Our earlier work described that the roots of two maize cultivars, grown hydroponically, differentially responded to cadmium (Cd) stress by initiating changes in medium pH depending on their Cd ...tolerance. The current study investigated the root exudation, elemental contents and antioxidant behavior of the same maize cultivars cv. 3062 (Cd-tolerant) and cv. 31P41 (Cd-sensitive) under Cd stress. Plants were maintained in a rhizobox-like system carrying soil spiked with Cd concentrations of 0, 10, 20, 30, 40 and 50 μmol/kg soil. The root and shoot Cd contents increased, while Mg, Ca and Fe contents mainly decreased at higher Cd levels, and preferentially in the sensitive cultivar. Interestingly, the K contents increased in roots of cv. 3062 at low Cd treatments. The Cd stress caused acidosis of the maize root exudates predominantly in cv. 3062. The concentration of various organic acids was significantly increased in the root exudates of cv. 3062 with applied Cd levels. This effect was diminished in cv. 31P41 at higher Cd levels. Cd exposure increased the relative membrane permeability, anthocyanin (only in cv. 3062), proline contents and the activities of peroxidases (POD) and superoxide dismutase (SOD). The only exception was the catalase activity, which was diminished in both cultivars. Root Cd contents were positively correlated with the secretion of acetic acid, oxalic acid, glutamic acid, citric acid, and succinic acid. The antioxidants like POD and SOD exhibited a positive correlation with the organic acids under Cd stress. It is likly that a high exudation of dicarboxylic organic acids improves nutrient uptake and activities of antioxidants, which enables the tolerant cultivar to acclimatize in Cd polluted environment.
•Maize cultivars differing in Cd tolerance were monitored for root exudates under Cd stress.•In the tolerant cultivar, Cd triggered a higher exudation of organic acids than in the sensitive one.•Plant Cd contents had antagonistic effect on the contents of Mg, Ca, Fe, K and Na.•Cd exposure increased the level of various antioxidants except for catalase.•In tolerant cultivar, exudation of organic acids maintained Mg, Ca and Na level under Cd stress.
Industrial wastewater pollution has become more grievous in the third world countries, where treatment and administration of industrial effluents are not being properly handled. About 80% of ...wastewater having arsenic (As) contamination are due to impurities in pesticides, chromated copper arsenate (CCA) wood preservatives, municipal solid waste incineration; leather industry; and consumption in the industry. Arsenic is a toxic metalloid, which is considered as a severe menace to the life of plants, animals and humans. Some As species such as As(III) and As(V) cause harmful effects on plants and animals. In order to treat As in industrial wastewater, various conventional methods are being employed. However, these methods face limitations in form of missing technical expertise and low effectiveness. Recently, microbial As remediation of industrial water has been evolved as a promising technology due to its public acceptance and cost effectiveness. The current review, for the first time, comprehensively summarizes the role of microbial remediation of As in industrial wastewater. In contrast to phytoremediation, the goal of using microbes is that dissolved arsenic species are converted microbially to arsine gas which is released into the atmosphere at non-toxic levels (dilution effect). In contrast to phytoremediation where arsenic is accumulated in plant material (waste production), this will not produce any solid or liquid waste - and this is just a key benefit of the microbial approach as the management of solid/liquid arsenic rich waste is a global concern and economic burden; however, it was so far only tested on laboratory scale with exception of biofilms that have been tested on pilot scale. Our review also indicated the huge undervalued potential and environmental friendly solution of microbial remediation of As contaminated industrial wastewater without solid/liquid waste production as conventional technologies do.
•First holistic review of microbes for arsenic (As) removal from industrial wastewater.•Microbes are promising, underestimated “eco-friendly nano-factories” for As removal.•Microbes can convert dissolved arsenic (As(III) and As(V)) into volatile arsine gas.•Arsine gas can be released into the atmosphere at non-toxic levels or captured.•Microbes can remove As from wastewater without producing toxic solid/liquid waste.
Heavy metals entered in the soil from numerous sources and reduce the crop growth, productivity, and the quality of the soil environment. Uptake of heavy metals by plants and microorganisms is ...synchronized through the influences of many factors, such as complex soil-plant and microorganism processes. Soil microorganisms are closely associated with soil fertility and are considered important indicators of healthy soils. Various microorganisms have different strategies and mechanisms for survival in heavy metal-contaminated environments such as biosorption, and secretion of compounds that form complexes with heavy metals. The present paper reviewed the recent literature pertaining to heavy metal uptake and tolerance mechanisms of the most important microbial genera viz Aeromonas, Bacillus, and Pseudomonas. This review also focused on the survival and adaptations of selected microbial genera in heavy metal polluted soil habitats which may be helpful in maintaining healthy conditions of agricultural soils. Overall, this review provided the comprehensive knowledge pertaining to heavy metals, their effects on living organisms, and the metal uptake and resistance mechanisms of the selected bacterial genera.
Soils contaminated with heavy metals such as Chromium (Cr) and Cadmium (Cd) severely impede plant growth. Several rhizospheric microorganisms support plant growth under heavy metal stress. In this ...study, Cr and Cd stress was applied to in vitro germinating seedlings of a Legume plant species, Sesbania sesban, and investigated the plant growth potential in presence and absence of Bacillus anthracis PM21 bacterial strain under heavy metal stress. The seedlings were exposed to different concentrations of Cr (25–75 mg/L) and Cd (100–200 mg/L) in Petri plates. Growth curve analysis of B. anthracis PM21 revealed its potential to adapt Cr and Cd stress. The bacteria supported plant growth by exhibiting ACC-deaminase activity (1.57–1.75 μM of α-ketobutyrate/h/mg protein), producing Indole-3-acetic acid (99–119 μM/mL) and exopolysaccharides (2.74–2.98 mg/mL), under heavy metal stress condition. Analysis of variance revealed significant differences in growth parameters between the seedlings with and without bacterial inoculation in metal stress condition. The combined Cr+Cd stress (75 + 200 mg/L) significantly reduced root length (70%), shoot length (24%), dry weight (54%) and fresh weight (57%) as compared to control. Conversely, B. anthracis PM21 inoculation to seedlings significantly increased (p ≤ 0.05) seed germination percentage (5%), root length (31%), shoot length (23%) and photosynthetic pigments (Chlorophyll a: 20%; Chlorophyll b: 16% and total chlorophyll: 18%), as compared to control seedlings without B. anthracis PM21 inoculation. The B. anthracis PM21 inoculation also enhanced activities of antioxidant enzymes, including superoxide dismutase (52%), peroxidase (66%), and catalase (21%), and decreased proline content (56%), electrolyte leakage (50%), and malondialdehyde concentration (46%) in seedlings. The B. anthracis PM21 inoculated seedlings of S. sesban exhibited significantly high (p ≤ 0.05) tissue deposition of Cr (17%) and Cd (16%) as compared to their control counterparts. Findings of the study suggested that B. anthracis PM21 endured metal stress through homeostasis of antioxidant activities, and positively impacted S. sesban growth and biomass. Further experiments in controlled conditions are necessary for investigating phytoremediation potential of S. sesban in metal-contaminated soils in presence of B. anthracis PM21 bacterial strain.
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•The potential of S. sesban against dual metal stress was investigated from Pakistan.•Enhanced metal tolerance of Sesbania in association with B. anthracis is reported first time.•Bioaugmentation of PGP B. anthracis positively influence the seedling growth and metal accumulation by Sesbania.
Fusarium solani (F. solani) is one of the most important pathogenic fungi, that cause Fusarium dry rot and Fusarium wilt in potato, responsible for low potato yield globally. However, the mechanistic ...understanding regarding the biocontrol of F. solani remains largely unknown. Here, we investigated the plant growth-promoting and antagonistic capability of Bacillus sp. PM31 against phytopathogen F. solani. The Bacillus sp. PM31, isolated from field-grown potato was analyzed for plant growth-promoting and extracellular enzyme activities. The strain PM31 exhibited phosphate, zinc, and potassium solubilization, nitrogen fixation, siderophore, exopolysaccharides production, and extracellular enzyme activities. The mycelial growth of F. solani was inhibited by strain PM31 with inhibition coefficient of 47.5. Under the storage conditions, inoculation of strain PM31 minimized the development of dry rot symptoms by 57% as compared to uninoculated diseased tubers. Under greenhouse conditions, inoculation of strain PM31 enhanced potato plant growth under fungal stress, while reduced the development of wilting, foot rot, chlorosis, and necrosis of inoculated potato plants by 92%, 75%, 64%, and 82%, respectively, as compared to diseased plants. Results inferred that the inoculation of native antagonistic Bacillus sp., PM31, could aid in global food security through biocontrol of important potato diseases viz. Fusarium dry rot and Fusarium wilt.
Cadmium (Cd) is highly toxic for plant metabolic processes even in low concentration due to higher retention rates, longer half-life and non-biodegradable nature. The current study was designed to ...assess the bioremediation potential of Cd tolerant PGPR, Serratia sp. CP-13 together with two differentially Cd tolerant maize cultivars (MMRI-Yellow, Sahiwal-2002) selected amongst ten cultivars after screening. The maize cultivars were grown under different Cd treatments (0, 6, 12, 18, 24, 30 µM) in Petri plates both with and without Serratia sp. CP-13 inoculation. Treated plants were analyzed for their biomass accumulation, chlorophylls, carotenoids, proline, anthocyanin, protein, malondialdehyde (MDA), H2O2 as well as for antioxidants (POD, SOD, CAT) and mineral elements (Ca, Mg, Zn, K, Fe, Na, Cd). The maize cultivar MMRI-Yellow (tolerant) and Sahiwal-2002 (sensitive) exhibited significant reduction in leaf area, nutrient contents, plant biomass, activity of antioxidants, total proteins, photosynthetic pigments as well as flavonoids with increased production of H2O2, proline, MDA and relative membrane permeability (RMP) under Cd stress. However, this reduction was cultivar specific and recorded higher in cv. Sahiwal-2002 as compared to MMRI-Yellow. Application of Serratia sp. CP-13 significantly augmented plant biomass, photosynthetic pigments, antioxidative machinery, as well as flavonoids and proline while diminishing H2O2, RMP MDA production even under Cd stress in studied cultivars. Furthermore, CP-13 inoculation assisted the Cd stressed plants to sustain an optimal level of essential nutrients (Ca, Mg, Zn, K, Fe) except for Na and Cd which responded antagonistically. It was inferred that both inoculated maize cultivars exhibited better health and metabolism but substantial Cd tolerance was acquired by the sensitive cv. Sahiwal-2002 than the tolerant cv. MMRI-Yellow under applied Cd regimes. Furthermore, studied maize cultivars depicted maximum Cd tolerance in order of 30 < 24 < 18 < 12 < 6 < 0 µM Cd treatments under Serratia sp. CP-13 inoculation. Findings of current work highlighted the importance of Serratia sp. CP-13 and its inoculation impact on morpho-physio-biochemical attributes of maize growth under Cd dominant environment, which is likely an addition towards efficient approaches for bacterially-assisted Cd bioremediation and minimal Cd retention in edible plant parts.
•First time, Serratia-maize synergy for differentially Cd tolerant cultivars has been explored.•Serratia sp. CP-13 diminishes Cd uptake and concomitant lipid peroxidation in maize cultivars.•Under CP-13 application, Cd susceptible cultivar exhibited improved antioxidants and nutrients than the tolerant one.•Serratia sp. CP-13 is a potential candidate for plant growth augmentation and Cd remediation plans.
Aims
Iron oxide nanoparticles (Fe2O3 NPs) were mycosynthesized using Trichoderma harzianum and applied to control brown rot of apple. The influence of Fe2O3 NPs on the quality of fruit was also ...studied.
Methods and Results
Diseased apple fruits with brown rot symptoms were collected, and the disease‐causing pathogen was isolated and identified as Fusarium oxysporum. To control this disease, mycosynthesis of Fe2O3 NPs was executed using T. harzianum. FTIR spectroscopy revealed the occurrence of stabilizing and reducing agents on NPs. X‐ray diffraction (XRD) analysis determined their average size (17.78 nm) and crystalline nature. Energy‐dispersive X‐ray (EDX) showed strong signals of iron, and scanning electron microscopy (SEM) displayed a high degree of polydispersity of synthesized NPs. Foliar application of NPs significantly reduced brown rot and helped fruits to maintain biochemical and organoleptic properties. Firmness and higher percentage of soluble solids, sugars and ascorbic acid depicted its good quality.
Conclusion
Environment‐friendly mycosynthesized Fe2O3 NPs can be effectively used to control brown rot of apple.
Significance and Impact of the Study
Trichoderma harzianum is a famous biocontrol agent, and the synthesis of NPs in its extract is an exciting avenue to control fungal diseases. Due to its nontoxic nature to human gut, it can be applied on all edible fruits.
Salinity poses serious threats to landscapes across the globe, decreasing the capacity of all types of terrestrial ecosystems in providing services by threatening our biodiversity, lowering ...agricultural productivity, deteriorating the environment, contaminating groundwater below standard level, enhancing flood risks, food security issues and restricting the economic growth of a community. Reclamation measures are required to reverse the process of land degradation caused by salinization; otherwise, the trend towards salinization is expected to grow beyond control in developing countries. The scientific community and the policy-makers around the globe have been testing long-term technologies including physicochemical, conventional breeding and genetic engineering involving state of the art molecular tools for more than three decades. Nevertheless, they have failed due to reasons like non-technical feasibility reports, reliability and affordability issues coupled with sustainability constraints at field level. This review discusses the potential prospects of Pennisetum genus (Poaceae) for integrated, sustainable, robust and profitable saline agriculture based on phytoremediation agro-technique. Our approach is the first ever record, providing a novel insight into a cost-effective biotech agro-technique. Pennisetum species are environment-friendly future candidates with prospects for all stakeholders to materialize higher average productivity at the field level, posing lesser competition for resources with standard conventional crops.
Soil microorganisms might be assessed for their capabilities of plant growth promotion in order to identify heat tolerant strategies for crop production. The planned study was conducted to determine ...the potential of heat tolerant plant growth promoting rhizobacteria (PGPR) in mitigating heat stress effects in tomato. Bacillus cereus was evaluated for plant growth promoting activities and assessed for 1-aminocyclopropane-1-carboxylate (ACC-deaminase) (0.76–C0.9 μM/mg protein/h), and exopolysaccharide (0.66–C0.91 mg/mL) under normal and heat stressed conditions. Plant growth regulators were evaluated through High Performance Liquid Chromatography. Bacterial inoculation effects on important physiological and biochemical parameters were evaluated under normal and heat stressed conditions in growth chamber. The morphological-physiological traits significantly revealed drastic effects on both of un-inoculated tomato varieties under heat stress conditions. Bacterial augmentation significantly promoted shoot, root length, leaf surface area, fresh and dry weight. Heat stress enhanced extracellular polymeric substances (EPS) production and cleavage of ACC into a-ketobutyrate and ammonia due to ACC-deaminase producing bacteria that significantly reduced the adverse effects of heat on tomato growth. In conclusion, the applied plant growth promoting rhizobacteria (PGPR) bacterial strain proved as potential candidate for improving tomato crop growing under heat stressed conditions. However, it is highly suggested to validate the current results by conducting field trials.
Grapefruit (Citrus paradisi) is a widely grown citrus and its fruit is affected by a variety of biotic and abiotic stress. Keeping in view the hazardous effects of synthetic fungicides, the recent ...trend is shifting towards safer and eco-friendly control of fruit diseases. The present study was aimed to diagnose the fruit rot disease of grapefruit and its control by using zinc oxide green nanoparticles (ZnO NPs). Fruit rot symptoms were observed in various grapefruit growing sites of Pakistan. Diseased samples were collected, and the disease-causing pathogen was isolated. Following Koch’s postulates, the isolated pathogen was identified as Rhizoctonia solani. For eco-friendly control of this disease, ZnO NPs were prepared in the seed extract of Trachyspermum ammi and characterized. Fourier transform infrared spectroscopy (FTIR) of these NPs described the presence of stabilizing and reducing compounds such as phenols, aldehyde and vinyl ether, especially thymol (phenol). X-ray diffraction (XRD) analysis revealed their crystalline nature and size (48.52 nm). Energy dispersive X-ray (EDX) analysis elaborated the presence of major elements in the samples, while scanning electron microscopy (SEM) confirmed the morphology of bio fabricated NPs. ZnO NPs exhibited very good anti-fungal activity and the most significant fungal growth inhibition was observed at 1.0 mg/ml concentration of green NPs, in vitro and in vivo. These findings described that the bioactive constituents of T. ammi seed extract can effectively reduce and stabilize ZnO NPs. It is a cost-effective method to successfully control the fruit rot disease of grapefruit.
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