What benefits of Bradyrhizobium elkanii have been cited in the scientific literature?
Peer-reviewed research has cited 11 distinct benefits for Bradyrhizobium elkanii, spanning nitrogen fixation, nutrient uptake, and crop yield across multiple host species — none constitute approved label claims; all are reported findings in the scientific literature.
A key mechanism cited for B. elkanii is rhizobitoxine production. Studies report this compound inhibits ACC synthase in the host-root ethylene pathway, reducing ethylene-mediated suppression of nodule primordium formation. On Macroptilium atropurpureum (Siratro), rhizobitoxine-producing strains showed roughly 10-fold greater nodulation competitiveness over non-producing mutants in late-stage nodulation assays.
In rice (Oryza sativa), peer-reviewed field trials associate strain SEMIA 587 with yield increments of approximately 1,000 kg/ha. In Phaseolus lunatus (lima bean), inoculation raised nodule counts from 1–12 to up to 277 nodules per plant, with shoot nitrogen reported up to 91% above controls in variety 'Raio de Sol' and shoot potassium up to 100% higher under co-inoculation.
Co-inoculation studies with Delftia sp. JD2 report improved soybean growth, nodulation rate, and pulse yield. Across cowpea trials, combinations including B. elkanii consistently improved dry weight and pod weight in peer-reviewed research. The species is also cited in the literature as associated with nitrogen fixation and nutrient solubilization in maize-legume intercropping systems.
1AAPFCO-accepted claims
Listing details- Nitrogen fixing.
Accepted wording, shown verbatim · source: AAPFCO Plant Biostimulant list
2Potential claims from the literature
Reported to produce rhizobitoxine, which enhances nodulation competitiveness approximately 10-fold compared to a non-rhizobitoxine-producing mutant strain on Macroptilium atropurpureum (Siratro), with this enhancement occurring at a late stage in the time-course of nodulation
Reported to enhance the nodulation process in host legumes by producing rhizobitoxine, which inhibits ACC synthase in the ethylene biosynthesis pathway of host roots, thereby overcoming ethylene-mediated negative regulation of nodule primordium formation
Reported to promote growth and increase yield of rice (Oryza sativa) in both laboratory and field trials, with inoculation of strain SEMIA 587 associated with yield increments of approximately 1000 kg/ha in field conditions
Reported to form nitrogen-fixing root nodules in compatible soybean genotypes (rj4/rj4), contributing to symbiotic nitrogen fixation
Reported to be enriched in maize-legume intercropping systems and associated with nitrogen fixation, nutrient solubilization, and other belowground ecosystem services
Reported to improve soybean growth, nodulation rate, and pulse yield when co-inoculated with Delftia sp. strain JD2
Reported to significantly increase root nodulation in Phaseolus lunatus, with nodule counts increasing from 1–12 nodules per plant in control treatments to up to 277 nodules per plant under inoculation
Reported to increase shoot nitrogen content in Phaseolus lunatus by up to 91% (in 'Raio de Sol') and 87% (in 'Cearense') compared to control treatments
Reported to increase shoot phosphorus content by up to 48% and shoot potassium content by up to 100%, and root potassium by up to 90% under co-inoculation, in Phaseolus lunatus
Reported to improve plant growth and biomass in Phaseolus lunatus varieties 'Raio de Sol' and 'Manteiga', and to improve post-cultivation soil indicators including pH and available P and K in specific genotype-microbe combinations
Reported to significantly increase cowpea shoot length when co-inoculated with Pseudarthrobacter phenanthrenivorans MKAG7, and nearly all rhizobacteria combinations including B. elkanii significantly improved cowpea dry weight and pod weight
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