Effect of combined application of selenium and hydrogen sulfide under salinity stress on yield, physiological traits and biofortification of strawberries in hydroponic cultivation

High levels of salinity usually cause osmotic stress, cell toxicity, excess of ions and, ultimately, nutritional disorders. In the case of many plant species, including strawberries, nutritional disorders entail oxidative stress. In this study, an experiment consisted of 2 factors as treatments. The first factor was anti-stress compounds at four levels (control, hydrogen sulfide (H2S), 200 μM sodium-hydrosulfide (NaHS) as the H2S donor by foliar application once a week, selenium (Se), 1 mg/L sodium selenate (Na2SeO4) in a nutrient solution through the roots, and H2S+Se). The second factor was salinity at two levels (0 and 40 mM NaCl) with 4 replications. Strawberry plants cv. 'Parus' were planted in 3 L plastic pots filled with cocopeat/perlite (v/v 1:1). According to the results, the treatments of H2S+Se, H2S, and Se alleviated the adverse effects of salinity on yield by 82, 66 and 63%, respectively. The H2S+Se treatment caused the highest values of inhibition percentage of free radicals (84%), anthocyanin content, vitamin C, and activity of antioxidant enzymes (catalase, superoxide dismutase, and peroxidase). As a result of the sodium selenate treatment, the concentration of selenium increased in all fruits, both in salt-stress and non-stress conditions, thereby causing the biofortification of selenium in strawberry fruits (2.67–3.02 mg/kg dry weight). Based on the findings of the present research, the combined use of the two anti-stress compounds further strengthened the enzymatic and non-enzymatic antioxidant system and, thus, reduced the adverse effects of salt stress on fruit yield. The combined use increased the antioxidant quality (vitamin C and anthocyanin content) and flavor of fruits. Therefore, biofortification can be deemed suitable for fruits with selenium.