English

Abstract

Biotic stress in the rhizospheric environment induces defense mechanism in plant via signaling between plant and nonpathogenic microbes. In order to evaluate the defense response of maize plant, in relation to beneficial bacteria, a jar experiment was conducted in diseased soil (infected with Fusarium oxysporum). Seed was inoculated with consortium of selected isolates of plant growth promoting rhizobacteria (PGPR, Mb4 (Bacillus spp.), Mb7 (Pseudomonas aeruginosa) and compost inhabiting bacteria (CIB, Cb4 (Serratia spp.) and Cb9 (Pseudomonas spp.). Inoculum was used as inducer of defense compounds in maize crop. Hoagland half strength solution was applied to meet the water and nutrient requirements of the plants. Treatments were arranged in completely randomized design under axenic condition and were repeated thrice. Results indicated that different combination of Mb4 (Bacillus spp.), Mb7 (Pseudomonas aeruginosa), Cb4 (Serratia spp.) and Cb9 (Pseudomonas spp.) showed 100 percent seed germination than un-inoculated control. Significantly higher root/shoot growth were observed in treatments, inoculated with consortium of selected isolates. Survival of maize plants in diseased environment is the result of physicochemical changes in plant. Proline contents were observed up to 4.97 μmol g -1 in bacterial inoculated treatment compared to un-inoculated control (1.760 μmolg -1 ). Consortium of above mentioned isolates helped to maintain the chlorophyll ‘a’ ‘b’ and higher relative water contents than control. Inoculation with different consortia of selected isolates reduced membrane permeability up to 54.18%. The higher catalase activity was 4.5 mM H 2O2 min -1 g -1 , while ascorbate peroxidase activity was 0.57 μM H2O2 min -1 g -1 due to inoculation with bacterial consortia. It is therefore concluded that consortium inoculation of compatible bacterial isolates induced physicochemical changes in stressed plant,