*3.2. In Vitro Control of R. solani*

#### 3.2.1. Antifungal Activity of Se-NPs and Minimum Inhibition Concentration

Metal nanoparticles such as silver nanoparticles [61,62], copper nanoparticles [63], and zinc nanoparticles [64] are wildly used for controlling fungal plant pathogens. However, selenium nanoparticles have strong antifungal activity, while they are rarely used for controlling fungal plant pathogens. Therefore, selenium nanoparticles were biosynthesized in this study to control *R. solani*. The antifungal activity of Se-NPs was assessed against *R. solani* using the agar well diffusion method; different concentrations of Se-NPs ranging from 1 to 0.0078 mM were tested as antifungal agent, as shown in Figure 2. Results illustrated that concentrations of Se-NPs of 1, 0.5, 0.25, 0.125, and 0.0625 mM had antifungal activity against *R. solani.* Moreover, 1 mM of Se-NPs had the maximum antifungal activity and gave an inhibition zone of 45 mm, whereas 0.0625 mM had the lowest antifungal activity against *R. solani* and gave an inhibition zone of 12 mm. From these data, 0.0625 was the minimum inhibition concentration for the controlling of *R. solani*.

**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.
