Bacillus megaterium-Mediated Synthesis of Selenium Nanoparticles and Their Antifungal Activity against Rhizoctonia solani in Faba Bean Plants

Abstract

Rhizoctonia root-rot disease causes severe economic losses in a wide range of crops, including Vicia faba worldwide. Currently, biosynthesized nanoparticles have become super-growth promoters as well as antifungal agents. In this study, biosynthesized selenium nanoparticles (Se-NPs) have been examined as growth promoters as well as antifungal agents against Rhizoctonia solani RCMB 031001 in vitro and in vivo. Se-NPs were synthesized biologically by Bacillus megaterium ATCC 55000 and characterized by using UV-Vis spectroscopy, XRD, dynamic light scattering (DLS), and transmission electron microscopy (TEM) imaging. TEM and DLS images showed that Se-NPs are mono-dispersed spheres with a mean diameter of 41.2 nm. Se-NPs improved healthy Vicia faba cv. Giza 716 seed germination, morphological, metabolic indicators, and yield. Furthermore, Se-NPs exhibited influential antifungal activity against R. solani in vitro as well as in vivo. Results revealed that minimum inhibition and minimum fungicidal concentrations of Se-NPs were 0.0625 and 1 mM, respectively. Moreover, Se-NPs were able to decrease the pre-and post-emergence of R. solani damping-off and minimize the severity of root rot disease. The most effective treatment method is found when soaking and spraying were used with each other followed by spraying and then soaking individually. Likewise, Se-NPs improve morphological and metabolic indicators and yield significantly compared with infected control. In conclusion, biosynthesized Se-NPs by B. megaterium ATCC 55000 are a promising and effective agent against R. solani damping-off and root rot diseases in Vicia faba as well as plant growth inducer.

Keywords: R. solani; Se-NPs; Vicia faba; nano-biosynthesis; plant disease; plant promotion; root rot.

Figure 1

Characterization of bacteriogenic Se-NPs produced by B. megaterium (A–D); (A) UV-Visible spectrum; (B) dynamic light scattering (DLS); (C) TEM image; (D) XRD.

Figure 2

Antifungal activity of different concentrations of Se-NPs against R. solani. Data are expressed as means ± standard deviations of triplicate assays. The different alphabetic superscripts in the same column are significantly different (p < 0.05) based on Tukey’s multiple comparison test.

Figure 3

Effect of Se-NPs on R. solani (A–C): (A) Linear growth at different incubation periods from 0 to 7 days; (B) Inhibition percentages of R. solani at different concentration of Se-NPs; (C) Linear growth on potato dextrose agar medium (PDA) plates at 7 days. Data are expressed as means ± standard deviations of triplicate assays. The different alphabetic superscripts in the same column are significantly different (p < 0.05) based on Tukey’s multiple comparison test.

Figure 4

Disease index scale (0–5); (A): 0, (B): 1, (C): 2, (D): 3, (E): 4, and (F): 5; the disease index was recorded after 45 days from sowing.

Figure 5

Effect of Se-NPs on the photosynthetic pigment’s indicators of (Vicia faba L.).

Figure 6

Effect of Se-NPs on the phenolics compounds of (Vicia faba L.).

Figure 7

Effect of Se-NPs on peroxidase isozymes of Vicia faba under pot conditions 1: Control (H.). 2: Control (Inf.). 3: Soaking Nano (H.). 4: Soaking Nano (Inf.). 5: Soaking + Spray Nano (H.). 6: Soaking + Spray Nano (Inf.). 7: Spray Nano (H.). 8: Spray Nano (Inf.).

Figure 8

Effect of Se-NPs on Polyphenol oxidase isozymes of Vicia faba under pot conditions Control (H.). 2: Control (Inf.). 3: Soaking Nano (H.). 4: Soaking Nano (Inf.). 5: Soaking + Spray Nano (H.). 6: Soaking + Spray Nano (Inf.). 7: Spray Nano (H.). 8: Spray Nano (Inf.).