Inducing drought tolerance in wheat through combined use of L-tryptophan and pseudomonas fluorescens

Abstract

Auxins, as phytohormones and osmo-protectant, play important role to alleviate the adverse effect of drought stress on plant growth. Some bacteria equipped with ACC-deaminase activity along with some other growth promoting traits are helpful in improving plant growth under stresses. The efficiency of these bacteria is further improved when inoculation is supplemented with exogenous plant growth regulators. The combined use of these bacteria with auxins may be more effective under stressed conditions. A pot experiment was conducted to evaluate the efficacy of Pseudomonas fluorescens containing ACC-deaminase in combination with L-tryptophan for reducing drought stress in wheat. The P. fluorescens and L-tryptophan (@ 25 ppm) were applied, solely and in combination, on wheat by inducing drought stress at different growth stages. The foliar application of L-tryptophan was started after 15 days of germination and was repeated every week up to 2 weeks after grain filling stage. The results showed significant reduction in all parameters under drought. However, combined application of L-tryptophan @ 25 ppm and P. fluorescens significantly improved plant height (45.65%), root length (81%), chlorophyll-a (94%), chlorophyll-b (72%), carotenoid contents (98%), relative water contents (33%), Na+/K+ ratio in leaves (49%) and grains (43%), spike length (64%) and 1000 grains weight (75%) under drought stress. Consequently, it may be concluded that combined use of L-tryptophan @ 25 ppm and P. fluorescens is an effective approach to improve wheat productivity under water limited conditions but it should be evaluated extensively under field studies before its recommendation to the farmers.