Contamination by fungi and bacteria during the in vitro propagation of plants leads to considerable losses of biological material and precludes phytosanitary certification. The anti-microbial effect of silver nanoparticles (AgNPs) may be an alternative for the eradication of in vitro contaminants. This study evaluated the microbicidal activity of AgNPs on a recurrent fungus during the micropropagation of stevia (Stevia rebaudiana Bertoni). First, the fungus was isolated and identified at a molecular level by the sequencing and analysis of the ITS4/ITS5 rDNA region. The results of the phylogenetic analysis of various fungal species showed that the strain under study (16-166-H) belongs to the genus Sordaria and is 99.64% similar to S. tomento-alba (strain CBS 260.78). Subsequently, the inhibition of the growth of S. tomento-alba was tested under different concentrations of AgNPs (0, 25, 50, 100, and 200 mg L⁻¹), observing that 50 and 100 mg L⁻¹ achieve ca. 50% growth inhibition (IC₅₀), while 200 mg L⁻¹ produces a drastic inhibition. On the other hand, the shape and size of AgNPs was examined using transmission electron microscopy (TEM), and the transport and accumulation of AgNPs in S. tomento-alba cells were monitored through multiphoton microscopy. The morphological and fluorescence analyses showed that AgNPs display different sizes, with larger nanoparticles retained in fungal cell walls while smaller AgNPs penetrate into fungal cells. Probably, apoplastic and symplastic mechanisms involved in the accumulation and transport of AgNPs affect the metabolic processes of the fungus, thus inhibiting its growth. These results suggest that AgNPs possess antifungal activity and can be used in the eradication of contaminants during the in vitro culture of plant species.

在植物的体外繁殖过程中，真菌和细菌的污染导致生物材料的大量损失，因此无法进行植物检疫认证。银纳米颗粒（AgNPs）的抗微生物作用可能是根除体外污染物的替代方法。这项研究评估了甜叶菊（Stevia rebaudiana Bertoni）的微繁殖过程中，AgNPs对再生真菌的杀微生物活性。首先，通过对ITS4 / ITS5 rDNA区域进行测序和分析在分子水平上分离和鉴定真菌。各种真菌种类的系统发育分析结果表明，所研究的菌株（16-166-H）属于Sordaria属，与S. tomento-alba相似率为99.64％。（应变CBS 260.78）。接着，生长的抑制tomento-粉S.是不同浓度的AgNPs的下测试（0，25，50，100，和200毫克的L ^-1），观察到50至100毫克的L ^-1达到约 50％的生长抑制（IC ₅₀），而200 mg L ^-1则产生强烈的抑制作用。另一方面，使用透射电子显微镜（TEM）检查了AgNPs的形状和大小，以及在绒毛链球菌中AgNPs的运输和积累。通过多光子显微镜监测细胞。形态和荧光分析表明，AgNPs显示不同的大小，较大的纳米颗粒保留在真菌细胞壁中，而较小的AgNPs渗透到真菌细胞中。可能，参与AgNP积累和运输的质外和共生机制会影响真菌的代谢过程，从而抑制其生长。这些结果表明，AgNP具有抗真菌活性，并且可以在植物体外培养过程中用于消除污染物。