Management of Ralstonia solanacearum in Tomato Using ZnO Nanoparticles Synthesized Through Matricaria chamomilla.

Matricaria chamomilla flower extract was used as a biocompatible material for synthesis of zinc oxide nanoparticles (ZnONPs). The synthesized NPs were evaluated for their antibacterial potential in vitro and in vivo against the Gram-negative bacterium Ralstonia solanacearum, which causes devastating bacterial wilt disease in tomato and other crops. Synthesized ZnONPs were further analyzed by UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy. The synthesized polydisperse ZnONPs were found to be in the size range of 8.9 to 32.6 nm, and at 18.0 µg ml-1 exhibited maximum in vitro growth inhibition of the pathogen R. solanacearum. Scanning electron microscopy analysis of affected bacterial cells showed morphological deformation such as disruption of the cell membrane and wall, and the leakage of cell contents. Results of in vivo studies also showed that application of ZnONPs to the artificially inoculated tomato plants with the pathogen R. solanacearum significantly enhanced the plant growth by reducing bacterial soil population and disease severity as compared with the untreated control. Biosynthesized ZnONPs could be an effective approach to control the bacterium R. solanacearum.

Eco-friendly Management of Bacterial Wilt in Tomato Using Dried Powder of the Wild Arid-Land Medicinal Shrub Rhazya stricta.

Bacterial wilt (BW) disease caused by Ralstonia solanacearum species complex is a devastating plant disease that inflicts heavy losses to the large number of economic host plants it infects. In this study, the potential of dried powder of the arid-land medicinal shrub Rhazya stricta to control BW of tomato was explored. Both, in vitro and in planta studies were conducted, using different concentrations of dried powder of plant parts, and applied (surface mulched or mixed) to infested soil at 0, 10, and 20 days before transplanting (DBT). Aqueous extract of leaves (16% w/v) was found to be as effective as streptomycin (100 ppm) in inhibiting the in vitro growth of R. solanacearum. As evident from the scanning electron micrograph, 16% aqueous extract of leaves produced severe morphological changes, such as rupture of the bacterial cell walls. Results from the greenhouse experiments demonstrated that the higher powder dose (succulent shoot), namely, 30 g/kg of soil mixed with infested soil 20 DBT, was found to be the most effective in controlling BW. It increased root length (cm), shoot length (cm), and plant fresh biomass (g) by 55, 42, and 40%, respectively, over control plants. Mixing of plant powder with the artificially infested (35 ml of 108 CFU/ml per kilogram of soil) pot soil was better than surface mulching. The 30 g/kg of soil dose mixed with soil increased root length (cm), shoot length (cm), and plant fresh biomass (g) of treated plants by 67, 36, and 46%, respectively, over control plants. A 37% decrease in disease severity over the control was observed with drench application of 30 g of powder per kilogram of soil applied once at 20 DBT. Our results indicated that the dried powder (30 g/kg of soil) of leaves or succulent shoots of R. stricta, thoroughly mixed with soil, 20 DBT, could act as an effective control method against BW.

Synthesis and bioactivities of silver nanoparticles capped with 5-amino-ß-resorcylic acid hydrochloride dihydrate.

BACKGROUND: Conjugated and drug loaded silver nanoparticles are getting an increased attention for various biomedical applications. Nanoconjugates showed significant enhancement in biological activity in comparison to free drug molecules. In this perspective, we report the synthesis of bioactive silver capped with 5-Amino-ß-resorcylic acid hydrochloride dihydrate (AR). The in vitro antimicrobial (antibacterial, antifungal), enzyme inhibition (xanthine oxidase, urease, carbonic anhydrase, α-chymotrypsin, cholinesterase) and antioxidant activities of the developed nanostructures was investigated before and after conjugation to silver metal. RESULTS: The conjugation of AR to silver was confirmed through FTIR, UV-vis and TEM techniques. The amount of AR conjugated with silver was characterized through UV-vis spectroscopy and found to be 9% by weight. The stability of synthesized nanoconjugates against temperature, high salt concentration and pH was found to be good. Nanoconjugates, showed significant synergic enzyme inhibition effect against xanthine and urease enzymes in comparison to standard drugs, pure ligand and silver. CONCLUSIONS: Our synthesized nanoconjugate was found be to efficient selective xanthine and urease inhibitors in comparison to Ag and AR. On a per weight basis, our nanoconjugates required less amount of AR (about 11 times) for inhibition of these enzymes.

Enhanced biocidal activity of Au nanoparticles synthesized in one pot using 2, 4-dihydroxybenzene carbodithioic acid as a reducing and stabilizing agent.

BACKGROUND: The conjugation of gold nanoparticles with biocides such as natural products, oligosaccharides, DNA, proteins has attracted great attention of scientists recently. Gold NPs covered with biologically important molecules showed significant enhancement in biological activity in comparison with the activity of the free biocides. However, these reports are not very systematic and do not allow to draw definitive conclusions. We therefore embarked in a systematic study related to the synthesis and characterization of biocidal activities of Au nanoparticles conjugated to a wide variety of synthetic and natural biomolecules. In this specific report, we investigated the activity of a synthetic biocide, 2-4, Dihydroxybenzene carbodithioic acid (DHT). RESULTS: Au nanoparticles (NP) with a mean size of about 20 nm were synthesized and functionalized in one pot with the help of biocide 2,4-Dihydroxybenzene carbodithioic acid (DHT) to reduce HAuCl4 in aqueous solution. Conjugation of DHT with gold was confirmed by FT-IR and the amount of DHT conjugated to the Au nanoparticles was found to be 7% by weight by measuring the concentration of DHT in the supernatant after centrifugation of the Au NPs. To ascertain the potential for in vivo applications, the stability of the suspensions was investigated as a function of pH, temperature and salt concentration. Antibacterial, antifungal, insecticidal and cytotoxic activities of the Au-DHT conjugates were compared with those of pure DHT and of commercially available biocides. In all cases, the biocidal activity of the Au-DHT conjugates was comparable to that of commercial products and of DHT. CONCLUSIONS: Since the DHT concentration in the Au-DHT conjugates was only about 7%, our results indicate that conjugation to the Au NPs boosts the biocidal activity of DHT by about 14 times. The suspensions were found to be stable for several days at temperatures of up to 100°C, salt concentrations up to 4 mol/L and a pH range of 2-13.

Mitigating Cd and bacterial wilt stress in tomato plants through trico-synthesized silicon nanoparticles and Trichoderma metabolites.

There has been a growing apprehension in recent years about the harmful effects of environmental pollutants on agricultural output, encompassing both living organisms and non-living factors that cause stress. In this study, the soil application of bulk silicon (Si), silicon nanoparticles (SiNPs) and Trichoderma metabolites (TM) were investigated alone or in combination for the management of an important abiotic stress i.e. Cd toxicity and biotic stress i.e. bacterial wilt (BW) in tomato plants. SiNPs were synthesized by Trichoderma and confirmed through XRD, FTIR, and Ranman spectrum analysis. Results showed that Si, SiNPs and TM were all effective treatments. The combine treatment of SiNPs and TM followed by SiNPs alone were superior over other treatments in mitigating Cd toxicity and reducing BW disease on tomato plants. The soil application of these treatments reduced the Cd toxicity by enhancing Cd-tolerance index, decreasing bioavailability of soil Cd, reducing Cd contents and translocation in plants, improving gaseous exchange, photosynthesis, and increasing the antioxidant enzyme activities and their transcriptions. These treatments significantly suppressed BW pathogen leading to the significant decrease in disease index and severity on plants. In vitro evaluation and scanning electron microscopic (SEM) analysis revealed that SiNPs and TM significantly disrupted the cellular morphology of BW pathogen Ralstonia solanacearum. Findings of this study proposes the possible use of SiNPs and TM in mitigating the Cd and BW stress in tomato plants and possibly in other crops.

Effects of soil fluoride pollution on wheat growth and biomass production, leaf injury index, powdery mildew infestation and trace metal uptake.

Fluoride (F) is an emerging pollutant that originates from multiple sources and adversely affects plant growth and nutrient bioavailability in soil. This greenhouse study investigated the effects of soil F (0, 10, 20, 50, 100, 200 mg kg-1) on morpho-physiological growth characteristics of wheat, soil F contents, and bioavailability and uptake of F, phosphorus (P), sulphur (S), potassium (K), calcium (Ca), magnesium (Mg), aluminium (Al), iron (Fe), manganese (Mn), silicon (Si) and zinc (Zn) by wheat. Higher F significantly reduced plant height and number of leaves particularly at early growth stages and increased visible leaf injury index. Powdery mildew infestation coincided with leafy injury and was higher in elevated soil F treatments. Fluoride treatments (>50 mg kg-1) significantly increased water (H2O)- and calcium chloride (CaCl2)-extractable F contents in soil. Water-extractable soil F contents from soil in all concentration were higher than CaCl2-extractable F. This increased F bioavailability resulted in significantly higher F uptake and accumulation in live leaves, dead leaves and grains of wheat which followed order: live leaves > dead leaves > grains. Leaf injury index and number of dead leaves correlated significantly positively with soil H2O- and CaCl2-extractable F contents. Patterns of nutrient (P, K, S) and trace metals (Al, Ca, Mg, Fe, Mn, Si, Zn) varied significantly with F concentrations and between live and dead leaves, and grains except for Zn. Dead leaves generally had higher nutrients and trace metals than live leaves and grains. Fluoride contents in live leaves, dead leaves and grains showed positive correlations with nutrient elements but negative with trace metals. Number of dead leaves correlated negatively with Al, Ca, Fe, Mg, S and Si but positively with P and Zn contents in dead leaves whereas leaf injury index showed positive correlation with Fe, K, P, Si, Zn, S but negative with Al, Ca and Mg contents. These observations provided evidence of higher F uptake and associated impairment in nutrient and trace metal accumulation which caused leaf injury accompanied by powdery mildew infestation in wheat. However, further research in the region is required to confirm the relationship between F pollution, leaf injury and trace metal accumulation in crops under field conditions.

Influence of variable biochar concentration on yield-scaled nitrous oxide emissions, Wheat yield and nitrogen use efficiency.

An important source of the destructive greenhouse gas, nitrous oxide (N2O) comes from the use of ammonium based nitrogen (N) fertilizers that release N2O in the incomplete conversion (nitrification) of NH4+ to NO3-1. Biochar has been shown to decrease nitrification rates and N2O emission. However, there is little information from semi-arid environments such as in Pakistan where conditions favor N2O emissions. Therefore, the object was to conduct field experiment to determine the impact of biochar rates in the presence or absence of urea amended soils on yield-scaled N2O emissions, and wheat yield and N use efficiency (NUE). The experiment on wheat (Triticum aestivum L.), had a randomized complete block design with four replications and the treatments: control, sole urea (150 kg N ha-1), 5 Mg biochar ha-1 (B5), 10 Mg biochar ha-1 (B10), urea + B5 or urea + B10. In urea amended soils with B5 or B10 treatments, biochar reduced total N2O emissions by 27 and 35%, respectively, over the sole urea treatment. Urea + B5 or + B10 treatments had 34 and 46% lower levels, respectively, of yield scaled N2O over the sole urea treatment. The B5 and B10 treatments had 24-38%, 9-13%, 12-27% and 35-43%, respectively greater wheat above-ground biomass, grain yield, total N uptake, and NUE, over sole urea. The biochar treatments increased the retention of NH4+ which likely was an important mechanism for reducing N2O by limiting nitrification. These results indicate that amending soils with biochar has potential to mitigate N2O emissions in a semi-arid and at the same time increase wheat productivity.

Biochar and urease inhibitor mitigate NH3 and N2O emissions and improve wheat yield in a urea fertilized alkaline soil.

In this study, we explored the role of biochar (BC) and/or urease inhibitor (UI) in mitigating ammonia (NH3) and nitrous oxide (N2O) discharge from urea fertilized wheat cultivated fields in Pakistan (34.01°N, 71.71°E). The experiment included five treatments [control, urea (150 kg N ha-1), BC (10 Mg ha-1), urea + BC and urea + BC + UI (1 L ton-1)], which were all repeated four times and were carried out in a randomized complete block design. Urea supplementation along with BC and BC + UI reduced soil NH3 emissions by 27% and 69%, respectively, compared to sole urea application. Nitrous oxide emissions from urea fertilized plots were also reduced by 24% and 53% applying BC and BC + UI, respectively, compared to urea alone. Application of BC with urea improved the grain yield, shoot biomass, and total N uptake of wheat by 13%, 24%, and 12%, respectively, compared to urea alone. Moreover, UI further promoted biomass and grain yield, and N assimilation in wheat by 38%, 22% and 27%, respectively, over sole urea application. In conclusion, application of BC and/or UI can mitigate NH3 and N2O emissions from urea fertilized soil, improve N use efficiency (NUE) and overall crop productivity.

Export of the HR eliciting protein, Harpin(Es), of the maize pathogen Erwinia stewartii is species-specific but is independent of the growth temperature.

The extra-cellular export of the HR-eliciting protein, Harpin(Es) of the maize pathogen Erwinia stewartii was studied to find out if the protein needs any species-specific signal for its export and to determine if the export of the protein to the medium is affected in any way by the growth temperature. Based upon the experimental evidence, it was proved that the protein (i.e., Harpin(Es)) does require its own export system (species-specific) to get out of the bacterial cell and can not be exported by the export system of even the very closely related bacterium, Erwinia amylovora. It was also found that the export of Harpin(Es) is, unlike the case of Harpin(Ea) (HR-eliciting protein of Erwinia amylovora), independent of the growth temperature.