title: Inoculation with an enhanced N2 -fixing Bradyrhizobium japonicum strain (USDA110) does not alter soybean (Glycine max Merr.) response to elevated [CO2 ].
abstract: This study tested the hypothesis that inoculation of soybean (Glycine max Merr.) with a Bradyrhizobium japonicum strain (USDA110) with greater N2 fixation rates would enhance soybean response to elevated [CO2 ]. In field experiments at the Soybean Free Air CO2 Enrichment facility, inoculation of soybean with USDA110 increased nodule occupancy from 5% in native soil to 54% in elevated [CO2 ] and 34% at ambient [CO2 ]. Despite this success, inoculation with USDA110 did not result in greater photosynthesis, growth or seed yield at ambient or elevated [CO2 ] in the field, presumably due to competition from native rhizobia. In a growth chamber experiment designed to study the effects of inoculation in the absence of competition, inoculation with USDA110 in sterilized soil resulted in nodule occupation of >90%, significantly greater (15) N2 fixation, photosynthetic capacity, leaf N and total plant biomass compared with plants grown with native soil bacteria. However, there was no interaction of rhizobium fertilization with elevated [CO2 ]; inoculation with USDA110 was equally beneficial at ambient and elevated [CO2 ]. These results suggest that selected rhizobia could potentially stimulate soybean yield in soils with little or no history of prior soybean production, but that better quality rhizobia do not enhance soybean responses to elevated [CO2 ].
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.|Department of Plant Biology and Ecology, Pharmacy Faculty, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Alava, 01007, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Sanz-Sáez
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
authors.forename: Katy D
authors.initials: KD
authors.lastname: Heath
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Burke
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.|Global Change and Photosynthesis Research Unit, USDA ARS, Urbana, IL, 61801, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Ainsworth
mesh_terms: D018533:Biomass; D020369:Bradyrhizobium / Q000502:physiology*; D002245:Carbon Dioxide / Q000494:pharmacology*; D009586:Nitrogen Fixation; D010788:Photosynthesis / Q000502:physiology; D012988:Soil Microbiology; D013025:Glycine max / Q000187:drug effects / Q000382:microbiology* / Q000502:physiology; D013559:Symbiosis
chemical_list: D002245:Carbon Dioxide
keywords: N2 fixation; elevated carbon dioxide; free air CO2 enrichment; nodulation; rhizobia