Nidá M. Salem

Green synthesis of silver nanoparticles using carob leaf extract and its antibacterial activity

BackgroundThis paper describes a rapid and eco-friendly method for green synthesis of silver nanoparticles from aqueous solution of silver nitrate using carob leaf extract (Ceratonia siliqua) in a single-pot process.ResultsFormation of stable silver nanoparticles at different concentrations of AgNO3 gave mostly spherical particles with a diameter ranging from 5 to 40 nm. It was observed that the use of carob leaf extract makes a fast and convenient method for the synthesis of silver nanoparticles and can reduce silver ions into silver nanoparticles within 2 min of reaction time without using any severe conditions. Green synthesis of silver nanoparticles (AgNPs) was characterized by UV-visible (UV–vis) spectroscopy, scanning electron microscopy, atomic absorption spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction (XRD). The UV–vis spectra gave surface plasmon resonance for synthesized silver nanoparticles at 420 nm. The XRD analysis showed that the AgNPs are crystalline in nature and have face-centered cubic geometry.ConclusionFurther, the AgNPs showed an effective antibacterial activity toward Escherichia coli pathogen.

Biosorption of copper(II) and lead(II) ions from aqueous solutions by modified loquat (Eriobotrya japonica) leaves (MLL)

A modified loquat leaves (MLL) for the removal of copper(II) and lead(II) ions from aqueous solutions has been investigated. The biosorption of copper(II) and lead(II) ions was found to be dependent on solution pH, initial metal ion concentrations, biosorbent dose, contact time, and temperature. The experimental equilibrium biosorption data were analyzed by three widely used two-parameters; Langmuir, Freundlich, and Temkin isotherm models. Langmuir isotherm model provided a better fit with the experimental data than other models by high correlation coefficients R 2 . Kinetic studies showed that pseudo-second order described the biosorption experimental data better than the pseudo-first order kinetic model.

Endophytic colonisation of squash by the fungal entomopathogen Beauveria bassiana (Ascomycota: Hypocreales) for managing Zucchini yellow mosaic virus in cucurbits

We investigated the potential of endophytic Beauveria bassiana to provide protection against Zucchini yellow mosaic virus (ZYMV), one of the most economically important viral diseases in cucurbits. Four selected B. bassiana strains were able to successfully colonise squash plants following foliar inoculation with the conidial suspension of each respective strain. However, no significant difference in percentage colonisation was observed among the tested B. bassiana strains. Disease incidence (percentage of plants showing ZYMV symptoms) and severity (rating based on a 5-point scale), sampled weekly for four weeks following the challenge inoculation of plants with ZYMV, were significantly lower in B. bassiana-inoculated plants as compared to control plants, regardless of the inoculated strain. This is, to our knowledge, the first report on the potential of endophytic B. bassiana to confer protection against plant viruses. Further studies should be conducted to determine whether such endophytic B. bassiana-mediated protection against ZYMV in squash extends to other cucurbits.

Diverse Array of New Viral Sequences Identified in Worldwide Populations of the Asian Citrus Psyllid (Diaphorina citri) Using Viral Metagenomics

ABSTRACT The Asian citrus psyllid, Diaphorina citri, is the natural vector of the causal agent of Huanglongbing (HLB), or citrus greening disease. Together; HLB and D. citri represent a major threat to world citrus production. As there is no cure for HLB, insect vector management is considered one strategy to help control the disease, and D. citri viruses might be useful. In this study, we used a metagenomic approach to analyze viral sequences associated with the global population of D. citri. By sequencing small RNAs and the transcriptome coupled with bioinformatics analysis, we showed that the virus-like sequences of D. citri are diverse. We identified novel viral sequences belonging to the picornavirus superfamily, the Reoviridae, Parvoviridae, and Bunyaviridae families, and an unclassified positive-sense single-stranded RNA virus. Moreover, a Wolbachia prophage-related sequence was identified. This is the first comprehensive survey to assess the viral community from worldwide populations of an agricultural insect pest. Our results provide valuable information on new putative viruses, some of which may have the potential to be used as biocontrol agents. IMPORTANCE Insects have the most species of all animals, and are hosts to, and vectors of, a great variety of known and unknown viruses. Some of these most likely have the potential to be important fundamental and/or practical resources. In this study, we used high-throughput next-generation sequencing (NGS) technology and bioinformatics analysis to identify putative viruses associated with Diaphorina citri, the Asian citrus psyllid. D. citri is the vector of the bacterium causing Huanglongbing (HLB), currently the most serious threat to citrus worldwide. Here, we report several novel viral sequences associated with D. citri.

Complete Genome Sequence of Diaphorina citri-associated C virus, a Novel Putative RNA Virus of the Asian Citrus Psyllid, Diaphorina citri

ABSTRACT We present here the complete nucleotide sequence and genome organization of a novel putative RNA virus identified in field populations of the Asian citrus psyllid, Diaphorina citri, through sequencing of the transcriptome followed by reverse transcription-PCR (RT-PCR). We tentatively named this virus Diaphorina citri-associated C virus (DcACV). DcACV is an unclassified positive-sense RNA virus.

Antifungal Activity of the Stinkwort (Inula graveolens) Extracts

Bioactive guided fractionation was carried out to determine the antifungal activity of the stinkwort weed, Inula graveolens, on various phytopathogenic fungi species. Dried shoots were extracted and partitioned in various solvent systems. The aqueous methanol extract (AqMeOH) inhibited the growth of several soil-borne fungi; Alternaria sp., Fusarium spp. and Rhizoctonia sp. in in-vitro plate assay. Fractionation of AqMeOH extract by column chromatography in dichloromethane/AqMeOH yielded twenty-two fractions of which Fraction #2, 3 and 4 showed antifungal activity. Further fractionation of the combined Fractions #2, 3 and 4 by column chromatography in solvent system benzene/ethyl acetate on fine silica columns, yielded seven sub fractions of which sub fraction #2 has the most antifungal activity on all fungi in the experiment. The fungitoxicity of sub fraction #2 in terms of percentage inhibition of mycelia growth of all tested-fusaria strains after seven days of incubation was higher compared to that obtained by the fungicide hymexazol (Tachigaren ® 70 WP). The AqMeOH extract significantly reduced browning length at the crown area, a Fusarium-known symptom in in-vivo experiments. Furthermore, the growth of Fusarium-treated cucumber plants was enhanced by drenching with AqMeOH extract. The activity of the extract was comparable to the activity of the fungicide hymexazol in improving plant health, and surpassed the fungicide activity in preventing the discoloration of the crown vascular tissue of cucumber at comparable concentrations.