Seaweed and microalgae as major actors of blue biotechnology to achieve plant stimulation and pest and pathogen biocontrol – a review of the latest advances and future prospects

Abstract

Modern agriculture needs proper solutions to face the current trend of pesticides and fertilizers reduction. One of the available leverages to support this transition is the use of bioproducts that are more environmentally friendly and less hazardous for human health. Among them, blue biotechnology and more precisely seaweed and microalgae gain interest every year in the scientific community. In agriculture, seaweeds (Macroalgae) have been used in the production of plant biostimulants while microalgae still remain unexploited. Microalgae are widely described as renewable sources of biofuels, bioingredients and biologically active compounds, such as polyunsaturated fatty acids (PUFAs), carotenoids, phycobiliproteins, sterols, vitamins and polysaccharides, which attract considerable interest in both scientific and industrial communities. They affect agricultural crops for enhancement of plant growth, seedling growth. They can also improve nutrient incorporation, fruit setting, resistance properties against pests and diseases, improving stress management (drought, salinity and temperature). The present review aimed at the interest of blue biotechnology in agronomy, with a specific focus on microalgae, their biological activities and their possible application in agriculture as a potentially sustainable alternative for enhanced crop performance, nutrient uptake and resilience to environmental stress. This review does not only present a comprehensive study of microalgae as plant biostimulants but also as biofertilizers, with a particular emphasis on future challenges these solutions will have to deal with, microalgae being able to synthesize secondary metabolites with potential biopesticidal action.

Cyanobacteria: A Natural Source for Controlling Agricultural Plant Diseases Caused by Fungi and Oomycetes and Improving Plant Growth

“…For instance, the regulation of cyanobacteria as fertilizers and biostimulants is currently not uniform from one country to another. EU Regulation 2019/1009 that will take effect in 2022 will open up the market for algae, microalgae and cyanobacteria, since organic fertilizers will no longer require marketing authorization, resulting in a great and beneficial impact for the agronomic sector [19]. Accordingly, there is an urgent need to update legislative knowledge on both cyanobacteria and microalgae, to create ISO (Carbon Footprint) certifications, and to establish model regulatory frameworks for importing and monitoring microorganism strains [141].…”

“…More recently, only a few dozen articles referring to the effect of cyanobacteria on plant pathogens were cited in the Scopus database (search for "cyanobacteria + versus + plant pathogens"). Cyanobacteria have been shown to reduce the infection of several fungal pathogens by acting directly against pathogen growth and indirectly stimulating plant defense responses [19][20][21][22]. Recent studies have shown that Anabaena minutissima treatment elicits tomato root defense barriers through the production of phenolic compounds [20], protects cutin and pectin structures in tomato fruits from the etiological agent of gray mold disease (Botrytis cinerea) [23], and elicits the expression of pathogenesis-related genes in cucumber plants [24].…”

Microalgae as next generation plant growth additives: Functions, applications, challenges and circular bioeconomy based solutions

“…Microalgal metabolites have been reported to improve soil fertility, impart resistance to plants against abiotic stress, stimulate defense response against pathogens and infection, and improve nutrient uptake from soil such as phosphorus (P), potassium (K), N, and minerals ( Berthon et al., 2021 ; Gonçalves, 2021 ). Several reports on the use of microalgae for the improvement of crop quality and productivity in various Agri-Horti crops have been published in recent years ( Abinandan et al., 2019 ; Gonçalves, 2021 ; Kapoore et al., 2021 ; Lee and Ryu, 2021 ).…”

Improving growing substrates by adding the seaweed Cystoseira baccata

“…For example, beach cast seaweed, especially of the brown kind, has traditionally been applied to crops grown on coastal areas (Metting et al 1990). Although the main agricultural use of seaweed has been in amendments or fertilizers directly applied to soil, the increasing development of "blue technology", which is based on marine organisms (Berthon et al 2021), has promoted the use of seaweed for a variety of agricultural purposes. In fact, seaweed is currently used in various forms in fertilizers.…”

“…In addition, they supply crops with substantial amounts mineral nutrients (Verkleij 1992;Cabrita et al 2016), vitamins (Bourgougnon et al 2011) and complex organic compounds, and primary and secondary metabolites (Biris-Dorhoi et al 2020). Furthermore, the enzymes and biocidal compounds they contain (Illera-Vives et al 2020) act as biostimulants facilitating crop development (Crouch et al 1992;Berthon et al 2021), and their good rheological properties can help avoid moisture losses. In any case, the agronomically significant properties of seaweeds differ among taxonomic groups, species, year, season or even location (Villares et al 2007;Adams et al 2011;Sharma et al 2012;Schiener et al 2015).…”