The Influence of an Ascophyllum Nodosum Seaweed Biostimulant on Interactions Between Arbuscular Mycorrhizal Fungi (Rhizophagus irregularis) and Medicago Truncatula

Seaweed biostimulants, such as the Ascophyllum nodosum extract (ANE) produced by Acadian Seaplants, are used globally to improve crop quality. The effects ANE have on soil microbial populations, and plant interactions with soil communities, is understudied. The objectives of this study were to (1) evaluate the direct effect of ANE on a globally distributed arbuscular mycorrhizal fungus Rhizophagus irregularius; and (2) test whether ANE influences plants ability to form mycorrhizal symbiosis. ANE had a significant effect on growth of R. irregularius during in vitro trials at concentrations of 0.01% and 0.05%, but not 0.1%. Greenhouse grown Medicago truncatula ANE drench treated plants grew larger and were faster to form mature mycorrhizal associations than controls, while foliar results were variable. Genes of M. truncatula associated with early signaling for mycorrhizae were expressed at significantly higher levels in plants treated with ANE as a foliar or drench compared to untreated controls.