## 3 Results and Discussion
The present results are consistent with those of [36; 37; 38], which showed that metallic Ag has an excellent inhibitory ability against both bacteria (_Escherichia coli_, _Staphylococcus aureus_ and _Pseudomonas aeruginosa_) and fungi (_Fusarium oxysporum_ and _Botrytis cinerea_). Figure 5 shows the spore germination rates of the _C. gloeosporoides_ contacted with the different Ag samples for periods of 1 and 15 min, respectively. For both contact periods, the spore germination rates of the treated samples were significantly lower than those of the untreated sample. Furthermore, for the Ag samples, the germination rates decrease by around 20% as the contact time was increased from 1 to 15 min. The germination rates also decreased with increasing particle size. For example, given a contact time of 15 min, the germination rate reduced from around 29% to 15% as the particle size increases from 92 nm to 1.2 um. It is noted that this trend is consistent with the plate test results (see Figure 4). Anthracnose appressorium formation is one of the most important structures invading a host [32]. Figure 6 presents OM images showing the appressorium formation of _C. gloeosporoides_ spores contacted with the treated and untreated samples. For the untreated sample, germination was observed after 2 h of cultivation, and the appressorium formation rate was equal to 40.2% \(\pm\) 6.2% after 8 h. In addition, germ tube and appressorium formation were observed after 4 and 6 h, respectively. However, for the treated samples, germ tube formation was not observed until 6 h of incubation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Particle Size** & **Film Thickness (nm)** & **Roughness (nm)** & **Contact Angle (\({}^{\circ}\))** \\ \hline Glass & - & 0.3 & 63 \(\pm\) 2 \\
92 nm & 10 & 5 \(\pm\) 2 & 43 \(\pm\) 2 \\
570 nm & 50 & 44 \(\pm\) 1 & 51 \(\pm\) 2 \\
1.2 μm & 50 & 73 \(\pm\) 3 & 73 \(\pm\) 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Roughness and contact angle measurements of different Ag particle samples. Figure 4: Conidia growth of _C. gloeosporoides_ for different Ag particle sizes and contact times. In addition, no appressorium formation was observed for any of the samples, even after 8 h. In other words, the results confirm the ability of the Ag particles to inhibit the formation of Anthracnose. Figure 7 shows the morphologies of the _C. gloeosporoides_ spores treated with different Ag particles for 15 min then incubated in PDA at 28 \({}^{\circ}\)C for 6 days. Note that for each sample, the left and right images present front and rear views of the colony morphology, respectively. It can be observed that the melanin precipitation in the treated samples was greatly reduced compared to that in the untreated (control) sample. Among the treated samples, the sample with a 1.2-\(\upmu\)m particle size had a particularly low melanin precipitation. [PERSON] (2018) showed that Anthracnose produce melanin to accumulate the swell pressure inside the press. In other words, the amount of melanin is one of the key factors determining the pathogenic ability of Anthracnose. Overall, the results presented in Figure 7 suggest that Ag particle treatment is effective at suppressing melanin expression and hence in limiting the activity of Anthracnose. Figure 8 shows the relative expressions of the lacase gene (LAC1), PKS, THR, SCD, Ecg and PEL genes following contact with the treated and un-treated samples. The results confirm that exposure to Ag particles resulted in a significant reduction in melanin synthesis compared to that for the untreated sample. Moreover, for each gene, the melanin synthesis reduced with an increasing particle size. Figure 5: Spore germination rate of _C. gloeosporoides_ for different Ag particle sizes and contact times. Figure 6: Formation of _C. gloeosporoides_ for different Ag particle sizes and contact times. Figure 9 shows the effect of the Ag nanoparticles on the extent of the anthracnose of the mango samples. Compared to the control sample, the pathogenicity of the _C.