The influence of silicon on growth, drought stress tolerance and defense against Neopestalotiopsis lusitanica, in Eucalyptus globulus.

Silicon (Si) is recognized as a beneficial element that enhances plant growth and stress tolerance in various species, although its effects in hardwoods remain unclear. This study evaluated the impact of Si supplementation on Eucalyptus globulus growth and its responses to drought and fungal infection. Two E. globulus genotypes were treated with 1 or 2 mM calcium silicate (CaSiO3), via substrate irrigation under nursery conditions, and Si content, plant growth, and productivity-related indicators were evaluated. After Si treatment, plants were subjected to drought stress using PEG-6000 or inoculated with Neopestalotiopsis lusitanica. In the drought-stressed plants, growth, stress markers, and antioxidant enzyme activities were evaluated. In the pathogen-inoculated, disease severity was assessed using mortality, lesion size, and symptom development. We observed that in genotype B, treatment with 2 mM CaSiO3 increased plant height by 60% and also increased photosynthetic pigments and starch content. In genotype A, the same treatment was particularly effective under stress conditions, increasing plant growth under drought stress by 50% and also reducing oxidative stress (decreasing proline, GSH and lipid peroxidation), enhancing glutamate dehydrogenase activity, and mitigating fungal infection by delaying lesion progression, symptom development and lowering plant mortality by 37.5% at the end of the trial. The effects were supported by the detection of Si in the leaves of both genotypes. These findings suggest that Si can enhance E. globulus growth and resilience and may represent a valuable tool in eucalyptus management, both in nurseries, where plants are often subjected to high-density cultivation and increased pathogen pressure, including emerging nursery-associated fungi such as Neopestalotiopsis sp, and under field conditions, where plants are frequently exposed to water limitations.