Nematicidal activity of some strains of Pseudomonas spp.

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Abstract

Culture filtrates of strains of Pseudomonas spp. were able to produce juvenile mortality of Meloidogyne javanica, the root-knot nematode in vitro. Seed treatment or soil drench with Pseudomonas sp. (strain 82 and 51) and Pseudomonas aeruginosa (strain-78) significantly reduced nematode population densities in soil and subsequent gall formation due to M. javanica in mungbean, under glasshouse conditions. P. aeruginosa strain-78 multiplied on talc powder and applied in soil reduced root-knot development and nematode population density under field conditions in mungbean used as first crop or succeeding crop. Strain-78 used with either Paecilomyces lilacinus or Bradyrhizobium japonicum suppressed root-knot disease compared with either antagonist used alone. Strain-78 applied in the soil amended with a brown seaweed (Sargassum tenerrimum) also inhibited root-knot development. The toxic principles of the strain-78 were partially characterized. The active factors were heat labile, sensitive to extreme pH values, polar in nature and having a molecular weight of less than 8000 MW.

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)

  • J. Racke et al.

    Isolation, formulation and antagonistic activity of rhizobacteria toward the potato cyst nematode Globodera pallida

    Soil Biology and Biochemistry

    (1992)
  • P. Ahl et al.

    Iron bound siderophores, cyanic acid and antibiotics involved in suppression of Thielaviopsis basicola by Pseudomonas fluorescens strain

    Journal of Phytopathology

    (1986)
  • N.I. Ali et al.

    Variation between strains of Pseudomonas bacterium. 1. Effects on root-infecting fungi

    Pakistan Journal of Biological Sciences

    (2001)
  • C.J. Beauchamp et al.

    Luminometric analysis of plant root colonization by bioluminescent Pseudomonas

    Canadian Journal of Microbiology

    (1993)
  • M. Bradford

    A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding

    Annals of Biochemistry

    (1976)
  • C.T. Bull et al.

    Relationship between root colonization and suppression of Gaeumannomyces graminis var. tritici by Pseudomonas fluorescens strain 2-79

    Phytopathology

    (1991)
  • D.J. Cayrol et al.

    Study of the nematocidal properties of the culture filtrate of the nematophagous fungus Paecilomyces lilacinus

    Review de Nematologie

    (1989)
  • P. Devidas et al.

    The effects of exotoxin (thuringiensin) from Bacillus thuringiensis on Meloidogyne incognita and Caenorhabditis elegans

    Plant Soil

    (1992)
  • G. De Meyer et al.

    Salicylic acid produced by the rhizobacterium Pseudomonas aeruginosa 7NSK2 induces resistance to leaf infection by Botrytis cinerea on bean

    Phytopathology

    (1997)
  • S. Gurusiddaiah 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)
  • K. Hasky-Günther et al.

    Resistance against the potato cyst nematode Globodera pallida systemically induced by the rhizobacteria Agrobacterium radiobacter (G12) and Bacillus sphaericus (B43)

    Fundamental and Applied Nematology

    (1998)
  • S. Hoffmann-Hergarten et al.

    Induced systemic resistance by rhizobacteria toward the cyst nematode Globodera pallida on potato

  • H. Höfte et al.

    Insecticidal crystal proteins of Bacillus thuringiensis

    Microbial Review

    (1989)
  • E.O. King et al.

    Two simple media for the demonstration of pycocyanin and fluorescin

    Journal of Laboratory and Clinical Medicine

    (1954)
  • J.W. Kloepper

    Plant growth-promoting rhizobacteria as biological control agents of soilborne disease

  • M. Leeman et al.

    Biocontrol of Fusarium wilt of radish in commercial greenhouse trials by seed treatment with Pseudomonas fluorescens WCS374

    Phytopathology

    (1995)
  • J. Leong

    Siderophores: their biochemistry and possible role in the biocontrol of plant pathogens

    Annual Review of Phytopathology

    (1986)
  • H.J. Miller

    Experiments in Molecular Genetics

    (1972)
  • R.O. Moris

    Genes specifying auxin and cytokinin biosynthesis in prokaryotes

  • M. Oostendorp et al.

    Seed treatment with antagonistic rhizobacteria for the suppression of Heterodera schachtii early root infection of sugar beet

    Review de Nematolgie

    (1989)
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