The effect of salt-tolerant antagonistic bacteria from tomato rhizosphere on plant growth promotion and damping-off disease suppression under salt-stress conditions

Thamodini Gaya Karunasinghe, Issa Hashil Al-Mahmooli, Abdullah Mohammed Al-Sadi, Rethinasamy Velazhahan*

*Corresponding author for this work

Research output: Contribution to journalArticle


A total of 24 morphologically distinct salt-tolerant bacteria were isolated from the tomato rhizosphere soil and tested in vitro against Pythium aphanidermatum, causing damping-off disease in tomato. Among them, five bacterial isolates viz., BTR1.0, BTR1.1, BTR4.4, BTR7.0 and BTR8.6 were found to inhibit the mycelial growth of P. aphanidermatum. The maximum antagonistic effect was shown by BTR1.0 followed by BTR7.0 and BTR1.1. Based on the MALDI Biotyper analysis, these bacterial isolates were identified as Serratia marcescens (BTR1.0 and BTR1.1), Pseudomonas aeruginosa (BTR7.0 and BTR8.6) and Alcaligenes faecalis (BTR4.4). Analysis of plant growth stimulating activity of bacterial strains revealed that A. faecalis BTR4.4 recorded the highest vigour index followed by S. marcescens BTR1.0. The biocontrol activity of bacterial antagonists against tomato damping-off was tested under salt-water irrigation. Among the bacterial strains tested, S. marcescens BTR1.1 was found to be highly effective under non-saline water irrigation, which suppressed the disease by 68% compared to infected control. However, at 50 mM NaCl concentration, S. marcescens strain BTR1.0, P. aeruginosa strain BTR7.0 and A. faecalis BTR4.4 provided a significant level of control of the disease. At 100 mM NaCl concentration, no significant effect of the bacterial strains on the disease incidence was observed.

Original languageEnglish
Pages (from-to)69-75
Number of pages7
JournalActa Agriculturae Scandinavica Section B: Soil and Plant Science
Issue number1
Publication statusPublished - Jan 2 2020
Externally publishedYes


  • Alcaligenes faecalis
  • biocontrol
  • damping-off
  • Lycopersicon esculentum
  • Pseudomonas aeruginosa
  • Serratia marcescens

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science

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