## 1 Introduction
Biostimulants contain beneficial substances and/or microorganisms and their application is a promising strategy to manage the nitrate accumulation issue in leafy vegetables such as rocket, also enhancing crop yield and quality; they are applied to plants or to the rhizosphere to stimulate natural processes, enhancing nutrient uptake and efficiency, tolerance to abiotic stress, and crop quality, independently, on their mineral element content [16]. Among the various biostimulant categories, those derived from marine algae (macroalgae), microalgae, and protein hydrolyses have demonstrated effectiveness in mitigating nitrate accumulation in rocket and similar leafy greens. In this respect, seaweed-based biostimulants, primarily extracted from brown algae species such as _Ascophyllum nodsum_ and _Ecklonia maxima_, have been shown to significantly reduce nitrate content in rocket leaves [17]. Research by [PERSON] et al. [18] demonstrated that the application of biostimulants based on brown algae and yeast reduced nitrate accumulation by approximately 10.6% in wild rocket leaves, compared to untreated controls. These extracts contain bioactive compounds, including polysaccharides (alginates, laminarin), phytohormones (auxins, cytokins), and osmolytes (betaines), that enhance nitrogen metabolism and assimilation [17]. Microalgal extracts similarly contribute to reduced nitrate accumulation through the action of various bioactive constituents and, particularly, Spirulina (_Arthospira platensis_) application reportedly alters nitrogen assimilation patterns, resulting both in lower tissue nitrate concentrations and higher nitrogen use efficiency [19]. The latter effects may be attributed to the complex array of amino acids, vitamins, and phytohormones present in microalgal biomass stimulating the activity of nitrate reductase. Protein hydrolyses, particularly those derived from leguminous plant species (Fabaceae), represent another valuable class of biostimulants for nitrate management. [PERSON] et al. [16] reported that the application of protein hydrolyses obtained from enzymatic hydrolysis of Fabaceae tissues resulted in a 24% decrease in nitrate content of wild rocket leaves, compared to untreated controls. The mentioned hydrolyses are a rich source of peptides and amino acids that enhance nitrogen metabolism and nitrate reductase activity, providing alternative nitrogen sources [16]. Some biostimulants were shown to exert similar effects like red light exposure, encouraging nitrate reductase activity in rocket leaves [20] and, additionally, they may increase photosynthetic efficiency, thereby fostering the availability of carbon skeletons necessary for nitrate assimilation [21]. These compounds also modify root architecture and function, potentially altering nitrogen uptake patterns to reduce nitrate accumulation [22]. Following ingestion, dietary nitrates undergo complex transformations within the human digestive system, starting from the reduction to nitrites; then, upon interactions with gastric acid, they can generate nitrogen oxide compounds, directly functioning as signaling molecules or forming more complex compounds, such as N-nitrosamines, with diverse physiological effects [6]. The genotype-dependent responses to biostimulant applications may reveal valuable synergistic combinations optimizing both production and nutritional quality of rocket leaves, while effectively limiting nitrate accumulation. The present research was conceived to support the development of sustainable rocket production systems meeting regulatory requirements for NO\({}_{3}\) content, while satisfying consumer demand for high-quality produce with optimal health-promoting properties. In this respect, the present study was aimed at assessing the interactions between plant biostimulants, derived from macroalgae, microalgae, and protein hydrolyses, and genetic potential, under different weather conditions, on rocket yield, nutritional profiles, and nitrate accumulation.