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Antagonistic effect of fluorescent pseudomonads against Macrophomina phaseolina that causes charcoal rot of groundnut

Shweta Bhatia1, Shivani Bhatia, R C Dubey

  • 1Department of Botany & Microbiology, Gurukul Kangri University, Hardwar 249404, India.

Indian Journal of Experimental Biology
|August 24, 2004
PubMed

Insights

Pseudomonas strains PS1 and PS2 effectively inhibit M. phaseolina growth through various mechanisms. Pseudomonas PS2 demonstrated superior antagonistic activity, significantly reducing fungal colony development.

Area of Science:

  • Microbiology
  • Plant Pathology
  • Biocontrol Agents

Background:

  • Macrophomina phaseolina (M. phaseolina) is a significant plant pathogen causing substantial crop losses.
  • Biological control using antagonistic microorganisms offers a sustainable alternative to chemical fungicides.
  • Pseudomonas species are known for their antagonistic properties against various plant pathogens.

Purpose of the Study:

  • To evaluate the antagonistic potential of Pseudomonas strains PS1 and PS2 against M. phaseolina.
  • To elucidate the mechanisms underlying the inhibition of M. phaseolina by Pseudomonas strains.
  • To compare the efficacy of PS1 and PS2 in controlling M. phaseolina growth.

Main Methods:

  • In vitro assessment of colony growth inhibition using Pseudomonas strains PS1 and PS2 on trypticase soy agar (TSM) plates.
  • Microscopic examination (light and scanning electron microscopy) of M. phaseolina hyphae treated with Pseudomonas.
  • Evaluation of inhibition by cell-free culture filtrates and volatile substances of Pseudomonas strains.
  • Assessment of antagonistic activity under iron-sufficient and iron-deficient conditions.

Main Results:

  • Pseudomonas PS2 and PS1 achieved maximum colony growth inhibition of M. phaseolina by 74% and 71%, respectively, after 5 days.
  • Microscopic analysis revealed hyphal coiling, vacuolation, coagulation, granulation, and lysis of M. phaseolina hyphae due to pseudomonads.
  • Cell-free culture filtrates of PS1 and PS2 inhibited M. phaseolina mycelial growth by 57% and 61% at 20% concentration, respectively.
  • Volatile substances from PS1 and PS2 inhibited M. phaseolina colony growth by 25% and 32%, with decreasing efficacy over time.
  • Both strains significantly reduced M. phaseolina growth in both iron-sufficient and iron-deficient conditions, with PS2 exhibiting stronger antagonism.

Conclusions:

  • Pseudomonas strains PS1 and PS2 possess significant antagonistic potential against M. phaseolina.
  • The antagonistic mechanisms involve direct hyphal damage and inhibition by both soluble and volatile metabolites.
  • Pseudomonas PS2 demonstrates superior efficacy in controlling M. phaseolina growth, highlighting its potential as a biocontrol agent.

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