Induction of resistance in host against the infection of leaf blight pathogen (Alternaria palandui) in onion (Allium cepa var aggregatum)

M. Karthikeyan*, V. Jayakumar, K. Radhika, R. Bhaskaran, R. Velazhahan, D. Alice

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


The Pseudomonas fluorescens isolate Pf1 was found to inhibit the growth of pathogen Alternaria palandui, in vitro. In the present study, foliar application of a talc-based formulation of Pf1 significantly reduced the incidence of leaf blight of onion, caused by A. palandui. Induction of defense-related proteins viz., chitinase, β-1,3 glucanase, peroxidase (PO) and polyphenol oxidase (PPO) by application of Pf1, was studied against A. palandui infection in resistant (IHR 56) and susceptible (MDU1) onion cultivars. Chitinase in both cultivars, with or without challenge-inoculation of A. palandui revealed changes in the isoform pattern. The Native-PAGE of PO showed induction of PO2 isoform in both the cultivars, in response to inoculation of pathogen. Isoform analysis of PPO also exhibited induction in the Pf1-treated plants challenged with pathogen. Similarly, the activity of β-1,3-glucanase was greatly induced in Pf1-treated plants, challenged with pathogen as compared to controls. Thus, the P. fluorescens-treated plants showed significant increase in the levels of the defense enzymes, in comparison to the plants challenged with the pathogen.

Original languageEnglish
Pages (from-to)371-377
Number of pages7
JournalIndian Journal of Biochemistry and Biophysics
Issue number6
Publication statusPublished - Dec 2005
Externally publishedYes


  • Alternaria palandui
  • Chitinase
  • Defense-related proteins
  • Induced systemic resistance
  • Leaf blight
  • Onion
  • Peroxidase
  • Polyphenol oxidase
  • Pseudomonas fluorescens
  • β-1,3 glucanase

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry


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