Predominant populations of indigenous soybean-nodulating Bradyrhizobium japonicum strains obtained from organic farming systems in Minnesota

Abstract

The local community of bradyrhizobia can be affected by applying inoculant bacteria to organic fields. Based on these results, soybean production in organic farms may be improved by displacing strains similar to USDA 4 with those better at nitrogen fixation and competitive ability than indigenous strains.

Nitrogen fixation and productivity of winter annual legume cover crops in Upper Midwest organic cropping systems

“…However, inoculation of legumes with highly effective rhizobia often fails when transferred to the field due to competition with existing endogenous rhizobia (Streeter 1994;Triplett and Sadowsky 1992). The success of the inoculant in the field may depend on genetic specificity (Mothapo et al 2013a;Thies et al 1992), environment (Pandey et al 2017;Parr et al 2011), soil pH (Wongphatcharachai et al 2015), and competition with endogenous strains (Brockwell et al 1995;Kosslak et al 1983;Thies et al 1992). Plant available soil N in the form of nitrate is also wellknown to inhibit nodulation (Streeter 1985).…”

Site-specific distribution and competitive ability of indigenous bean-nodulating rhizobia isolated from organic fields in Minnesota

“…2). This similarity value was shown to represent clonal isolates in previous studies (Johnson et al, 2004;Wongphatcharachai et al, 2015). Genetic diversity (H ) and richness (ACE) of dry bean-rhizobia 35 Several of the unidentified dry bean-rhizobia shared the same genotype, but were represented by fewer than 5 isolates.…”

“…Root nodules were harvested after 4 weeks and the concentration of indigenous dry bean-rhizobia in each soil was calculated based on the most probable number (MPN) of cells g −1 soil. Nodules were surface-sterilized and placed into individual wells of a 96-well plate containing 100 l of 0.85% NaCl (Somasegaran and Hoben, 1994;Wongphatcharachai et al, 2015). Each nodule was crushed with a sterile loop and streaked onto a tryptone-yeast extract (TY) agar plate (Beringer, 1974).…”

“…HFERP DNA fingerprinting and genetic diversity of indigenous dry bean-rhizobia isolated from organic farms Seven reference strains and approximately 30 indigenous Rhizobium isolates obtained from each sample were further characterized via HFERP DNA fingerprinting as described previously (Johnson et al, 2004;Wongphatcharachai et al, 2015). Genetic diversity was evaluated based on HFERP DNA fingerprint profiles.…”

“…Red Hawk, was used as the trap host to isolate indigenous dry beanrhizobia from each soil sample. Seeds were surface sterilized as previously described (Wongphatcharachai et al, 2015) and each soil sample was decimally diluted with sterile-distilled water (10 −1 through 10 −6 ). A 1.0 ml aliquot of each dilution was inoculated to seedlings.…”