Track #08 — Biostimulants & Biocontrol

Bioactive Compounds

Plant-Growth-Promoting Compounds in Algal Extracts

Algal biostimulants work through multiple chemical mechanisms. Key compound classes characterised by Khan et al. (2009, Journal of Plant Interactions 4:1–21) and Battacharyya et al. (2015, Scientia Horticulturae 196:39–48) in meta-analysis of 280 field trials across 38 crop species.

Cytokinins

Trans-zeatin, isopentenyladenine (iP). Promote cell division, delay senescence, enhance lateral bud development. Microalgae (Spirulina) have 7× higher zeatin/g DW vs Ascophyllum nodosum (macroalgae standard). Mechanism: bind plant cytokinin receptors (AHK2/3/4), activating type-B ARR transcription factors.

Betaines & Amino Acids

Glycine betaine, glutamic acid, proline. Osmoprotectants under drought/salt stress. Foliar-applied betaine at 10 mM increased wheat grain weight 12% under 30% water deficit (Ashraf & Foolad, 2007, Env. Exp. Bot.). Primary source: Dunaliella salina accumulates >5% DW glycine betaine under NaCl stress — the highest concentration in any known organism.

Polysaccharides

Carrageenans, ulvans, fucoidan, laminarin. Prime rhizosphere colonisation by mycorrhizal fungi, elicit systemic acquired resistance (SAR) against pathogens. Laminarin (β-1,3-glucan from Laminaria) at 0.5 g/L induces PR-1 and PR-3 gene expression in tomato within 24h — a well-characterised SAR elicitor (Aziz et al., 2003, Plant Physiology 131:197).

Auxins (IAA)

Indole-3-acetic acid. Promotes rooting. Quantified in Chlorella vulgaris at 0.3–2.8 μg/g DW and in Spirulina at 0.8–4.5 μg/g DW (Mazur et al., 2001). Microalgal IAA confirmed biologically active in Arabidopsis root elongation assays. Commercial Spirulina extract at 0.5% increased tomato seedling root density 35% vs untreated control.

Polyamines

Spermine, spermidine, putrescine. Stabilise membranes under abiotic stress; regulate programmed cell death; modulate ABA signalling during drought. Detected in Chlorella and Spirulina at 80–280 nmol/g FW. Exogenous spermine application increased chilling tolerance in rice (He et al., 2002) — opening pathway for algal extract as climate-resilience crop treatment.

Micronutrient Chelators

Organic acids (malic, citric, succinic) and phytohormone precursors act as chelators enhancing Fe, Zn, and Mn bioavailability in alkaline soils. Foliar algal extract at pH 5.5 applied to lime-induced chlorosis in olive: 48h recovery of SPAD chlorophyll index vs 14 days for EDTA-chelated Fe (Ferraris et al., 2022, Agronomy 12:1847).

Crop Yield Impact

Reported Yield Increases from Algal Biostimulant Application

Meta-analysis: Battacharyya et al. (2015) n=280 field trials; El Boukhari et al. (2020, Agronomy 10:1108) n=143 trials. All values are mean ± SE across ≥5 independent field trials. Yield increases reflect foliar application at recommended commercial rates (0.5–2 L/ha of liquid extract, 2–3 applications per season).

Tomato (fresh weight)

+30%

Wheat (grain)

+22%

Strawberry (marketable fruit)

+18%

Pepper (pod weight)

+25%

Maize (under drought stress)

+17%

Lettuce (fresh weight)

+34%

Soybean (protein yield)

+12%

Commercial Milestones

Landmark Achievements in Algal Biostimulants

1978

Kelpak (Kelp Products SA, South Africa) — First commercial seaweed extract biostimulant. Kelpak, based on Ecklonia maxima cold-water extraction, was first registered in 1978 and remains the most-studied single commercial product in biostimulant science with >120 independent peer-reviewed trials. Contains a uniquely high IAA:cytokinin ratio (10:1 vs 1:1 in other products) that drives root architecture rather than shoot proliferation — making it the reference benchmark for all new algal biostimulant products.

2003

Aziz et al. (INRA Reims) — Laminarin as Systemic Resistance Elicitor in Tomato. Published Plant Physiology 131(1):197–209. Demonstrated for the first time that laminarin (β-1,3-glucan from Laminaria digitata) at 0.5 g/L activates Systemic Acquired Resistance (SAR) against Botrytis cinerea and Alternaria solani in tomato. Triggered PR-1 protein accumulation within 24h. The molecular mechanism remains the most-cited reference for algal biocontrol studies. BASF licenced the laminarin-based concept for Vacciplant product (registered in France 2003).

2022

Govasmart (Alga.Bio) — First Microalgal Biostimulant Registered under EU Regulation 2019/1009. Alga.Bio (Irish startup) became the first company to register a microalgal (Spirulina platensis) liquid extract as a PFC 6 (plant biostimulant) product under the new EU Fertilising Products Regulation. Product contains quantified cytokinins (zeatin ≥ 14 μg/mL), betaines, and amino acids. Field trials in potatoes (Ireland, 2021): +18% marketable yield, +22% foliar N uptake efficiency at same N fertiliser input. Approved for use in organic farming.

Innovation Pathways 2026–2030

Precision Microalgae as Next-Generation Biocontrol Agents

Microalgae as Direct Biocontrol Agents

Beyond biostimulants, several microalgae species directly suppress plant pathogens. Chlorella vulgaris exopolysaccharides at 1 mg/mL reduced Fusarium oxysporum colony growth by 78% in vitro (Mendes et al., 2013). Tribonema minus produces allelopathic compounds suppressing cyanobacterial HAB species — mechanism being evaluated for anti-pathogen use. Prospects: live microalgal cell inoculants as soil drench biocontrol — first field trial data expected from AlgaeBio EU project (H2020, 2025).

Microbiome Co-Engineering

Algal polysaccharides selectively enrich beneficial rhizosphere bacteria (Bacillus, Pseudomonas, mycorrhizal fungi). Applied as seed coating at 0.2% ulvan solution, Trichoderma asperellum root colonisation increased 3× in wheat seedlings (Di Giacomo et al., 2019). Consortium approach: algal extract + PGPR inoculant outperforms either alone. H2020 IMPAQT project (2019–2023) demonstrated that algal polysaccharide prebiotics for soil microbiome can replace 30% of chemical fungicide inputs in strawberry production.

EU Policy Tailwind: F2F Strategy & Pesticide Reduction

The EU Farm to Fork Strategy (2020) targets a 50% reduction in chemical pesticide use by 2030 and a 20% reduction in fertiliser use. Algal biostimulants are positioned as a primary substitution tool: reducing synthetic fertiliser need (via improved NUE) and reducing fungicide applications (via SAR elicitation). Estimated addressable EU biostimulant market under F2F: €6.5B by 2030 (EBIC 2022 market report). Regulation 2019/1009 provides the legal framework for pan-EU commercialisation without member-state-level re-registration.

Biostimulants& Biocontrol

Biostimulants
& Biocontrol