Algae and Their Metabolites as Potential Bio-Pesticides

Abstract

An increasing human population necessitates more food production, yet current techniques in agriculture, such as chemical pesticide use, have negative impacts on the ecosystems and strong public opposition. Alternatives to synthetic pesticides should be safe for humans, the environment, and be sustainable. Extremely diverse ecological niches and millions of years of competition have shaped the genomes of algae to produce a myriad of substances that may serve humans in various biotechnological areas. Among the thousands of described algal species, only a small number have been investigated for valuable metabolites, yet these revealed the potential of algal metabolites as bio-pesticides. This review focuses on macroalgae and microalgae (including cyanobacteria) and their extracts or purified compounds, that have proven to be effective antibacterial, antiviral, antifungal, nematocides, insecticides, herbicides, and plant growth stimulants. Moreover, the mechanisms of action of the majority of these metabolites against plant pests are thoroughly discussed. The available information demonstrated herbicidal activities via inhibition of photosynthesis, antimicrobial activities via induction of plant defense responses, inhibition of quorum sensing and blocking virus entry, and insecticidal activities via neurotoxicity. The discovery of antimetabolites also seems to hold great potential as one recent example showed antimicrobial and herbicidal properties. Algae, especially microalgae, represent a vast untapped resource for discovering novel and safe biopesticide compounds.

Seaweed as a Natural Source against Phytopathogenic Bacteria

“…The influence of laminarin in SA accumulation on plants is controversial. Some studies observed an increase of SA in plants when stimulated with that compound [ 47 , 225 ], but other studies observed the inhibition of SA accumulation. SA is derived from the phenylpropanoid pathway and some studies established a correlation between SA accumulation and the increase in phenylalanine ammonia-lyase (PAL), a defense enzyme [ 229 ] that is a precursor of SA [ 230 ].…”

“…Their exploitation is already vast in some industries, encompassing the food, cosmeceutical, and agricultural industries [ 42 ], but the search for other bioactivities has also been growing. One of them is the antimicrobial activity from algae compounds against phytopathogens [ 41 , 46 ], which remains poorly described against bacterial phytopathogens when compared with the amount of data reported regarding antibacterial activity against human pathogens [ 47 ]. Several compounds’ families have exhibited antimicrobial activity against a wide range of phytopathogens, such as pigments (carotenoids), fatty acids, sterols, terpenes, polysaccharides, phenolic compounds, proteins, and peptides [ 44 , 45 , 48 ].…”

A New Biocontrol Tool to Fight Potato Late Blight Based on Willaertia magna C2c Maky Lysate

“…Pandit et al [ 33 ] summarized existing and incoming strategies to control plant pathogens using biological approaches, for example, the use of microbial strains and natural compounds to provide a natural protection. Algae (micro and macro) possess antibacterial, antiviral, antifungal, nematicide, insecticidal and herbicidal properties and represent a vast reservoir of unknown properties [ 34 ]. Amoebas are even less known and represent a considerable reservoir of unknown properties.…”

Potential of microalgae and cyanobacteria to improve soil health and agricultural productivity: a critical view

“…161 More importantly, the eld-level evaluation of microalgae or their cellular extracts is critical for the widespread acceptance of their application as an agronomic practice in green agriculture. The insecticidal properties of several macro-and microalgae as well as cyanobacteria have been reported and recently reviewed by Asimakis et al 162 The crude ethanolic extracts of a cyanobacterium (Nostoc carneum), green algae (Parachlorella kessleri, Ulva intestinalis, and Cladophora glomerata), and stonewort (Chara vulgaris) showed insecticidal activity against cotton leafworm (Spodoptera littoralis) when treated against the 2nd and 4th instars in the in vitro assay. 163 The ethanolic crude extracts contained an array of saturated and unsaturated fatty acids (particularly polyunsaturated u-6 linoleic, palmitic, oleic, myristic, a-linolenic, and 7,10-hexadecadienoic acids), essential oils, and phytol and other terpene compounds, and their effects were inhibitory to larval duration, percent pupal formation, pupal duration and weight, moth emergence (%), fecundity and longevity of adults, hatching of eggs, sex ratios, and even larvalpupal-moth malformations.…”