Soil salinity leading to sodium toxicity is developing into a massive challenge for agricultural productivity globally, inducing osmotic, ionic, and redox imbalances in plants. Considering the predicted increase in salinization risk with the ongoing climate change, applying plant growth-promoting rhizobacteria (PGPR) is an environmentally safe method for augmenting plant salinity tolerance. The present study examined the role of halotolerant Bacillus sp. BSE01 as a promising biostimulant for improving salt stress endurance in chickpea. Application of PGPR significantly increased the plant height, relative water content, and chlorophyll content of chickpea under both non-stressed and salt stress conditions. The PGPR-mediated tolerance towards salt stress was accomplished by the modulation of hormonal signaling and conservation of cellular ionic, osmotic, redox homeostasis. With salinity stress, the PGPR-treated plants significantly increased the indole-3-acetic acid and gibberellic acid contents more than the non-treated plants. Furthermore, the PGPR-inoculated plants maintained lower 1-aminocyclopropane-1-carboxylic acid and abscisic acid contents under salt treatment. The PGPR-inoculated chickpea plants also exhibited a decreased NADPH oxidase activity with reduced production of reactive oxygen species compared to the non-inoculated plants. Additionally, PGPR treatment led to increased antioxidant enzyme activities in chickpea under saline conditions, facilitating the reactive nitrogen and oxygen species detoxification, thereby limiting the nitro-oxidative damage. Following salinity stress, enhanced K+ /Na+ ratio and proline content were noted in the PGPR-inoculated chickpea plants. Therefore, Bacillus sp. BSE01, being an effective PGPR and salinity stress reducer, can further be considered to develop a bioinoculant for sustainable chickpea production under saline environments.
Keywords: Antioxidant enzyme; biostimulant; chickpea; phytohormone; reactive oxygen species; secretory trichome.
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