Nanobiotecnologie per il miglioramento della protezione delle piante

The increasing salinization of arable lands exposes crops to abiotic stresses, requiring the adoption of novel, sustainable and efficient technologies to counteract yield reductions. In recent years, prolonged drought conditions contributed to the intrusion of saline water from the sea into rivers and wells, furtherly increasing the overall salinity levels. Nano-biotechnological approaches, including Plant Growth Promoting Microorganisms (PGPM) and Engineered Nanomaterials (ENMs) to mitigate salt stress in economically significant crops such as tomato (Solanum lycopersicum L.) hold promise to regulate plant responses. In addition, the use of ENMs could be an applied solution as agricultural nanofertilization, due to their unique properties contributing to improve crop performance and to decrease environmental impact, through a diminished usage of conventional fertilizers. The present work aims to assess the effects of PGPMs (microbial consortia) combined with SiO2 nanoparticles (NPs) on salt stress tolerance during the cultivation of industrial tomato (cv. Heinz 3402). The experiments consisted of different phases: a preliminary study aimed at optimizing experimental conditions, including the determination of the optimal saline concentration and the selection of the most promising consortium. The selected consortium was then combined with silicon nanoparticles and its physiological and transcriptomic effects in the plant were assessed. The results showed a positive role of SiO2 NPs in reducing lipid peroxidation of plant roots under salt stress condition, although it did not affect proline content. On the other hand, microbial consortium inoculum appears to play a role in the reduction of salt stress biomarkers, including proline content and lipid peroxidation. Furthermore, X-ray fluorescence elemental maps analyses showed a greater accumulation of silicon into the stems treated with Na2SiO3, as compared to SiO2 NPs treatment and untreated control, suggesting a greater silicon translocation in its ionic form. The reduced SiO2 NPs translocation (as compared with sodium metasilicate) results in a differential gene expression regulation. Interestingly, chloroplast functions have been observed in the modulation of silicon-mediated salt stress response. The use of ENMs demonstrated considerable potential, not only for inducing stress tolerance, as exemplified in the case of nano-Si, but also as a sustainable alternative to conventional fertilizers application. In a parallel study, Zea mays L. plants were treated with Fe3O4 NPs to assess a controlled release of iron, a vital element for plant physiology. While no significant morphological differences were observed, FeCl3 treated plants showed reduced photosynthetic activity as well as increased stomatal transpiration and lipid peroxidation, while Fe3O4 NPs treatments resembled untreated controls and FeCl3 treated plants. Furthermore, the transcriptional analysis via RT-qPCR on target genes in RNA extracted from leaves and roots has revealed an influence of iron treatments on iron transport mechanisms and the response to oxidative stress. The approaches explored on different plants of agri-food interest, utilizing multiple nano-biotechnological strategies (with PGPM, nanofertilizers, or through their combination) showed a high potential of implementation in the modern agricultural practices and scale-up to field experimental conditions. Moreover, the approaches utilized may also contribute to develop and to adopt novel strategies in assessment and in characterization of the risk associated to nano-biotechnological solutions.