Suppression of Bacterial Leaf Spot by Green Synthesized Silica Nanoparticles and Antagonistic Yeast Improves Growth, Productivity and Quality of Sweet Pepper

Abstract

Plants are challenged with many kinds of biotic stresses caused by different living organisms, which result in various types of diseases, infections, and damage to crop plants and ultimately affect crop productivity. Plant disease management strategies based on current approaches are necessary for sustainable agriculture. A pot experiment was carried out under greenhouse conditions to evaluate the potential of green synthesized silica nanoparticles (SiO₂-NPs) and antagonistic yeast (Saccharomyces cerevisiae) against pepper bacterial leaf spot disease, caused by Xanthomonas vesicatoria. In addition, to assess their efficacy and suppressive effects in reducing disease severity and improving sweet pepper growth, productivity, and quality. Results revealed that the combination of BCA (5%) and SiO₂-NPs (150 ppm) was the most effective treatment for reducing disease severity and improving vegetative growth characters, mineral contents (N, P, K, Ca, Mg, and Si in leaves), as well as stimulating polyphenol oxidase (PPO) activity of sweet pepper leaves at 90 days from transplanting, while also at harvesting time enhancing sweet pepper fruit yield quality parameters significantly. In conclusion, green synthesized silica nanoparticles combined with antagonistic yeast have the potential to suppress a bacterial leaf spot disease with ecologically-sound management, while also boosting sweet pepper growth, productivity, and quality.

Keywords: Nano-SiO2; bacterial spot disease; bio-control yeast; nanotechnology; sustainability; sweet pepper.

Figure 1

Pepper plant leaves with bacterial spot symptoms have brown lesions surrounded by yellow halos, from which bacteria were isolated.

Figure 2

Colonial morphology on: (A) Nutrient agar medium, (B) Peptone Sucrose Agar (PSA) medium, and (C) Glycerol agar medium.

Figure 3

Transmission electron microscopy (TEM) image of silica nanoparticles (SiO₂-NPs).

Figure 4

Sweet pepper plant leaves with inoculation and treatments of SiO₂-NPs and BCA. (A) Control, (B) Artificial inoculation symptoms caused by Xanthomonas vesicatoria, (C) Suppression of pepper bacterial leaf spot disease after treatments with (150 ppm SiO₂-NPs and 5% BCA).

Figure 5

Vegetative growth parameters of sweet pepper at 90 days after transplanting, as affected by different treatments of SiO₂-NPs (ppm), and BCA (%) without and with bacterial infection. (a) plant height, (b) number of branches per plant, and (c) number of leaves per plant. Error bars represent the mean ± standard deviation (SD) of the data of 5 replications. Different letter(s) above the error bars indicate statistically significant differences at (p ≤ 0.05).

Figure 6

Polyphenol oxidase (PPO) activity, (change in absorbance min⁻¹ g⁻¹ of fresh tissue), of sweet pepper leaves as influenced by different treatments of SiO₂-NPs (ppm), and BCA (%) without and with bacterial infection. Error bars represent the mean ± SD of the data of 5 replications. Different letter(s) above the error bars indicate statistically significant differences at (p ≤ 0.05).

Figure 7

Pepper fruit yield and quality parameters at harvesting time, as affected by different treatments of SiO₂-NPs (ppm), and BCA (%) without and with bacterial infection. (a) fruit length, (b) fruit diameter, (c) fruit number per plant, and (d) fruit weight per plant. Error bars represent the mean ± SD of the data of 5 replications. Different letter(s) above the error bars indicate statistically significant differences at (p ≤ 0.05).