Halotolerant plant growth-promoting bacteria: Prospects for alleviating salinity stress in plants

As one of the major non-biological stresses, soil salinity negatively affects agricultural productivity, microbial communities, and agricultural economics in impacted areas and is a significant agrarian problem worldwide that has expanded in the last few decades. The use of glycophytes (salt-sensitive plants) is the primary limitation to such an agricultural approach. However, halophytes, which are proficient at obtaining essential micro/macronutrients from exceedingly saline environments and thrive under conditions in which salinity-sensitive crops are either unproductive or inefficient, are prime candidates for utilization in these circumstances. In addition, the bacterial microbiome associated with the roots of halophytic plants is a useful resource for the isolation of salt-tolerant bacteria with multiple plant growth-promoting characteristics, such as the production of different phytohormones, dissolution of insoluble inorganic phosphates, siderophore production, molecular nitrogen fixation, the activity of 1-aminocyclopropane-l-carboxylic acid (ACC) deaminase enzyme, and pathogen suppression, which enhance salinity tolerance of these plants as well as glycophytes and thereby stimulate the growth of plants under salinity-induced stress. The most dominant among reported halotolerant bacterial genera in most of the halophytic plants are Halomonas, Bacillus, Streptomyces, Oceanobacillus, and Pseudomonas. Here, it is shown that a wide range of halotolerant bacteria with a variety of plant growth-promoting characteristics may provide an important resource for augmenting crop tolerance to salinity and thereby boosting saline soil-based agriculture.