Plant and Soil

, Volume 382, Issue 1–2, pp 165–173

Effect of drought on Bradyrhizobium japonicum populations in Midwest soils

  • Coralie Barthelemy-Delaux
  • David Marburger
  • Pierre-Marc Delaux
  • Shawn Conley
  • Jean-Michel Ané
Regular Article

DOI: 10.1007/s11104-014-2155-0

Cite this article as:
Barthelemy-Delaux, C., Marburger, D., Delaux, PM. et al. Plant Soil (2014) 382: 165. doi:10.1007/s11104-014-2155-0

Abstract

Background and aims

Bradyrhizobium japonicum and soybean (Glycine max (L.) Merr.) form a symbiotic association which allows for biological nitrogen fixation (BNF) to help meet the nitrogen (N) requirement of soybean plants. Rhizobial inoculants are not always used in soybean production in the Midwestern USA because of high naturalized soil populations, but drought conditions experienced in the region during the 2012 growing season may have led to a decline in numbers resulting in the need for inoculation the following growing season. Therefore, the effect of drought on B. japonicum population size was investigated in this study.

Methods

Drought conditions, 8 weeks long or 4 weeks long preceded (STOP) or followed (START) by 4 weeks of normal watering, were simulated in two contrasting soil types in a greenhouse setting with soybeans as host plants. Drought conditions were monitored by measuring water content. Population size of B. japonicum was quantified using quantitative real-time polymerase chain reaction (qPCR) and most probable number (MPN) methods and compared to population from non-drought treatment.

Results

Using both quantification methods, the response of B. japonicum to drought treatments was minimal.

Conclusions

Drought conditions 4 to 8 weeks long did not reduce B. japonicum population size to levels which would affect soybean growth and development.

Keywords

Drought Rhizobia Quantitative PCR MPN Inoculants Nitrogen fixation 

Supplementary material

11104_2014_2155_MOESM1_ESM.jpg (98 kb)
Fig. S1Bradyrhizobium japonicum population response to the FC (upper) and NO (lower) water regimes for the silt loam soil from the second experiment (circles). Population size was calculated from the qPCR cycler-calculated linear regression coefficients derived from the standards (i.e. known amounts of B. japonicum) within each run. Population size was adjusted to CFU g-1 dry soil, and population data are expressed as log10 CFU g-1 dry soil. Corresponding soil water content (%) for each water regime is also displayed (triangles). Shown are means ± SE. Means for population include nine observations (3 reps x 3 tech reps) and three observations (3 reps) for soil water content estimates (JPEG 97 kb)
11104_2014_2155_MOESM2_ESM.jpg (101 kb)
Fig. S2Bradyrhizobium japonicum population response to the FC (upper) and NO (lower) water regimes for the sandy soil from the second experiment (circles). Population size was calculated from the qPCR cycler-calculated linear regression coefficients derived from the standards (i.e. known amounts of B. japonicum) within each run. Population size was adjusted to CFU g-1 dry soil, and population data are expressed as log10 CFU g-1 dry soil. Corresponding soil water content (%) for each water regime is also displayed (triangles). Shown are means ± SE. Means for population include nine observations (3 reps x 3 tech reps) and three observations (3 reps) for soil water content estimates (JPEG 100 kb)
11104_2014_2155_MOESM3_ESM.jpg (156 kb)
Fig. S3Effect of watering treatments on plant growth. A) Plants after one month of NO and START treatment are dead whereas B) plants undergoing STOP and FC treatments are healthy. Pictures were taken one month after the beginning of the first experiment. (JPEG 155 kb)

Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Coralie Barthelemy-Delaux
    • 1
  • David Marburger
    • 1
  • Pierre-Marc Delaux
    • 1
  • Shawn Conley
    • 1
  • Jean-Michel Ané
    • 1
  1. 1.Department of AgronomyUniversity of Wisconsin—MadisonMadisonUSA

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