Influence of introduced potential biocontrol agents on maize seedling growth and bacterial community structure in the rhizosphere

• Published in: Soil biology & biochemistry 2004-11, Vol.36 (11), p.1775-1784
• Main Authors: Kozdrój, J., Trevors, J.T., van Elsas, J.D.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; biological control agents; Chemical, physicochemical, biochemical and biological properties; community structure; corn; Fatty acid profiling; Fundamental and applied biological sciences. Psychology; genes; genetic markers; gfp marker; Introduced pseudomonads; Maize rhizosphere; Microbial community; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant pathogenic bacteria; Pseudomonas corrugata; Pseudomonas putida; Ralstonia solanacearum; rhizosphere; seedling growth; soil bacteria; soil inoculation; Soil science; Zea mays
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2004.04.034

Two species of Pseudomonas chromosomally tagged with gfp, which had shown antagonistic activity against the tomato pathogen Ralstonia solanacearum in a previous study, were assessed for their impact in the rhizosphere of maize. Plant growth characteristics, numbers of indigenous heterotrophic bacteria, changes in the bacterial community structure according to the r/K strategy concept, and shifts in MIDI-FAME profiles of culturable bacterial fractions as well as total rhizosphere microbial communities were determined in relation to seed and soil treatment with the exogenous pseudomonads. The maize rhizosphere proved to be a suitable habitat for the introduced P. chlororaphis IDV1 and P. putida RA2, which showed good survival after introduction. However, both inoculants showed a small growth-reducing effect towards maize, which might have been caused by the high densities of inoculants used (i.e. competition for nutrients and action of metabolites produced) and/or changes in microbial community structure (both culturable bacterial fraction and the total microflora). Probably, an altered balance among the indigenous maize rhizosphere populations occurred. Thus, the culturable bacteria, as well as the total microflora in the rhizosphere, changed in response to the introduced pseudomonads, and their development was dependent on the growth stage of the plant. The FAME analyses showed that these microbial communities comprised different populations, and were separated according to, first, the method used (direct versus cultivation-based), second, sampling time, and, finally, inoculation level.