Metal nanoparticles against fungicide resistance: alternatives or partners?

Copper nanoparticles interfere with insecticide sensitivity, fecundity and endosymbiont abundance in olive fruit fly Bactrocera oleae (Diptera: Tephritidae)

BACKGROUND

The potential of copper nanoparticles (Cu-NPs) to be used as an alternative control strategy against olive fruit flies (Bactrocera oleae) with reduced sensitivity to the pyrethroid deltamethrin and the impact of both nanosized and bulk copper hydroxide (Cu(OH)2) on the insect's reproductive and endosymbiotic parameters were investigated.

RESULTS

The application of nanosized and bulk copper applied by feeding resulted in significant levels of adult mortality, comparable to or surpassing those achieved with deltamethrin at recommended doses. Combinations of Cu-NPs or copper oxide nanoparticles (CuO-NPs) with deltamethrin significantly enhanced the insecticide's efficacy against B. oleae adults. When combined with deltamethrin, Cu-NPs significantly reduced the mean total number of offspring compared with the control, and the number of stings, pupae, female and total number of offspring compared with the insecticide alone. Both bulk and nanosized copper negatively affected the abundance of the endosymbiotic bacterium Candidatus Erwinia dacicola which is crucial for the survival of B. oleae larvae.

CONCLUSION

The Cu-NPs can aid the control of B. oleae both by reducing larval survival and by enhancing deltamethrin performance in terms of toxicity and reduced fecundity, providing an effective anti-resistance tool and minimizing the environmental footprint of synthetic pesticides by reducing the required doses for the control of the pest. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Antifungal Properties of Bio-AgNPs against D. pinodes and F. avenaceum Infection of Pea (Pisum sativum L.) Seedlings

Ascochyta blight and Fusarium root rot are the most serious fungal diseases of pea, caused by D. pinodes and F. avenaceum, respectively. Due to the lack of fully resistant cultivars, we proposed the use of biologically synthesized silver nanoparticles (bio-AgNPs) as a novel protecting agent. In this study, we evaluated the antifungal properties and effectiveness of bio-AgNPs, in in vitro (poisoned food technique; resazurin assay) and in vivo (seedlings infection) experiments, against D. pinodes and F. avenaceum. Moreover, the effects of diseases on changes in the seedlings' metabolic profiles were analyzed. The MIC for spores of both fungi was 125 mg/L, and bio-AgNPs at 200 mg/L most effectively inhibited the mycelium growth of D. pinodes and F. avenaceum (by 45 and 26%, respectively, measured on the 14th day of incubation). The treatment of seedlings with bio-AgNPs or fungicides before inoculation prevented the development of infection. Bio-AgNPs at concentrations of 200 mg/L for D. pinodes and 100 mg/L for F. avenaceum effectively inhibited infections' spread. The comparison of changes in polar metabolites' profiles revealed disturbances in carbon and nitrogen metabolism in pea seedlings by both pathogenic fungi. The involvement of bio-AgNPs in the mobilization of plant metabolism in response to fungal infection is also discussed.

Potential Antifungal Effect of Copper Oxide Nanoparticles Combined with Fungicides against Botrytis cinerea and Fusarium oxysporum

Copper oxide nanoparticles (NCuO) have emerged as an alternative to pesticides due to their antifungal effect against various phytopathogens. Combining them with fungicides represents an advantageous strategy for reducing the necessary amount of both agents to inhibit fungal growth, simultaneously reducing their environmental release. This study aimed to evaluate the antifungal activity of NCuO combined with three fungicide models separately: Iprodione (IPR), Tebuconazole (TEB), and Pyrimethanil (PYR) against two phytopathogenic fungi: Botrytis cinerea and Fusarium oxysporum. The fractional inhibitory concentration (FIC) was calculated as a synergism indicator (FIC ≤ 0.5). The NCuO interacted synergistically with TEB against both fungi and with IPR only against B. cinerea. The interaction with PYR was additive against both fungi (FIC > 0.5). The B. cinerea biomass was inhibited by 80.9% and 93% using 20 mg L-1 NCuO + 1.56 mg L-1 TEB, and 40 mg L-1 NCuO + 12 µg L-1 IPR, respectively, without significant differences compared to the inhibition provoked by 160 mg L-1 NCuO. Additionally, the protein leakage and nucleic acid release were also evaluated as mechanisms associated with the synergistic effect. The results obtained in this study revealed that combining nanoparticles with fungicides can be an adequate strategy to significantly reduce the release of metals and agrochemicals into the environment after being used as antifungals.

Biofabrication of novel silver and zinc oxide nanoparticles from Fusarium solani IOR 825 and their potential application in agriculture as biocontrol agents of phytopathogens, and seed germination and seedling growth promoters

Introduction: Plant pathogenic microorganisms adversely affect the growth and yield of crops, which consequently leads to losses in food production. Metal-based nanoparticles (MNPs) can be a remedy to solve this problem. Methods: Novel silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) were biosynthesized from Fusarium solani IOR 825 and characterized using Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and measurement of Zeta potential. Antibacterial activity of NPs was evaluated against four plant pathogenic strains by determination of the minimum inhibitory (MIC) and biocidal concentrations (MBC). Micro-broth dilution method and poisoned food technique were used to assess antifungal activity of NPs against a set of plant pathogens. Effect of nanopriming with both types of MNPs on maize seed germination and seedlings growth was evaluated at a concentration range of 1-256 μg mL-1. Results: Mycosynthesis of MNPs provided small (8.27 nm), spherical and stable (zeta potential of -17.08 mV) AgNPs with good crystallinity. Similarly, ZnONPs synthesized by using two different methods (ZnONPs(1) and ZnONPs(2)) were larger in size (117.79 and 175.12 nm, respectively) with Zeta potential at -9.39 and -21.81 mV, respectively. The FTIR spectra showed the functional groups (hydroxyl, amino, and carboxyl) of the capping molecules on the surface of MNPs. The values of MIC and MBC of AgNPs against bacteria ranged from 8 to 256 μg mL-1 and from 512 to 1024 μg mL-1, respectively. Both types of ZnONPs displayed antibacterial activity at 256-1024 μg mL-1 (MIC) and 512-2048 μg mL-1 (MBC), but in the concentration range tested, they revealed no activity against Pectobacterium carotovorum. Moreover, AgNPs and ZnONPs inhibited the mycelial growth of Alternaria alternata, Fusarium culmorum, Fusarium oxysporum, Phoma lingam, and Sclerotinia sclerotiorum. MIC and MFC values of AgNPs ranged from 16-128 and 16-2048 μg mL -1, respectively. ZnONPs showed antifungal activity with MIC and MFC values of 128-2048 μg mL-1 and 256-2048 μg mL-1, respectively. The AgNPs at a concentration of ≥32 μg mL-1 revealed sterilization effect on maize seeds while ZnONPs demonstrated stimulatory effect on seedlings growth at concentrations of ≥16 μg mL-1 by improving the fresh and dry biomass production by 24% and 18%-19%, respectively. Discussion: AgNPs and ZnONPs mycosynthesized from F. solani IOR 825 could be applied in agriculture to prevent the spread of pathogens. However, further toxicity assays should be performed before field evaluation. In view of the potential of ZnONPs to stimulate plant growth, they could be crucial in increasing crop production from the perspective of current food assurance problems.

Discovery of Hyrtinadine A and Its Derivatives as Novel Antiviral and Anti-Phytopathogenic-Fungus Agents

Plant diseases caused by viruses and fungi have a serious impact on the quality and yield of crops, endangering food security. The use of new, green, and efficient pesticides is an important strategy to increase crop output and deal with the food crisis. Ideally, the best pesticide innovation strategy is to find and use active compounds from natural products. Here, we took the marine natural product hyrtinadine A as the lead compound, and designed, synthesized, and systematically investigated a series of its derivatives for their antiviral and antifungal activities. Compound 8a was found to have excellent antiviral activity against the tobacco mosaic virus (TMV) (inactivation inhibitory effect of 55%/500 μg/mL and 19%/100 μg/mL, curative inhibitory effect of 52%/500 μg/mL and 22%/100 μg/mL, and protection inhibitory effect of 57%/500 μg/mL and 26%/100 μg/mL) and emerged as a novel antiviral candidate. These compound derivatives displayed broad-spectrum fungicidal activities against 14 kinds of phytopathogenic fungi at 50 μg/mL and the antifungal activities of compounds 5c, 5g, 6a, and 6e against Rhizoctonia cerealis are higher than that of the commercial fungicide chlorothalonil. Therefore, this study could lay a foundation for the application of hyrtinadine A derivatives in plant protection.