Stimulation of plant secondary metabolites synthesis in soilless cultivated strawberries (Fragaria × ananassa Duchesne) using zinc-alginate microparticles

Abstract

An innovative approach to stimulate the production of plant secondary metabolites (PSM) is the use of encapsulated bioactive agents. Zinc-alginate microparticles [microspheres (ALG/Zn) and microcapsules (CS/ALG/Zn)] were applied near the root zone of soilless cultivated strawberries (Fragaria x ananassa Duchesne) to ensure a constant supply of an essential micronutrient zinc ions throughout the whole period of maturation. Both, ALG/Zn and CS/ALG/Zn had a positive effect on PSM (total polyphenols, total flavonoids, total anthocyanins, and flavan-3-ols) synthesis and increased antioxidant activity in two strawberry varieties (Albion and San Andreas). Treatments with Zn-alginate microparticles resulted in no visible damages on the plant and fruits. A two-year study revealed an increase of similar to 34% in total polyphenolic compounds and similar to 23% in total flavonoids in the San Andreas variety. The highest increase in antioxidant activity [ABTS (similar to 37%) and DPPH (similar to 38%)] was observed in the San Andreas variety treated with CS/ALG/Zn. Respectively high increase in anthocyanins was observed in both varieties (similar to 54% and similar to 61%, respectively) treated with CS/ALG/Zn. Treatments with zinc-alginate microparticles resulted in a successful stimulation of PSM synthesis and increased strawberries' nutritive value. Encapsulation of zinc ions proved to be simple, sustainable, and environmentally favorable to produce strawberries fortified with important bioactive compounds.