Microbial consortia: Promising probiotics as plant biostimulants for sustainable agriculture

Plant biostimulants are applied to improve crop production and nutritional quality of agrifood products. They are often included in agricultural management practices aimed at reducing chemical inputs, increasing productivity and recovering the natural equilibrium in agro-ecosystems. The widely accepted definition of plant biostimulants (see EBIC, 2013; du Jardin, 2015) is: substance(s) and/ormicro-organisms whose function when applied to plants or the soil rhizosphere stimulates the natural processes to enhance/benefit nutrient uptake and efficiency, tolerance to abiotic stress, and crop quality. Typically, biostimulants do not have a direct action against pests. Commercial formulations may contain a mix of: humic and fulvic acids, amino acids, seaweeds or plant extracts, natural poly- and oligo-mers, chemical elements (Al, Co, Na, Se, and Si), beneficial fungi or bacteria (du Jardin, 2015; Yakhin et al., 2017). Not all listed components are “biological,” which makes the term “bio”-stimulant somewhat ambiguous. The “bio” designation may be attributed to the living organism components, and their natural substances. Instead, the non-organic factors can be considered as positive effectors of the “biological” processes that regulate the plant physiology, metabolism, morphology and interactions within the agroecosystem.