Bacillus subtilis SQR 9 can control Fusarium wilt in cucumber by colonizing plant roots
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Fusarium wilt is one of the major constraints on cucumber production worldwide. Several strategies have been used to control the causative pathogen, Fusarium oxysporum f. sp. cucumerinum J. H. Owen, including soil solarization, fungicide seed treatment and biological control. In this study, F. oxysporum f. sp. cucumerinum was successfully controlled by a newly isolated strain, Bacillus subtilis SQR 9, in vitro and in vivo. Greenhouse experiments were carried out to evaluate the effect of inoculation and solid fermentation of organic fertilizer with B. subtilis SQR 9, hereby defined as bio-organic fertilizer (BIO), on the control of Fusarium wilt. In comparison with the control, the wilt incidence was significantly reduced (49–61% reduction) by application of BIO. The rhizosphere population of F. oxysporum f. sp. cucumerinum, as detected both by selective plating and realtime PCR, was significantly lower in BIO-treated plants than the control. The localization of bacterial cells, pattern of colonization and survival of B. subtilis SQR 9 in the rhizsosphere of cucumber, was examined by fluorescent microscopy and explored following recovery of the green fluorescent protein (gfp)-labeled SQR 9 with the new gfp-marked shuttle vector pHAPII through selective plating. The preferential sites of the labeled strain were the differentiation and elongation zone, root hair and the lateral root junctions. The population of the strain was 106 cfu/g root in rhizoplane. These results indicate that the strain was able to survive well in the rhizosphere of cucumber, suppressed growth of F. oxysporum in the rhizosphere of cucumber and protected the host from the pathogen.
KeywordsColonization Bio-organic fertilizer Fusarium wilt Rhizosphere Bacillus subtilis
This research was financially supported by Chinese Ministry of Science and Technology (2007CB109304 and 2009120) and Science and Technology Bureau of Jiangsu Province (BE2009672 and BA2008027). We would like to thank Dr. Hongsheng Wu from Nanjing University of Information Science and Technology, Nanjing, China, for his kind correction of the manuscript.
- Armstrong GM, Armstrong JK (1981) Formae speciales and races of Fusarium oxysporum causing wilt disease. In: Nelson PE, Toussoun TA, Cook RJ (eds) Fusarium: disease, biology, and taxonomy. Pennsylvania State University Press, University Park, pp 391–399Google Scholar
- Erhart E, Burian KH, Stich K (1999) Suppression of Pythium ultimum by biowaste composts in relation to compost microbial biomass, activity and content of phenolic compounds. J Phytopathol 147:299–305Google Scholar
- Eva Z, Hans M (1986) Characterization of signals promoting gene expression on the Staphylococcus aureus plasmid pUB110 and development of a Gram-positive expression vector system. DNA 3:219–225Google Scholar
- Gamalero E, Lingua G, Capr FG, Fusconi A, Berta G, Lemanceau P (2004) Colonization pattern of primary tomato roots by Pseudomonas fluorescens A6RI characterized by dilution plating, flow cytometry, fluorescence, confocal and scanning electron microscopy. FEMS Microbiol Ecol 48:79–87PubMedCrossRefGoogle Scholar
- Komada H (1975) Development of a selective medium for qualitative isolation of Fusarium oxysporum from natural soil. Rev Plant Protec Res 8:114–125Google Scholar
- Rasmussen R (2001) Quantification on the Lightcycler. In: Meuer S, Wittwer C, Nakagawara K (eds) Rapid cycle real-time PCR: methods and applications. Springer, Berlin, pp 129–144Google Scholar
- Sambrook J, Fitsch EF, Maniatis T (1989) Molecular cloning: a laboratory manual. Cold Spring Harbor LaboratoryGoogle Scholar
- Sneath PHA (1986) Endospore-forming gram-positive rods and cocci. In: Sneath PHA (ed) Bergey's manual of systematic bacteriology, vol. 2. Williams and Wilkins, Baltimore, pp 1104–1138, ISBN 0–683–07893–3Google Scholar
- Sun X, Chen Y, Wu C, Yang G, Guo B, Shen D (2006) Functional evaluation of a novel constitutive promoter F1 of Bacillus pumilus, as a rice epiphytic strain, and construction of an efficient expression an secretion system under the control of F1. Biotechnol Lett 28:979–985PubMedCrossRefGoogle Scholar