Fusarium oxysporum FO12 enhances plant performance by modulating the phytohormone profile and soil properties as a function of the inoculation method

Abstract Background and aims Endophytic fungi such as the non-pathogenic strain Fusarium oxysporum FO12 have emerged as useful allies for plants as they could promote plant growth and protect from stresses. However, its performance under natural soil conditions and the effectiveness of different inoculation methods have not been evaluated before. The objectives of this study were to assess the ability of FO12 to enhance plant growth and nutrition in sunflower and wheat plants grown on soils differing in texture and organic matter content, pH, and nutrient availability, and to compare the effectiveness of two different inoculation methods (seed dressing, and soil treatment). Methods Firstly, we developed in vivo experiments to evaluate the ability of FO12 to increase nutrient availability. Secondly, we assessed the potential of FO12 for enhancing plant growth and nutrition in sunflower and wheat plants (in vivo) grown on four non-calcareous and calcareous soils with different nutrients availability (Fe, Zn and P); and the effectiveness of two different FO12 application methods, seed dressing (Sd) and soil treatment (St). Results FO12 modified the pH of the culture medium, and significantly increased the potential Fe availability by 202%, and Zn availability by 52% and P availability by 7% (but not significantly) compared to the non-inoculated control (in vitro). Both FO12 application methods boosted plant growth by increasing plant height as well as sunflower and wheat reproductive biomass by up to 27 − 31% and 28–34% in non-calcareous and calcareous soils (in vivo), respectively. FO12 additionally increased macro- and micronutrient uptake, especially with St. Finally, the fungus induced changes in the plant phytohormone profile, mainly with Sd, which consistently increased jasmonic acid (47%), jasmonyl isoleucine (511%) and 1-Aminocyclopropane-1-carboxylic acid (226%), and decreased indoleacetic acid (39%) across all four soils and in both crops, in comparison with the non-inoculated plants. Conclusions FO12 stimulates plant growth by altering soil properties and physiological plant processes, and its effects on plant nutrition and production depend on the plant species and soil type. Graphical Abstract