Alkaline extract of the seaweed Ascophyllum nodosum stimulates arbuscular mycorrhizal fungi and their endomycorrhization of plant roots
A 2021 study published in Scientific Reports by researchers from Dalhousie University and Acadian Plant Health investigated how an alkaline extract of the brown seaweed Ascophyllum nodosum (ANE) supports the development of arbuscular mycorrhizal fungi (AMF) and enhances their colonization of plant roots .
Mycorrhizal fungi form symbiotic relationships with over 80% of land plants, extending root surface area and improving nutrient uptake, soil structure, and stress tolerance. In this study, the researchers examined both the direct effects of ANE on the AMF species Rhizophagus irregularis and its indirect effects on mycorrhization in Medicago truncatula, a model legume plant.
The results showed that ANE significantly stimulated AMF spore germination, germ tube elongation, and hyphal branching, with the strongest effect observed at low concentrations (0.1 g/L). In greenhouse trials, plants treated with ANE as a soil drench developed mycorrhizal associations 3.1 times faster and had 29% greater leaf area than untreated controls. Foliar applications also increased fungal colonization and gene activity linked to symbiosis, though they did not enhance plant size to the same extent .
At the molecular level, ANE-treated plants showed early upregulation of key genes responsible for fungal accommodation, including ENOD11, DMI2, DMI3, IPD3, and VAPYRIN. This suggests that ANE not only promotes fungal growth directly but also primes the plant’s internal signaling systems to welcome beneficial microbes.
The study concludes that aqueous alkaline extracts of A. nodosum can accelerate and strengthen plant–fungus symbiosis, offering farmers an additional biological tool to improve soil health, nutrient efficiency, and resilience in sustainable agriculture.