Effects of extracellular metabolites from a dark septate endophyte at different growth stages on maize growth, root structure and root exudates

Dark septate endophytes (DSE) are fungi that can stimulate seed germination and seedling growth in many plant species. Although DSE active metabolites have been investigated there have been few studies on the role of DSE extracellular metabolites as plant biostimulants. The purpose of the current study was to (i) determine the changes in growth, nutrient uptake, and root development of maize exposed to DSE extracellular metabolites at different incubation times, and (ii) determine the effects of DSE extracellular metabolites on maize root exudation at different incubation times. Maize seedlings were exposed to DSE extracellular metabolites for different incubation times. Maize seedling growth, nutrition and root structure indicators were determined, and maize root exudates were extracted for non-targeted metabolomic analysis. The addition of DSE extracellular metabolites cultured for 12 days had the best effect on biomass and chlorophyll content increase, root development and nutrient uptake in maize. Metabolomic analysis of maize root exudates identified a total of 94 metabolites belonging to different chemical groups. Among them, the contents of lipids and lipid-like molecules in maize root exudates accounted for the largest proportion. The proportion of lipids and lipid-like molecules in maize root exudates treated with DSE extracellular metabolites increased. Compared with other treatments, the contents of organic acids and derivatives in maize root exudates with DSE extracellular metabolites cultured for 12 days accounted for the largest proportion. Pathway analysis shows that root exudates had a greater influence on glycerophospholipid metabolism and amino sugar and nucleotide sugar metabolism. These findings clearly indicate that DSE extracellular metabolites have the potential to be developed as plant growth stimulators and that the addition of DSE extracellular metabolites may affect many metabolic processes in maize roots.