Poonam Patel
Sushil Kumar
Arpan Modi
Ajay Kumar

Fungal symbionts are the category of endophytes residing in plants. In recent decades, endophytes have been well researched and documented for their beneficial role to mitigate plant abiotic stress, including drought, heat, flooding, salt stress, cold, oxidative stress, depletion in nutrients, pollutants, etc. (which depletes crop production). Fungal endophyte establishes diverse associations with its host plant (such as mutualistic, symbiotic, parasitic, or commensalistic) and are related to dynamic environments to develop and propagate into the host. In this chapter, we focus and discuss on the fungal endophytes and their tolerance mechanism that they display against abiotic stress in host plants.