Nematicidal activity of some strains of Pseudomonas spp.
Introduction
Biological control of soilborne plant pathogens with bacteria has been studied as an alternative or complementary approach to physical and chemical disease control measures for over 70 years (Weller, 1988). Many species of Pseudomonas promote plant growth and reduce populations of deleterious rhizoplane fungi and bacteria when used as seed or root inoculants (Schroth and Hancock, 1981). Some of these plant growth-promoting rhizobacteria (PGPR) produce iron-chelating siderophores (De Meyer and Höfte, 1997), antibiotics or hydrogen cyanide (Ahl et al., 1986), and these compounds have been implicated in the reduction of deleterious and pathogenic rhizosphere microorganisms, creating an environment more favorable for root growth (Leong, 1986). Seed bacterization of radish with Pseudomonas fluorescens WCS374 significantly suppressed Fusarium wilt disease (Leeman et al., 1995).
Antagonistic bacteria have been repeatedly shown to be promising microorganisms for the biological control of plant-parasitic nematodes. In a screening program, 16 bacterial isolates out of 179 isolated from root and cysts caused a significant (>25%) reduction in Globodera pallida penetration of potato roots (Racke and Sikora, 1992). A 68% reduction of sugar beet cyst nematode root invasion was obtained by application of the rhizobacterium P. fluorescens P523 to beet seeds (Oostendorp and Sikora, 1990). Soil application with Pseudomonas aeruginosa significantly controlled root rot–root knot disease complex in tomato (Siddiqui et al., 2000, Siddiqui and Ehteshamul-Haque, 2000). Overall, little is known about the mechanisms involved in the suppression of plant-parasitic nematodes. Bacillus thuringiensis has shown some toxic activity against plant-parasitic nematodes (Walker, 1971, Devidas and Rehberger, 1992). Recently, living and heat-killed cells of Rhizobium etli G12 induced in potato roots systemic resistance against G. pallida infection (Hoffmann-Hergarten et al., 1997, Hasky-Günther et al., 1998). Induced systemic resistance in potato to G. pallida was triggered by heat-killed cells and purified LPS, extracted from the outer membrane of R. etli strain G12 (Reitz et al., 2000).
Since soilborne root-infecting fungi and plant-parasitic nematodes are the common inhabitants of almost all the agricultural fields causing severe losses to crops, agents having the capabilities of controlling these diverse groups of pathogens could be of practical significance. In our previous study, Pseudomonas isolates showed promising results in the suppression of root-infecting fungi including Macrophomina phaseolina, Fusarium solani and Rhizoctonia solani (Ali et al., 2001). Our objectives were (i) to investigate the effects of these Pseudomonas isolates against the root-knot nematode (Meloidogyne javanica) under laboratory, greenhouse, and field conditions, (ii) to partially characterize the active nematicidal principle(s) of a strain-78 of P. aeruginosa and (iii) to find out the compatibility of the strain-78 with other potential biocontrol agents and organic amendments. Results from these studies should contribute to a better understanding of the complex interactions among root-knot nematode, introduced saprophytic bacteria, other soil microorganisms and host plant. Such information would be of help in the isolation and characterization of the active nematicidal agents that should eventually lead to the development of nematicide(s) of bacterial origin.
Section snippets
Laboratory experiments
The bacterial strains used in this study were obtained from the Department of Genetics, University of Karachi (Table 1). All the bacterial strains were maintained at 6 °C on King's B medium (King et al., 1954) before use. The inoculum was produced by transferring two loop-ful of the bacterium from a 5-day-old culture to 100 ml KB liquid medium and incubated at room temperature on a shaker (150 rpm) for 48 h. The bacterial cells were centrifuged (4500×g, 15 min), supernatant was discarded and the
Laboratory experiments
Culture filtrate of the bacterial strains (14, 38, 51, 66, 71, 72, 78, 80 and 82) showed nematicidal effects (P<0.05) killing the second stage juveniles of M. javanica to a varying extent (Table 1). There was an increase in mortality rate of juveniles as the length of exposure to the culture filtrate increased. In dual culture plate assay, P. aeruginosa inhibited radial growth of P. lilacinus producing zone of inhibition of 6 mm. Likewise, P. aeruginosa produced a zone of inhibition of 2 mm
Discussion
Our results indicate that the selected strains of Pseudomonas sp., and P. aeruginosa have significant potential as commercial biological control agents against M. javanica, the root-knot nematode. In the initial screening all the 20 strains of Pseudomonas sp., and P. aeruginosa showed antagonistic activity towards M. javanica juveniles in vitro. Seventy percent of the strains caused >25% juvenile mortality while, 30% of the total strains tested produced more than 50% nematode deaths. Thus, the
Acknowledgements
We thank Dr Maqsood Ali Ansari of the Department of Genetics, University of Karachi for providing bacterial cultures and curing of the plasmid of Pseudomonas aeruginosa strain-78 and Dr S. Sarwar Alam of National Institute of Agriculture and Biology, Faisalabad for providing mungbean seeds.
References (40)
- et al.
Isolation, formulation and antagonistic activity of rhizobacteria toward the potato cyst nematode Globodera pallida
Soil Biology and Biochemistry
(1992) - et al.
Iron bound siderophores, cyanic acid and antibiotics involved in suppression of Thielaviopsis basicola by Pseudomonas fluorescens strain
Journal of Phytopathology
(1986) - et al.
Variation between strains of Pseudomonas bacterium. 1. Effects on root-infecting fungi
Pakistan Journal of Biological Sciences
(2001) - et al.
Luminometric analysis of plant root colonization by bioluminescent Pseudomonas
Canadian Journal of Microbiology
(1993) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding
Annals of Biochemistry
(1976)- et al.
Relationship between root colonization and suppression of Gaeumannomyces graminis var. tritici by Pseudomonas fluorescens strain 2-79
Phytopathology
(1991) - et al.
Study of the nematocidal properties of the culture filtrate of the nematophagous fungus Paecilomyces lilacinus
Review de Nematologie
(1989) - et al.
The effects of exotoxin (thuringiensin) from Bacillus thuringiensis on Meloidogyne incognita and Caenorhabditis elegans
Plant Soil
(1992) - et al.
Salicylic acid produced by the rhizobacterium Pseudomonas aeruginosa 7NSK2 induces resistance to leaf infection by Botrytis cinerea on bean
Phytopathology
(1997) - et al.
Characterization of an antibiotic produced by a strain of Pseudomonas fluorescens inhibitory to Gaeumannomyces graminis var. tritici and Pythium spp
Antimicrobial Agents Chemotherapy
(1986)
Resistance against the potato cyst nematode Globodera pallida systemically induced by the rhizobacteria Agrobacterium radiobacter (G12) and Bacillus sphaericus (B43)
Fundamental and Applied Nematology
Induced systemic resistance by rhizobacteria toward the cyst nematode Globodera pallida on potato
Insecticidal crystal proteins of Bacillus thuringiensis
Microbial Review
Two simple media for the demonstration of pycocyanin and fluorescin
Journal of Laboratory and Clinical Medicine
Plant growth-promoting rhizobacteria as biological control agents of soilborne disease
Biocontrol of Fusarium wilt of radish in commercial greenhouse trials by seed treatment with Pseudomonas fluorescens WCS374
Phytopathology
Siderophores: their biochemistry and possible role in the biocontrol of plant pathogens
Annual Review of Phytopathology
Experiments in Molecular Genetics
Genes specifying auxin and cytokinin biosynthesis in prokaryotes
Seed treatment with antagonistic rhizobacteria for the suppression of Heterodera schachtii early root infection of sugar beet
Review de Nematolgie
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