Bacteria-induced systemic resistance and growth promotion in Glycine max L. Merrill upon challenge inoculation with Fusarium oxysporum

In the present study, two bacterial strains along with Pseudomonas sp. strain VS1 were employed and screened on the basis of plant growth-promotion characteristics. Strains showed in vitro antibiosis against the test fungal pathogen Fusarium oxysporum together with plant growth-promotion properties that included indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid and inorganic phosphorus solubilization production. The activities of stress responsive enzymes that included lipoxygenase, phenylalanine ammonia-lyase, catalase, peroxidase and superoxide dismutase were reported in bacteria and control-treated soybean plants. Bacteria treated seeds showed higher enzymatic activities in leaves in comparison with fungal spore treated seeds and were considered as positive control. Treatment with bacteria resulted in remarkable increase in the chlorophyll content in leaves as compared to water (negative control) and fungal spore treated seeds (P < 0.05). Soybean seeds treated with bacteria were subjected to fungal spore stress at 0 day after seeding, strain SJ(5) significantly enhanced emergence at 28 days after seeding than other treated seeds and positive control. The fresh weight of both shoot and root of plant was significantly increased when soybean seeds were treated with bacteria in the presence of fungal spores as compared to positive control. The dry weights of both roots and shoots were significantly increased by the bacterial treatments as compared to positive control (P < 0.05). Strain treated seeds significantly enhanced root and shoot length together with a number of lateral roots when spore suspension was applied at 0 day after seeding. Moreover, soybean plants treated with strain SJ(5) exhibited significantly greater root and shoot weights as compared to the other treated plants when fungal spore suspension was applied at 0 day after seeding.