Fungal Biostimulants for Sustainable Agriculture

Plant biostimulants (PBs) modify the microbial composition of the soil and stimulate plant growth. They can be supplied to either plants or soil/rhizosphere, thereby augmenting the activities supporting nutrient uptake, endurance against abiotic/biotic stresses, and crop quality. They do not increase crop yields directly such as conventional fertilizers but regarded as a resort in agricultural management techniques for shrinking the dependence on chemicals-based fertilizers, boosting productivity, and restoring the natural equilibrium in agroecosystems. Thus, PBs utilization is a sustainable practice that would augment the agricultural yield without compromising environmental safety. This category includes a wide range of organic substances, bacteria, and fungi. Among several PBs types, the fungal endophytes (reside inside a plant for at least a portion of its life cycle without manifesting as a disease) are proposed to be the significant biostimulants that promote crop’ growth and productivity. The arbuscular mycorrhizal fungi (AMF), based on fungal plant biostimulants (FPBs), boost plants’ development by employing different modes. These include (1) nutrient solubilization of insoluble minerals (potassium, phosphorus, zinc), organic acids, and so on; (2) amelioration of abiotic stresses such as drought, salinity, temperatures, and heavy metals; (3) crop protection from disease and pest attack by activation of immune responses in plants; and (4) enhancement of soil fertility. This chapter summarizes the FPBs function as PBs, highlighting their use as alternatives to chemical fertilizers and their mode of action, which have immense potential to support a sustainable agriculture system.