To date, soil salinity becomes a huge obstacle for food production worldwide since salt stress is one of the major factors limiting agricultural productivity. It is estimated that a significant loss of crops (20–50%) would be due to drought and salinity. To embark upon this harsh situation, numerous strategies such as plant breeding, plant genetic engineering, and a large variety of agricultural practices including the applications of plant growth-promoting rhizobacteria (PGPR) and seed biopriming technique have been developed to improve plant defense system against salt stress, resulting in higher crop yields to meet human’s increasing food demand in the future. In the present review, we update and discuss the advantageous roles of beneficial PGPR as green bioinoculants in mitigating the burden of high saline conditions on morphological parameters and on physio-biochemical attributes of plant crops via diverse mechanisms. In addition, the applications of PGPR as a useful tool in seed biopriming technique are also updated and discussed since this approach exhibits promising potentials in improving seed vigor, rapid seed germination, and seedling growth uniformity. Furthermore, the controversial findings regarding the fluctuation of antioxidants and osmolytes in PGPR-treated plants are also pointed out and discussed.

Global warming and climate change have contributed to the rise of weather extremes. Severe drought and soil salinization increase because of rising temperatures. Economically important crop production and plant growth and development are hindered when facing various abiotic stresses. Plant endophytic bacteria live inside host plants without causing visible harm and can be isolated from surface-sterilized plant tissues. Using plant endophytic bacteria to stimulate plant growth and increase environmental stress tolerance has become an alternative approach besides using the traditional breeding and genetically modifying approaches to select or create new crop types resistant to different environmental stresses. The plant endophytic bacterium, Priestia megaterium (previously known as Bacillus megaterium) strain BP-R2, was isolated from the surface-sterilized root tissues of the salt marsh halophyte Bolboschoenus planiculmis. The bacteria strain BP-R2 showed high tolerance to different sodium chloride (NaCl) concentrations and produced the auxin plant hormone, indole acetic acid (IAA), under various tested growth conditions. Inoculation of Arabidopsis and pak choi (Brassica rapa L. R. Chinensis Group) plants with the strain BP-R2 greatly enhanced different growth parameters of the host plants under normal and salt and drought stress conditions compared to that of the mock-inoculated plants. Furthermore, the hydrogen peroxide (H2O2) content, electrolyte leakage (EL), and malondialdehyde (MDA) concentration accumulated less in the BP-R2-inoculated plants than in the mock-inoculated control plants under salt and drought stresses. In summary, the plant endophytic bacterium strain BP-R2 increased host plant growth and stress tolerance to salt and drought conditions.

Plant endophytic bacteria live inside host plants, can be isolated from surface-sterilized plant tissues, and are non-pathogenic. These bacteria can assist host plants in obtaining more nutrients and can improve plant growth via multiple mechanisms. Certain Gram-negative Burkholderia species, including rhizobacteria, bioremediators, and biocontrol strains, have been recognized for their plant-growth-promoting abilities, while other isolates have been identified as opportunistic plant or human pathogens. In this study, we observed the auxin production, siderophore synthesis, and phosphate solubilization abilities of B. seminalis strain 869T2. Our results demonstrated that strain 869T2 promoted growth in Arabidopsis, ching chiang pak choi, pak choi, loose-leaf lettuce, romaine lettuce, red leaf lettuce, and Chinese amaranth. Leafy vegetables inoculated with strain 869T2 were larger, heavier, and had more and larger leaves and longer and heavier roots than mock-inoculated plants. Furthermore, inoculations of strain 869T2 into hot pepper caused increased flower and fruit production, and a higher percentage of fruits turned red. Inoculation of strain 869T2 into okra plants resulted in earlier flowering and increased fruit weight. In conclusion, the plant endophytic bacterium Burkholderia seminalis 869T2 exerted positive effects on growth and production in several plant species.

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Heading leafy vegetables (HLVs) are essential horticultural crops that feed many people worldwide. An increasing global population demands more cropping systems, leading to stresses such as fertilizer overuse and soil salination, decreasing in crop productivity and agricultural sustainability. Hence, developing those eco-friendly farming strategies that could simultaneously reduce fertilizer usage and increase crop harvest is urgent for agriculture. An endophytic bacterium Burkholderia seminalis 869T2 with pyrroloquinoline quinone (PQQ) producing ability were applied as biostimulant for vegetable seedlings under greenhouse or field conditions. Two globally important HLVs, cabbage and head lettuce, were preliminarily tested, and further examinations under in-field farming during two different seasons were carried out to develop an endophytic biostimulants (EBs)-assisted lettuce production system. In this study, we confirmed that B. seminalis 869T2 is versatile EBs for HLVs, which significantly promote plant growth and enhance the qualities of crops by increasing the harvested head weight, size and nutrient composition. Nevertheless, the harvest was accelerated by two weeks, together with higher product qualities and 50% fertilizing cost savings per hectare. Our study provides an in-field EBs-assisted management for lettuce production that could decrease costs and increase the product’s value. The results highlight the importance of endophytic bacteria that deserve further investigation due to their enigmatic symbiotic relationships with their hosts and potential usage in the agro-industry.

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To date, soil salinity becomes a huge obstacle for food production worldwide since salt stress in plants is one of the major factors limiting agricultural productivity. It is estimated that a significant loss of crops (20%–50%) would be due to drought and salinity. To embark upon this harsh situation, numerous strategies such as plant breeding, plant genetic engineering, and a large variety of agricultural practices including the applications of plant growth-promoting rhizobacteria (PGPR) and seed biopriming technique have been developed to improve plant defense system against salt stress, resulting in higher crop yields to meet human’s increasing food demand in the future. In the present review, we update and discuss the advantageous roles of beneficial PGPR as green bioinoculants in mitigating the burden of high saline conditions on morphological parameters and on physio-biochemical attributes of plant crops via diverse mechanisms. In addition, the applications of PGPR as a useful tool in seed biopriming technique are also updated and discussed since this approach exhibits promising potentials in improving seed vigor, rapid seed germination, and seedling growth uniformity, Furthermore, the controversial findings regarding the fluctuation of antioxidants and osmolytes in PGPR-treated plants are also pointed out and discussed.