African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6191

Full Length Research Paper

The functional characterisation of soybean (Glycine max L.) rhizospheric bacteria indigenous to Ethiopian soils

Diriba Temesgen
  • Diriba Temesgen
  • Department of Microbial, Cellular and Molecular Biology, College of Natural Sciences, Addis Ababa University, Cellular and Molecular Biology, P. O. Box 1176, Ethiopia.
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Marta Maluk
  • Marta Maluk
  • James Hutton Institute, Invergowrie, Ecological Sciences, Dundee DD2 5DA, Scotland, UK.
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Euan K. James
  • Euan K. James
  • James Hutton Institute, Invergowrie, Ecological Sciences, Dundee DD2 5DA, Scotland, UK.
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Pietro P. M. Iannetta
  • Pietro P. M. Iannetta
  • James Hutton Institute, Invergowrie, Ecological Sciences, Dundee DD2 5DA, Scotland, UK.
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Fassil Assefa
  • Fassil Assefa
  • Department of Microbial, Cellular and Molecular Biology, College of Natural Sciences, Addis Ababa University, Cellular and Molecular Biology, P. O. Box 1176, Ethiopia.
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  •  Received: 11 July 2019
  •  Accepted: 03 September 2019
  •  Published: 31 October 2019

Abstract

Ethiopia remains a net importer of soybean partly due to low average yields which may be improved by inoculation with rhizobia and/or plant growth promoting rhizobacteria (PGPR). The functional characterisation of 231 rhizobacteria isolated from the rhizosphere of soybean grown in 102 soils collected from different pedo-climatic regions of Ethiopia was carried out. Isolates were initially characterised by Gram staining and then functionally for:  indole-3-acetic acid production; phosphate solubilisation; growth on a nitrogen-free medium; and, resistance to the pathogenic fungus Fusarium oxysporum. A sub-set of 72 of the best performing isolates were tested in vitro for: production of bioprotectants; polysaccharide degradation; and their relative capacity to maintain growth in response to extremes of: temperature; pH; salinity; antibiotics; pesticides; and, heavy metals. Twenty isolates with the best PGPR potential were identified via 16S rRNA gene sequencing. Seventeen isolates were Gram-negative: Pseudomonas (7); Stenotrophomonas (5); Acinetobacter (3); Enterobacter (1); and Achromobacter (1). Gram-positive types were: Bacillus (2); and, Microbacterium (1). Of the six of the most promising PGPR tested on soybean plants, Achromobacter and Acinetobacter significantly enhanced soybean seed germination, seedling growth and plant vigour index compared to non-inoculated plants.                                                                               

Key words: Soybean, Ethiopia, plant growth promoting rhizobacteria, plant growth promoting rhizobacteria (PGPR), seedling vigour.