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.
Highlights
The term algae encompasses a wide range of photosynthetic organisms that are found primarily in freshwater and marine environments, certain representatives can thrive in terrestrial niches, either on their own or by developing symbiotic relationships with other organisms [1,2]
The aqueous extracts of three brown algae Cystoseira myriophylloides, Laminaria digitata, and Fucus spiralis, that were applied as spray or drench, had a protective effect against Verticillium wilt disease that was caused by the fungus Verticillium dahliae, in greenhouse tomato seedlings [18]
Extensive research in the past decades on macro- and microalgal species has resulted in the discovery of an impressive array of extracts and bioactive compounds with pesticidal action for application in agricultural practices
Summary
The term algae encompasses a wide range of photosynthetic organisms that are found primarily in freshwater and marine environments, certain representatives can thrive in terrestrial niches, either on their own or by developing symbiotic relationships with other organisms [1,2]. The term biopesticide may encompass naturally occurring compounds (e.g., sodium bicarbonate, sodium acetate), biochemical substances that are produced naturally by various organisms or by genetically-modified plants, as well as microorganisms (bacteria, viruses, fungi, algae etc.) that are used to control pests in agricultural practices. In this regard, algal components have been shown to efficiently suppress plant pathogenic bacteria, including the genera Agrobacterium, Pseudomonas, Xanthomonas, and Erwinia, which are associated with serious diseases of important crops that form the nutritional basis of most human societies, such as rice and potato plants [16,17,18]. This review focuses on the current knowledge of algal bioactive substances with known pesticidal action
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