Publications by authors named "Maqshoof Ahmad"

14 Publications

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Plant-growth-promoting Bacillus and Paenibacillus species improve the nutritional status of Triticum aestivum L.

PLoS One 2020 1;15(12):e0241130. Epub 2020 Dec 1.

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

Wheat is one of the best-domesticated cereal crops and one of the vital sources of nutrition for humans. An investigation was undertaken to reveal the potential of novel bio-inoculants enriching micronutrients in shoot and grains of wheat crop to eliminate the hazards of malnutrition. Sole as well as consortia inoculation of bio-inoculants significantly enhanced mineral nutrients including zinc (Zn) and iron (Fe) concentrations in shoot and grains of wheat. Various treatments of bio-inoculants increase Zn and Fe content up to 1-15% and 3-13%, respectively. Sole inoculation of Bacillus aryabhattai (S10) impressively improves the nutritious of wheat. However, the maximum increase in minerals contents of wheat was recorded by consortia inoculation of Paenibacillus polymyxa ZM27, Bacillus subtilis ZM63 and Bacillus aryabhattai S10. This treatment also showed a maximum bacterial population (18 × 104 cfu mL-1) in the rhizosphere. The consortium application of these strains showed up to a 17% increase in yield. It is evident from the results that the consortium application was more effective than sole and co-inoculation. A healthy positive correlation was found between growth, yield, and the accessibility of micronutrients to wheat crops at the harvesting stage. The present investigations revealed the significance of novel bacterial strains in improving the nutritional status of wheat crops. These strains could be used as bio-inoculants for the biofortification of wheat to combat hidden hunger in developing countries.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0241130PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7707572PMC
January 2021

Integrated use of phosphate-solubilizing Bacillus subtilis strain IA6 and zinc-solubilizing Bacillus sp. strain IA16: a promising approach for improving cotton growth.

Folia Microbiol (Praha) 2021 Feb 24;66(1):115-125. Epub 2020 Oct 24.

Department of Soil Science, University College of Agriculture and Environmental Sciences, Islamia University of Bahawalpur, Bahawalpur, Pakistan.

Mineral nutrition of crop plants is one of the major challenges faced by modern agriculture, particularly in arid and semi-arid regions. In alkaline calcareous soils, the availability of phosphorus and zinc is critically less due to their fixation and precipitation as complexes. Farmers use fertilizers to fulfill crop requirements, but their efficacy is less, which increases production costs. Plant growth-promoting rhizobacteria (PGPR) can improve the availability of crop nutrients through solubilizing the insoluble compounds of phosphorus and zinc in soil. In the present study, a total of 40 rhizobacterial isolates were isolated from cotton rhizosphere and screened for improving cotton growth through the solubilization of phosphorus and zinc. Out of these 40 isolates, seven isolates (IA2, IA3, IA6, IA7, IA8, IA13, and IA14) efficiently solubilized insoluble rock phosphate while seven isolates (IA10, IA16, IA20, IA23, IA24, IA28, and IA30) were more efficient in solubilizing insoluble zinc oxide. In liquid media, strain IA7 (2.75 μg/mL) solubilized the highest amount of phosphate while the highest concentration of soluble zinc was observed in the broth inoculated with strain IA20 (3.94 μg/mL). Seven phosphate-solubilizing and seven zinc-solubilizing strains were evaluated using jar trial to improve the growth of cotton seedlings, and the results were quite promising. All the inoculated treatments showed improvement in growth parameters in comparison with control. Best results were shown by the combined application of IA6 and IA16, followed by the combination of strains IA7 and IA20. Based on the jar trial, the selected isolates were further characterized by plant growth-promoting characters such as siderophores production, HCN production, ammonia production, and exopolysaccharides production. These strains were identified through 16S rRNA sequencing as Bacillus subtilis IA6 (accession # MN005922), Paenibacillus polymyxa IA7 (accession # MN005923), Bacillus sp. IA16 (accession # MN005924), and Bacillus aryabhattai IA20 (accession # MN005925). It is hence concluded that the integrated use of phosphate-solubilizing and zinc-solubilizing strains as potential inoculants can be a promising approach for improving cotton growth under semi-arid conditions.
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http://dx.doi.org/10.1007/s12223-020-00831-3DOI Listing
February 2021

Halotolerant potassium solubilizing plant growth promoting rhizobacteria may improve potassium availability under saline conditions.

Environ Monit Assess 2020 Oct 12;192(11):697. Epub 2020 Oct 12.

Department of Soil Science, The Islamia University of Bahawalpur, Bahawalpur, 63100, Pakistan.

Environmental change is one of the primary issues faced by the farming community. Low rainfall and high temperature in arid and semiarid regions lead to the development of secondary salinisation, thus making the problem more severe. Under saline conditions, sodium is the most crucial cation that competes with potassium (K) and adversely affects plant metabolism by inhibiting plant enzymatic activities. Potassium-solubilising bacteria (KSB) play a vital role in solubilising fixed potassium and making it accessible to plants. In the current study, 42 KSB strains were isolated from paddy rhizosphere soil grown under salt-affected conditions. The plant-growth-promoting (PGP) properties of these rhizobacteria were also evaluated. Thirteen KSB strains, positive for all tested PGP traits, were evaluated for potassium solubilisation under sodium stress, namely, 0%, 3%, 5% and 7% NaCl stress. The five best strains (Acinetobacter pittii strain L1/4, A. pittii strain L3/3, Rhizobium pusense strain L3/4, Cupriavidus oxalaticus strain L4/12 and Ochrobactrum ciceri strain L5/1) based on the K-solubilising potential were identified by amplification, sequencing and bioinformatic analysis of the 16S rDNA sequences. The maximum potassium solubilisation was measured at 30 °C and pH 7 with glucose as carbon source. The application of these KSB strains significantly improved the shoot length, fresh weight, dry weight and chlorophyll contents of paddy plants grown under saline conditions. Hence, these strains could be halotolerant KSB bioinoculants that can be used to protect plants against salt stress.
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http://dx.doi.org/10.1007/s10661-020-08655-xDOI Listing
October 2020

Appraising the potential of EPS-producing rhizobacteria with ACC-deaminase activity to improve growth and physiology of maize under drought stress.

Physiol Plant 2021 Jun 11;172(2):463-476. Epub 2020 Oct 11.

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan.

Rhizobacteria containing 1-aminocyclopropane-1-carboxylic acid-deaminase (ACC-deaminase) and exopolysaccharides (EPS) activity are important to induce stress tolerance in plants. The present study was conducted to screen and characterize plant growth-promoting rhizobacteria (PGPR) with ACC-deaminase and EPS-producing activity for improving maize growth under drought stress. Eighty-five rhizobacterial strains were isolated from the rain-fed areas, among those 69 isolates were able to utilize ACC and 31 strains were found positive for EPS production. These strains containing ACC-deaminase and/or EPS-producing activity were subjected to drought tolerance assay by inducing water stress in media using polyethylene glycol 6000. Based on results of the drought tolerance bioassay, 12 most prominent strains were selected to evaluate their growth-promoting abilities in maize under water-stressed conditions by conducting jar trial. The impact of strains on maize growth parameters was variable. Strains with co-existence of ACC-deaminase and EPS-producing activity showed comparatively better results than those with either ACC-deaminase or EPS-producing activity only. These strains were also significantly better in improving the plant physiological parameters including photosynthesis rate, stomatal conductance, vapor pressure, water-use efficiency and transpiration rate. The strain D with co-existence of ACC-deaminase and EPS-producing activity was significantly better in colonizing maize roots, improving plant growth and physiological parameters. The strain was named as Bacillus velezensis strain D (accession number MT367633) as confirmed through results of 16S rRNA partial gene sequencing. It is concluded that the strains with co-existence of ACC-deaminase and EPS-producing activity could be better suited for improving crop growth and physiology under drought stress.
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http://dx.doi.org/10.1111/ppl.13212DOI Listing
June 2021

Perspectives of Microbial Inoculation for Sustainable Development and Environmental Management.

Front Microbiol 2018 5;9:2992. Epub 2018 Dec 5.

World Vegetable Center, Tainan, China.

How to sustainably feed a growing global population is a question still without an answer. Particularly farmers, to increase production, tend to apply more fertilizers and pesticides, a trend especially predominant in developing countries. Another challenge is that industrialization and other human activities produce pollutants, which accumulate in soils or aquatic environments, contaminating them. Not only is human well-being at risk, but also environmental health. Currently, recycling, land-filling, incineration and pyrolysis are being used to reduce the concentration of toxic pollutants from contaminated sites, but too have adverse effects on the environment, producing even more resistant and highly toxic intermediate compounds. Moreover, these methods are expensive, and are difficult to execute for soil, water, and air decontamination. Alternatively, green technologies are currently being developed to degrade toxic pollutants. This review provides an overview of current research on microbial inoculation as a way to either replace or reduce the use of agrochemicals and clean environments heavily affected by pollution. Microorganism-based inoculants that enhance nutrient uptake, promote crop growth, or protect plants from pests and diseases can replace agrochemicals in food production. Several examples of how biofertilizers and biopesticides enhance crop production are discussed. Plant roots can be colonized by a variety of favorable species and genera that promote plant growth. Microbial interventions can also be used to clean contaminated sites from accumulated pesticides, heavy metals, polyaromatic hydrocarbons, and other industrial effluents. The potential of and key processes used by microorganisms for sustainable development and environmental management are discussed in this review, followed by their future prospects.
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http://dx.doi.org/10.3389/fmicb.2018.02992DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6289982PMC
December 2018

Preliminary study on phosphate solubilizing strain Q3 and sp. strain Q6 for improving cotton growth under alkaline conditions.

PeerJ 2018 4;6:e5122. Epub 2018 Jul 4.

Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad, Punjab, Pakistan.

Background: Low phosphorus availability limits crop production in alkaline calcareous soils in semi-arid regions including Pakistan. Phosphate solubilizing bacteria may improve crop growth on alkaline calcareous soils due to their ability to enhance P availability.

Methods: Twenty rhizobacterial isolates (Q1-Q20) were isolated from rhizosphere of cotton and characterized for their growth promoting attributes . The selected phosphate solubilizing isolates were further screened for their ability to improve cotton growth under axenic conditions (jar trial). The phosphorus solubilization capacities of selected strains were quantified and these strains were identified through 16S rDNA sequencing.

Results: Isolates Q2, Q3, Q6, Q7, Q8, Q13 and Q14 were able to solubilize phosphate from insoluble sources. Most of these isolates also possessed other traits including catalase activity and ammonia production. The growth promotion assay showed that Q3 was significantly better than most of the other isolates followed by Q6. Maximum root colonization (4.34 × 10 cfu g) was observed in case of isolate Q6 followed by Q3. The phosphorus solubilization capacities of these strains were quantified, showing a maximum phosphorus solubilization by Q3 (optical density 2.605 ± 0.06) followed by the Q6 strain. The strain Q3 was identified as (accession # KX788864) and Q6 as sp. (accession # KX788865) through 16S rDNA sequencing.

Discussion: The bacterial isolates varied in their abilities for different growth promoting traits. The selected PGPR strain Q3 and sp. strain Q6 have multifarious growth promoting traits including ability to grow at higher EC and pH levels, and phosphorus solubilizing ability. These strains can efficiently colonize cotton roots under salt affected soils and help plants in phosphorus nutrition. It is concluded that both strains are potential candidates for promoting cotton growth under alkaline conditions, however further investigation is required to determine their potential for field application.
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http://dx.doi.org/10.7717/peerj.5122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035724PMC
July 2018

Biodiesel production from algae grown on food industry wastewater.

Environ Monit Assess 2018 Apr 10;190(5):271. Epub 2018 Apr 10.

University of Agriculture Faisalabad (Sub-campus Burewala), Faisalabad, Pakistan.

Algae have an ample potential to produce biodiesel from spent wash of food industry. In addition, it is cheaper and presents an environment friendly way to handle food industry wastewater. This study was conducted to optimize the growth of microalgal strains and to assess biodiesel production potential of algae using untreated food industry wastewater as a source of nutrients. The food industry wastewater was collected and analyzed for its physicochemical characteristics. Different dilutions (10, 20, 40, 80, and 100%) of this wastewater were made with distilled water, and growth of two microalgal strains (Cladophora sp. and Spyrogyra sp.) was recorded. Each type of wastewater was inoculated with microalgae, and biomass was harvested after 7 days. The growth of both strains was also evaluated at varying temperatures, pH and light periods to optimize the algal growth for enhanced biodiesel production. After optimization, biodiesel production by Spyrogyra sp. was recorded in real food industry wastewater. The algal biomass increased with increasing level of food industry wastewater and was at maximum with 100% wastewater. Moreover, statistically similar results were found with algal growth on 100% wastewater and also on Bristol's media. The Cladophora sp. produced higher biomass than Spyrogyra sp. while growing on food industry wastewater. The optimal growth of both microalgal strains was observed at temperature 30 °C, pH: 8, light 24 h. Cladophora sp. was further evaluated for biodiesel production while growing on 100% wastewater and found that this strain produced high level of oil and biodiesel. Algae have an ample potential to produce biodiesel from spent wash of food industry. In addition, it is cheaper and presents an environment friendly way to handle food industry wastewater.
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http://dx.doi.org/10.1007/s10661-018-6641-3DOI Listing
April 2018

Zinc solubilizing Bacillus spp. potential candidates for biofortification in maize.

Microbiol Res 2017 Sep 8;202:51-60. Epub 2017 Jun 8.

Department of Forestry, Range and Wildlife Management, University College of Agriculture and Environmental Sciences, The Islamia University of Bahawalpur, Pakistan.

Bioaugmentation of Zn solubilizing rhizobacteria could be a sustainable intervention to increase bioavailability of Zn in soil which can be helpful in mitigation of yield loss and malnutrition of zinc. In present study, a number of pure rhizobacterial colonies were isolated from maize rhizosphere and screened for their ability to solubilize zinc oxide. These isolates were screened on the basis of zinc and phosphate solubilization, IAA production, protease production, catalase activity and starch hydrolysis. All the selected isolates were also positive for oxidase activity (except ZM22), HCN production (except ZM27) and utilization of citrate. More than 70% of isolates produces ammonia, hydrogen cyanide, siderophores, exopolysaccharides and cellulase. More than half of isolates also showed potential for urease activity and production of lipase. The ZM31 and S10 were the only isolates which showed the chitinase activity. All these isolates were evaluated in a jar trial for their ability to promote growth of maize under axenic conditions. Results revealed that inoculation of selected zinc solubilizing rhizobacterial isolates improved the growth of maize. In comparison, isolates ZM20, ZM31, ZM63 and S10 were best compared to other tested isolates in stimulating the growth attributes of maize like shoot length, root length, plant fresh and dry biomass. These strains were identified as Bacillus sp. (ZM20), Bacillus aryabhattai (ZM31 and S10) and Bacillus subtilis (ZM63) through 16S rRNA sequencing. This study indicated that inoculation of Zn solubilizing strains have potential to promote growth and can be the potential bio-inoculants for biofortification of maize to overcome the problems of malnutrition.
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http://dx.doi.org/10.1016/j.micres.2017.06.001DOI Listing
September 2017

Synergistic use of biochar, compost and plant growth-promoting rhizobacteria for enhancing cucumber growth under water deficit conditions.

J Sci Food Agric 2017 Dec 9;97(15):5139-5145. Epub 2017 Jun 9.

Department of Environmental Sciences, University of California Riverside, Riverside, CA, USA.

Background: Limited information is available about the effectiveness of biochar with plant growth-promoting rhizobacteria (PGPR) and compost. A greenhouse study was conducted to evaluate the effect of biochar in combination with compost and PGPR (Pseudomonas fluorescens) for alleviating water deficit stress. Both inoculated and un-inoculated cucumber seeds were sown in soil treated with biochar, compost and biochar + compost. Three water levels - field capacity (D0), 75% field capacity (D1) and 50% field capacity (D2) - were maintained.

Results: The results showed that water deficit stress significantly suppressed the growth of cucumber; however, synergistic use of biochar, compost and PGPR mitigated the negative impact of stress. At D2, the synergistic use of biochar, compost and PGPR caused significant increases in shoot length, shoot biomass, root length and root biomass, which were respectively 88, 77, 89 and 74% more than in the un-inoculated control. Significant improvements in chlorophyll and relative water contents as well as reduction in leaf electrolyte leakage demonstrated the effectiveness of this approach. Moreover, the highest population of P. fluorescens was observed where biochar and compost were applied together.

Conclusion: These results suggest that application of biochar with PGPR and/or compost could be an effective strategy for enhancing plant growth under stress. © 2017 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.8393DOI Listing
December 2017

Relationship between in vitro characterization and comparative efficacy of plant growth-promoting rhizobacteria for improving cucumber salt tolerance.

Arch Microbiol 2016 May 9;198(4):379-87. Epub 2016 Feb 9.

Department of Environmental Sciences, University of California, Riverside, CA, USA.

Phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC)-deaminase activity and production of siderophores and indole acetic acid (IAA) are well-known traits of plant growth-promoting rhizobacteria (PGPR). Here we investigated the expression of these traits as affected by salinity for three PGPR strains (Pseudomonas fluorescens, Bacillus megaterium and Variovorax paradoxus) at two salinity levels [2 and 5 % NaCl (w/v)]. Among the three strains, growth of B. megaterium was the least affected by high salinity. However, P. fluorescens was the best strain for maintaining ACC-deaminase activity, siderophore and IAA production under stressed conditions. V. paradoxus was the least tolerant to salts and had minimal growth and low PGPR trait expression under salt stress. Results of experiment examining the impact of bacterial inoculation on cucumber growth at three salinity levels [1 (normal), 7 and 10 dS m(-1)] revealed that P. fluorescens also had good rhizosphere competence and was the most effective for alleviating the negative impacts of salinity on cucumber growth. The results suggest that in addition to screening the PGPR regarding their effect on growth under salinity, PGPR trait expression is also an important aspect that may be useful for selecting the most promising PGPR bacterial strains for improving plant tolerance to salinity stress.
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http://dx.doi.org/10.1007/s00203-016-1197-5DOI Listing
May 2016

Effectiveness of halo-tolerant, auxin producing Pseudomonas and Rhizobium strains to improve osmotic stress tolerance in mung bean (Vigna radiata L.).

Braz J Microbiol 2013 Dec 10;44(4):1341-8. Epub 2014 Mar 10.

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan.

Halo-tolerant, auxin producing bacteria could be used to induce salt tolerance in plants. A number of Rhizobium and auxin producing rhizobacterial strains were assessed for their ability to tolerate salt stress by conducting osmoadaptation assay. The selected strains were further screened for their ability to induce osmotic stress tolerance in mung bean seedlings under salt-stressed axenic conditions in growth pouch/jar trials. Three most effective strains of Rhizobium and Pseudomonas containing ACC-deaminase were evaluated in combination, for their ability to induce osmotic stress tolerance in mung bean at original, 4, and 6 dS m(-1) under axenic conditions. Results showed that sole inoculation of Rhizobium and Pseudomonas strains improved the total dry matter up to 1.4, and 1.9 fold, respectively, while the increase in salt tolerance index was improved up to 1.3 and 2.0 fold by the Rhizobium and Pseudomonas strains, respectively. However, up to 2.2 fold increase in total dry matter and salt tolerance index was observed due to combined inoculation of Rhizobium and Pseudomonas strains. So, combined application of Rhizobium and Pseudomonas strains could be explored as an effective strategy to induce osmotic stress tolerance in mung bean.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3958208PMC
http://dx.doi.org/10.1590/s1517-83822013000400045DOI Listing
December 2013

The role of mycorrhizae and plant growth promoting rhizobacteria (PGPR) in improving crop productivity under stressful environments.

Biotechnol Adv 2014 Mar-Apr;32(2):429-48. Epub 2013 Dec 28.

University College of Agriculture, University of Sargodha, Sargodha, Pakistan.

Both biotic and abiotic stresses are major constrains to agricultural production. Under stress conditions, plant growth is affected by a number of factors such as hormonal and nutritional imbalance, ion toxicity, physiological disorders, susceptibility to diseases, etc. Plant growth under stress conditions may be enhanced by the application of microbial inoculation including plant growth promoting rhizobacteria (PGPR) and mycorrhizal fungi. These microbes can promote plant growth by regulating nutritional and hormonal balance, producing plant growth regulators, solubilizing nutrients and inducing resistance against plant pathogens. In addition to their interactions with plants, these microbes also show synergistic as well as antagonistic interactions with other microbes in the soil environment. These interactions may be vital for sustainable agriculture because they mainly depend on biological processes rather than on agrochemicals to maintain plant growth and development as well as proper soil health under stress conditions. A number of research articles can be deciphered from the literature, which shows the role of rhizobacteria and mycorrhizae alone and/or in combination in enhancing plant growth under stress conditions. However, in contrast, a few review papers are available which discuss the synergistic interactions between rhizobacteria and mycorrhizae for enhancing plant growth under normal (non-stress) or stressful environments. Biological interactions between PGPR and mycorrhizal fungi are believed to cause a cumulative effect on all rhizosphere components, and these interactions are also affected by environmental factors such as soil type, nutrition, moisture and temperature. The present review comprehensively discusses recent developments on the effectiveness of PGPR and mycorrhizal fungi for enhancing plant growth under stressful environments. The key mechanisms involved in plant stress tolerance and the effectiveness of microbial inoculation for enhancing plant growth under stress conditions have been discussed at length in this review. Growth promotion by single and dual inoculation of PGPR and mycorrhizal fungi under stress conditions have also been discussed and reviewed comprehensively.
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http://dx.doi.org/10.1016/j.biotechadv.2013.12.005DOI Listing
November 2014

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 Feb 6;63:170-6. Epub 2012 Dec 6.

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan.

High ethylene concentration under different environmental stresses such as salinity is one of the contributing factors for premature senescence of different plant parts. Plants under salinity stress produce increased levels of ethylene which inhibit the plant growth and physiology thus deteriorating the quality of the produce. Some plant growth promoting rhizobacteria (PGPR) have the ability to improve quality of crops through reduction in detrimental effects of salinity on plant growth and physiology by lowering endogenous level of ethylene along with other mechanisms. Two field trials were conducted to evaluate the Rhizobium and Pseudomonas containing ACC-deaminase for their efficacy to reduce the effect of salinity on physiology, ionic and nutrient balance of mung bean. Results showed that salinity stress adversely affected the physiological parameters of mung bean. It decreased the CO(2) assimilation, stomatal conductance of water, relative water content, photosynthetic rate, transpiration rate and chlorophyll contents in mung bean but inoculation of either Rhizobium or Pseudomonas alone reduced adverse effect of salinity significantly. However, co-inoculation with Rhizobium and Pseudomonas was the most effective treatment and it diluted the adverse effects of salinity on relative water contents and CO(2) assimilation rate thus improving the photosynthetic rate, water use efficiency and chlorophyll content over the un-inoculated control. Co-inoculation improved the ionic balance and also increased the phosphorus and protein concentration in grain of mung bean. The results suggested that these strains could be effectively used to improve the growth, physiology and quality of mung bean under salt-affected conditions.
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http://dx.doi.org/10.1016/j.plaphy.2012.11.024DOI Listing
February 2013

Inducing salt tolerance in mung bean through coinoculation with rhizobia and plant-growth-promoting rhizobacteria containing 1-aminocyclopropane-1-carboxylate deaminase.

Can J Microbiol 2011 Jul 19;57(7):578-89. Epub 2011 Jul 19.

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan.

Twenty-five strains of plant-growth-promoting rhizobacteria (PGPR) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase and 10 strains of rhizobia were isolated from rhizosphere soil samples and nodules of mung bean. They were screened in separate trials under salt-stressed axenic conditions. The three most effective strains of PGPR (Mk1, Pseudomonas syringae ; Mk20, Pseudomonas fluorescens ; and Mk25, Pseudomonas fluorescens biotype G) and Rhizobium phaseoli strains M1, M6, and M9 were evaluated in coinoculation for their growth-promoting activity at three salinity levels (original, 4 dS·m(-1), and 6 dS·m(-1)) under axenic conditions. The results showed that salinity stress significantly reduced plant growth but inoculation with PGPR containing ACC deaminase and rhizobia enhanced plant growth, thus reducing the inhibitory effect of salinity. However, their combined application was more effective under saline conditions, and the combination Mk20 × M6 was the most efficient for improving seedling growth and nodulation. The effect of high ethylene concentrations on plant growth and the performance of these strains for reducing the negative impact of saline stress was also evaluated by conducting a classical triple-response bioassay. The intensity of the classical triple response decreased owing to inoculation with these strains, with the root and shoot lengths of inoculated mung bean seedlings increasing and stem diameter decreasing, which is a typical response to the dilution in a classical triple response bioassay. Thus, coinoculation with PGPR containing ACC deaminase and Rhizobium spp. could be a useful approach for inducing salt tolerance and thus improving growth and nodulation in mung bean under salt-affected conditions.
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http://dx.doi.org/10.1139/w11-044DOI Listing
July 2011