Biostimolanti contro gli stress abiotici: effetti mitiganti di un biostimolante a base di estratti di alghe e lievito applicato su pomodoro (Solanum lycopersicum L.) in condizioni di stress idrico

The lack of water represents one of the main problems in modern agriculture. This abiotic stress causes heavy crop losses in the face of increasing food demand due to the growth of the world population. Therefore, the research and development of new technologies to be applied in the agricultural field are necessary to improve crop productivity. One possible solution is the application of plant biostimulants. Biostimulants are defined as any substance or microorganism able to improve plant health and growth. These products act by stimulating one or more biological processes, such as nutrient use efficiency, tolerance to abiotic stresses, qualitative traits, or bioavailability of nutrients in the rhizosphere. Biostimulants have no negative effects on the environment and allow a reduction in the use of chemical fertilizers. Furthermore, they are part of a circular economy context because these substances are often derived from industrial waste products. This process allows to recycle and decrease wastes, supporting environmental sustainability. In the present study, the mitigation effects of ERANTHIS®, a commercial biostimulant based on seaweed (Ascophyllum nodosum and Laminaria digitata) and yeast extracts, produced by the Greenhas Group (Canale, CN, Italy), were tested on tomato (Solanum lycopersicum var. MicroTom), grown under drought stress conditions. The project is aimed to confirm a previous study related to the application of ERANTHIS® against drought stress (Campobenedetto et al., 2021) and to evaluate its effects on fruit production and quality. Hence, biochemical and molecular analyses were carried out on tomato (leaves and fruits) biostimulant-treated or untreated plants and grown in standard or drought stress conditions. On leaves, the levels of plant stress response markers, such as hydrogen peroxide (H2O2), antioxidant enzymes (SOD, CAT, POX and GST), osmolytes (proline and glycine betaine), and nonprotein thiols were measured along with a transcriptomic profile obtained by RNA-Seq analysis. On ripe fruits, qPCR analyses were carried out to measure the expression of genes related to development and ripening, including genes involved in lycopene biosynthesis. In order to correlate gene expression to metabolite production, a spectrophotometric quantification of lycopene was also performed. In general, the stressed-treated plants showed a lower antioxidant response, with decreased levels of H2O2, proline, glycine betaine, and thiols, and lower activity of the antioxidant enzymes compared to untreated plants. These results are correlated to a down-regulation of several stressrelated genes. The lycopene content in fruits collected from treated plants resulted higher compared to untreated plant fruits. These results agree with molecular analysis, in which an up-regulation of the genes involved in fruit development and lycopene biosynthesis were observed. In conclusion, the results obtained in this thesis support the hypothesis that the biostimulant ERANTHIS® is able to mitigate the effects of drought stress in tomatoes by improving plant yield and fruit quality.