Alleviation of Salt Stress by Plant Growth-Promoting Bacteria in Hydroponic Leaf Lettuce

Mediterranean areas with intensive agriculture are characterized by high salinity of groundwater. The use of this water in hydroponic cultivations can lead to nutrient solutions with an electrical conductivity that overcomes the tolerance threshold of many vegetable species. Plant growth-promoting rhizobacteria (PGPR) were shown to minimize salt stress on several vegetable crops but the studies on the application of PGPR on leafy vegetables grown in hydroponics are rather limited and have not been used under salt stress conditions. This study aimed to evaluate the use of plant growth-promoting bacteria to increase the salt tolerance of leaf lettuce grown in autumn and spring in a floating system, by adding a bacterial biostimulant (1.5 g L−1 of TNC BactorrS13 a commercial biostimulant containing 1.3 × 108 CFU g−1 of Bacillus spp.) to mineral nutrient solutions (MNS) with two salinity levels (0 and 20 mM NaCl). Leaf lettuce plants showed a significant reduction of growth and yield under salt stress, determined by the reduction of biomass, leaf number, and leaf area. Plants showed to be more tolerant to salinity in autumn than in spring. The inhibition of lettuce plant growth due to salt stress was significantly alleviated by the addition of the bacterial biostimulant to the MNS, which had a positive effect on plant growth and fresh and dry biomass accumulation of the unstressed lettuce in both cultivation seasons, and maintained this positive effect in brackish MNS, with similar or even significantly higher values of morphologic, physiologic, and yield parameters than those recorded in control unstressed plants.

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Plant Growth-Promoting Bacteria: An Emerging Tool for Sustainable Crop Production Under Salt Stress

Bioremediation of Salt Affected Soils: An Indian Perspective ◽

10.1007/978-3-319-48257-6_6 ◽

2017 ◽

pp. 101-131 ◽

Cited By ~ 3

Author(s):

Shiv Ram Singh ◽

Deeksha Joshi ◽

Nidhi Tripathi ◽

Pushpa Singh ◽

Tapendra Kumar Srivastava

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Crop Production ◽

Plant Growth Promoting Bacteria ◽

Sustainable Crop Production ◽

Plant Growth Promoting ◽

Growth Promoting

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Bioprospecting desert plant Bacillus endophytic strains for their potential to enhance plant stress tolerance

Scientific Reports ◽

10.1038/s41598-019-54685-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 8

Author(s):

Ameerah Bokhari ◽

Magbubah Essack ◽

Feras F. Lafi ◽

Cristina Andres-Barrao ◽

Rewaa Jalal ◽

...

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Growth Promotion ◽

Stress Conditions ◽

Desert Plant ◽

Plant Growth Promoting Bacteria ◽

Fresh Weight ◽

Pgp Traits ◽

Plant Growth Promoting ◽

Growth Promoting

AbstractPlant growth-promoting bacteria (PGPB) are known to increase plant tolerance to several abiotic stresses, specifically those from dry and salty environments. In this study, we examined the endophyte bacterial community of five plant species growing in the Thar desert of Pakistan. Among a total of 368 culturable isolates, 58 Bacillus strains were identified from which the 16 most divergent strains were characterized for salt and heat stress resilience as well as antimicrobial and plant growth-promoting (PGP) activities. When the 16 Bacillus strains were tested on the non-host plant Arabidopsis thaliana, B. cereus PK6-15, B. subtilis PK5-26 and B. circulans PK3-109 significantly enhanced plant growth under salt stress conditions, doubling fresh weight levels when compared to uninoculated plants. B. circulans PK3-15 and PK3-109 did not promote plant growth under normal conditions, but increased plant fresh weight by more than 50% when compared to uninoculated plants under salt stress conditions, suggesting that these salt tolerant Bacillus strains exhibit PGP traits only in the presence of salt. Our data indicate that the collection of 58 plant endophytic Bacillus strains represents an important genomic resource to decipher plant growth promotion at the molecular level.

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Rhizobacteria Isolated from Saline Soil Induce Systemic Tolerance in Wheat (Triticum aestivum L.) against Salinity Stress

Agronomy ◽

10.3390/agronomy10070989 ◽

2020 ◽

Vol 10 (7) ◽

pp. 989 ◽

Cited By ~ 2

Author(s):

Noshin Ilyas ◽

Roomina Mazhar ◽

Humaira Yasmin ◽

Wajiha Khan ◽

Sumera Iqbal ◽

...

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Salinity Stress ◽

Plant Biomass ◽

Growth Promotion ◽

Soluble Sugar ◽

Wheat Crop ◽

Plant Growth Promoting Bacteria ◽

Plant Growth Promoting ◽

Growth Promoting

Halo-tolerant plant growth-promoting rhizobacteria (PGPR) have the inherent potential to cope up with salinity. Thus, they can be used as an effective strategy in enhancing the productivity of saline agro-systems. In this study, a total of 50 isolates were screened from the rhizospheric soil of plants growing in the salt range of Pakistan. Out of these, four isolates were selected based on their salinity tolerance and plant growth promotion characters. These isolates (SR1. SR2, SR3, and SR4) were identified as Bacillus sp. (KF719179), Azospirillum brasilense (KJ194586), Azospirillum lipoferum (KJ434039), and Pseudomonas stutzeri (KJ685889) by 16S rDNA gene sequence analysis. In vitro, these strains, in alone and in a consortium, showed better production of compatible solute and phytohormones, including indole acetic acid (IAA), gibberellic acid (GA), cytokinin (CK), and abscisic acid (ABA), in culture conditions under salt stress. When tested for inoculation, the consortium of all four strains showed the best results in terms of improved plant biomass and relative water content. Consortium-inoculated wheat plants showed tolerance by reduced electrolyte leakage and increased production of chlorophyll a, b, and total chlorophyll, and osmolytes, including soluble sugar, proline, amino acids, and antioxidant enzymes (superoxide dismutase, catalase, peroxidase), upon exposure to salinity stress (150 mM NaCl). In conclusion, plant growth-promoting bacteria, isolated from salt-affected regions, have strong potential to mitigate the deleterious effects of salt stress in wheat crop, when inoculated. Therefore, this consortium can be used as potent inoculants for wheat crop under prevailing stress conditions.

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Halotolerant-Koccuria rhizophila (14asp)-Induced Amendment of Salt Stress in Pea Plants by Limiting Na+ Uptake and Elevating Production of Antioxidants

Agronomy ◽

10.3390/agronomy11101907 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1907

Author(s):

Amir Abdullah Khan ◽

Tongtong Wang ◽

Tayyaba Hussain ◽

Amna ◽

Fayaz Ali ◽

...

Keyword(s):

Antioxidant Enzymes ◽

Salt Stress ◽

Plant Growth ◽

Growth Promotion ◽

Antioxidant Systems ◽

Plant Growth Promoting Bacteria ◽

Mineral Contents ◽

Root And Shoot Length ◽

Plant Growth Promoting ◽

Growth Promoting

Endophytic bacteria are useful for their safe services in plant growth improvement and for ameliorating abiotic and biotic stresses. Salt-tolerant plant-growth-promoting Kocuria rhizophila 14asp (accession number KF 875448) was investigated for its role in pea plants under a saline environment. Salt stress (75 mM and 150 mM NaCl) was subjected to two pea varieties, peas2009 and 9800-10, in a greenhouse under a complete randomized design. Different parameters such as plant growth promotion, relative water content, chlorophyll, antioxidants, and mineral contents were analyzed to elucidate the extent of tolerance persuaded by PGPB (plant-growth-promoting bacteria). Exhibition of adverse effects was noticed in uninoculated varieties. However, inoculation of K. rhizophila improved the morphological parameters, antioxidant enzymes, and minimized the uptake of Na+ in plants under various saline regimes. Pea variety 9800-10 exhibited more tolerance than peas2009 in all traits, such as root and shoot length, fresh and dry biomass, chlorophyll contents, and antioxidant enzymes. Our results showed that halotolerant K. rhizophila inoculation plays a vital role in enhancing plant growth by interacting ingeniously with plants through antioxidant systems, enduring saline conditions.

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Isolation of Endophytic Plant Growth-Promoting Bacteria Associated with the Halophyte Salicornia europaea and Evaluation of their Promoting Activity Under Salt Stress

Current Microbiology ◽

10.1007/s00284-016-1096-7 ◽

2016 ◽

Vol 73 (4) ◽

pp. 574-581 ◽

Cited By ~ 55

Author(s):

Shuai Zhao ◽

Na Zhou ◽

Zheng-Yong Zhao ◽

Ke Zhang ◽

Guo-Hua Wu ◽

...

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Plant Growth Promoting Bacteria ◽

Salicornia Europaea ◽

Plant Growth Promoting ◽

Growth Promoting

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Gene expression patterns in shoots of Camelina sativa with enhanced salinity tolerance provided by plant growth promoting bacteria producing 1-aminocyclopropane-1-carboxylate deaminase or expression of the corresponding acdS gene

Scientific Reports ◽

10.1038/s41598-021-83629-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zohreh Heydarian ◽

Margaret Gruber ◽

Cathy Coutu ◽

Bernard R. Glick ◽

Dwayne D. Hegedus

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Acc Deaminase ◽

Camelina Sativa ◽

Fine Tuning ◽

Plant Growth Promoting Bacteria ◽

Salt Stress Response ◽

Expression Of Genes ◽

Plant Growth Promoting ◽

Growth Promoting

AbstractGrowth of plants in soil inoculated with plant growth promoting bacteria (PGPB) producing 1-aminocyclopropane-1-carboxylate (ACC) deaminase or expression of the corresponding acdS gene in transgenic lines reduces the decline in shoot length, shoot weight and photosynthetic capacity triggered by salt stress in Camelina sativa. Reducing the levels of ethylene attenuated the salt stress response as inferred from decreases in the expression of genes involved in development, senescence, chlorosis and leaf abscission that are highly induced by salt to levels that may otherwise have a negative effect on plant growth and productivity. Growing plants in soil treated with Pseudomonas migulae 8R6 negatively affected ethylene signaling, auxin and JA biosynthesis and signalling, but had a positive effect on the regulation of genes involved in GA signaling. In plants expressing acdS, the expression of the genes involved in auxin signalling was positively affected, while the expression of genes involved in cytokinin degradation and ethylene biosynthesis were negatively affected. Moreover, fine-tuning of ABA signaling appears to result from the application of ACC deaminase in response to salt treatment. Moderate expression of acdS under the control of the root specific rolD promoter or growing plants in soil treated with P. migulae 8R6 were more effective in reducing the expression of the genes involved in ethylene production and/or signaling than expression of acdS under the more active Cauliflower Mosaic Virus 35S promoter.

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ACC deaminase in plant growth-promoting bacteria (PGPB): An efficient mechanism to counter salt stress in crops

Microbiological Research ◽

10.1016/j.micres.2020.126439 ◽

2020 ◽

Vol 235 ◽

pp. 126439 ◽

Cited By ~ 13

Author(s):

Ma. del Carmen Orozco-Mosqueda ◽

Bernard R. Glick ◽

Gustavo Santoyo

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Acc Deaminase ◽

Plant Growth Promoting Bacteria ◽

Efficient Mechanism ◽

Plant Growth Promoting ◽

Growth Promoting

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Alleviation of Salt Stress on Wheat (Triticum aestivum L.) by Plant Growth Promoting Bacteria strains Bacillus halotolerans MSR-H4 and Lelliottia amnigena MSR-M49

Journal of Advances in Microbiology ◽

10.9734/jamb/2020/v20i130208 ◽

2020 ◽

pp. 44-58

Author(s):

Ibrahim El-Akhdar ◽

Tamer Elsakhawy ◽

Hanaa A. Abo-Koura

Keyword(s):

Salt Stress ◽

Plant Growth ◽

Crop Production ◽

Halophilic Bacteria ◽

Wheat Plant ◽

Dry Weight ◽

Plant Growth Promoting Rhizobacteria ◽

Plant Growth Promoting Bacteria ◽

Plant Growth Promoting ◽

Growth Promoting

The plant growth-promoting rhizobacteria (PGPR) application could reduce the use of synthetic fertilizers and increase the sustainability of crop production. Halophilic bacteria that have PGPR characteristics can be used in different environmental stresses. Two different strains isolated, purified, characterized as a PGPRs and phylogenetic identification using 16sRNA which was revealed to be closest matched at 99% with Bacillus halotolerans and Lelliottia amnigena. The isolates possessed plant growth promoting properties as exopolysaccharides (EPS) and indole acetic acid (IAA) production, Bacillus halotolerans had the ability to fix elemental nitrogen and the two strains have the ability to P-solubilization. Furthermore, the strains were evaluated in alleviation of different levels of salt stress on wheat plant at two experiments (Pots and a Field). Strains under study conditions significantly increased the plant height, straw dry weight (DW g plant-1), spike number, 1000 grain DW recorded 31.550 g with Lelliottia amnigena MSR-M49 compared to un-inoculated and other strain in field, grain yield recorded 2.77 (ton fed-1) with Lelliottia amnigena as well as N% and protein content in grains recorded 1.213% and 6.916 respectively with inoculation with Lelliottia amnigena, also, spikes length, inoculated wheat show reduction in both proline accumulation in shoots and roots especially with Lelliottia amnigena recorded 2.79 (mg g-1DW), inoculation significantly increased K+ in root-shoot, K+/Na+ in root-shoot and reduced Na+ in root-shoot compared with control. This confirmed that this consortium could provide growers with a sustainable approach to reduce salt effect on wheat production.

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