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Plant Growth-Promoting Rhizobacteria Isolated from Degraded Habitat Enhance Drought Tolerance of Acacia (Acacia abyssinica Hochst. ex Benth.) Seedlings.

ABSTRACT: Drought stress (DS) is the most impacting global phenomenon affecting the ecological balance of a particular habitat. The search for potential plant growth-promoting rhizobacteria (PGPR) capable of enhancing plant tolerance to drought stress is needed. Thus, this study was initiated to evaluate the effect of inoculating Acacia abyssinica seedlings with PGPR isolated from rhizosphere soil of Ethiopia to enhance DS tolerance. The strains were selected based on in vitro assays associated with tolerance to drought and other beneficial traits such as salinity, acidity, temperature, heavy metal tolerances, biofilm formation, and exopolysaccharide (EPS) production. The strains with the best DS tolerance ability were selected for the greenhouse trials with acacia plants. The results indicate that out of 73 strains, 10 (14%) were completely tolerant to 40% polyethylene glycol. Moreover, 37% of the strains were strong biofilm producers, while 66 (90.41%) were EPS producers with a better production in the medium containing sucrose at 28 ± 2°C and pH 7 ± 0.2. Strains PS-16 and RS-79 showed tolerance to 11% NaCl. All the strains were able to grow in wider ranges of pH (4-10) and temperature (15-45°C) and had high tolerance to heavy metals. The inoculated bacterial strains significantly (p ≤ 0.05) increased root and shoot length and dry biomass of acacia plants. One of the strains identified as P. fluorescens strain FB-49 was outstanding in enhancing DS tolerance compared to the single inoculants and comparable to consortia. Stress-tolerant PGPR could be used to enhance acacia DS tolerance after testing other phytobeneficial traits.

SUBMITTER: Getahun A

PROVIDER: S-EPMC7646561 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that survive within the range of plant rhizosphere and can promote plant growth. The effects of PGPR in promoting plant growth, activating soil nutrients, reducing fertilizer application, and improving the resistance of plant inducible system have been widely investigated. However, few studies have investigated PGPR as elicitors of tolerance to abiotic stresses, especially drought stress. In this study, the effects of Acinetobacter calcoaceticus X128 on the photosynthetic rate (Pn), stomatal conductance (Gs), intracellular CO2 concentration (Ci), and total chlorophyll content [Chl(a+b)] of Sambucus williamsii Hance seedling leaves under moderate drought stress and drought-rewatering conditions were determined. Compared with those of uninoculated seedlings, the average Pn values during the entire drought stress of inoculated seedlings increased by 12.99%. As the drought duration was lengthened, Ci of uninoculated leaves continued to increase after rapidly declining, whereas Gs continuously decreased. Furthermore, their photosynthetic properties were simultaneously restricted by stomatal and non-stomatal factors. After X128 inoculation, Ci and Gs of S. williamsii Hance leaves continued to decrease, and their photosynthetic properties were mainly restricted by stomatal factors. At the end of the drought stress, water stress reduced [Chl(a?+?b)] of S. williamsii Hance leaves by 13.49%. However, X128 inoculation decreased this deficit to only 7.39%. After water supply was recovered, Pn, Gs, and [Chl(a+b)] in uninoculated leaves were reduced by 14.23%, 12.02%, and 5.86%, respectively, relative to those under well-watered conditions. However, Ci increased by 6.48%. Compared with those of uninoculated seedlings, Pn, Gs, and [Chl(a+b)] in X128-inoculated seedlings were increased by 9.83%, 9.30%, and 6.85%, respectively. Therefore, the inoculation of X128 under arid environments can mitigate the reduction of chlorophyll, delay the restriction caused by non-stomatal factors to Pn in plant leaves under water stress, and can be more conducive to the recovery of photosynthetic functions of leaves after water supply is recovered.

Project description:Switchgrass (Panicum virgatum) is a perennial crop producing deep roots and thus highly tolerant to soil water deficit conditions. However, seedling establishment in the field is very susceptible to prolonged and periodic drought stress. In this study, a "sandwich" system simulating a gradual water deletion process was developed. Switchgrass seedlings were subjected to a 20-day gradual drought treatment process when soil water tension was increased to 0.05 MPa (moderate drought stress) and leaf physiological properties had expressed significant alteration. Drought-induced changes in leaf proteomes were identified using the isobaric tags for relative and absolute quantitation (iTRAQ) labeling method followed by nano-scale liquid chromatography mass spectrometry (nano-LC-MS/MS) analysis. Additionally, total leaf proteins were processed using a combinatorial library of peptide ligands to enrich for lower abundance proteins. Both total proteins and those enriched samples were analyzed to increase the coverage of the quantitative proteomics analysis. A total of 7006 leaf proteins were identified, and 257 (4% of the leaf proteome) expressed a significant difference (p < 0.05, fold change <0.6 or >1.7) from the non-treated control to drought-treated conditions. These proteins are involved in the regulation of transcription and translation, cell division, cell wall modification, phyto-hormone metabolism and signaling transduction pathways, and metabolic pathways of carbohydrates, amino acids, and fatty acids. A scheme of abscisic acid (ABA)-biosynthesis and ABA responsive signal transduction pathway was reconstructed using these drought-induced significant proteins, showing systemic regulation at protein level to deploy the respective mechanism. Results from this study, in addition to revealing molecular responses to drought stress, provide a large number of proteins (candidate genes) that can be employed to improve switchgrass seedling growth and establishment under soil drought conditions (Data are available via ProteomeXchange with identifier PXD004675).

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Plant Growth-Promoting Rhizobacteria Isolated from Degraded Habitat Enhance Drought Tolerance of Acacia (Acacia abyssinica Hochst. ex Benth.) Seedlings.

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