To control the disease caused by Sclerotinia sclerotiorum, a total of 15 isolates of the Trichoderma species was screened for the biosynthesis of silver nanoparticles (AgNPs). Among them, the highest yield occurred in the synthesis of AgNPs using a cell-free aqueous filtrate of T.virens HZA14 producing gliotoxin. The synthetic AgNPs were charactered by SEM, EDS, TEM, XRD, and FTIR. Electron microscopy studies revealed that the size of AgNPs ranged from 5–50 nm and had spherical and oval shapes with smooth surfaces. Prepared AgNPs interacted with protein, carbohydrate and heterocyclic compound molecules, and especially, interaction patterns of AgNPs with the gliotoxin molecule were proposed. The antifungal activity assays demonstrated that percentage inhibition of the prepared AgNPs was 100, 93.8 and 100% against hyphal growth, sclerotial formation, and myceliogenic germination of sclerotia at a concentration of 200 μg/mL, respectively. The direct interaction between nanoparticles and fungal cells, including AgNPs’ contact, accumulation, lamellar fragment production and micropore or fissure formation on fungal cell walls, was revealed by SEM and EDS. These will extend our understanding of the mechanisms of AgNPs’ action for preventing diversified fungal disease.
Bacterial wilt of eggplant is the most destructive disease caused by Ralstonia solanacearum throughout the world. Eleven bacterial strains with high antagonistic activity were obtained from 245 rhizobacteria. Based on analysis of morphology, 16S rRNA sequences, fatty acid profiles, gyrA and rpoB genes, they were identified as Pseudomonas putida (IMA3), Paenibacillus polymyxa (IMA5), Bacillus cereus (IMA4, IMA7 and IMA11) and the “operational group Bacillus amyloliquefaciens” (IMA1, IMA2, IMA6, IMA8, IMA9 and IMA10). The lipopeptide compounds produced by each strain also were determined. The biocontrol tests demonstrated that co-inoculation by strain IMA5 and the pathogen gave the greatest biocontrol efficiency of 87.0% and 69.2% 30 and 40 days after co-inoculation, respectively. Plant growth promotion tests revealed that IMA5 markedly promoted eggplant growth, enhancing aboveground seedling length and biomass by 60.8% and by 107.6% and underground root length and biomass by 33.0% and 69.2%, respectively. Hence, strain IMA5 could be considered for developing potential biocontrol agents and for promoting plant growth characteristics, to aid the management of the pathogen R. solanacearum in eggplants.
Ralstonia solanacearum is the most destructive pathogen, causing bacterial wilt disease of eggplant. The present study aimed to develop green synthesis and characterization of silver chloride nanoparticles (AgCl-NPs) by using a native bacterial strain and subsequent evaluation of their antibacterial activity against R. solanacearum. Here, a total of 10 bacterial strains were selected for the biosynthesis of AgCl-NPs. Among them, the highest yield occurred in the synthesis of AgCl-NPs using a cell-free aqueous filtrate of strain IMA13. Ultrastructural observation revealed that the AgCl-NPs were spherical and oval with smooth surfaces and 5–35 nm sizes. XRD analysis studies revealed that these particles contained face-centered cubic crystallites of metallic Ag and AgCl. Moreover, FTIR analysis showed the presence of capping proteins, carbohydrates, lipids, and lipopeptide compounds and crystalline structure of AgCl-NPs. On the basis of phylogenetic analysis using a combination of six gene sequences (16S, gyrA, rpoB, purH, polC, and groEL), we identified strain IMA13 as Bacillus mojavensis. Three kinds of lipopeptide compounds, namely, bacillomycin D, iturin, and fengycin, forming cell-free supernatant produced by strain IAM13, were identified by MALDI-TOF mass spectrometry. Biogenic AgCl-NPs showed substantial antibacterial activity against R. solanacearum at a concentration of 20 µg/mL−1. Motility assays showed that the AgCl-NPs significantly inhibited the swarming and swimming motility (61.4 and 55.8%) against R. solanacearum. Moreover, SEM and TEM analysis showed that direct interaction of AgCl-NPs with bacterial cells caused rupture of cell wall and cytoplasmic membranes, as well as leakage of nucleic acid materials, which ultimately resulted in the death of R. solanacearum. Overall, these findings will help in developing a promising nanopesticide against phytopathogen plant disease management.
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