Biostimulant Effects of Chaetomium globosum and Minimedusa polyspora Culture Filtrates on Cichorium intybus Plant: Growth Performance and Metabolomic Traits

In this study, we investigated the biostimulant effect of fungal culture filtrates obtained from and on growth performance and metabolomic traits of chicory ( ) plants. For the first time, we showed that culture filtrate exerts a direct plant growth-promoting effect through an increase of biomass, both in shoots and roots, and of the leaf area. Conversely, no significant effect on morphological traits and biomass yield was observed in plants treated with culture filtrate. Based on H-NMR metabolomics data, differential metabolites and their related metabolic pathways were highlighted. The treatment with and culture filtrates stimulated a common response in roots involving the synthesis of 3-OH-butyrate through the decrease in the synthesis of fatty acids and sterols, as a mechanism balancing the NADPH/NADP ratio. The fungal culture filtrates differently triggered the phenylpropanoid pathway in plants: culture filtrate increased phenylalanine and chicoric acid in the roots, whereas culture filtrate stimulated an increase of 4-OH-benzoate. Chicoric acid, whose biosynthetic pathway in the chicory plant is putative and still not well known, is a very promising natural compound playing an important role in plant defense. On the contrary, benzoic acids serve as precursors for a wide variety of essential compounds playing crucial roles in plant fitness and defense response activation. To the best of our knowledge, this is the first study that shows the biostimulant effect of and culture filtrates on growth and metabolome, increasing the knowledge on fungal bioresources for the development of biostimulants.