Induced resistance and control of charcoal rot in Cicer arietinum (chickpea) by Pseudomonas fluorescens

Abstract

Pseudomonas fluorescens isolate 4-92 induced systemic resistance against charcoal rot disease in chickpea (Cicer arietinum L.) caused by Macrophomina phaseolina (Tassi) Goidanich. Time-course accumulation of pathogenesis-related (PR) proteins (chitinases and glucanases) in chickpea plants inoculated with P. fluorescens was significantly (P = 0.05) higher than in control plants. The level of chitinases and glucanases increased by 6.6- to 7-fold up to 4 days postinoculation; thereafter, little decrease in the activity of PR proteins was observed. Root-colonizing populations of P. fluorescens were at a maximum 2 days after transplantation at different inoculum concentrations, and decreased over time. Inoculation of root tips of chickpea by P. fluorescens, 2,6-dichloroisonicotinic acid, and o-acetylsalicylic acid induced systemic resistance against charcoal rot. Disease was 33 to 55.5% higher in control plants than in plants inoculated with chemical inducers or P. fluorescens. Single treatment of plants with P. fluorescens increased disease resistance by 33%, whereas combined application of P. fluorescens with either of the chemical inducers was most effective in inducing the resistance by 2- to 2.25-fold. The time-course study shows that an interval of at least 2 days was required between induction treatment and challenge inoculation. Biocontrol efficacy of P. fluorescens against charcoal rot disease in chickpea was demonstrated under greenhouse conditions.Key words: biological control, induced resistance, Macrophomina phaseolina, Pseudomonas fluorescens.