Phylogeny and nitrogen fixation potential ofBradyrhizobiumspecies isolated from the legume cover cropPueraria phaseoloides(Roxb.) Benth. in Eastern Cameroon

Abstract

Pueraria is an herbaceous, perennial legume crop originating in Asia. Pueraria phaseoloides (Roxb.) Benth. (tropical kudzu) is frequently introduced into production systems and is used as green manure, a cover crop and a forage plant, making it important economically. We used P. phaseoloides as a trap crop to study and characterize soil rhizobia in Eastern Cameroon. Bacteria were isolated from fresh nodules collected from field-grown P. phaseoloides roots. The 16S-23S rRNA internal transcribed spacer (ITS) sequences from 30 bacterial isolates were amplified by polymerase chain reaction (PCR) and the reaction products were sequenced. Phylogenetic analysis revealed that all isolates were ascribed to the genus Bradyrhizobium and were grouped into three clusters of Bradyrhizobium sp. strains, one cluster of B. yuanmingense strains, and one cluster of B. elkanii strains. Acetylene reduction assay (ARA) results indicated that the B. yuanmingense strains had significantly higher nitrogen fixation potential and that they could be used as inoculants to enhance nitrogen fixation in Pueraria grown in Eastern Cameroon. ARTICLE HISTORY

The Nodule Microbiome: N2-Fixing Rhizobia Do Not Live Alone

“…Thus, core microbiomes need to be elucidated for major crops from diverse agricultural regions of the world because abiotic factors, soil geochemistry, and water availability all have a powerful influence on plant diversity and microbial populations. Efforts to learn more about indigenous rhizosphere microbiomes are being pursued in several countries, including Pakistan (Mukhtar et al 2016), Cameroon (Sarr et al 2016), and Sudan (Idris et al 2015). It will also be interesting to determine whether various microbes are conserved in similar environments.…”

Symbiotic N2-Fixation Estimated by the15N Tracer Technique and Growth ofPueraria phaseoloides(Roxb.) Benth. Inoculated withBradyrhizobiumStrain in Field Conditions

“…Prior to this field experiment, rhizobial strains were isolated from Pueraria nodules collected from the experimental site and other neighboring fields and subjected to DNA-based molecular analysis [ 9 ]. The results showed that the native strains for Pueraria in the experimental field clustered into 3 groups corresponding to Bradyrhizobium yuanmingense , B. elkanii , and B. sp.…”

“…By assessing their nitrogen fixation potential using the Acetylene Reduction Assay (ARA), it appeared the B. yuanmingense strains, and S3-4 in particular, showed a significant highest potential. Therefore, Bradyrhizobium yuanmingense S3-4 identified as an efficient Pueraria symbiont [ 9 ] was used in this field experiment. From glycerol stock, it was streaked on YMA agar plates [ 24 ] for one week.…”

“…Yield increments of cassava are related to soil quality improvement which includes soil erosion limitation, increase of soil organic carbon and nitrogen following a good decomposition of Pueraria litters. The phylogenetic diversity of nitrogen-fixing bacteria in the root nodules of Pueraria in Eastern Cameroon was previously investigated [ 9 ]. Using molecular biology techniques, these authors identified three groups of Bradyrhizobium species corresponding to B.…”

“…The importance of this work is to improve the nitrogen fixation potential and growth of Pueraria through field inoculations with effective strains of Bradyrhizobium , enabling enhancement of the input of nitrogen in the soil via biological process, to shorten the fallow period of Pueraria and put the land in faster use, as well as reduce environmental hazards that the use of chemical fertilizers to increase yields often poses. In this paper, we report on the effects of inoculating Pueraria with the selected efficient B. yuanmingense S3-4 strain [ 9 ] on its N 2 -fixation, dry biomass production, total N uptake, nitrogen fertilizer use efficiency, and soil fertility through a field experiment. Symbiotic nitrogen fixation was estimated using the 15 N tracer technique and Ipomoea batatas (L.) Lam.…”