Survival and Competitiveness of Bradyrhizobium japonicum Strains 20 Years after Introduction into Field Locations in Poland

Abstract

bIt was previously demonstrated that there are no indigenous strains of Bradyrhizobium japonicum forming nitrogen-fixing root nodule symbioses with soybean plants in arable field soils in Poland. However, bacteria currently classified within this species are present (together with Bradyrhizobium canariense) as indigenous populations of strains specific for nodulation of legumes in the Genisteae tribe. These rhizobia, infecting legumes such as lupins, are well established in Polish soils. The studies described here were based on soybean nodulation field experiments, established at the Poznań University of Life Sciences Experiment Station in Gorzyń , Poland, and initiated in the spring of 1994. Long-term research was then conducted in order to study the relation between B. japonicum USDA 110 and USDA 123, introduced together into the same location, where no soybean rhizobia were earlier detected, and nodulation and competitive success were followed over time. Here we report the extra-long-term saprophytic survival of B. japonicum strains nodulating soybeans that were introduced as inoculants 20 years earlier and where soybeans were not grown for the next 17 years. The strains remained viable and symbiotically competent, and molecular and immunochemical methods showed that the strains were undistinguishable from the original inoculum strains USDA 110 and USDA 123. We also show that the strains had balanced numbers and their mobility in soil was low. To our knowledge, this is the first report showing the extra-long-term persistence of soybean-nodulating strains introduced into Polish soils and the first analyzing the long-term competitive relations of USDA 110 and USDA 123 after the two strains, neither of which was native, were introduced into the environment almost 2 decades ago.

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

“…Even though the concentration of dry bean-rhizobia was significantly affected by crop in the year prior to sampling, many dry bean-rhizobia were obtained from many organic fields (fields D3 in Clay, D12 in Dakota, D8-D9 in Morrison, D23 in Redwood, and D17 in Yellow Medicine county) where soybean were planted prior to sampling and where dry beans were not grown four years prior to our analyses (Table 1). This attests to the extraordinary saprophytic survival of rhizobia when added to soils (Jensen and Sorensen, 1987;Narożna et al, 2015).…”

Influence of Seed Inoculation with Commercial Bacterial Inoculants (Bradyrhizobium Japonicum) on Growth and Yield of Soybean

“…As a result of this treatment, a high seed yield can be obtained with no or limited nitrogen fertilization of soybean plants (Zuffo et al, 2018). The bacteria Bradyrhizobium japonicum are rare in Polish soils (Narożna et al, 2015). The inoculation of seed with preparations containing symbiotic bacteria is therefore justified, especially if no soybean was previously grown in a given field (Tewari et al, 2003).…”

Response of Pulses to Seed or Soil Application of Rhizobial Inoculants

“…Rhizobia are ubiquitous soil microorganisms but the diversity and density of soil populations of these bacteria depend on many different factors such as: soil properties, crop rotation, agricultural practices and also to the great extent on the presence of wild species of leguminous plants in a given area [3,4]. For example in Poland, where soybean is not an indigenous plant and where this crop is not grown frequently soils are usually void or deficient in rhizobia nodulating soybean [5]. On the contrary, Polish soils are colonized with high populations, up to 8.5 .…”

“…Inoculation of legume seeds with commercial inoculants containing preselected strains of root-nodule bacteria is a common agriculture practice, which helps to ensure an effective symbiosis, particularly when natural soil populations of these bacteria are deficient, ineffective or only partially effective [3][4][5][6][7]. Response of legumes to inoculation is determined by a variety of factors such as the presence or absence of indigenous rhizobial populations in soil, soil physicochemical constrains, soil nitrogen availability and climatic conditions [5][6][7][8][9]. In the case of soils in which symbiotic bacteria of particular leguminous plants do not occur pre-sowing seed treatment with inoculants containing these bacteria is highly recommended and this treatment usually results in a significant yield increases [8][9][10][11][12].…”

“…Results of greenhouse and field studies conducted in several countries indicate that as few as 10-20 cells of indigenous rhizobia g -1 of soil can markedly reduce or even eliminate statistically significant responses of various legumes to inoculation [7,8]. Rhizobial inoculants are most often applied onto seeds of legumes shortly before sowing, but in-furrow soil inoculation during sowing is also possible but studies on the effectiveness of this method in comparison to seed inoculation are limited, particularly with respect to soils containing high numbers of indigenous rhizobia [5,9,13].…”