Management of potato brown rot disease using chemically synthesized CuO-NPs and MgO-NPs

Abstract

Background: Potatoes are a crucial vegetable crop in Egypt in terms of production and consumption. However, the potato industry suffers significant annual losses due to brown rot disease. This study aimed to suppress Ralstonia solanacearum (R. solanacearum), the causative agent of brown rot disease in potatoes, using efficient and economical medications such as CuO and MgO metal oxide nanoparticles, both in vitro and in vivo, to reduce the risk of pesticide residues.

Results: CuO and MgO metal oxide nanoparticles were synthesized via a simple chemical process. The average particle size, morphology, and structure of the nanoparticles were characterized using UV-visible spectroscopy, transmission electron microscopy (TEM), zeta potential analysis, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The growth of R. solanacearum was strongly inhibited by CuO and MgO NPs at a concentration of 3 mg/mL, resulting in zones of inhibition (ZOI) of 19.3 mm and 17 mm, respectively. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CuO-NPs and MgO-NPs were 0.5, 0.6, and 0.6, 0.75 mg/mL, respectively. When applied in vivo through seed dressing and tuber soaking at their respective MIC concentrations, CuO-NPs and MgO-NPs significantly reduced the incidence of brown rot disease to 71.2% and 69.4%, respectively, compared to 43.0% and 39.5% in bulk CuSO₄ and bulk MgSO₄ treatments, respectively. Furthermore, CuO-NPs and MgO-NPs significantly increased the yield, total chlorophyll content, and enzyme efficiency of potato plants compared with the infected control plants. TEM revealed that the bacterial cytomembrane was severely damaged by nanomechanical forces after interaction with CuO-NPs and MgO-NPs, as evidenced by lipid peroxidation and ultrastructural investigations.

Conclusion: The results of this study suggest that CuO-NPs and MgO-NPs can be used as intelligent agents to manage plant pathogens in agriculture. The use of metal oxide nanoparticles could provide a risk-free alternative for treating plant diseases, which are currently one of the biggest challenges faced by the potato industry in Egypt. The significant increase in yield, photosynthetic pigments, enzymatic activity, and total phenol-promoted resistance to R. solanacearum in potato plants treated with CuO-NPs and MgO-NPs compared to infected control plants highlights the potential benefits for the potato industry in Egypt. Further investigations are needed to explore using metal oxide nanoparticles for treating other plant diseases.

Keywords: Brown rot disease; Chlorophyll; CuO-NPs; Lipid peroxidation; MgO-NPs; Potato; R. solanacearum.

Fig. 1

UV-vis spectrum of the synthesized CuO-NPs, showing a peak at approximately 220 nm with an absorption value of 0.2

Fig. 2

TEM photograph of CuO-NPs showing smooth, spherical, and loosely distributed NPs with particle sizes ranging from 3.59 to 6.05 nm, homogeneously distributed

Fig. 3

Histogram of the zeta potential distribution of CuO-NPs, showing a zeta potential of -39 mV

Fig. 4

FTIR spectra of CuO-NPs measured at wavenumbers of 400–4000 cm^− 1. Strong bands were visible at 3440.7, 1636.78, and 432.11 cm^− 1

Fig. 5

XRD spectra of CuO nanopowder used to detect its crystalline nature. It shows two sharp peaks at 2θ of 35.544° and 38.709° with reference code (00-048-1548)

Fig. 6

UV-vis absorption spectra of synthesized MgO-NPs showing maximum surface plasmon resonance (SPR) at 200 nm

Fig. 7

TEM photograph of MgO-NPs showing spherical shapes and particle sizes ranging from 3.71 to 6.58 nm, homogeneously distributed

Fig. 8

Histogram of the zeta potential distribution of MgO-NPs, showing a zeta potential of − 43 mV

Fig. 9

FTIR spectra of MgO-NPs measured at wavenumbers of 400–4000 cm^− 1. Strong bands were visible at 3436.16, 2079.31, 1637.64, and 669.05 cm^− 1

Fig. 10

XRD spectra of the MgO nanopowder used to detect its crystalline nature. It shows two sharp peaks at 2θ of 43.006° and 62.447° with reference code (04-007-3846)

Fig. 11

Seeded agar plate with R. solanacearum treated with different nanosolutions on TZC medium: (1) gentamicin, (2) MgO-NPs, and (3) CuO-NPs.

Fig. 12

Seeded agar plates with R. solanacearum treated with different concentrations (mg/mL) of the prepared nanosolutions. The numbers 1–10 represent different concentrations of NPs: (1) 3 mg/mL, (2) 1.5 mg/mL, (3) 1 mg/mL, (4) 0.75 mg/mL, (5) 0.6 mg/mL, (6) 0.5 mg/mL, (7) 0.43 mg/mL, (8) 0.37 mg/mL, (9) 0.33 mg/mL and (10) 0.3 mg/mL)

Fig. 13

Photographs showing the mode of action of NPs against R. solanacearum: a control cells without NPs, b cells treated with CuO-NPs, c the magnified cells treated with CuO-NPs, d cells treated with MgO-NPs, e the magnified cells treated with MgO-NPs

Fig. 14

A Healthy plants without intervention and B treated plants. Bacterial wilt disease symptoms in the infected control plants were particularly severe. In contrast, the disease indices of potato plants exposed to CuO-NPs or MgO-NPs showed a decrease in disease incidence compared to bulk CuSO₄ and bulk MgSO₄