Physiological and Biochemical Responses of Tomato Plants to White Mould Affected by Silver Nanoparticles

Tomato (Solanum lycopersicum L.) is one of the most widely cultivated vegetables globally and its production is frequently affected by biotic factors, such as Sclerotinia sclerotiorum, the causal agent of white mould. This study aims to evaluate the direct effect of silver nanoparticles (AgNPs) on the in vitro growth of S. sclerotiorum, measured by mycelial growth velocity index (MGVI) and mycelial diameter (MD), in addition to the in vivo effects on tomato plants infected with S. sclerotiorum at epidemiological, physiological and biochemical scales. The results showed that both MGVI and MD decreased as AgNP concentrations increased, indicating a direct inhibitory effect of AgNPs on S. sclerotiorum. In the in vivo experiments, plants pretreated with AgNPs showed lower white mould severity, reflected in lower lesion size (LS) and area under the disease progress curve (AUDPC) values. These results were associated with preserved concentrations of photosynthetic pigments and the maximum quantum efficiency of photosystem II (F_v/F_m). The reduction in cellular damage, due to lower symptom severity, was correlated with decreased enzymatic activities of SOD, CAT, POX and APX. On the other hand, PAL activity was significantly higher in treated plants, suggesting an enhanced activation of defence pathways. In conclusion, the application of AgNPs preserved photosynthetic capacity by mitigating cellular infection and strengthened the defence response of tomato plants, showing its potential as an effective control strategy against S. sclerotiorum. However, additional studies are required to evaluate the performance of the AgNPs under field conditions, particularly in regions where the disease is endemic.