*2.4. In Vivo Antifungal Activity*

The antifungal activity of "Nitric-extract" was finally tested *in vivo* on citrus (oranges and lemons) and apple fruits artificially infected by *P. digitatum* and *P. expansum*, respectively. Results are summarized below.

#### 2.4.1. Antifungal Activity on Oranges

Three days post inoculation with *P. digitatum* P1PP0 of oranges, all concentrations of "Nitric-extract" significantly reduced rot severity compared to the water control (treatment ID01) (Figure 3). However, except for "Nitric-extract" applied as such (ID02), each of the other concentrations was not statistically different from the respective control.

**Figure 3.** Rot severity caused by *Penicillium digitatum* strain P1PP0 in orange (*Citrus* × *sinensis*) fruits cv. Valencia treated with water (ID01) or nitric-extract as such (ID02), 75% Nitric-extract (ID04), 50% Nitric-extract (ID06), 25% Nitric-extract (ID08) and respective controls (NaNO3 0.17 g/mL—ID03; NaNO3 0.17 g/mL diluted in sterile distilled water (sdw) at 75%—ID05; NaNO3 0.17 g/mL diluted in sdw at 50%—ID07; NaNO3 0.17 g/mL diluted in sdw at 25%—ID09) 3 days after inoculation. Values sharing the same letters are not statistically different according to Tukey's HSD (honestly significant difference) test (*p* ≤ 0.05). Bars represent SD.

Five days after inoculation (Figure 4), all concentrations of "Nitric-extract" still demonstrated values of rot severity significantly lower than the water control (treatment ID01); however, in this case, only treatment with "Nitric-extract" at 25% (ID08) significantly differed from the respective control (ID09), although this difference was not statistically significant in comparison to the other control treatments (ID03, ID05, ID07).
