Identification and distribution of microsymbionts associated with soybean nodulation in Mozambican soils

Abstract

Indigenous soybean rhizobial strains were isolated from root nodules sampled from farmers’ fields in Mozambique to determine their identity, distribution and symbiotic relationships. Plant infection assays revealed variable nodulation and symbiotic effectiveness among the 43 bacterial isolates tested. Strains from Ruace generally promoted greater whole-plant growth than the others. 16S rRNA-RFLP analysis of genomic DNA extracted from the rhizobial isolates produced different banding patterns, a clear indication of high bacterial diversity. However, the multilocus sequence analysis (MLSA) data showed alignment of the isolates with B. elkanii species. The 16S rRNA sequences of representative soybean isolates selected from each 16S rRNA-RFLP cluster showed their relatedness to B. elkanii, as well as to other Bradyrhizobium species. But a concatenated phylogeny of two housekeeping genes (glnII and gyrB) identified the soybean nodulating isolates as Bradyrhizobium, with very close relatedness to B. elkanii. The nifH and nodC sequences also showed that the majority of the test soybean isolates were closely related to B. elkanii, albeit the inconsistency with some isolates. Taken together, these findings suggest that the B. elkanii group are the preferred dominant microsymbiont of soybean grown in Mozambican soils. Furthermore, the distribution of soybean rhizobia in the agricultural soils of Mozambique was found to be markedly influenced by soil pH, followed by the concentrations of plant-available P and Mn. This study suggested that the identified isolates TUTMJM5, TUTMIITA5A and TUTLBC2B can be used as inoculants for increased soybean production in Mozambique.

Symbiotic effectiveness and ecologically adaptive traits of native rhizobial symbionts of Bambara groundnut (Vigna subterranea L. Verdc.) in Africa and their relationship with phylogeny

“…12 Gyogluu et al . 34,35 and Mohammed et al . 36 also found that inoculating different legumes with N 2 -fixing native rhizobia from various African countries led to greater photosynthetic functioning and increased accumulation of biomass in glasshouse experiments.…”

Exploiting Biological Nitrogen Fixation: A Route Towards a Sustainable Agriculture

“…Soybean ( Glycine max ) legume has the highest contribution of BNF; this species fixes annually ~16.4 million tons of N [ 89 ]. The main microsymbionts of soybean belong to Bradyrhizobium species [ 90 ].…”

Rhizobia as a Source of Plant Growth-Promoting Molecules: Potential Applications and Possible Operational Mechanisms

“…In pea plants, deficiencies in gibberellins and brassinosteroids were associated with impaired nodulation, pointing to their significant role in the symbiotic process and subsequent plant growth (Ferguson et al, 2005;Foo et al, 2016). The significant roles of the legume-rhizobia symbiosis in enhancing plant growth and productivity has been demonstrated in several legumes including soybean (Glycine max), mung bean (Vigna radiata), chickpea (Cicer aerietinum), common bean (Phaseolus vulgaris), cowpea (Vigna unguiculata), Bambara groundnut (Vigna subterranea) and Kersting's groundnut (Dashti et al, 1998;Shaharoona et al, 2006;Chihaoui et al, 2015;Gyogluu et al, 2018;Mohammed et al, 2018;Abdiev et al, 2019;Dabo et al, 2019;Ibny et al, 2019). However, a major limitation to tapping the maximum benefit of the symbiosis is related to its susceptibility to diverse environmental stress factors.…”