Biostimulatory Effects of Seaweed Extracts and Beneficial Fungi and Bacteria on Crop Performance and Chemical Profile of Sonchus oleraceus, Cichorium spinosum and Scolymus hispanicus

Climate change necessitates direct measures in horticultural crop production, including the adoption of sustainable agronomic practices, such as the use of biostimulants and the inclusion of alternative species in agroecosystems. The aim of the present study was to evaluate the effect of two biostimulant formulations, one based on beneficial bacteria and fungi and the other based on seaweed extracts, on the growth, nutritional value, and bioactive properties of three wild edible species, namely, Sonchus oleraceus, Cichorium spinosum, and Scolymus hispanicus, grown in a greenhouse under optimal conditions. Our results indicate that biostimulant application had a variable effect on crop performance depending on the biostimulant formulation and species, with Bactiva showing a clear beneficial effect on the fresh weight, number of leaves, and leaf area of S. oleraceus (increased by 63.2%, 32.4%, and 51.1%, respectively, compared to the control), while seaweed extracts mostly improved the crop performance of S. hispanicus and the number of leaves and the Soil Plant Analysis Development (SPAD) index of C. spinosum (increased by 1.1% and 24.8%, respectively, compared to the control). Moreover, Bactiva significantly increased the leaf protein content of all the studied species (increased by 2.1%, 5.2%, and 6.9% for S. oleraceus, C. spinosum, and S. hispanicus, respectively, compared to the control), whereas a varied response was observed for the rest of the macronutrients, depending on the species and biostimulant. Similarly, the macromineral content (N, P, and K) increased for the application of Bactiva and/or seaweed extracts in S. oleraceus (increased by 2.1%, 22.4%, and 14.0% for N, P and K, respectively, compared to the control) and C. spinosum (increased by 5.2%, 19.3%, and 14.7% for N, P, and K, respectively, compared to the control) leaves, while for S. hispanicus leaves, only N and K increased for Bactiva (increase by 7.0% and 17.9% for N and K, respectively, compared to the control). Finally, the use of the studied biostimulants had a varied effect on the polyphenol content of the three species, and the antioxidant activity also varied among the three assays implemented. In conclusion, the use of biostimulants on these underexplored species showed promising results in terms of crop performance and chemical composition/. However, considering that the plants were subjected to optimal conditions, further research is needed to reveal the stress-mitigating effects of these biostimulant formulations for their integration as a sustainable agronomic tool for the commercial exploitation of wild edible greens.