Short communication. Inoculum density-dependent restriction of nodulation in the soybean-Bradyrhizobium japonicum symbiosis

S. M. Lohrke, C. J. Madrzak, H. G. Hur, A. K. Judd, James H Orf, Michael J Sadowsky

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Bradyrhizobium japonicum USDA 110 is restricted for nodulation by Glycine max PI 417566 at relatively high inoculum levels (108-109 cells). Nodulation restriction conditioned by PI 417566 was suppressed at inoculation levels of 104-106 cells, although nodulation was delayed relative to that seen on a permissive soybean genotype. Over the range of concentrations tested (104-109 cells) on soybean cv. Kasota, there was no influence of inoculum concentration on nodulation by USDA 110 or by D4.2-5, a Tn5-induced, nodulation-competent mutant of USDA 110. The few nodules produced by USDA 110 on PI 417566 contained normal levels of nodulin-23, nodulin-26, cdc-2 gene, and LB23. Phenylalanine ammonia lyase mRNA levels were about 15% greater, 2 days post inoculation, when PI 417566 was inoculated with USDA 110 than was seen when strain D4.2-5 was the inoculum. There were no differences seen in the expression of chalcone synthase in nodulation-permissive or -restrictive plant genotypes inoculated with USDA 110 or D4.2-5. These results suggest that inoculum size and host defense-related responses may influence host-controlled restriction of nodulation in the B. japonicum soybean symbiosis.

Original languageEnglish (US)
Pages (from-to)59-70
Number of pages12
JournalSymbiosis
Volume29
Issue number1
StatePublished - Jan 1 2000

Keywords

  • Bradyrhizobium japonicum
  • Chalcone synthase (CHS)
  • Inoculum density
  • Nodulation-restriction
  • Phenylalanine ammonia lyase (PAL)

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