Abstract
Four commercial composts were added to soil to study their effect on plant growth, total rhizosphere microflora, and incidence of plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of tomato plants. Three of the compost treatments significantly improved plant growth, while one compost treatment significantly depressed it. Compost amendments caused only small variations in the total numbers of bacteria, actinomycetes, and fungi in the rhizosphere of tomato plants. A total of 709 bacteria were isolated from the four compost treatments and the soil control to determine the percentage of PGPR in each treatment. The PGPR tests measured antagonism to soilborne root pathogens, production of indoleacetic acid, cyanide, and siderophores, phosphate solubilization, and intrinsic resistance to antibiotics. Our results show that the addition of some composts to soil increased the incidence in the tomato rhizosphere of bacteria exhibiting antagonism towards Fusarium oxysporum f. sp. radicis-lycopersici, Pyrenochaeta lycopersici, Pythium ultimum, and Rhizoctonia solani. The antagonistic effects observed were associated with marked increases in the percentage of siderophore producers. No significant differences were observed in the percentage of cyanogens, whereas the percentages of phosphate solubilizers and indoleacetic acid producers were affected, respectively, by one and two compost treatments. Intrinsic resistance to antibiotics was only marginally different among the rhizobacterial populations. Our results suggest that compost may stimulate the proliferation of antagonists in the rhizosphere and confirm previous reports indicating that the use of composts in container media has the potential to protect plants from soilborne root pathogens.
Full Text
The Full Text of this article is available as a PDF (208.6 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Boehm M. J., Madden L. V., Hoitink H. A. Effect of organic matter decomposition level on bacterial species diversity and composition in relationship to pythium damping-off severity. Appl Environ Microbiol. 1993 Dec;59(12):4171–4179. doi: 10.1128/aem.59.12.4171-4179.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bric J. M., Bostock R. M., Silverstone S. E. Rapid in situ assay for indoleacetic Acid production by bacteria immobilized on a nitrocellulose membrane. Appl Environ Microbiol. 1991 Feb;57(2):535–538. doi: 10.1128/aem.57.2.535-538.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Döbereiner J., Baldani V. L. Selective infection of maize roots by streptomycin-resistant Azospirillum lipoferum and other bacteria. Can J Microbiol. 1979 Nov;25(11):1264–1269. doi: 10.1139/m79-199. [DOI] [PubMed] [Google Scholar]
- Gordon S. A., Weber R. P. COLORIMETRIC ESTIMATION OF INDOLEACETIC ACID. Plant Physiol. 1951 Jan;26(1):192–195. doi: 10.1104/pp.26.1.192. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gould W. D., Hagedorn C., Bardinelli T. R., Zablotowicz R. M. New selective media for enumeration and recovery of fluorescent pseudomonads from various habitats. Appl Environ Microbiol. 1985 Jan;49(1):28–32. doi: 10.1128/aem.49.1.28-32.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lambert B., Leyns F., Van Rooyen L., Gosselé F., Papon Y., Swings J. Rhizobacteria of maize and their antifungal activities. Appl Environ Microbiol. 1987 Aug;53(8):1866–1871. doi: 10.1128/aem.53.8.1866-1871.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McKinley V. L., Vestal J. R. Biokinetic analyses of adaptation and succession: microbial activity in composting municipal sewage sludge. Appl Environ Microbiol. 1984 May;47(5):933–941. doi: 10.1128/aem.47.5.933-941.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schroth M. N., Hancock J. G. Selected topics in biological control. Annu Rev Microbiol. 1981;35:453–476. doi: 10.1146/annurev.mi.35.100181.002321. [DOI] [PubMed] [Google Scholar]