Open AccessArticle

Ameliorating the Drought Stress for Wheat Growth through Application of ACC-Deaminase Containing Rhizobacteria along with Biogas Slurry

Rizwan Yaseen

^1,*,

Omar Aziz

²,

Muhammad Hamzah Saleem

³,

Muhammad Riaz

⁴,

Muhammad Zafar-ul-Hye

¹,

Muzammal Rehman

⁵,

Shafaqat Ali

^6,7,*

Muhammad Rizwan

⁶

Mohammed Nasser Alyemeni

⁸,

Hamed A. El-Serehy

⁹,

Fahad A. Al-Misned

⁹ and

Parvaiz Ahmad

^10,11

Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60800, Pakistan

Department of Soil & Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan

MOA Key Laboratory of Crop Ecophysiology and Farming System Core in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China

⁴

Root Biology Center, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China

⁵

School of Agriculture, Yunnan University, Kunming 650504, China

⁶

Department of Environmental Sciences and Engineering, Government College University, Faisalabad 38000, Pakistan

⁷

Department of Biological Sciences and Technology, China Medical University, Taichung 40402, Taiwan

⁸

Botany and Microbiology Department, College of Science, King Saud University, Riyadh l1451, Saudi Arabia

⁹

Department of Zoology, College of Science, King Saud University, Riyadh l1451, Saudi Arabia

¹⁰

Botany and Microbiology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia

¹¹

Department of Botany, S.P. College, Kothi Bagh, Srinagar 190001, India

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Sustainability 2020, 12(15), 6022; https://doi.org/10.3390/su12156022

Submission received: 17 July 2020 / Revised: 20 July 2020 / Accepted: 23 July 2020 / Published: 27 July 2020

(This article belongs to the Special Issue Advances and Challenges in the Sustainable Water Management)

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Figure 1
Effect of plant growth-promoting rhizobacteria (PGPR) and biogas slurry (BGS) on the photosynthetic (a) and transpiration (b) rates (µmol m−2 s−1) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3). "> Figure 2
Effect of PGPR and BGS on the stomatal conductance (vpm) (a) and sub-stomatal conductance (mmol m−2 s−1) (b) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3). "> Figure 3
Effect of PGPR and BGS on the chlorophyll content (a) and water-use efficiency (b) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3). "> Figure 4
Effect of PGPR and BGS on the catalase (µmol H2O2 min−1 g−1 fw) (a) and ascorbate peroxidase (µmol Ascorbate min−1 mg−1 fw) (b) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3). ">

Versions Notes

Abstract

The temperature increase around the world is leading to generation of drought, which is a big threat to the productivity of crops. Abiotic stresses like drought increase the ethylene level in plants. In higher plants, 1-aminocyclopropane-1-carboxylate (ACC) is considered as the immediate precursor of ethylene biosynthesis. The application of ACC-deaminase (ACCD) possessing rhizobacteria could ameliorate the harmful results of drought stress by transforming ACC into non-harmful products. Biogas slurry (BGS) improves the water-holding capacity and structure of the soil. Thus, we speculated that the integrated application of ACCD possessing rhizobacteria and BGS might be an efficient approach to mitigate the drought stress for better wheat productivity. A field experiment was conducted under skipped irrigation situations. On the tillering stage (SIT) and flowering stage (SIF), the irrigations were skipped, whereas the recommended four irrigations were maintained in the control treatment. The results of this field experiment exposed that the ACCD possessing rhizobacterial inoculations with BGS considerably improved the stomatal and sub-stomatal conductance, transpiration and photosynthetic rates up to 98%, 46%, 38%, and 73%, respectively, compared to the respective uninoculated controls. The Pseudomonas moraviensis with BGS application improved the grain yield and plant height up to 30.3% and 24.3%, respectively, where irrigation was skipped at the tillering stage, as compared to the uninoculated controls. The data obtained revealed that the P. moraviensis inoculation + BGS treatment significantly increased the relative water content (RWC), catalase (CAT) activity, ascorbate peroxidase (APX) activity, as well as grain and shoot phosphorus contents, up to 37%, 40%, 75%, 19%, and 84%, respectively, at SIF situation. The results depicted that the P. moraviensis with BGS application under drought stress could be applied for enhancing the physiological, yield, and growth attributes of wheat.

Keywords:

organic matter; PGPR; antioxidant activity; skipped irrigation

1. Introduction

Climate change is posing serious threats to worldwide food security. Sustainable crop production has become a big challenge. Owing to rapid changes in rainfall patterns and temperature, crop productivity and yields are going to decline [1,2,3]. Worldwide, drought stress is considered as the most imperative crop production limiting factor. Drought stress induces limited supply of water [4], reduces photosynthesis [5], causes hormonal imbalances [6], and hampers mineral uptake [7], which eventually lead to a reduction in plant yield [8,9]. Moreover, drought stress accelerates ethylene biosynthesis, which reduces root development and elongation [10].

The plant growth-promoting rhizobacteria (PGPR) provides tolerance to plants against drought and enhance crop productivity [11,12]. The drought-tolerant PGPR provide systemic resistance and endorse plant growth [13,14]. Under drought stress, ethylene biosynthesis regularization has been observed by using PGPR producing ACC-deaminase (ACCD) [15]. The ACCD producing PGPR cleave ACC into α-ketobutyrate and ammonia [16,17]. Besides ethylene regularization, the PGPR also endorse growth of plants by manipulating and modifying the synthesis of phytohormones (cytokinins, auxins, or gibberellic acid) [14], development of better root architecture for increasing the water uptake [16], increasing the nutrients uptake by roots [4], and exopolysaccharides production [18].

However, to mitigate the drought-stress effects, the imperative role of organic amendments to improve the availability of nutrients and the soil’s water-holding capacity cannot be denied. Biogas slurry (BGS) is derived from the anaerobic decomposition of plant biomass and organic waste in a biogas digester, which is converted into biofuels [19]. BGS is one of the organic fertilizers that could enhance the fertility of soil and thus crop production [20,21]. BGS also contains abundant nutrients, amino acids, and bioactive substances [22]. The dried form of BGS could increase soil fertility and organic matter, which resultantly increase crop productivity [23]. The PGPR application with organic amendments increased the yield, quality, and growth of peanut [24,25], cucumber [26], and mung bean [27] through reducing the abiotic stress hazards [28]. The combined application of PGPR with BGS improve the quality and yield of the crops and soil health [29,30]. The integrated application of organic wastes and rhizobacteria is helpful in increasing the available potassium, phosphorus, nitrogen, sequestered organic carbon, soil pH, and also crop production [11,27,31].

Wheat (Triticum aestivum L.) is widely cultivated, spanning 17% of the world’s arable land [32]. Throughout the world, the demand for wheat has increased up to 510 million tons, increasing with the population growth rate [33,34]. Wheat cultivation under limited supply of water considerably reduces its productivity. However, wheat demand is increasing with population growth. Therefore, it is time to increase the productivity of wheat in drought-stressed areas.

To date, there is no report demonstrating the role of BGS in ameliorating water-deficit stress. In the recent past, the scientists concentrated on the application of ACCD producing PGPR for mitigating the water-deficit stress. The aim and novelty of the current experiment are to observe the integrated effects of BGS and PGPR producing ACCD for the mitigation of drought stress. The current study was conducted with the supposition that the combined effect of BGS and drought-tolerant PGPR producing ACCD could be very effective in alleviating the drought-stress effect for enhancing wheat productivity.

2. Materials and Methods

A field experiment was conducted on an experimental farm of the Department of Soil Science, Bahauddin Zakariya University, Multan, Pakistan, to evaluate the effectiveness of ACCD producing PGPR and BGS for improving the antioxidant activities, physiology, growth, and agronomic yield of wheat.

2.1. Pre-Sowing Soil Analysis

The physico-chemical properties of composite soil samples were noted before sowing of the crop (Table 1). The electrical conductivity (EC_e) and soil pH (pH_s) were determined [35]. The organic matter contents were found out through the Walkley [36] methodology. The available phosphorus was assessed through the Olsen and Sommers [37] methodology, whereas for extractable potassium the Chapman and Pratt [38] method was applied. The Moodie et al. [39] protocol was followed in the determination of soil texture. For soil free lime content (CaCO₃) determination, the procedure described by Allison and Moodie [39] was followed.

2.2. Experimental Setup

Three PGPR containing ACCD, i.e., Pseudomonas moraviensis, Bacillus amyloliquefaciens, and Alcaligenes faecalis, along with the BGS, were used in the experiment. The irrigation was skipped at the tillering (SIT) and flowering (SIF) stages of the crop while there were four irrigations applied during normal irrigation (NI). These treatments were arranged in three replications under a randomized complete block design (RCBD), with three factorial arrangements. Both inoculated and uninoculated seeds were drilled in plots having a size of 15 m² in a well-prepared field. The BGS was collected and air-dried and applied according to the treatment plan. Fertilization was done by applying a recommended dose of NPK as 120, 90, and 60 kg ha⁻¹, using urea, triple super phosphate, and a muriate of potash, respectively. At the time of field preparation, the total P and K fertilizers were applied, whereas the urea was broadcasted in three split doses (1/3 before sowing, 1/3 at tillering, and 1/3 at the flowering stages of the wheat crop).

2.3. Preparation of Rhizobacterial Inocula and Seed Inoculation and Biogas Slurry

The rhizobacterial inocula were prepared in Dworkin and Foster (DF) salt minimal medium in 500 mL Erlenmeyer flasks [40]. A loopful of the respective strains were inoculated in flasks containing DF salt minimal media. These flasks were left at 28 ± 2 °C temperature for 72 h at 100 rpm in a shaking incubator. A uniform population 10⁷–10⁸ CFU mL⁻¹ of rhizobacteria were obtained by adding sterilized distilled water at a 540 nm wavelength by using a spectrophotometer (Biotechnology Medical Services, UV-1602, BMS, Canada). Wheat seeds were inoculated with the respective rhizobacterial inoculum. The sterilized clay, sugar solution (10%), and peat were used for seed dressing. The BGS was acquired from a biogas plant working in Ferozpur, Multan, Pakistan. The BGS was analyzed [41] with a pH of 7.5 and EC of 2.95 dS m⁻¹, as well as a 1.04% total potassium, 1.75% total phosphorus, 1.45% total nitrogen, and 38.5% organic carbon concentration.

2.4. Characteristics of the PGPR Strains

The El-Tarabily [42] methodology was followed to measure the ACC-deaminase activity of the rhizobacteria. The indole acetic acid (IAA) production was measured with and without L-tryptophan in broth media on a spectrophotometer [43]. The Goldstein [44] methodology was followed for assessing the phosphorus solubilizing ability of the rhizobacterial strains. The exopolysaccharides production ability of the rhizobacterial strains were noted [45]. The MacFaddin [46] methodology was used to observe the catalase activity. The characteristics of the PGPR strains are provided in Table 2.

2.5. Plant Physiological Parameters

The physiological attributes of the fully expanded wheat flag leaves were observed at 10:30 a.m.–12:30 p.m. by using a Portable Infrared Gas Analyzer (LCA-4, Germany). The photosynthetic photon flux density of the IRGA was 1200–1400 lmol m⁻²s⁻¹ for determining the stomatal conductance, substomatal conductance, transpiration, and photosynthetic rates. The SPAD chlorophyll meter (SPAD–502, Konika-Minolta, Japan) was used to measure the chlorophyll contents at the stage of flowering and tillering [47]. Water-use efficiency was measured by dividing the transpiration rate by the photosynthetic rate.

2.6. Relative Water Content, Electrolyte Leakage, Total Phenolics, and Proline in Plant Leaves

The relative water content (RWC) of the leaves was measured by putting them in 10 mL test tubes in the fridge for 48 h at 4 °C [48]. Then fully turgid and dry weights were calculated. The RWC was calculated by using formula as follows:

RWC (%) = \frac{Fully turgid weight - Dry weight}{Fresh weight - Dry weight} \times 100

(1)

The electrolyte leakage (EL) in the leaves was noted according to the methodology used by Jambunathan [49].

The uniform leaves discs were placed in 10 mL test tubes with distilled (DI) water and vortexed for 2 h. Then the electrical conductivity (EC₀) was measured. These test tubes were put in a fridge overnight and another electrical conductivity (EC₁) reading was measured. At a 121 °C temperature, the test tubes were autoclaved for 20 min. After cooling the medium, the final electrical conductivity reading (EC₂) was taken. For determining the EL of the wheat leaves, the following formula was used:

EL (%) = \frac{{EC}_{1} - {EC}_{0}}{{EC}_{2} - {EC}_{0}} \times 100

(2)

The Giannakoula et al. [50] protocol was followed in the determination of total phenolics, by mixing the 100 µL Folin-Ciocalteu reagent (0.25 N) and 20 µL crude leaf extract and adding 0.2 M Na₂CO₃ solution (100 µL). The sample was incubated at room temperature for two hours and the optical density was noted at 760 nm. Total phenolics were calculated according to a standard curve of Gallic acid.

The proline contents in the fresh tissues were determined by grounding them with 3% sulfosalicylic acid. After centrifugation, the 2 mL supernatant was mixed in 10 mL of ninhydrin acid and acetic acid and boiled for 60 min. Toluene was added after cooling, and at 520 nm the absorbance of the mixture was noted by a spectrophotometer [51].

2.7. Enzymatic Antioxidant Activity Assay

The catalase (CAT) activity was measured in a reaction mixture containing the crude leaf extract, H₂O₂ solution (10 mM), and KH₂PO₄ buffer (50 m M). The H₂O₂ reduction was measured at 240 nm absorbance for three minutes at 25 ± 2 °C [52].

The ascorbate peroxidase (APX) enzyme activity was measured in a reaction mixture containing the crude leaf extract, H₂O₂ solution (10 mM), ascorbic acid solution (660 µL), and KH₂PO₄ buffer (50 mM). The H₂O₂ reduction was measured at 290 nm absorbance for three minutes at 25±2 °C by a spectrophotometer [53].

2.8. Measurement of Growth and Yield Parameters and Mineral Nutrients of Plant

The plant height (cm) and number of tillers (m⁻¹), as well as the straw, grain, biological yield, and 1000-grain weight (g) were collected at crop harvest. The Kjeldahl method was used to determine the nitrogen concentration. The phosphorus contents were measured by using the standard method used by Chapman and Prat [38]. A flame photometer (Jenway PFP-7, UK) was used for determining the potassium contents [41].

2.9. Statistical Analysis

Three-way analysis of variance (ANOVA) was used to analyze the data and the RCBD design was followed in the experiment [54]. “Statistix 9.0^®”, a computer-based statistical software, was used for analyzing the data. For comparing the significance of the treatments, the HSD test was applied at a 5% probability (p < 0.05).

3. Results

3.1. Growth Physiology

The results showed that the combined use of rhizobacteria with BGS significantly increased the photosynthetic rate compared to the uninoculated control (no BGS) at SIT and SIF (Figure 1a). At SIT and SIF, the photosynthetic rate was increased up to 73.8% and 72.9%, respectively, with the P. moraviensis + BGS treatment compared to the uninoculated control. The transpiration rate was significantly increased up to 38% and 36%, respectively, due to the effect of the ACCD rhizobacteria + BGS at SIT and SIF with respect to their corresponding uninoculated controls (Figure 1b). The P. moraviensis + BGS gave a significant improvement in stomatal conductance of the wheat leaves during NI and under the SIT and SIF situations, i.e., up to 68%, 58%, and 73%, respectively, compared to their respective uninoculated controls (Figure 2a). P. moraviensis, B. amyloliquefaciens, and A. faecalis showed that the substomatal conductance was significantly improved at SIT and SIF (Figure 2b).

The ACCD containing rhizobacterial strains showed high chlorophyll contents with the BGS application in wheat flag leaves (Figure 3a). However, drought stress significantly reduced the chlorophyll contents both in the uninoculated and inoculated plants. The chlorophyll contents were maximally increased up to 15% and 26% at SIF and SIT, respectively, due to the P. moraviensis inoculation. The water-use efficiency was increased up to 39% in B. amyloliquefaciens + BGS compared to the uninoculated control (Figure 3b), which significantly mitigated the effect of the drought stress.

3.2. Relative Water Content, Electrolyte Leakage, Proline Content, and Total Phenolic Content

The data showed that the RWC in the wheat flag leaves was significantly increased with PGPR inoculations and BGS (Table 3). The P. moraviensis inoculation + BGS treatment showed that, at the SIT situation, the RWC increased up to 37.6%, and at the SIF situation, increased up to 35.9% compared to their corresponding controls. In contrast to RWC, the EL was significantly reduced with the application of PGPR with BGS at the SIF and SIT situations (Table 3). A significant reduction in EL was seen with the P. moraviensis + BGS, i.e., up to 34% at SIT and up to 25% at SIF compared to their respective controls.

The proline and total phenolic contents were reduced significantly compared to their respective uninoculated and unamended controls in the inoculated wheat plant’s leaves (Table 3). The treatment P. moraviensis + BGS decreased the total phenolic contents up to 45% and 33% at SIT and SIF, respectively. Similarly, the P. moraviensis inoculation with BGS decreased the proline content about 43.7% at the SIF stage and up to 47.4% at the SIT stage compared to the corresponding uninoculated controls.

3.3. The Enzymatic Antioxidant Activity

The rhizobacterial inoculation alone and with BGS interaction significantly increased the CAT and APX contents in wheat (Figure 4a,b). The CAT activity was observed as at its maximum at the SIT situation. The CAT activity was maximally increased up to 72.4% and 40.5% at the SIF and SIT stages due to the P. moraviensis with BGS amendment compared to their respective controls. The APX was also significantly increased with the P. moraviensis inoculation with BGS amendment at normal and skipped irrigation situations (SIT and SIF). At the SIT stage, a significant increase (42.4%) was noted in APX activity with a P. moraviensis inoculation with BGS amendment compared to the unamended control. The APX contents were significantly increased at the SIF stage up to 75.1%, 47.1%, and 43.8% with the P. moraviensis, A. faecalis, and B. amyloliquefaciens application, respectively, compared to the uninoculated controls.

3.4. Growth and Agronomic Yield

The data of the field experiment presented in Table 4 showed that the ACC-deaminase possessing PGPR inoculation with BGS application improved the plant height under drought conditions. Under drought conditions created by SIT, the P. moraviensis + BGS treatment revealed up to a 24.3% increase compared to the uninoculated control in plant height. However, at SIF, the maximum plant height was increased (10.6%) with the B. amyloliquefaciens + BGS treatment compared to the control. At the NI situation, the number of tillers was increased up to 64% with the A. faecalis + BGS treatment compared to the uninoculated control (Table 4). As the SIT stage, B. amyloliquefaciens + BGS significantly increased (up to 22.9%) the number of tillers and mitigated the drought effects. Table 4 shows that the PGPR strains with BGS significantly enhanced the biological, grain, and straw yield, as well as the 1000-grain weight. At the NI, SIT and SIF stages, the straw yield was increased up to 13.8%, 24.3%, and 11.8% with P. moraviensis + BGS, respectively, compared to their respective uninoculated controls.

3.5. Mineral Nutrition

The data obtained from the field trial revealed that the nitrogen, phosphorus, and potassium contents were increased at all drought levels in the straw and grain of wheat acquired by PGPR inoculations with BGS application (Table 5). Nitrogen contents in the shoot and grain were improved significantly up to 32.3% and 31.7%, respectively, at NI with P. moraviensis + BGS compared to their respective uninoculated controls. The shoot and grain nitrogen were considerably raised up to 38.8% and 39.7%, respectively, with the P. moraviensis + BGS treatment compared to their corresponding uninoculated controls at the SIT situation.

The P. moraviensis with BGS application acquired an improvement at the SIF, SIT, and NI stages in grain phosphorus contents up to 19.4%, 24.3%, and 26.6%, respectively, compared to their respective uninoculated controls. The A. faecalis + BGS also acquired shoot phosphorus increments up to 84%, 80%, and 31% at the SIF, SIT and NI situations, respectively, compared to their respective uninoculated controls of wheat. The P. moraviensis + BGS revealed a significant increment in potassium content in wheat shoot (42.8%) and grains (48.8%) compared to their uninoculated controls at the SIT stage.

4. Discussion

Drought stress inhibits the production as well as growth of wheat. Under drought stress, the effect of a BGS application has remained unexplored up to date. The integrated application of ACCD containing rhizobacteria with BGS as an organic amendment for enhancing wheat productivity has been rarely exploited.

The data revealed that the growth of the uninoculated plants was severely influenced due to drought stress. Whereas, the growth, physiology, and productivity of the wheat plants was efficiently improved with the use of ACCD possessing rhizobacterial inoculation amended with BGS. Hussain et al. [4] reported that the ACCD possessing rhizobacteria had significantly improved the root length, proposing a positive influence of ACCD activity under stress conditions. Chandra et al. [55] described that the ACCD possessing rhizobacteria have specific capabilities to hydrolyze the ACC biosynthesis in roots. Under stress conditions, the ACCD containing rhizobacteria decreased the biosynthesis of stress ethylene, which enhances the induced systemic tolerance in plants [56,57,58].

The growth and yield parameters of wheat were improved, which might be due to better root growth, eventually increasing the water and nutrient uptake. The synergistic effects of the ACCD activity and auxin of rhizobacteria might be the crucial factors that contributed to root proliferation during drought stress [59]. Beside this, the rhizobacterial strains produce exopolysaccharides that create a biofilm on the root surface that could enhance the nutrients and water [18,60].

The valuable influence of a BGS amendment and inoculations of rhizobacteria were also obvious given the increased physiological parameters compared to the uninoculated controls. However, drought stress adversely affected these gaseous exchange attributes by decreasing the energy utilization capacity [61,62]. The results obtained from the experiment showed that the integrated application of BGS and ACCD possessing rhizobacteria increased the stomatal conductance and transpiration rate, which increased the photosynthetic rate as described by Naveed et al. [63] and Ahmad et al. [64].

Owing to a decrease in RWC, turgor pressure and cell expansion were reduced [65]. The EL in the leaves was increased under the stressed conditions [66,67,68]. Whereas, with the integrated application of the BGS and ACCD possessing rhizobacteria, the EL was reduced, showing an increment in relative tolerance [69]. This might be due to the application of the BGS that increased the hydraulic conductivity, water-holding capacity, structure, and volumetric moisture content of the soil [70,71,72]. The chlorophyll contents in the wheat flag leaves were increased due to ACCD possessing rhizobacteria that might suppress ethylene biosynthesis under drought stress [4,73,74].

The total phenolic and proline contents could maintain cellular turgor and reduce the water potential. The proline and total phenolic contents were significantly higher under drought stress in the leaves of wheat plants that were not inoculated [75,76]. Whereas, with the integrated application of the BGS and ACCD possessing rhizobacteria, the proline and total phenolic contents were reduced compared to the uninoculated controls. Naveed et al. [63] also described that under stress conditions the proline contents were increased, but reduced with ACCD possessing rhizobacterial treatments. The APX and CAT enzymes in wheat plants were increased in the rhizobacterial inoculated treatments. Our findings were correlated with the results of Sandhya et al. [77], who noted that the ACC level was decreased in the root zone due to the ACCD activity of the rhizobacterial strains.

Under water-deficit stress, the concentrations of N, P, and K were increased in the grains and straw due to the integrated application of the BGS and ACCD rhizobacteria. This could be due to root proliferation. That resulted in the efficient uptake of nutrients and the production of more root biomass, which exploited more soil volume. The rhizobacteria might have enhanced the solubility of the mineral nutrients due to the production of organic acids and siderophores and an increase in phosphorus solubilization activity in the rhizosphere of plants [74,78]. The BGS application also enhanced the nutrient uptake and biomass yield [70].

5. Conclusions

It can be inferred from the present study that the integrated application of BGS and ACCD possessing rhizobacteria gave better results as compared to their separate application. Our observations depicted that the combined application of BGS and rhizobacteria with ACCD activity could be an effective approach for increasing the productivity of wheat under drought conditions. The ACC-deaminase containing rhizobacteria has a better potential to be used as a biofertilizer and could be used to increase wheat productivity in arid regions. The Pseudomonas moraviensis strain showed more effectiveness in enhancing the yield as compared to other strains. The future perspectives include that these rhizobacteria with ACCD activity should be studied in other crop species. Consortia of these rhizobacteria should be explored to get their maximum benefits and roles in nutrient cycling.

Author Contributions

Conceptualization, M.N.A.; data curation, R.Y., O.A., M.H.S., M.R. (Muhammad Riaz), M.R. (Muhammad Rizwan), M.N.A. and H.A.E.-S.; formal analysis, M.R. (Muhammad Riaz) and M.Z.-u.-H.; funding acquisition, O.A., M.R. (M.R.), S.A., H.A.E.-S., F.A.A.-M. and P.A.; investigation, O.A., M.R. (Muhammad Riaz), M.R. (Muhammad Rizwan) and M.N.A.; methodology, M.H.S. and M.R. (Muzammal Rehman); project administration, M.Z.-u.-H. and M.N.A.; resources, M.H.S., S.A., F.A.A.-M. and P.A.; software, M.H.S., M.Z.-u.-H., S.A. and P.A.; supervision, S.A. and P.A.; visualization, M.R. (Muzammal Rehman), H.A.E.-S. and F.A.A.-M.; writing—original draft, R.Y., O.A., M.R. (Muhammad Riaz) and M.Z.-u.-H.; writing—review & editing, R.Y., M.R. (Muzammal Rehman), M.R. (Muhammad Rizwan), H.A.E.-S. and F.A.A.-M. All authors have read and agreed to the published version of the manuscript.

Funding

The authors would like to extend their sincere appreciation to the Researchers Supporting Project Number (RSP-2020/19), King Saud University, Riyadh, Saudi Arabia. The authors are also grateful to Higher Education Commission (HEC) Islamabad, Pakistan for its support.

Acknowledgments

The authors would like to extend their sincere appreciation to the Researchers Supporting Project Number (RSP-2020/19), King Saud University, Riyadh, Saudi Arabia. The authors highly acknowledge the Bahauddin Zakariya University Multan, Pakistan, for its support.

Conflicts of Interest

The authors declare that there is no conflict of interest.

Abbreviations

ACC	1-Aminocyclopropane-1-carboxylate
ACCD	ACC-deaminase
ANOVA	Analysis of variance
BGS	Biogas slurry
CAT	Catalase
CFU	Colony forming unit
EC	Electrical conductivity
EL	Electrolyte leakage
HSD	Honest Significant Difference
IAA	Indole acetic acid
NI	Normal irrigation
PGPR	Plant growth promoting rhizobacteria
ppm	Parts per million
RCBD	Randomized complete block design
rpm	Resolution per minute
RWC	Relative water content
SIF	Skipped irrigation flowering stage
SIT	Skipped irrigation tillering stage
WUE	Water-use efficiency

References

Saleem, M.H.; Ali, S.; Rehman, M.; Hasanuzzaman, M.; Rizwan, M.; Irshad, S.; Shafiq, F.; Iqbal, M.; Alharbi, B.M.; Alnusaire, T.S. Jute: A potential candidate for phytoremediation of metals—A review. Plants 2020, 9, 258. [Google Scholar] [CrossRef] [Green Version]
Saleem, M.H.; Ali, S.; Seleiman, M.F.; Rizwan, M.; Rehman, M.; Akram, N.A.; Liu, L.; Alotaibi, M.; Al-Ashkar, I.; Mubushar, M. Assessing the correlations between different traits in copper-sensitive and copper-resistant varieties of jute (Corchorus capsularis L.). Plants 2019, 8, 545. [Google Scholar] [CrossRef] [PubMed] [Green Version]
Rehman, M.; Liu, L.; Bashir, S.; Saleem, M.H.; Chen, C.; Peng, D.; Siddique, K.H. Influence of rice straw biochar on growth, antioxidant capacity and copper uptake in ramie (Boehmeria nivea L.) grown as forage in aged copper-contaminated soil. Plant Physiol. Biochem. 2019, 138, 121–129. [Google Scholar] [CrossRef] [PubMed]
Hussain, M.; Farooq, S.; Hasan, W.; Ul-Allah, S.; Tanveer, M.; Farooq, M.; Nawaz, A. Drought stress in sunflower: Physiological effects and its management through breeding and agronomic alternatives. Agric. Water Manag. 2018, 201, 152–166. [Google Scholar] [CrossRef]
Rivas, R.; Falcão, H.; Ribeiro, R.; Machado, E.; Pimentel, C.; Santos, M. Drought tolerance in cowpea species is driven by less sensitivity of leaf gas exchange to water deficit and rapid recovery of photosynthesis after rehydration. S. Afr. J. Bot. 2016, 103, 101–107. [Google Scholar] [CrossRef]
Sharma, A.; Wang, J.; Xu, D.; Tao, S.; Chong, S.; Yan, D.; Li, Z.; Yuan, H.; Zheng, B. Melatonin regulates the functional components of photosynthesis, antioxidant system, gene expression, and metabolic pathways to induce drought resistance in grafted Carya cathayensis plants. Sci. Total Environ. 2020, 136675. [Google Scholar] [CrossRef] [PubMed]
Canavar, Ö.; Kaptan, M.A. Changes In macro and micro plant nutrients of sunflower (Helianthus annuus L.) under drought stress. Sci. Pap. Ser. A. Agron. 2014, 57, 1. [Google Scholar]
Fahad, S.; Bajwa, A.A.; Nazir, U.; Anjum, S.A.; Farooq, A.; Zohaib, A.; Sadia, S.; Nasim, W.; Adkins, S.; Saud, S. Crop production under drought and heat stress: Plant responses and management options. Front. Plant Sci. 2017, 8, 1147. [Google Scholar] [CrossRef] [Green Version]
Khan, M.N.; Zhang, J.; Luo, T.; Liu, J.; Rizwan, M.; Fahad, S.; Xu, Z.; Hu, L. Seed priming with melatonin coping drought stress in rapeseed by regulating reactive oxygen species detoxification: Antioxidant defense system, osmotic adjustment, stomatal traits and chloroplast ultrastructure perseveration. Ind. Crops Prod. 2019, 140, 111597. [Google Scholar] [CrossRef]
Kulkarni, M.; Phalke, S. Evaluating variability of root size system and its constitutive traits in hot pepper (Capsicum annum L.) under water stress. Sci. Hortic. 2009, 120, 159–166. [Google Scholar] [CrossRef]
Saleem, M.H.; Fahad, S.; Adnan, M.; Ali, M.; Rana, M.S.; Kamran, M.; Ali, Q.; Hashem, I.A.; Bhantana, P.; Ali, M.; et al. Foliar application of gibberellic acid endorsed phytoextraction of copper and alleviates oxidative stress in jute (Corchorus capsularis L.) plant grown in highly copper-contaminated soil of China. Environ. Sci. Pol. Res. 2020. [Google Scholar] [CrossRef] [PubMed]
Saleem, M.H.; Ali, S.; Kamran, M.; Iqbal, N.; Azeem, M.; Tariq Javed, M.; Ali, Q.; Zulqurnain Haider, M.; Irshad, S.; Rizwan, M. Ethylenediaminetetraacetic Acid (EDTA) Mitigates the Toxic Effect of Excessive Copper Concentrations on Growth, Gaseous Exchange and Chloroplast Ultrastructure of Corchorus capsularis L. and Improves Copper Accumulation Capabilities. Plants 2020, 9, 756. [Google Scholar] [CrossRef] [PubMed]
Kasim, W.A.; Osman, M.E.; Omar, M.N.; El-Daim, I.A.A.; Bejai, S.; Meijer, J. Control of drought stress in wheat using plant-growth-promoting bacteria. J. Plant Growth Regul. 2013, 32, 122–130. [Google Scholar] [CrossRef]
Yaseen, R.; Zafar-ul-Hye, M.; Hussain, M. Integrated application of ACC-deaminase containing plant growth promoting rhizobacteria and biogas slurry improves the growth and productivity of wheat under drought stress. Int. J. Agric. Biol. 2019, 21, 869–878. [Google Scholar]
Vurukonda, S.S.K.P.; Vardharajula, S.; Shrivastava, M.; SkZ, A. Enhancement of drought stress tolerance in crops by plant growth promoting rhizobacteria. Microbiol. Res. 2016, 184, 13–24. [Google Scholar] [CrossRef]
Kaushal, M.; Wani, S.P. Plant-growth-promoting rhizobacteria: Drought stress alleviators to ameliorate crop production in drylands. Ann. Microbiol. 2016, 66, 35–42. [Google Scholar] [CrossRef]
Raghuwanshi, R.; Prasad, J.K. Perspectives of rhizobacteria with ACC deaminase activity in plant growth under abiotic stress. In Root Biology; Springer: Berlin/Heidelberg, Germany, 2018; pp. 303–321. [Google Scholar]
Vanderlinde, E.M.; Harrison, J.J.; Muszyński, A.; Carlson, R.W.; Turner, R.J.; Yost, C.K. Identification of a novel ABC transporter required for desiccation tolerance, and biofilm formation in Rhizobium leguminosarum bv. viciae 3841. FEMS Microbiol. Ecol. 2010, 71, 327–340. [Google Scholar] [CrossRef] [Green Version]
Maqbool, S.; Ul Hassan, A.; JavedAkhtar, M.; Tahir, M. Integrated use of biogas slurry and chemical fertilizer to improve growth and yield of okra. Sci. Lett. 2014, 2, 56–59. [Google Scholar]
Chen, R.; Blagodatskaya, E.; Senbayram, M.; Blagodatsky, S.; Myachina, O.; Dittert, K.; Kuzyakov, Y. Decomposition of biogas residues in soil and their effects on microbial growth kinetics and enzyme activities. Biomass Bioenergy 2012, 45, 221–229. [Google Scholar] [CrossRef]
Islam, F.; Yasmeen, T.; Arif, M.S.; Ali, S.; Ali, B.; Hameed, S.; Zhou, W. Plant growth promoting bacteria confer salt tolerance in Vigna radiata by up-regulating antioxidant defense and biological soil fertility. Plant. Growth Regul. 2016, 80, 23–36. [Google Scholar] [CrossRef]
Liu, W.K.; Yang, Q.-C.; Du, L. Soilless cultivation for high-quality vegetables with biogas manure in China: Feasibility and benefit analysis. Renew. Agric. Food Syst. 2009, 24, 300–307. [Google Scholar] [CrossRef]
Islam, M.R.; Rahman, S.M.E.; Rahman, M.M.; Oh, D.H.; Ra, C.S. The effects of biogas slurry on the production and quality of maize fodder. Turk. J. Agric. For. 2010, 34, 91–99. [Google Scholar]
Parveen, A.; Saleem, M.H.; Kamran, M.; Haider, M.Z.; Chen, J.-T.; Malik, Z.; Rana, M.S.; Hassan, A.; Hur, G.; Javed, M.T. Effect of citric acid on growth, ecophysiology, chloroplast ultrastructure, and phytoremediation potential of jute (Corchorus capsularis L.) seedlings exposed to copper stress. Biomolecules 2020, 10, 592. [Google Scholar] [CrossRef] [PubMed]
Kamran, M.; Parveen, A.; Ahmar, S.; Malik, Z.; Hussain, S.; Chattha, M.S.; Saleem, M.H.; Adil, M.; Heidari, P.; Chen, J.-T. An overview of hazardous impacts of soil salinity in crops, tolerance mechanisms, and amelioration through selenium supplementation. Int. J. Mol. Sci. 2019, 21, 148. [Google Scholar] [CrossRef] [Green Version]
Ahamd, M.; Zeshan, M.S.H.; Nasim, M.; Zahir, Z.A.; Nadeem, S.M.; Nazli, F.; Jamil, M. Improving the productivity of cucumber through combined application of organic fertilizers and pseudomonas fluorescens. Pak. J. Agric. Sci. 2015, 52, 1011–1016. [Google Scholar]
Iqbal, M.A.; Khalid, M.; Zahir, Z.A.; Ahmad, R. Auxin producing plant growth promoting rhizobacteria improve growth, physiology and yield of maize under saline field conditions. Int. J. Agric. Biol. 2016, 18, 37–45. [Google Scholar] [CrossRef]
Jabeen, N.; Ahmad, R. Growth response and nitrogen metabolism of sunflower (Helianthus annuus L.) to vermicompost and biogas slurry under salinity stress. J. Plant Nutr. 2017, 40, 104–114. [Google Scholar] [CrossRef]
Tan, F.; Wang, Z.; Zhouyang, S.; Li, H.; Xie, Y.; Wang, Y.; Zheng, Y.; Li, Q. Nitrogen and phosphorus removal coupled with carbohydrate production by five microalgae cultures cultivated in biogas slurry. Bioresour. Technol. 2016, 221, 385–393. [Google Scholar] [CrossRef]
Chen, G.; Zhao, G.; Zhang, H.; Shen, Y.; Fei, H.; Cheng, W. Biogas slurry use as N fertilizer for two-season Zizania aquatica Turcz. Nutr. Cycl. Agroecosyst. 2017, 107, 303–320. (In Chinese) [Google Scholar] [CrossRef]
Wu, S.; He, H.; Inthapanya, X.; Yang, C.; Lu, L.; Zeng, G.; Han, Z. Role of biochar on composting of organic wastes and remediation of contaminated soils—A review. Environ. Sci. Pollut. Res. 2017, 24, 16560–16577. [Google Scholar] [CrossRef]
Ayers, R.; Westcot, D. Water Quality for Agriculture; FAO: Roma, Italy, 1985; Available online: http://www.fao.org/DOCReP/003/T0234e/T0234E00.htm (accessed on 23 July 2020).
Zafar, S.; Hasnain, Z.; Anwar, S.; Perveen, S.; Iqbal, N.; Noman, A.; Ali, M. Influence of melatonin on antioxidant defense system and yield of wheat (Triticum aestivum L.) genotypes under saline condition. Pak. J. Bot. 2019, 51, 1987–1994. [Google Scholar] [CrossRef] [Green Version]
Imran, M.; Sun, X.; Hussain, S.; Ali, U.; Rana, M.S.; Rasul, F.; Saleem, M.H.; Moussa, M.G.; Bhantana, P.; Afzal, J. Molybdenum-induced effects on nitrogen metabolism enzymes and elemental profile of winter wheat (Triticum aestivum L.) under different nitrogen sources. Int. J. Mol. Sci. 2019, 20, 3009. [Google Scholar] [CrossRef] [PubMed] [Green Version]
Laboratory, R.S. Diagnosis and Improvement of Saline and Alkali Soils; US Department of Agriculture: Washington, DC, USA, 1954; pp. 6–7.
Walkley, A. An examination of methods for determining organic carbon and nitrogen in soils 1.(with one text-figure.). J. Agric. Sci. 1935, 25, 598–609. [Google Scholar] [CrossRef]
Olsen, S.; Sommers, L.; Page, A. Methods of soil analysis. Part 1982, 2, 403–430. [Google Scholar]
Chapman, H.D.; Pratt, P.F. Methods of Analysis for Soils, Plants, and Waters; University of California, Division of Agricultural Sciences: Berkeley, CA, USA, 1961; pp. 7–8. [Google Scholar]
Moodie, C.; Smith, H.; McCreery, R. Laboratory Manual for Soil Fertility, (Mimeographed); Washington State College: Washington, DC, USA, 1959. [Google Scholar]
Dworkin, M.; Foster, J. Experiments with some microorganisms which utilize ethane and hydrogen. J. Bacteriol. 1958, 75, 592. [Google Scholar] [CrossRef] [PubMed] [Green Version]
Ryan, J.; Estefan, G.; Rashid, A. Soil and Plant. Analysis Laboratory Manual; ICARDA: Cairo, India, 2001; pp. 15–17. [Google Scholar]
El-Tarabily, K.A. Promotion of tomato (Lycopersicon esculentum Mill.) plant growth by rhizosphere competent 1-aminocyclopropane-1-carboxylic acid deaminase-producing streptomycete actinomycetes. Plant Soil 2008, 308, 161–174. [Google Scholar] [CrossRef]
Glickmann, E.; Dessaux, Y. A critical examination of the specificity of the salkowski reagent for indolic compounds produced by phytopathogenic bacteria. Appl. Environ. Microbiol. 1995, 61, 793–796. [Google Scholar] [CrossRef] [Green Version]
Goldstein, A.H. Bacterial solubilization of mineral phosphates: Historical perspective and future prospects. Am. J. Altern. Agric. 1986, 1, 51–57. [Google Scholar] [CrossRef]
Ashraf, M.; Hasnain, S.; Berge, O.; Mahmood, T. Inoculating wheat seedlings with exopolysaccharide-producing bacteria restricts sodium uptake and stimulates plant growth under salt stress. Biol. Fertil. Soils 2004, 40, 157–162. [Google Scholar] [CrossRef]
MacFaddin, J. Enterobacteriaceae and Other Intestinal Bacteria. In Biochemical Tests for Identification of Medical Bacteria; Williams & Wilkins: Baltimore, MD, USA, 1980; pp. 439–464. [Google Scholar]
HussainF, B. Use of chlorophyll meter sufficiency indices for nitrogen management of irrigated rice in Asia. Agron. J. 2000, 92, 875–879. [Google Scholar]
Teulat, B.; Zoumarou-Wallis, N.; Rotter, B.; Salem, M.B.; Bahri, H.; This, D. QTL for relative water content in field-grown barley and their stability across Mediterranean environments. Theor. Appl. Genet. 2003, 108, 181–188. [Google Scholar] [CrossRef] [PubMed]
Jambunathan, N. Determination and detection of reactive oxygen species (ROS), lipid peroxidation, and electrolyte leakage in plants. In Plant Stress Tolerance; Springer: Berlin/Heidelberg, Germany, 2010; pp. 291–297. [Google Scholar]
Giannakoula, A.E.; Ilias, I.F.; Maksimović, J.J.D.; Maksimović, V.M.; Živanović, B.D. The effects of plant growth regulators on growth, yield, and phenolic profile of lentil plants. J. Food Compos. Anal. 2012, 28, 46–53. [Google Scholar] [CrossRef]
Bates, L.S.; Waldren, R.P.; Teare, I. Rapid determination of free proline for water-stress studies. Plant Soil 1973, 39, 205–207. [Google Scholar] [CrossRef]
Cakmak, I.; Marschner, H. Magnesium deficiency and high light intensity enhance activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase in bean leaves. Plant Physiol. 1992, 98, 1222–1227. [Google Scholar] [CrossRef] [PubMed] [Green Version]
Guo, X.-Y.; Zhang, X.-S.; Huang, Z.-Y. Drought tolerance in three hybrid poplar clones submitted to different watering regimes. J. Plant Ecol. 2010, 3, 79–87. [Google Scholar] [CrossRef]
Steel, R.G. Pinciples and Procedures of Statistics a Biometrical Approach; McGraw-Hill: New York, NY, USA, 1997; p. 666. [Google Scholar]
Chandra, D.; Srivastava, R.; Glick, B.R.; Sharma, A.K. Drought-tolerant Pseudomonas spp. improve the growth performance of finger millet (Eleusine coracana L. Gaertn.) under non-stressed and drought-stressed conditions. Pedosphere 2018, 28, 227–240. [Google Scholar] [CrossRef]
Nagargade, M.; Tyagi, V.; Singh, M. Plant growth-promoting rhizobacteria: A biological approach toward the production of sustainable agriculture. In Role of Rhizospheric Microbes in Soil; Springer: Berlin/Heidelberg, Germany, 2018; pp. 205–223. [Google Scholar]
Rana, M.S.; Hu, C.X.; Shaaban, M.; Imran, M.; Afzal, J.; Moussa, M.G.; Elyamine, A.M.; Bhantana, P.; Saleem, M.H.; Syaifudin, M. Soil phosphorus transformation characteristics in response to molybdenum supply in leguminous crops. J. Environ. Manag. 2020, 268, 110610. [Google Scholar] [CrossRef]
Saleem, M.; Ali, S.; Rehman, M.; Rana, M.; Rizwan, M.; Kamran, M.; Imran, M.; Riaz, M.; Hussein, M.; Elkelish, A.; et al. Influence of phosphorus on copper phytoextraction via modulating cellular organelles in two jute (Corchorus capsularis L.) varieties grown in a copper mining soil of Hubei Province, China. Chemosphere 2020, 248, 126032. [Google Scholar] [CrossRef]
Gontia-Mishra, I.; Sapre, S.; Kachare, S.; Tiwari, S. Molecular diversity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing PGPR from wheat (Triticum aestivum L.) rhizosphere. Plant Soil 2017, 414, 213–227. [Google Scholar] [CrossRef]
Hussain, M.B.; Zahir, Z.A.; Asghar, H.N.; Mahmood, S. Scrutinizing rhizobia to rescue maize growth under reduced water conditions. Soil Sci. Soc. Am. J. 2014, 78, 538–545. [Google Scholar] [CrossRef]
Saleem, M.H.; Kamran, M.; Zhou, Y.; Parveen, A.; Rehman, M.; Ahmar, S.; Malik, Z.; Mustafa, A.; Anjum, R.M.A.; Wang, B. Appraising growth, oxidative stress and copper phytoextraction potential of flax (Linum usitatissimum L.) grown in soil differentially spiked with copper. J. Environ. Manag. 2020, 257, 109994. [Google Scholar] [CrossRef] [PubMed]
Ahmed, C.B.; Rouina, B.B.; Boukhris, M. Effects of water deficit on olive trees cv. Chemlali under field conditions in arid region in Tunisia. Sci. Hortic. 2007, 113, 267–277. [Google Scholar] [CrossRef]
Naveed, M.; Hussain, M.B.; Zahir, Z.A.; Mitter, B.; Sessitsch, A. Drought stress amelioration in wheat through inoculation with Burkholderia phytofirmans strain PsJN. Plant Growth Regul. 2014, 73, 121–131. [Google Scholar] [CrossRef]
Ahmad, M.; Zahir, Z.A.; Khalid, M.; Nazli, F.; Arshad, M. Efficacy of Rhizobium and Pseudomonas strains to improve physiology, ionic balance and quality of mung bean under salt-affected conditions on farmer’s fields. Plant Physiol. Biochem. 2013, 63, 170–176. [Google Scholar] [CrossRef] [PubMed]
Castillo, P.; Escalante, M.; Gallardo, M.; Alemano, S.; Abdala, G. Effects of bacterial single inoculation and co-inoculation on growth and phytohormone production of sunflower seedlings under water stress. Acta Physiol. Plant. 2013, 35, 2299–2309. [Google Scholar] [CrossRef]
Saleem, M.H.; Fahad, S.; Rehman, M.; Saud, S.; Jamal, Y.; Khan, S.; Liu, L. Morpho-physiological traits, biochemical response and phytoextraction potential of short-term copper stress on kenaf (Hibiscus cannabinus L.) seedlings. PeerJournal 2020, 8, e8321. [Google Scholar] [CrossRef] [PubMed] [Green Version]
Saleem, M.H.; Ali, S.; Irshad, S.; Hussaan, M.; Rizwan, M.; Rana, M.S.; Hashem, A.; Abd_Allah, E.F.; Ahmad, P. Copper uptake and accumulation, ultra-structural alteration, and bast fibre yield and quality of fibrous jute (Corchorus capsularis L.) plants grown under two different soils of China. Plants 2020, 9, 404. [Google Scholar] [CrossRef] [Green Version]
Saleem, M.H.; Ali, S.; Rehman, M.; Rizwan, M.; Kamran, M.; Mohamed, I.A.; Bamagoos, A.A.; Alharby, H.F.; Hakeem, K.R.; Liu, L. Individual and combined application of EDTA and citric acid assisted phytoextraction of copper using jute (Corchorus capsularis L.) seedlings. Environ. Technol. Innov. 2020, 19, 100895. [Google Scholar] [CrossRef]
Pereyra, M.; Zalazar, C.; Barassi, C. Root phospholipids in Azospirillum-inoculated wheat seedlings exposed to water stress. Plant Physiol. Biochem. 2006, 44, 873–879. [Google Scholar] [CrossRef]
Barbosa, R.H.; Tabaldi, L.A.; Miyazaki, F.R.; Pilecco, M.; Kassab, S.O.; Bigaton, D. Foliar copper uptake by maize plants: Effects on growth and yield. Ciência Rural 2013, 43, 1561–1568. [Google Scholar] [CrossRef]
Garg, R.N.; Pathak, H.; Das, D.; Tomar, R. Use of flyash and biogas slurry for improving wheat yield and physical properties of soil. Environ. Monit. Assess. 2005, 107, 1–9. [Google Scholar] [CrossRef]
Du, H.; Gao, W.; Li, J.; Shen, S.; Wang, F.; Fu, L.; Zhang, K. Effects of digested biogas slurry applicationmixed with irrigation water on nitrate leaching during wheat-maize rotation in the North China Plain. Agric. Water Manag. 2019, 213, 882–893. [Google Scholar] [CrossRef]
Saleem, M.H.; Fahad, S.; Khan, S.U.; Din, M.; Ullah, A.; Sabagh, A.E.L.; Hossain, A.; Llanes, A.; Liu, L. Copper-induced oxidative stress, initiation of antioxidants and phytoremediation potential of flax (Linum usitatissimum L.) seedlings grown under the mixing of two different soils of China. Environ. Sci. Pollut. Res. 2020, 27, 5211–5221. [Google Scholar] [CrossRef] [PubMed]
Saleem, M.H.; Fahad, S.; Khan, S.U.; Ahmar, S.; Khan, M.H.U.; Rehman, M.; Maqbool, Z.; Liu, L. Morpho-physiological traits, gaseous exchange attributes, and phytoremediation potential of jute (Corchorus capsularis L.) grown in different concentrations of copper-contaminated soil. Ecotoxicol. Environ. Saf. 2020, 189, 109915. [Google Scholar] [CrossRef] [PubMed]
Saleem, M.H.; Rehman, M.; Fahad, S.; Tung, S.A.; Iqbal, N.; Hassan, A.; Ayub, A.; Wahid, M.A.; Shaukat, S.; Liu, L.; et al. Leaf gas exchange, oxidative stress, and physiological attributes of rapeseed (Brassica napus L.) grown under different light-emitting diodes. Photosynthetica 2020, 58, 836–845. [Google Scholar] [CrossRef]
Rana, M.; Bhantana, P.; Sun, X.-C.; Imran, M.; Shaaban, M.; Moussa, M.; Hamzah Saleem, M.; Elyamine, A.; Binyamin, R.; Alam, M.; et al. Molybdenum as an Essential Element for Crops: An Overview. Int. J. Sci. Res. Growth 2020, 24, 18535. [Google Scholar]
Saleem, M.H.; Rehman, M.; Kamran, M.; Afzal, J.; Noushahi, H.A.; Liu, L. Investigating the potential of different jute varieties for phytoremediation of copper-contaminated soil. Environ. Sci. Pollut. Res. 2020. [Google Scholar] [CrossRef]
Saleem, M.H.; Rehman, M.; Zahid, M.; Imran, M.; Xiang, W.; Liu, L. Morphological changes and antioxidative capacity of jute (Corchorus capsularis, Malvaceae) under different color light-emitting diodes. Braz. J. Bot. 2019, 42, 581–590. [Google Scholar] [CrossRef]

Figure 1. Effect of plant growth-promoting rhizobacteria (PGPR) and biogas slurry (BGS) on the photosynthetic (a) and transpiration (b) rates (µmol m⁻² s⁻¹) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3).

Figure 2. Effect of PGPR and BGS on the stomatal conductance (vpm) (a) and sub-stomatal conductance (mmol m⁻² s⁻¹) (b) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3).

Figure 3. Effect of PGPR and BGS on the chlorophyll content (a) and water-use efficiency (b) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3).

Figure 4. Effect of PGPR and BGS on the catalase (µmol H₂O₂ min⁻¹ g⁻¹ fw) (a) and ascorbate peroxidase (µmol Ascorbate min⁻¹ mg⁻¹ fw) (b) of wheat plants under drought-stress conditions. Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (±standard deviation; n = 3).

Table 1. Physical and chemical attributes of the soil for the wheat field trial.

Characteristics	Unit	Value
Textural Class		sandy clay loam
Sand	%	54
Silt	%	26
Clay	%	20
pH_s	-	7.9
EC_e	dS m⁻¹	2.42
Organic Matter	%	0.58
CaCO₃	%	0.59
Total Nitrogen	%	0.04
Available Phosphorus	mg kg⁻¹	7.1
Extractable Potassium	mg kg⁻¹	107

Table 2. Characterization of the rhizobacterial strains.

Characteristics		Alcaligenes faecalis	Bacillus amyloliquefaciens	Pseudomonas moraviensis
ACC-deaminase activity (nmol α-ketobutyrateg⁻¹ protein h⁻¹)		384	435	532
IAA production (mg L⁻¹)	Without L–Tryptophan	2.21	6.12	5.63
IAA production (mg L⁻¹)	With L–Tryptophan (1 g L⁻¹)	15.33	14.32	22.23
Phosphate solubilization		-	-	-
Exopolysaccharides production ability		-	-	-
Catalase activity		-	-	-

Table 3. Effect of ACC-deaminase containing PGPR and BGS on the relative water content, electrolyte leakage, proline content, and total phenolic content of wheat plants under drought-stress conditions.

Treatments	Electrolyte Leakage (%)						Relative Water Content (%)
	NI		SIT		SIF		NI		SIT		SIF
	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS
No PGPR	64 c–f	57 f–k	80 a	73 ab	69 bc	68 b–d	60 e–j	67 b–g	45 k	52 i–k	52 i–k	57 g–j
A. faecalis	50 k–n	55 h–m	73 ab	61 c–h	63 c–f	58 f–k	69 a–f	71 a–c	50 jk	59 f–j	61 d–j	59 f–j
B. amyloliquefaciens	55 g–m	49 l–n	62 c–g	66 b–e	61 d–i	59 e–j	63 c–h	76 ab	57 g–j	56 h–j	60 d–j	70 a–e
P. moraviensis	47 mn	45 n	56 f–l	53 i–m	51 k–n	52 j–n	71 a–d	78 a	59 f–j	61 c–i	65 c–h	71 a–d
	Proline Content (µg g⁻¹)						Total Phenolic (µg g⁻¹)
No PGPR	0.47 c–f	0.45 c–g	0.63 ab	0.71 a	0.52 cd	0.63 a	99 g–j	90 h–j	165 b	192 a	183 a	160 b
A. faecalis	0.43 c–h	0.37 f–i	0.50 c–e	0.65 a	0.41 e–i	0.42 d–i	72 kl	88 jk	132 c	112 fg	122 c–f	113 e–g
B. amyloliquefaciens	0.36 g–i	0.41 e–i	0.53 bc	0.48 c–e	0.44 c–g	0.44 c–h	90 ij	70 l	135 c	132 c	131 cd	130 c–e
P. moraviensis	0.33 i	0.39 e–i	0.40 e–i	0.38 f–i	0.33 hi	0.41 e–i	67 l	58 l	106 f–i	114 d–g	107 f–h	91 h–j

Note: Treatments sharing similar letters do not have an Honest Significant Difference between each other at p ≤ 0.05 (n = 3). NI is normal irrigation; SIT is skipped irrigation at tillering; SIF is skipped irrigation at flowering; and BGS is biogas slurry.

Table 4. Effect of ACC-deaminase containing PGPR and BGS on the plant height (cm), number of tillers (m⁻¹), 1000-grain weight (g), grain yield (Mg ha⁻¹), straw yield (Mg ha⁻¹), and biological yield (Mg ha⁻¹) of wheat plants under drought-stress conditions.

Treatments	Plant Height (cm)						Number of Tillers (m⁻¹)
	NI		SIT		SIF		NI		SIT		SIF
	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS
No PGPR	82 de	82 c–e	63 ij	62 j	76 d–h	75 e–h	214 jk	284 b–e	215 jk	216 i–k	213 k	222 h–k
A. faecalis	90 a–c	92 a	70 g–i	70 g–i	83 b–e	84 b–d	302 bc	353 a	232 g–k	243 f–k	280 b–f	295 bc
B. amyloliquefaciens	91 ab	93 a	69 h–j	74 f–h	79 d–f	84 b–d	317 ab	345 a	251 e–j	265 c–g	253 e–i	269 c–g
P. moraviensis	93 a	93 a	72 f–h	78 d–g	84 b–d	84b–d	307 b	347 a	243 f–k	256 d–h	268 c–g	294 b–d
	1000-Grain Weight (g)						Grain Yield (Mg ha⁻¹)
No PGPR	36 c–g	37 c–g	29 i	31 i	31 hi	36 e–g	3.16 d–g	3.34 b–f	2.29 j	2.40 ij	3.05 e–h	2.91 gh
A. faecalis	40 a–c	41 ab	30 i	32 hi	35 f–h	38 b–f	3.47 b–d	3.72 ab	2.84 gh	2.82 gh	3.34 b–f	3.32 c–f
B. amyloliquefaciens	40 a–d	39 a–d	31 hi	32 hi	36 c–g	36 d–g	3.39 b–e	3.63 a–c	2.74 hi	2.98 f–h	3.30 c–f	3.31 c–f
P. moraviensis	41 ab	42 a	32 hi	34 gh	38 b–g	39 a–e	3.62 a–c	3.90 a	2.98 f–h	3.05 e–h	3.19 dg	3.19 d–g
	Straw Yield (Mg ha⁻¹)						Biological Yield (Mg ha⁻¹)
No PGPR	5.05 b–f	5.28 a–e	4.05 i	4.12 i	4.80 c–h	4.80 c–h	10.9 d–f	11.7 c–f	8.4 g	10.0 fg	9.9 fg	11.0 d–f
A. faecalis	5.27 a–e	5.54 ab	4.35 g–i	4.71 d–i	4.92 b–h	5.29 a–e	12.7 b–d	14.1 ab	10.5 ef	11.3 c–f	11.3 d–f	11.6 c–f
B. amyloliquefaciens	5.18 a–e	5.46 a–c	4.26 hi	4.64 e–i	5.08 b–f	5.00 b–g	12.1 c–e	12.8 a–d	10.6 ef	10.8 d–f	11.2 d–f	11.6 c–f
P. moraviensis	5.36 a–d	5.75 a	4.49 f–i	5.03 b–f	5.33 a–d	5.36 a–d	13.2 a–c	14.7 a	10.6 ef	11.4 c–f	11.7 c–f	12.2 b–e

Table 5. Effect of ACC-deaminase containing PGPR and BGS on the nitrogen, phosphorus, and potassium contents (%) in the grain and straw of wheat under drought-stress conditions.

Treatments	Grain Nitrogen (%)						Shoot Nitrogen (%)
	NI		SIT		SIF		NI		SIT		SIF
	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS	No BGS	BGS
No PGPR	1.56 h–k	1.83 c–f	1.15 q	1.27 o–q	1.25 pq	1.30 n–q	1.21 d–f	1.44 bc	0.79 j	1.02 g–i	1.01 g–i	1.17 e–g
A. faecalis	1.88 b–e	2.02 a–c	1.32 m–q	1.46 k–o	1.49 j–n	1.53 h–l	1.36 cd	1.51 a–c	0.93 ij	1.03 g–i	1.22 d–f	1.24 de
B. amyloliquefaciens	1.79 d–g	1.95 a–d	1.35 l–p	1.50 i–m	1.69 e–i	1.70 e–h	1.44 bc	1.53 ab	1.05 f–i	0.95 h–j	1.17 e–g	1.26 de
P. moraviensis	2.08 ab	2.13 a	1.47 k–n	1.60 g–k	1.68 f–j	1.80 d–g	1.59 ab	1.61 a	1.14 e–g	1.10 e–h	1.23 de	1.35 cd
	Grain Phosphorus (%)						Shoot Phosphorus (%)
No PGPR	0.54 e–i	0.54 e–i	0.44 k	0.45 jk	0.49 i–k	0.51 g–j	0.27 c–e	0.27 c–e	0.12 i	0.14 hi	0.15 g–i	0.21 d–f
A. faecalis	0.61 b–d	0.65 ab	0.50 g–k	0.52 f–i	0.57 d–g	0.54 d–i	0.31 a–c	0.36 a	0.13 i	0.21 e–g	0.19 f–h	0.29 bc
B. amyloliquefaciens	0.60 b–e	0.57 c–g	0.50 h–k	0.52 f–i	0.54 e–i	0.56 d–h	0.29 bc	0.30 bc	0.17 f–i	0.20 fg	0.14 hi	0.22 d–f
P. moraviensis	0.63 a–c	0.68 a	0.54 e–i	0.55 d–i	0.56 d–h	0.58 c–f	0.32 a–c	0.35 ab	0.22 d–f	0.22 d–f	0.22 d–f	0.27 cd
	Grain Potassium (%)						Shoot Potassium (%)
No PGPR	0.47 f–i	0.54 d–f	0.36 jk	0.31 k	0.40 i–k	0.39 i–k	0.94 i–k	1.15 c–g	0.79 k	0.98 h–j	0.84 jk	0.97 h–j
A. faecalis	0.64 a–c	0.70 a	0.43 h–j	0.45 g–j	0.52 d–g	0.50 e–h	1.25 b–e	1.31 bc	1.16 c–g	1.12 e–h	1.03 g–i	1.17 c–g
B. amyloliquefaciens	0.54 d–f	0.67 ab	0.50 e–h	0.48 e–h	0.48 e–h	0.51 e–h	1.15 c–g	1.39 ab	1.06 g–i	1.07 f–i	1.09 e–i	1.12 e–h
P. moraviensis	0.65 ab	0.71 a	0.53 d–f	0.54 d–f	0.60 b–d	0.56 c–e	1.29 b–d	1.51 a	1.18 c–g	1.13 d–h	1.22 c–f	1.24 b–e

Note: Treatments sharing similar letters do not have an Honest Significant Difference with each other at p ≤ 0.05 (n = 3). The NI is normal irrigation; SIT is skipped irrigation at tillering; SIF is skipped irrigation at flowering; and BGS is biogas slurry.

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Yaseen, R.; Aziz, O.; Saleem, M.H.; Riaz, M.; Zafar-ul-Hye, M.; Rehman, M.; Ali, S.; Rizwan, M.; Nasser Alyemeni, M.; El-Serehy, H.A.; et al. Ameliorating the Drought Stress for Wheat Growth through Application of ACC-Deaminase Containing Rhizobacteria along with Biogas Slurry. Sustainability 2020, 12, 6022. https://doi.org/10.3390/su12156022

AMA Style

Yaseen R, Aziz O, Saleem MH, Riaz M, Zafar-ul-Hye M, Rehman M, Ali S, Rizwan M, Nasser Alyemeni M, El-Serehy HA, et al. Ameliorating the Drought Stress for Wheat Growth through Application of ACC-Deaminase Containing Rhizobacteria along with Biogas Slurry. Sustainability. 2020; 12(15):6022. https://doi.org/10.3390/su12156022

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Yaseen, Rizwan, Omar Aziz, Muhammad Hamzah Saleem, Muhammad Riaz, Muhammad Zafar-ul-Hye, Muzammal Rehman, Shafaqat Ali, Muhammad Rizwan, Mohammed Nasser Alyemeni, Hamed A. El-Serehy, and et al. 2020. "Ameliorating the Drought Stress for Wheat Growth through Application of ACC-Deaminase Containing Rhizobacteria along with Biogas Slurry" Sustainability 12, no. 15: 6022. https://doi.org/10.3390/su12156022

APA Style

Yaseen, R., Aziz, O., Saleem, M. H., Riaz, M., Zafar-ul-Hye, M., Rehman, M., Ali, S., Rizwan, M., Nasser Alyemeni, M., El-Serehy, H. A., Al-Misned, F. A., & Ahmad, P. (2020). Ameliorating the Drought Stress for Wheat Growth through Application of ACC-Deaminase Containing Rhizobacteria along with Biogas Slurry. Sustainability, 12(15), 6022. https://doi.org/10.3390/su12156022

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