Root-promoting Biostimulant Enhances Salinity Tolerance in Wild and Cultivated Rocket Salads

Abstract Rocket salads ( Diplotaxis spp. and Eruca spp.) are leafy vegetables appreciated for their typical taste and nutritional value. When exposed to salt stress, these plants undergo morpho-physiological and metabolic changes. The aim of the study was to investigate the efficacy of a “root-promoting biostimulant” (Radifarm ® ) applied during germination (Experiment 1) and during the growth cycle (Experiment 2) on two rocket species under salt stress. Experiment 1 explored if Radifarm ® can protect seed from salt stress in early-stage development. Different salt levels (0, 150 and 200 mM NaCl) were combined with different Radifarm ® concentrations (0, 0.5, 1, 2.5, 5 mL L − 1 ). Experiment 2 investigated how Radifarm ® can promote plant growth after transplantation when irrigated with saline water (0, 150, and 200 mM NaCl) until harvest. Experiment 1 showed that salt stress significantly affected the germination of rocket salads. The addition of Radifarm ® did not improve the germination of D. tenuifolia grown under any salt conditions, but it was beneficial for E. sativa when the highest level of Radifarm ® was applied. In Experiment 2, the application of Radifarm ® significantly reduced the symptoms of salt stress in both species. In E. sativa , salt stress affected all growth parameters (plant height, leaf number and area). However, under 200 mM NaCl, plants fully recovered when Radifarm ® was applied. The same recovery was observed for chlorophyll content in both species. Radifarm ® also contributed to increase protein and lipid content compared to plants under salt stress. This study showed that Radifarm ® was able to protect both species from salt stress.