Bacillus safensis filtrate-based ZnO nanoparticles control black heart rot disease of apricot fruits by maintaining its soluble sugars and carotenoids

Black heart rot is a serious disease of apricot and it has been reported to be caused by Alternaria solani, around the world. The present research was designed to control this disastrous disease using zinc oxide nanoparticles (b-ZnO NPs). These NPs were synthesized in the filtrate of a useful bacterium (Bacillus safensis) and applied to control black heart rot of apricot. After synthesis, the reduction of b-ZnO NPs was confirmed by UV-visible spectroscopy, at 330 nm. Fourier transform infrared (FTIR) spectra ensured the presence of multiple functional groups (alcohols, phenols, carboxylic acids, nitro compounds and amines) on the surface of b-ZnO NPs. X-Ray diffraction (XRD) analysis elucidated their average size (18 nm) while scanning electron microscopy (SEM) micrograph described the spherical shape of b-ZnO NPs. The synthesized b-ZnO NPs were applied in four different concentrations (0.25 mg/ml, 0.50 mg/ml, 0.75 mg/ml, 1.0 mg/ml) under both in vitro and in vivo conditions. These NPs were very efficient in inhibiting mycelial growth (85.1%) of A. solani at 0.75 mg/ml concentration of NPs, in vitro. Same concentration also performed best, in vivo, and significantly reduced disease incidence (by 67%) on self-inoculated apricot fruit. Apart from this, application of b-ZnO NPs helped apricot fruit to maintain its quality under fungal-stress conditions. The decay of apricot fruit was reduced and they maintained greater firmness and higher weight. Moreover, b-ZnO NPs treated fruits controlled black heart rot disease by maintaining higher contents of ascorbic acid, soluble sugars and carotenoids. These b-ZnO NPs were produced in powder form for their easy carriage to the farmers' fields.

Methyl eugenol aromatherapy: a delivery system facilitating the simultaneous application of male annihilation and sterile insect technique against the peach fruit fly

BACKGROUND

The peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae) is an economically important polyphagous, quarantine pest endemic to South and South-East Asia. The male annihilation technique (MAT) and the sterile insect technique (SIT) are environmentally benign techniques used to suppress fruit fly populations on an area-wide basis. The MAT and SIT are typically used sequentially to avoid killing released sterile males; however, MAT and SIT potentially could be used simultaneously and thereby increase the overall efficiency of control programmes. Mating competitiveness of sterile males against wild counterparts is critical for the success of the SIT. Feeding on a semiochemical, methyl eugenol (ME) has been reported to enhance the male mating performance of many Bactrocera spp., including B. zonata, but its use in SIT operational programmes is limited owing to the absence of a viable delivery system.

RESULTS

In the present study, we demonstrated that ME aromatherapy, a practical method for large-scale delivery of ME olfactorily, enhances the mating success of treated B. zonata males. ME aromatherapy application to 5-day-old immature males for a duration of 5 h resulted in increased mating success of males tested when sexually mature, compared to untreated males. The ME-aromatized males also exhibited reduced attraction to ME-lure.

CONCLUSION

A practical delivery system for applying ME by aromatherapy to mass-reared males was developed. ME-aromatherapy enhanced male mating success and suppressed their subsequent attraction to ME, thus enabling the application of MAT and SIT at the same time. © 2023 Society of Chemical Industry.

Spherical Fe2O3 nanoparticles inhibit the production of aflatoxins (B1 and B2) and regulate total soluble solids and titratable acidity of peach fruit

Aflatoxin is a group I carcinogen and causes significant public health and food safety risks, throughout the world. This study was carried out to assess the levels of aflatoxin contamination in diseased peach (Prunus persica L.) fruit and their control using myco-synthesized iron oxide nanoparticles (Fe2O3 NPs). Diseased peach fruit were diagnosed to be infected with Aspergillus flavus. The isolated pathogen was cultured under UV light (365 nm) and exposed to ammonium hydroxide (31 %) vapors, which confirmed its ability to produce aflatoxin. For the control of this disease, Fe2O3 NPs were synthesized in the filtrate of a biocontrol fungus (Trichoderma harzianum) and characterized before analyzing their potential in disease control. FTIR spectrum described the presence of capping and reducing agents (secondary amines, alcohol, alkyne and aromatic compounds) on the surface of Fe2O3 NPs. X-ray Diffraction (XRD) described the crystalline size (7.78), while the spherical shape of Fe2O3 NPs was described by the SEM analysis. The EDX spectrum indicated the successful formation of Fe2O3 NPs by showing strong signals of iron (74.38 %). All concentrations displayed mycelial growth inhibition, in vitro and the greatest growth reduction (65.4 %) was observed at 1 mg/ml concentration of NPs. At the same concentration of Fe2O3 NPs, significant control of fruit rot of peach was also observed, in vivo. Treatment of Fe2O3 NPs maintained higher soluble solids, sucrose, total sugar, ascorbic acid, titratable acidity and firmness of peach fruit. Diseased fruit were further investigated for the presence and detection of aflatoxins. All three methods viz. thin layer chromatography (TLC), enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC) confirmed a higher production of aflatoxins in control plants, while this production was significantly reduced in Fe2O3 NPs-treated peach fruit.

Concurrent application of bacterial-mediated and mycosynthesized ZnO nanofungicides to maintain high ascorbic acid and delay postharvest decay of apricot

Quality of apricot fruit is affected by different biotic stresses during growth, harvesting and storage. Due to fungal attack, huge losses of its quality and quantity are observed. The present research was designed for the diagnoses and management of postharvest rot disease of apricot. Infected apricot fruit were collected, and the causative agent was identified as A. tubingensis. To control this disease, both bacterial-mediated nanoparticles (b-ZnO NPs) and mycosynthesized nanoparticles (f-ZnO NPs) were used. Herein, biomass filtrates of one selected fungus (Trichoderma harzianum) and one bacterium (Bacillus safensis) were used to reduce zinc acetate into ZnO NPs. The physiochemical and morphological characters of both types of NPs were determined. UV-vis spectroscopy displayed absorption peaks of f-ZnO NPs and b-ZnO NPs at 310-380 nm, respectively, indicating successful reduction of Zinc acetate by the metabolites of both fungus and bacteria. Fourier transform infrared (FTIR) determined the presence of organic compounds like amines, aromatics, alkenes and alkyl halides, on both types of NPs, while X-ray diffraction (XRD) confirmed nano-size of f-ZnO NPs (30 nm) and b-ZnO NPs (35 nm). Scanning electron microscopy showed flower-crystalline shape for b-ZnO NPs and spherical-crystalline shape for f-ZnO NPs. Both NPs showed variable antifungal activities at four different concentrations (0.25, 0.50, 0.75 and 1.00 mg/ml). Diseases control and postharvest changes in apricot fruit were analyzed for 15 days. Among all treatments, 0.50 mg/ml concentration of f-ZnO NPs and 0.75 mg/ml concentration of b-ZnO NPs exhibited the strongest antifungal activity. Comparatively, f-ZnO NPs performed slightly better than b-ZnO NPs. Application of both NPs reduced fruit decay and weight, maintained higher ascorbic acid contents, sustained titratable acidity, and preserved firmness of diseased fruit. Our results suggest that microbial synthesized ZnO NPs can efficiently control fruit rot, extend shelf life, and preserve the quality of apricot.

Impact of bacterial synthesized nanoparticles on quality attributes and postharvest disease control efficacy of apricot and loquat

Postharvest fungal attacks on fruits such as apricots and loquats are common. Diseased fruit samples were collected from Murree's local fruit markets. The disease-causing pathogens were identified utilizing molecular, microscopic, and morphological characteristics. Alternaria alternata and Aspergillus niger were identified as the pathogens responsible for brown rot in loquat and black rot in apricot. To combat these fruit diseases, iron oxide (Fe2 O3 ) nanoparticles were synthesized using Bacillus subtilis and were characterized using various techniques. X-ray diffraction examination validated the size of iron oxide nanoparticles. The presence of several capping agents in the synthesized nanoparticles was confirmed by Fourier transform infrared analysis. Scanning electron microscopy revealed the spherical morphology of nanoparticles, whereas energy-dispersive X-ray proved the presence of different elemental compositions. After completing antifungal activities in vitro and in vivo, it was discovered that a nanoparticle concentration of 1.0 mg/mL efficiently suppressed the growth of fungal mycelia. Fungi growth was effectively inhibited in fruit samples treated with 1.0 mg/mL nanoparticles. The results of successful in vitro and in vivo antifungal activities imply that iron oxide (Fe2 O3 ) nanoparticles play an important role in ensuring fruit quality against pathogenic attacks. Bacterial-mediated iron oxide can be widely used because it is less expensive and less harmful to the environment than chemically manufactured fertilizers.

Effect of green Fe2O3 nanoparticles in controlling Fusarium fruit rot disease of loquat in Pakistan

The subtropical fruit known as the loquat is prized for both its flavour and its health benefits. The perishable nature of loquat makes it vulnerable to several biotic and abiotic stressors. During the previous growing season (March-April 2021), loquat in Islamabad showed signs of fruit rot. Loquat fruits bearing fruit rot symptoms were collected, and the pathogen that was causing the disease isolated and identified using its morphology, microscopic visualisation, and rRNA sequence. The pathogen that was isolated was identified as Fusarium oxysporum. Green synthesized metallic iron oxide nanoparticles (Fe2O3 NPs) were employed to treat fruit rot disease. Iron oxide nanoparticles were synthesized using a leaf extract of the Calotropis procera. Characterization of NPs was performed by different modern techniques. Fourier transform infrared spectroscopy (FTIR) determined the existence of stabilizing and reducing compounds like phenol, carbonyl compounds, and nitro compounds, on the surface of Fe2O3 NPs. X-ray diffraction (XRD) explained the crystalline nature and average size (~49 nm) of Fe2O3 NPs. Energy dispersive X-ray (EDX) exhibited Fe and O peaks, and scanning electron microscopy (SEM) confirmed the smaller size and spherical shape of Fe2O3 NPs. Following both in vitro and in vivo approaches, the antifungal potential of Fe2O3 NPs was determined, at different concentrations. The results of both in vitro and in vivo analyses depicted that the maximum fungal growth inhibition was observed at concentration of 1.0 mg/mL of Fe2O3 NPs. Successful mycelial growth inhibition and significantly reduced disease incidence suggest the future application of Fe2O3 NPs as bio fungicides to control fruit rot disease of loquat.

Exploration of plant growth promoting traits and regulatory mechanisms of Bacillus anthracis PM21 in enhancing salt stress tolerance in maize

Bacillus species have been reported to reduce the negative effects of salt stress on plants; the involvement of Bacillus anthracis PM21 and the internal mechanisms involved in this process are unclear. The effects of PM21 inoculation on maize plants under salt stress were investigated in this study. The study aimed to assess the ability of Bacillus anthracis PM21 to endure high levels of salinity stress while preserving the concentration of plant growth regulators. The biomass, photosynthetic pigments, relative water content (RWC), antioxidants, osmoprotectants, inorganic ion contents, regulation of plant hormones and expression of antioxidants enzyme encoded genes were investigated under normal and salinity stress conditions. Bacillus anthracis PM21 produced a significant amount of 1-aminocyclopropane-1-carboxylate deaminase enzyme (ACC deaminase) and exopolysaccharides (EPS) under salt stress and normal conditions. PM21 also produced plant growth stimulants including indole acetic acid, gibberellic acid (GA3), kinetin, and siderophore under salinity stress and normal conditions. Under salt stress, PM21 inoculation markedly increased plant growth indices, stimulate antioxidant enzyme mechanisms, osmoprotectants, and chlorophyll content. The use of qRT-PCR to analyze the transcription of targeted genes indicated greater expression of antioxidant-encoded genes and inferred their possible function in salinity stress tolerance. Our findings shed light on the functions of PM21 and its regulatory mechanisms in plant salt stress tolerance, as well as the importance of PM21 in this process. This study will provide a thorough analysis of the theoretical framework for adopting PM21 in agricultural production as an eco-friendly method to enhance crop growth and yield under salinity stress.

Application of phyto-fabricated zinc oxide nanoparticles to diminish brown spot of pear whilst maintaining its quality

Pyrus communis is a common fruit of temperate region, its domestication and origin is at two different points, Asia and China. Pear fruits bearing brown spot symptoms were picked, and pathogen was isolated and poured on Potato Dextrose Agar (PDA) media. On basis of molecular and molecular analyses, this isolated pathogen was identified as Alternaria alternata. Zinc oxide nanoparticles (ZnO NPs) were prepared from Theveti peruviana leaf extract and were characterized through various techniques Fourier Transform Infrared Spectroscopy (FTIR) analysis of prepared ZnO NPs depicted the presence of agents responsible for stabilization and reduction such as alkenes, alkynes, nitro compounds, alkyl halides, aromatic compounds and aliphatic amines. X-ray diffraction (XRD) analysis confirmed the size (27 nm) and crystalline nature of ZnO NPs. Scanning electron microscopy (SEM) depicted the irregular shape of the prepared ZnO NPs. Mass percentage of zinc (79.84%) and oxygen (20.16%) was depicted using Energy Dispersive X-Ray (EDX) analysis. The in vitro and in vivo antifungal activity (A.F) of prepared NPs against A. alternata was confirmed by poisoned food technique and wound inoculation method. On the basis of which it was concluded that 1.0 mg/mL concentration of ZnO NPs could effectively inhibit A. alteranata growth and minimize the risk of brown spot of pear. SEM images of A. alternata under 1 mg/mL NPs showed the deformation in morphology of A. alternata. ZnO NPs also aided in the preservation of its various organoleptic and biochemical properties. The high percentage of soluble solids, firmness, ascorbic acid and sugars demonstrated its high quality. It has been concluded that 1 mg/mL ZnO NPs can effectively control brown spot of pear while maintaining its quality. In addition, the method might be applied to control emerging diseases in an ecofriendly way to meet the global food demand. RESEARCH HIGHLIGHTS: Isolation and characterization of pathogen causing brown spot in pear. Pathogenicity of A. alternata was checked on healthy fruits. Thevetia peruviana leaf extract was used for the synthesis, characterization and antifungal assay of ZnO Nanoparticles. Green synthesized nanoparticles can be economically effective alternative fungicide for the large scale in agriculture fields.

Bio-fabrication of zinc oxide nanoparticles from Picea smithiana and their potential antimicrobial activities against Xanthomonas campestris pv. Vesicatoria and Ralstonia solanacearum causing bacterial leaf spot and bacterial wilt in tomato

Due to an inevitable disadvantage of chemical or physical synthesis routes, biosynthesis approach to nanoparticles, especially metallic oxide is attractive nowadays. Metallic oxides nanoparticles present a new approach to the control of plant pathogens. ZnO nanoparticles (ZNPs) have very important role in phytopathology. In current study, biosynthesized ZNPs were tested against two devastating bacterial pathogens including Xanthomonas campestris pv. vesicatoria and Ralstonia solanacearum causing bacterial leaf spot and bacterial wilt in tomato. ZNPs were produced using a new extract from the plant Picea smithiana using an environmentally friendly, cost-effective and simple procedure. Zinc acetate was added to P. smithiana extract, stirred and heated to 200 °C. The white precipitation at the bottom were clear indication of synthesis of nanoparticles, which were further dried by subjecting them at 450 °C. X-ray diffraction pattern determined that the ZNPs had a crystallite size of about 26 nm, Fourier transform infrared spectroscopy indicated a peak between 450 and 550 cm^-1 and the particle size estimated by dynamic light scattering was about 25 nm on average. Scanning electron microscopic analysis indicated that the particles were hexagonal in shape 31 nm in diameter. Antibacterial tests showed ZNPs synthesized by P. smithiana resulted in clear inhibition zones of 20.1 ± 1.5 and 18.9 ± 1.5 mm and 44.74 and 45.63% reduction in disease severity and 78.40 and 80.91% reduction in disease incidence in X. compestris pv. vesicatoria and R. solanacearum respectively at concentration of 100 µg/ml. Our findings reveal that the concentration of ZNPs was important for their efficient antibacterial activity. Overall, the biosynthesized ZNPs have been found to have effective antimicrobial activities against bacterial wilt and bacterial leaf spot in tomato.

Biodegradation of monocrotophos by Brucella intermedia Msd2 isolated from cotton plant

Widespread and inadequate use of Monocrotophos has led to several environmental issues. Biodegradation is an ecofriendly method used for detoxification of toxic monocrotophos. In the present study, Msd2 bacterial strain was isolated from the cotton plant growing in contaminated sites of Sahiwal, Pakistan. Msd2 is capable of utilizing the monocrotophos (MCP) organophosphate pesticide as its sole carbon source for growth. Msd2 was identified as Brucella intermedia on the basis of morphology, biochemical characterization and 16S rRNA sequencing. B. intermedia showed tolerance of MCP up to 100 ppm. The presence of opd candidate gene for pesticide degradation, gives credence to B. intermedia as an effective bacterium to degrade MCP. Screening of the B. intermedia strain Msd2 for plant growth promoting activities revealed its ability to produce ammonia, exopolysaccharides, catalase, amylase and ACC-deaminase, and phosphorus, zinc and potassium solubilization. The optimization of the growth parameters (temperatures, shaking rpm, and pH level) of the MCP-degrading isolate was carried out in minimal salt broth supplemented with MCP. The optimal pH, temperature, and rpm for Msd2 growth were observed as pH 6, 35 °C, and 120 rpm, respectively. Based on optimization results, batch degradation experiment was performed. Biodegradation of MCP by B. intermedia was monitored using HPLC and recorded 78% degradation of MCP at 100 ppm concentration within 7 days of incubation. Degradation of MCP by Msd2 followed the first order reaction kinetics. Plant growth promoting and multi-stress tolerance ability of Msd2 was confirmed by molecular analysis. It is concluded that Brucella intermedia strain Msd2 could be beneficial as potential biological agent for an effective bioremediation for polluted environments.

Biofilm formation and flocculation potential analysis of halotolerant Bacillus tequilensis and its inoculation in soil to mitigate salinity stress of chickpea

Application of beneficial microbes in soil is an important avenue to control plant stresses. In this study, the salinity tolerance of halotolerant bacteria (Bacillus tequilensis) was investigated and the bacterium was inoculated in the soil to mitigate salinity stress. The results revealed the highest floc yield and biofilm formation ability of B. tequilensis at 100 mM NaCl concentration. Fourier transformed infrared spectroscopy depicted the presence of carbohydrates and proteins which binds with sodium ions (Na+) and provide tolerance against salinity. Using PCR, plant growth-promoting bacterial genes viz., 1-aminocyclopropane-1-carboxylate deaminase and pyrroloquinoline quinone were successfully amplified from the genome of B. tequilensis. In the saline soil, B. tequilensis was inoculated and chickpea plants were grown. The bacterial strain improved the physiology, biochemistry, and antioxidant enzyme activities of the chickpea plant under salt stress. Plants inoculated with B. tequilensis exhibited higher relative water content, higher photosynthetic pigments, lower levels of hydrogen peroxide (H2O2) and malondialdehyde, and improved enzymatic activity for the scavenging of reactive oxygen species. The findings of this study suggest the sustainable use of B. tequilensis to mitigate the salinity stress of chickpea and other crops. This bacterium not only helps in the alleviation of the toxic effects of salt but also increases plant growth along with a reduction in crop losses due to salinity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01280-1.

Integrated Application of Salicylic Acid and PGPRs to Control Fusarium Wilt of Chickpea

BACKGROUND

Fusarium wilt and Ascochyta blight are the most important diseases of chickpea. The current study was designed to investigate the individual and combined effect of salicylic acid (SA) with Pseudomonas stutzeri and Pseudomonas putida to suppress Fusarium wilt and promote growth of chickpea varieties: Thal-2006 and Punjab-2008.

METHODS

At the time of sowing, inoculum of Fusarium oxysporum was applied to the soil and the incidence of Fusarium wilt was recorded after 60 days. The seeds were inoculated with Pseudomonas stutzeri and Pseudomonas putida prior to sowing. Chickpea plants were treated with salicylic acid at seedling stage.

RESULTS

The combination of P. stutzeri and SA significantly increased root length (166% and 145%), shoot height (50% and 47%) and shoot biomass (300% and 233%) in cv. Thal-2006 and cv. Punjab-2008, respectively, in infected plants. Similarly, the combined treatment of P. putida + SA, also enhanced the plant growth parameters of chickpea varieties. Maximum reduction in disease severity was observed in both P. stutzeri + SA (90% and 84%) and P. putida + SA (79% and 77%) treatments in cv. Thal-2006 and Punjab-2008, respectively. Both P. putida + SA and P. stutzeri + SA treatments resulted in increased leaf relative water and total protein content, peroxidase, superoxide dismutase, phenylalanine ammonia-lyase and polyphenol oxidase activities in both resistant (cv. Thal-2006) and susceptible (cv. Punjab-2008) cultivars. Both treatments also significantly reduced malondialdehyde (MDA) and proline content in cv. Thal-2006 and Punjab-2008. Cultivar Thal-2006 was more effective than cv. Punjab-2008.

CONCLUSIONS

The results suggested that, in combination, salicylic acid and P. stutzeri may play an important role in controlling Fusarium wilt diseases by inducing systemic resistance in chickpea.

Reprisal of Schima superba to Mn stress and exploration of its defense mechanism through transcriptomic analysis

One of the most diverse protein families, ATP-binding cassette (ABC) transporters, play a role in disease resistance, heavy metal tolerance, and food absorption.Differentially expressed genes contribute in the investigation of plant defense mechanisms under varying stress conditions. To elucidate the molecular mechanisms involved in Mn metal stress, we performed a transcriptomic analysis to explore the differential gene expression in Schima superba with the comparison of control. A total of 79.84 G clean data was generated and 6558 DEGs were identified in response to Mn metal stress. Differentially expressed genes were found to be involved in defense, signaling pathways, oxidative burst, transcription factors and stress responses. Genes important in metal transport were more expressive in Mn stress than control plants. The investigation of cis-acting regions in the ABC family indicated that these genes might be targeted by a large variety of trans-acting elements to control a variety of stress circumstances. Moreover, genes involved in defense responses, the mitogen-activated protein kinase (MAPK) signaling and signal transduction in S. superba were highly induced in Mn stress. Twenty ABC transporters were variably expressed on 1st, 5th, and 10th day of Mn treatment, according to the qRT PCR data. Inclusively, our findings provide an indispensable foundation for an advanced understanding of the metal resistance mechanisms. Our study will enrich the sequence information of S. superba in a public database and would provide a new understanding of the molecular mechanisms of heavy metal tolerance and detoxification.

Antifungal activity of Zinc nitrate derived nano Zno fungicide synthesized from Trachyspermum ammi to control fruit rot disease of grapefruit

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.

Deciphering distinct biological control and growth promoting potential of multi-stress tolerant Bacillus subtilis PM32 for potato stem canker

Plant growth-promoting rhizobacteria (PGPR) represent a set of microorganisms that play significant role in improving plant growth and controlling the phytopathogens. Unpredictable performance after the application of PGPR has been observed when these were shifted from in-vitro to in-vivo conditions due to the prevalence of various abiotic stress conditions. During growing period, the potato crop is subjected to a combination of biotic and abiotic stresses. Rhizoctonia solani, a soil-borne plant pathogen, causes reduced vigor and yield of potato crop worldwide. In the current study, multi-stress-tolerant rhizobacterial strain, Bacillus subtilis PM32, was isolated from field-grown potato with various plant growth promoting (PGP) traits including zinc and potassium solubilization, biological nitrogen fixation, ammonia and siderophore, as well as extracellular enzyme productions (cellulase, catalase, amylase, protease, pectinase, and chitinase). The strain PM32 exhibited a distinct potential to support plant growth by demonstrating production of indole-3-acetic acid (102.6 μM/mL), ACC-deaminase activity (1.63 μM of α-ketobutyrate/h/mg protein), and exopolysaccharides (2.27 mg/mL). By retarding mycelial growth of R. solani the strain PM32 drastically reduced pathogenicity of R. solani. The strain PM32 also suppressed the pathogenic activity significantly by impeding mycelial expansion of R. solani with inhibition co-efficient of 49.87. The B. subtilis PM32 also depicted significant tolerance towards salt, heavy metal (Pb), heat and drought stress. PCR based amplification of ituC and acds genes coding for iturin and ACC-deaminase activity respectively indicated potential of strain PM32 for lipopeptides production and ACC deaminase enzyme activity. Results of both in-vitro and pot experiments under greenhouse conditions depicted the efficiency of B. subtilis PM32 as a promising bio-control agent for R. solani infection together with enhanced growth of potato plants as deciphered from biomass accumulation, chlorophyll a, b, and carotenoid contents. Therefore, it was envisioned that application of indigenous multi-stress tolerant PGPR may serve to induce biotic and abiotic stress tolerance in crops/plants for pathogen control and sustainable global food supply.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01067-2.

Evaluation of virulence potential of Aspergillus tubingensis and subsequent biochemical and enzymatic defense response of cotton

Aspergillus tubingensis is a causative known pathogen of various important crops, worldwide. The existing study was aimed to examine the virulence potential of A. tubingensis on resistant (NIA-Sadori) and susceptible (CIM-573) cultivars of cotton. For this purpose, both cultivars were inoculated with pathogen and altered morphology of diseased leaves was observed with light and scanning electron microscope. Disease severity was measured and estimated to be 68.7 and 27.1% in susceptible and resistant cultivars, respectively. To understand and compare defense mechanism of resistant and susceptible cultivars, different biochemical and enzymatic changes were observed. After the infection of A. tubingensis, increase in the concentrations of sugar, total protein, proline, phenol, and phenylalanine ammonia lyase (PAL) was more prominent in resistant cultivar, than the susceptible one. Moreover, due to increased number of dead cells, significantly higher electrolyte leakage was detected in susceptible cultivar. Principal component analysis confirmed the effect of A. tubingensis on growth attributes and various physiological and biochemical activities of cotton. These findings help us to suggest a possible role of proline content, protein content, and PAL activity in resistance mechanism of Cotton plant.

PacBio Single-Molecule Long-Read Sequencing Reveals Genes Tolerating Manganese Stress in Schima superba Saplings

Schima superba (Theaceae) is a subtropical evergreen tree and is used widely for forest firebreaks and gardening. It is a plant that tolerates salt and typically accumulates elevated amounts of manganese in the leaves. With large ecological amplitude, this tree species grows quickly. Due to its substantial biomass, it has a great potential for soil remediation. To evaluate the thorough framework of the mRNA, we employed PacBio sequencing technology for the first time to generate S. Superba transcriptome. In this analysis, overall, 511,759 full length non-chimeric reads were acquired, and 163,834 high-quality full-length reads were obtained. Overall, 93,362 open reading frames were obtained, of which 78,255 were complete. In gene annotation analyses, the Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Genes (COG), Gene Ontology (GO), and Non-Redundant (Nr) databases were allocated 91,082, 71,839, 38,914, and 38,376 transcripts, respectively. To identify long non-coding RNAs (lncRNAs), we utilized four computational methods associated with protein families (Pfam), Cooperative Data Classification (CPC), Coding Assessing Potential Tool (CPAT), and Coding Non-Coding Index (CNCI) databases and observed 8,551, 9,174, 20,720, and 18,669 lncRNAs, respectively. Moreover, nine genes were randomly selected for the expression analysis, which showed the highest expression of Gene 6 (Na_Ca_ex gene), and CAX (CAX-interacting protein 4) was higher in manganese (Mn)-treated group. This work provided significant number of full-length transcripts and refined the annotation of the reference genome, which will ease advanced genetic analyses of S. superba.

Functional Annotation of a Full-Length Transcriptome and Identification of Genes Associated with Flower Development in Rhododendronsimsii (Ericaceae)

Rhododendronsimsii is one of the top ten famous flowers in China. Due to its historical value and high aesthetic, it is widely popular among Chinese people. Various colors are important breeding objectives in Rhododendron L. The understanding of the molecular mechanism of flower color formation can provide a theoretical basis for the improvement of flower color in Rhododendron L. To generate the R.simsii transcriptome, PacBio sequencing technology has been used. A total of 833,137 full-length non-chimeric reads were obtained and 726,846 high-quality full-length transcripts were found. Moreover, 40,556 total open reading frames were obtained; of which 36,018 were complete. In gene annotation analyses, 39,411, 18,565, 16,102 and 17,450 transcriptions were allocated to GO, Nr, KEGG and COG databases, correspondingly. To identify long non-coding RNAs (lncRNAs), we utilized four computational methods associated with Protein families (Pfam), Cooperative Data Classification (CPC), Coding Assessing Potential Tool (CPAT) and Coding Non Coding Index (CNCI) databases and observed 6170, 2265, 4084 and 1240 lncRNAs, respectively. Based on the results, most genes were enriched in the flavonoid biosynthetic pathway. The eight key genes on the anthocyanin biosynthetic pathway were further selected and analyzed by qRT-PCR. The F3'H and ANS showed an upward trend in the developmental stages of R. simsii. The highest expression of F3'5'H and FLS in the petal color formation of R. simsii was observed. This research provided a huge number of full-length transcripts, which will help to proceed genetic analyses of R.simsii. native, which is a semi-deciduous shrub.

Characterization of bio-fabricated silver nanoparticles for distinct anti-fungal activity against sugarcane phytopathogens

Advanced research, development, and application of silver nanoparticles is proceeding in recent times due to their incredible utilization in various fields. Present study was focused on the production, characterization, and antifungal activities of silver nanoparticles (AgNPs). An environment friendly extracellular biosynthetic approach was adopted to produce the AgNPs by using bacteria, fungi, and sugarcane husk. Agents used for reduction of silver to nanoparticles were taken from culture filtrate of plant growth promoting bacteria, Fusarium oxysporum and supernatant extract of sugarcane husk. Nanoparticles were also characterized by scanning electron microscopy (SEM). Synthesis of colloidal AgNPs was observed by UV-Visible diffused reflectance spectroscopy (UV-Vis DRS). Primary peak of surface plasmon resonance band was noticed around 339.782, 336.735, and 338.258 nm for bacterial, fungal, and sugarcane husk produced AgNPs. Structure of all biologically produced nanoparticles were crystalline cubic with nano size of 45.41, 49.06, and 42.75 nm for bacterial, fungal, and sugarcane husk-based nanoparticles, respectively as calculated by Debye-Scherrer equation using XRD. Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of various compounds that aid in the reduction, capping, and stability of AgNPs. The antifungal activity of AgNPs was also investigated for sugarcane fungal pathogens Colletotricum falcatum and Fusarium moniliforme. All nanoparticles exhibit prominent antifungal activities. Maximum zone of fungal inhibition was noticed about 18, 19, and 21 mm for C. falcatum while 21, 20, and 24 mm for F. moniliforme in case of bacterial, fungal, and plant-based nanoparticles (15 ppm), respectively. Best fungal inhibition was observed under application of sugarcane husk based AgNPs. Moreover, biologically produced AgNPs responded better towards the suppression of F. moniliforme in comparison to C. falcatum. Mentioned sources in present study can be ecofriendly nano-factories for biosynthesis of AgNPs and mankind should benefit from their commercial application.

Mechanistic elucidation of germination potential and growth of Sesbania sesban seedlings with Bacillus anthracis PM21 under heavy metals stress: An in vitro study

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.

Cd-tolerant SY-2 strain of Stenotrophomonas maltophilia: a potential PGPR, isolated from the Nanjing mining area in China

Microbial and plant assisted bioremediation is an emerging way for the remediation of soils polluted with heavy metals. To screen the cadmium tolerant bacteria, soil samples were collected from Nanjing mining area, China. The average cadmium content of the mine soil reached 45.71 mg/kg, which was indicating serious pollution and potential ecological risk. From the mine soil, six cadmium tolerant plant growth-promoting rhizobacteria (PGPR) were isolated. The isolated bacterial strain "SY-2" showed maximum cadmium tolerance and it was selected for further experimentation. This strain was identified as Stenotrophomonas maltophilia by 16S rRNA gene sequencing (GenBank accession number MG597057). SY-2 was found to tolerate maximum cadmium at 1.0 mM concentration. This strain also exhibited good adsorption capacity (up to 35.7%) of heavy metal at 0.5 mM concentration. The results of this study exhibited organic phosphorus solubilization (37.08 mg/L) and IAA biosynthesis (15.11 mg/L) ability of isolated S. maltophilia. Scanning electron microscopy (SEM) revealed cell shrinkage and the cell wall of S. maltophilia was very rough. Moreover, the energy dispersive X-ray (EDX) analysis endorsed the adsorption of Cd ions on the surface of biomass. FT-IR study described the presence of functional groups and the nature of chemical bonds, before and after cadmium stress. At 0.25 mM cadmium concentration, S. maltophilia treated seeds of Capsicum annuum L. developed 1.46 times longer roots than untreated seeds. The results of this study helped us to conclude that SY-2 strain of S. maltophilia possesses significant metal tolerance and bioremediation potential against cadmium. In the future, this strain can be used as a microbial remediation agent to detoxify heavy metals in contaminated soils.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (10.1007/s13205-020-02524-7s) contains supplementary material, which is available to authorized users.

Microbe-EDTA mediated approach in the phytoremediation of lead-contaminated soils using maize (Zea mays L.) plants

In the current study, we investigated the potential of Cronobacter sakazakii- ethylenediaminetetraacetic acid (EDTA) assisted phytoremediation potential of Zea mays L. to remediate lead (Pb)-contaminated soils. The C. sakazakii exhibited various stress tolerance mechanisms via plant growth promoting (PGP) traits, intrinsic extracellular enzyme production and antibiotic resistance. A greenhouse experiment was conducted to examine the dual effects of plant growth promoting endophytic bacteria (PGPEB)-chelator synergy in maize plants under different Pb contaminated soil regimes. C. sakazaii-EDTA (5 mM EDTA kg^-1) complex significantly (p < 0.05) enhanced plant growth and biomass (48.91%); chlorophyll a, b and carotenoid contents (27.26%, 25.02% and 42.09%); relative water content (61.33%); proline content (63.60%); root and shoot Pb accumulation capacity (52.31% and 44.71%) in Pb contaminated soils. This may suggest the efficacy of current approach in enhancing plant tolerance capability toward Pb-uptake and phytoremediation capacity. Moreover, maize plants showed differential response to Pb availability in soil-1 (S1; Pb spiked soil, 500 mg kg^-1) and soil-2 (S2; aged-contaminated soil) under various treatments. We describe the intriguing role of C. sakazakii-EDTA-maize system for Pb decontamination which can be used as a base line to explore the proposed combinatorial approach for long-term trails under field conditions for reclamation of Pb-contaminated soils.HighlightsThe PGPEB-EDTA mediated potential of Z. mays against Pb spiked and industrial contaminated soils is noticed.Increased tolerance of Z. mays against Pb in association with C. sakazakii, and EDTA is reported first time.Enhanced accumulation of metals by Z. mays is reported under combined treatment of C. sakazakii, and EDTA.Inoculation of plants with C. sakazakii, and EDTA has positive effects on growth and accumulation of Pb by Z. mays.

Scanning electron microscopy of bio-fabricated Fe2 O3 nanoparticles and their application to control brown rot of citrus

Citrus is the leading fruit crop of Pakistan and exported to different parts of the world. Due to suitable weather condition, this crop is affected by different biotic factors which seriously deteriorate its quality and quantity. During the months of November 2018 to January 2019, citrus brown rot symptoms were recurrently observed on sweet oranges in National Agricultural Research Centre (NARC), Islamabad. Causal agent of citrus brown rot was isolated, characterized, and identified as Fusarium oxysporum. For environment-friendly control of this disease, leaf extract of Azadirachta indica was used for the green synthesis of iron oxide (Fe₂ O₃ ) nanoparticles. These nanoparticles were characterized before their application for disease control. Fourier transform infrared spectroscopy (FTIR) of these synthesized nanoparticles described the presence of stabilizing and reducing compounds like alcohol, phenol, carboxylic acid, and alkaline and aromatic compounds. X-Ray diffraction (XRD) analysis revealed the crystalline nature and size (24 nm) of these nanoparticles. Energy dispersive X-Ray (EDX) analysis elaborated the presence of major elements in the samples. Scanning electron microscopy (SEM) confirmed the spinal shaped morphology of prepared nanoparticles. Successfully synthesized nanoparticles were evaluated for their antifungal potential. Different concentrations of Fe₂ O₃ nanoparticles were used and maximum mycelial inhibition was observed at 1.0 mg/ml concentration. On the basis of these findings, it could be concluded that Fe₂ O₃ nanoparticles, synthesized in the leaf extract of A. indica, can be successfully used for the control of brown rot of sweet oranges.

Multi-stress tolerant PGPR Bacillus xiamenensis PM14 activating sugarcane (Saccharum officinarum L.) red rot disease resistance

Sustainability in crop production has emerged as one of the most important concerns of present era's agricultural systems. Plant growth promoting bacteria (PGPB) has been characterized as a set of microorganisms used for enhancing plant growth and a tool for biological control of phytopathogens. However, the inconsistent performance of these bacteria from laboratory/greenhouse to field level has emerged due to prevailing abiotic stresses in fields. Sugarcane crop encounters a combination of biotic and abiotic stresses during its long developmental stages. Nevertheless, the selection of antagonistic PGPB with abiotic stress tolerance would be beneficial for end-user by the successful establishment of product with required effects under field conditions. Stress tolerant Bacillus xiamenensis strain (PM14) isolated from the sugarcane rhizosphere grown in the fields was examined for various PGP activities, enzyme assays, and antibiotic resistance. Strain was screened for in vitro tolerance against drought, salinity, heat stress, and heavy metal toxicity. Inhibition co-efficient of B. xiamenensis PM14 was also calculated against six phyto-pathogenic fungi, including Colletotrichum falcatum (53.81), Fusarium oxysporum (68.24), Fusarium moniliforme (69.70), Rhizoctonia solani (71.62), Macrophomina phaseolina (67.50), and Pythium splendens (77.58). B. xiamenensis is reported here for the first time as the rhizospheric bacterium which possesses resistance against 12 antibiotics and positive results for all in vitro PGP traits except HCN production. Role of 1-aminocyclopropane-1-carboxylate deaminase in the amelioration of biotic and abiotic stress was also supported by the amplification of acds gene. Moreover, in vitro and in vivo experiments revealed B. xiamenensis as the potential antagonistic PGPR and bio-control agent. Results of greenhouse experiment against sugarcane red rot indicated that inoculation of B. xiamenensis to sugarcane plants could suppress the disease symptoms and enhance plant growth. Augmented production of antioxidative enzymes and proline content may lead to the induced systemic resistance against red rot disease of sugarcane. Thus, the future application of native multi-stress tolerant bacteria as bio-control agents in combination with current heat, drought, salinity, and heavy metal tolerance strategy could contribute towards the global food security.

Deciphering metal toxicity responses of flax (Linum usitatissimum L.) with exopolysaccharide and ACC-deaminase producing bacteria in industrially contaminated soils

Rapid industrialization is the main reason of heavy metals contamination of soil colloids and water reservoirs. Heavy metals are persistent inorganic pollutants; deleterious to plants, animals and human beings because of accumulation in food chain. The aim of the current work was to evaluate the role of indole acetic acid (IAA), exopolysaccharide (EPS) and ACC-deaminase producing plant growth promoting rhizobacteria (PGPR) i.e .B. gibsonii PM11 and B. xiamenensis PM14 in metal phytoremediation of metals, their survival and plant growth promotion potential in metal polluted environment as well as alterations in physio-biochemical responses of inoculated L. usitatissimum plants towards heavy metal toxicity. Two bacterial strains Bacillus gibsonii (PM11) and Bacillus xiamenensis (PM14), previously isolated from sugarcane's rhizosphere, were screened for metal tolerance (50 mg/l to 1000 mg/l) and plant growth promoting traits like IAA, ACC-deaminase, EPS production and nitrogen fixing ability under metal stress. The response of flax plant (Linum usitatissimum L.) was analyzed in a pot experiment containing both industrially contaminated and non-contaminated soils. Experiment was comprised of six different treatments, each with three replicates. At the end of the experiment, role of metal tolerant plant growth promoting bacterial inoculation was elucidated by analyzing the plant growth parameters, chlorophyll contents, antioxidative enzymes, and metal uptake both under standard and metal contaminated rhizospheres. Results revealed that root and shoot length, plant's fresh and dry weight, proline content, chlorophyll content, antioxidant enzymatic activity was increased in plants inoculated with plant growth promoting bacteria as compared to non-inoculated ones both in non-contaminated and industrial contaminated soils. In current study, inoculation of IAA, EPS and ACC-deaminase producing bacteria enhances plant growth and nutrient availability by minimizing metal-induced stressed conditions. Moreover, elevated phytoextraction of multi-metals from industrial contaminated soils by PGPR inoculated L. usitatissimum plants reveal that these strains could be used as sweepers in heavy metals polluted environment.

Resistance associated metabolite profiling of Aspergillus leaf spot in cotton through non-targeted metabolomics

Aspergillus tubingensis is an important pathogen of economically important crops. Different biotic stresses strongly influence the balance of metabolites in plants. The aim of this study was to understand the function and response of resistance associated metabolites which, in turn are involved in many secondary metabolomics pathways to influence defense mechanism of cotton plant. Analysis of non-targeted metabolomics using ultra high performance liquid chromatography-mass spectrometry (UPLC-MS) revealed abundant accumulation of key metabolites including flavonoids, phenylpropanoids, terpenoids, fatty acids and carbohydrates, in response to leaf spot of cotton. The principal component analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA) and partial least squares discriminant analysis (PLS-DA) score plots illustrated the evidences of variation between two varieties of cotton under mock and pathogen inoculated treatments. Primary metabolism was affected by the up regulation of pyruvate and malate and by the accumulation of carbohydrates like cellobiose and inulobiose. Among 241 resistance related (RR) metabolites, 18 were identified as resistance related constitutive (RRC) and 223 as resistance related induced (RRI) metabolites. Several RRI metabolites, identified in the present study were the precursors for many secondary metabolic pathways. These included phenylpropanoids (stilbenes and furanocoumarin), flavonoids (phlorizin and kaempferol), alkaloids (indolizine and acetylcorynoline) and terpenoids (azelaic acid and oleanolic acid). Our results demonstrated that secondary metabolism, primary metabolism and energy metabolism were more active in resistant cultivar, as compared to sensitive cultivar. Differential protein and fatty acid metabolism was also depicted in both cultivars. Accumulation of these defense related metabolites in resistant cotton cultivar and their suppression in susceptible cotton cultivar revealed the reason of their respective tolerance and susceptibility against A. tubingensis.

Microbial diversity response in thallium polluted riverbank soils of the Lanmuchang

Thallium (Tl) is a toxic element, but little is known about microbial communities' response to TI mobilization and sequestration. Here, we characterize the microbial communities and their feedbacks to Tl-pollution in riverbank soils to understand the distribution of microbial metal tolerance. These soils have been affected by pollution sourced from a Tl-rich mineralized area in Lanmuchang, Guizhou, China. In all studied soil samples, Proteobacteria, Acidobacteria, and Actinobacteria were revealed relatively in higher abundance at the phylum level. The results indicated that a number of microbial communities including Gemmatimonadetes, and Actinobacteria were correlated with total Tl, suggesting potential roles of these microbes to Tl tolerance. The patterns of phylogenetic beta-diversity in studied samples showed a high diversity of the microbial community in soils with high Tl concentrations. Sequence analysis of microbial community indicated that most of the environmental parameters in soils were associated with the major phylogenetic groups such as Gemmobacteria, Bryobacteria, Proteobacteria, Actinobacteria, Firmicutes, and Rhodobacteria. Some species of microbes, Nocardioides (genus), Actinomycetales (Order), Ralstonia (phyla) and Sphingomonas (genus) might are tolerant of Tl. These results provide direction to the microbial communities in the presence of elevated Tl concentration in Lanmuchang and shed light on bioremediation of Tl polluted locations.

Residual effects of biochar and phosphorus on growth and nutrient accumulation by maize (Zea mays L.) amended with microbes in texturally different soils

The purpose of study was to examine the residual effects of two types of biochar amendments, two phosphorus (P) fertilizer levels, phosphorus solubilizing bacteria (PSB) and arbuscular mycorrhizal fungs (AMF) on plant growth, nutrients absorption and root architecture of Zea mays L. in texturally different soils. Biochar signficantly increased nutrients absorption and plant biomass production with P-fertilization and microbial inoculantion. Texturally different soils enhanced the plant biomass and nutrients absorption in their independent capacity on addition of biochar, microbial inoculants and P-fertilization. It was shown that mycorrhizal inoculation had positive influence on plant root and shoot biomass in both soils irrespective to the biochar type used. Root colonization was notably increased in biochar + mycorrhizae (B + M) inocultaed plants. It was shown that mycorrhizal inoculation had positive influence on nutrients absorption by plant roots and it had high content of P, potassium, calcium and magnesium in plants at all biochar and P levels. Without P fertilization, biochar amendments significantly promoted shoot P content and root colonization. The P application significantly influenced soil microbial activity in terms of nutrient concentration and plant growth. Root attributes were significantly inclined by microbial inoculation. Residual effects of biochar and P significantly enhanced the nutreints absorption and maize plant growth. Thus, we concluded that residual biochar and P fertilizer showed positive effects on nutrients absorption and maize plant growth promotion in differently textured soils. Microbial inoculants further stimulated the plant biomass production and nutrients absorption due to effective root colonization.

Assisted phytoremediation of chromium spiked soils by Sesbania Sesban in association with Bacillus xiamenensis PM14: A biochemical analysis

Due to anthropogenic activities, chromium (Cr) contamination is ubiquitous with deleterious effects on plant and soil microbiota. Present study was designed to address beneficial effects of Bacillus xiamenensis PM14 on Sesbania sesban. Its physiological and biochemical attributes along with enhanced antioxidant enzyme activities under different levels of Cr toxicity (50, 100 and 200 mg kg^-1) were evaluated. After harvesting at 50 days of sowing, plant growth attributes (root and shoot length, fresh and dry weight), physiological parameters (chlorophyll a, b and carotenoid content), antioxidant activities (superoxide dismutase, peroxidase and catalase), malondialdehyde content, electrolyte leakage, proline, relative water content and total Cr uptake in S. sesban were recorded. Experiment was statistically managed as complete randomized design (CRD). Results revealed that Cr stress reduced plant growth, relative water content at all levels of Cr contamination. However, inoculation of B. xiamenensis PM14 positively influence all parameters of S. sesban both under normal and stressed conditions. Inoculation of B. xiamenensis PM14 promoted plant growth (root length 17.08%, shoot length 28.36%) physiological attributes (chlorophyll a 55.26%, chlorophyll b 59.13%), antioxidant activities (superoxide dismutase 30.09%, peroxidase 6.96% and catalase 0.89%), relative water content 25.79%, enhanced total Cr uptake 47.33% and reduced proline 12.33%, malondialdehyde content 27.53% and electrolyte leakage 2.73% in S. sesban at 200 mg kg^-1 Cr stress as compared to uninoculated plants grown under the same level of Cr. Our findings revealed first report of B. xiamenensis as phytoremediator and its inoculation on Sesbania plant. It also exposed dual effects of B. xiamenensis to ameliorate Cr stress along with improved plant growth and induced heavy metal stress tolerance in spiked soils.

Mechanistic elucidation of germination potential and growth of wheat inoculated with exopolysaccharide and ACC- deaminase producing Bacillus strains under induced salinity stress

The potential of plant growth regulating microorganisms present in the soil can be explored towards the purpose of identifying salt tolerant strategies and crop cultivars. Current study was designed to elucidate the capabilities of salt stress tolerant plant growth promoting rhizobacteria (PGPR) Bacillus siamensis (PM13), Bacillus sp. (PM15) and Bacillus methylotrophicus (PM19) in undermining the effects of salt stress on wheat seedling. Strains were characterized for their IAA (81-113 μM/ml), ACC-deaminase (0.68-0.95 μM/mg protein/h) and exopolysaccharide (EPS) (0.62-0.97 mg/ml) producing activity both under normal and NaCl stressed conditions. Effects of bacterial inoculation on germination and seedling growth of wheat variety Pakistan-13 was observed under induced salinity stress levels (0, 4, 8, 16 dS/m). All the morpho-physiological characteristics of wheat seedlings were affected drastically by the NaCl stress and the growth parameters expressed a negative relationship with increased NaCl levels. PGPR application had a very positive influence on germination rate of wheat seedlings, root and shoot length, photosynthetic pigments etc. Elongated roots and enhanced vegetative shoot growth as well as seedling's fresh and dry weights were highest in plants treated with B. methylotrophicus PM19. Sequestration of Na⁺ ion by EPS production and degradation of exuded ACC into a-ketobutyrate and ammonia by ACCD bacteria efficiently reduced the impact of salinity stress on wheat growth. Current findings suggested that the used PGPR strains are potential candidates for improving crop growth in salt stressed agricultural systems. However further research validation would be necessary before large scale/field application.

Osmotin: A plant defense tool against biotic and abiotic stresses

Plants are prone to a number of pathogens and abiotic stresses that cause various disorders. However, plants possess a defense mechanism to cope with these stresses. The osmotin protein belongs to the PR-5 family of Pathogenesis-related (PR) proteins, which are produced in response to diseases caused by various biotic and abiotic stresses. Osmotin uses a signal transduction pathway to inhibit the activity of defensive cell wall barriers and increases its own cytotoxic efficiency. However, in response to cytotoxic effects, this pathway stimulates a mitogen-activated protein kinase (MAPK) cascade that triggers changes in the cell wall and enables osmotin's entrance into the plasma membrane. This mechanism involves cell wall binding and membrane perturbation, although the complete mechanism of osmotin activity has not been fully elucidated. Osmotin possesses an acidic cleft that is responsible for communication with its receptor in the plasma membrane of fungi. Osmotin is also involved in the initiation of apoptosis and programmed cell death, whereas its overexpression causes the accumulation of proline in transgenic plants. A higher concentration of osmotin can cause the lysis of hyphae tips. This review highlights the role of osmotin protein in the plant defense mechanism and its mode of action against numerous pathogens in wild and transgenic plants.

Influence of endophytic Bacillus pumilus and EDTA on the phytoextraction of Cu from soil by using Cicer arietinum

In developing countries, soil contamination with metals is ubiquitous, which poses a serious threat to the ecosystem. The current study was designed to screen out the nested belongings of Cicer arietinum plants and Bacillus pumilus (KF 875447) in extracting copper (Cu) from contaminated soils. A pot experiment was executed by growing C. arietinum seedlings either inoculated with B. pumilus or uninoculated along with the application of 5 mM ethylenediaminetetraacetic acid (EDTA). Plants were subjected to three different concentrations of Cu (250, 350, and 500 ppm) for 48 days. An increase in Cu uptake was observed in C. arietinum plants inoculated with B. pumilus as compared to uninoculated ones. C. arietinum exhibited improved values for different growth parameters in the presence of B. pumilus, that is, root length (37%), shoot length (31%), whole plant fresh as well as (45%) dry weight (27%), and chlorophyll contents (32%). More than 70% of tolerance index (TI) was observed for plants at 500 ppm Cu treatment. Addition of B. pumilus and EDTA significantly increased metal uptake by C. arietinum up to 19 and 36%, respectively, while the application of B. pumilus and EDTA in combination increased metal accumulation by 41%. The calculated bioaccumulation and translocation factor (TF) revealed that C. arietinum possess phytoextraction potential for Cu, and this ability is significantly improved with application of B. pumilus and EDTA amendments.

Correlation studies on nitrogen for sunflower crop across the agroclimatic variability

Nitrogen (N) fertilizer is an important yield limiting factor for sunflower production. The correlation between yield components and growth parameters of three sunflower hybrids (Hysun-33, Hysun-38, Pioneer-64A93) were studied with five N rates (0, 60, 120, 180, 240 kg ha(-1)) at three different experimental sites during the two consecutive growing seasons 2008 and 2009. The results revealed that total dry matter (TDM) production and grain yield were positively and linearly associated with leaf area index (LAI), leaf area duration (LAD), and crop growth rate (CGR) at all three sites of the experiments. The significant association of yield with growth components indicated that the humid climate was most suitable for sunflower production. Furthermore, the association of these components can be successfully used to predict the grain yield under diverse climatic conditions. The application of N at increased rate of 180 kg ha(-1) resulted in maximum yield as compared to standard rate (120 kg ha(-1)) at all the experimental sites. In this way, N application rate was significantly correlated with growth and development of sunflower under a variety of climatic conditions. Keeping in view such relationship, the N dose can be optimized for sunflower crop in a particular region to maximize the productivity. Multilocation trails help to predict the input rates precisely while taking climatic variations into account also. In the long run, results of this study provides basis for sustainable sunflower production under changing climate.

Effect of plant growth-promoting rhizobacteria inoculation on cadmium (Cd) uptake by Eruca sativa

Microbe-assisted phyto-remediation approach is widely applied and appropriate choice to reduce the environmental risk of heavy metals originated from contaminated soils. The present study was designed to screen out the nested belongings of Eruca sativa plants and Pseudomonas putida (ATCC 39213) at varying cadmium (Cd) levels and their potential to deal with Cd uptake from soils. We carried out pot trial experiment by examining the soil containing E. sativa seedlings either treated with P. putida and/or untreated plants subjected to three different levels (ppm) of Cd (i.e., 150, 250, and 500). In all studied cases, we observed an increase in Cd uptake for E. sativa plants inoculated with P. putida than those of un-inoculated plants. Cd toxicity was assessed by recording different parameters including stunted shoot growth, poor rooting, and Cd residual levels in the plants that were not inoculated with P. putida. Significant difference (p < 0.05) of different growth parameters for inoculated vs non-inoculated plants was observed at all given treatments. However, among the different treatments, E. sativa exhibited increased values for different growth parameters (except proline contents) at lower Cd levels than those of their corresponding higher levels, shoot length (up to 27 %), root length (up to 32 %), whole fresh plant (up to 40 %), dry weight (up to 22 %), and chlorophyll contents (up to 26 %). Despite the hyperaccumulation of Cd in whole plant of E. sativa, P. putida improved the plant growth at varying levels of Cd supply than those of associated non-inoculated plants. Present results indicated that inoculation with P. putida enhanced the Cd uptake potential of E. sativa and favors the healthy growth under Cd stress.

Diazotrophs-assisted phytoremediation of heavy metals: a novel approach

Heavy metals, which have severe toxic effects on plants, animals, and human health, are serious pollutants of the modern world. Remediation of heavy metal pollution is utmost necessary. Among different approaches used for such remediation, phytoremediation is an emerging technology. Research is in progress to enhance the efficiency of this plant-based technology. In this regard, the role of rhizospheric and symbiotic microorganisms is important. It was assessed by enumeration of data from the current studies that efficiency of phytoremediation can be enhanced by assisting with diazotrophs. These bacteria are very beneficial because they bring metals to more bioavailable form by the processes of methylation, chelation, leaching, and redox reactions and the production of siderophores. Diazotrophs also posses growth-promoting traits including nitrogen fixation, phosphorous solubilization, phytohormones synthesis, siderophore production, and synthesis of ACC-deaminase which may facilitate plant growth and increase plant biomass, in turn facilitating phytoremediation technology. Thus, the aim of this review is to highlight the potential of diazotrophs in assisting phytoremediation of heavy metals in contaminated soils. The novel current assessment of literature suggests the winning combination of diazotroph with phytoremediation technology.

Phyto-Extraction of Nickel by Linum usitatissimum in Association with Glomus intraradices

Plants show enhanced phytoremediation of heavy metal contaminated soils particularly in response to fungal inoculation. Present study was conducted to find out the influence of Nickel (Ni) toxicity on plant biomass, growth, chlorophyll content, proline production and metal accumulation by L. usitatissimum (flax) in the presence of Glomus intraradices. Flax seedlings of both inoculated with G. intraradices and non-inoculated were exposed to different concentrations i.e., 250, 350 and 500 ppm of Ni at different time intervals. Analysis of physiological parameters revealed that Ni depressed the growth and photosynthetic activity of plants. However, the inoculation of plants with arbuscular mycorrhizae (G. intraradices) partially helped in the alleviation of Ni toxicity as indicated by improved plant growth under Ni stress. Ni uptake of non- mycorrhizal flax plants was increased by 98% as compared to control conditions whereas inoculated plants showed 19% more uptake when compared with the non-inoculated plants. Mycorrhizal plants exhibited increasing capacity to remediate contaminated soils along with improved growth. Thus, AM assisted phytoremediation helps in the accumulation of Ni in plants to reclaim Ni toxic soils. Based on our findings, it can be concluded that the role of flax plants and mycorrhizal fungi is extremely important in phytoremediation.

The potential of the flora from different regions of Pakistan in phytoremediation: a review

Soil and water quality is greatly affected by environmental pollution due to the increasing trend of urbanization and industrialization. In many developing countries, including Pakistan, the situation is more alarming as no preventive measures are still taken to tackle the problem. Although in developed countries, many techniques are used to remediate the environment including phytoremediation. It is the most eco-friendly technique in which plants are used to remove pollutants from the environment. Pakistan has also a great diversity of plants which could be used for the remediation of environmental pollutants. To our knowledge, few studies from Pakistan were reported about the use of flora for phytoremediation. According to recent literature, 50 plant species from Pakistan are studied for remediation purposes. In this review, the potential of different plant species for phytoremediation from Pakistan has been discussed along with their comparison to other countries to relate future perspectives.