of our strains are modest, as among the 28 tested isolates, only six produced auxins, six produced siderophores, whereas three solubilized phosphates. Only two strains possess the three activities. The rrs gene sequences from eight representative strains selected following ARDRA and REP-PCR results revealed that they were members of the genus Bradyrhizobium. Six strains were then retained for further molecular analysis. The glnII, recA, gyrB, dnaK, and rpoB housekeeping gene sequence phylogeny showed that some strains were close to B. lupini LMG28514T whereas others may constitute new genospecies in the genus Bradyrhizobium. The strains were unable to nodulate Glycine max and Phaseolus vulgaris and effectively nodulated L. luteus, L. cosentinii, L. angustifolius, Chamaecytisus albidus, and Retama monosperma. The nodC and nodA symbiotic gene phylogenies showed that the strains are members of the genistearum symbiovar.

Diversity of Plant Growth Promoters (PGP) Isolated from Agricultural Fields of Bangladesh

“…These findings supported earlier studies where rhizobia were isolated from woody legumes in general and Dryland acacia tree species in particular were able to tolerate higher salinity [24][25] . The range of salinity tolerance in rhizobia can vary significantly between species, and even within strains of the same species 26 . While Assefa (1993) 27 discovered that some strains of slow-growing rhizobia from woody legumes were more tolerant to NaCl than fast-growing species, Zerhari et al 28 reported that fast-growing rhizobia isolated from some Acacia species were tolerant to high NaCl concentrations compared to slow-growing strains.…”

Lupin, a Unique Legume That Is Nodulated by Multiple Microsymbionts: The Role of Horizontal Gene Transfer

“…microsymbionts and their closest relatives. Recently, two new putative Bradyrhizobium genospecies within the genistearum symbiovar were identified [ 79 , 80 ]. As could be expected, all lupin-nodulating species in the genus Bradyrhizobium are phylogenetically close, according to a 16S rRNA gene sequence-derived tree ( Figure 1 ).…”