Impacts of Salt Stress on the Rhizosphere and Endophytic Bacterial Role in Plant Salt Alleviation

Abstract

Salinity stress is among the key challenges for sustainable food production. It is continuously increasing against the backdrop of constant climate change and anthropogenic practices leading to a huge drop in soil, water, and cultivated crop quality and productivity. Halotolerant plants represent hot spots for endophytic bacteria which may have mechanisms to overcome salt stress. This research initiative aims to highlight the possible exploitation of bacterial endophytes as a microbial biotechnology tool in the productive success of plants exposed to saline stress. We started by solely studying the mechanisms of stress tolerance by plants and halotolerant bacteria. After that, we focused on the beneficial mechanisms of endophytic bacteria in salt stress mitigation. On one side, potent bacterium works by promoting plant performances by facilitating the plant’s nutrient uptake (P, K, Zn, N, and Fe) and by promoting the production of growth hormones (IAA and CKs). On the other side, they balance stress phytohormones (ABA, JA, GA, and ACC) produced by plants in case of soil salt augmentation. The selected potent endophytic bacteria could be exploited and applied to ameliorate the production and salt tolerance of food crops. Lastly, we elucidated deeper advanced technologies including (i) genomics unveiling the plant’s culture-dependent and culture-independent microbiomes, (ii) metabolomics focusing on genes’ metabolic pathways to discover novel secondary metabolites, (iii) transcriptomics studying gene expression, and (iv) proteomics delimiting proteins expressed in stress alleviation. These technologies have been used to understand the plant–bacterial mechanisms of interaction to combat salt stress.