When there are changing of environmental conditions such as extreme temperature, insufficient water and toxic chemicals, this will force plants to adapt or succumb with this selective pressure. Climate changes have result in elevated atmospheric carbon dioxide, temperature and ultraviolet radiation. These are predicted to increase plant stress, photosynthetic activity and water utilization. There is also in increasing the incidence of plant disease and herbivore. Plant has evolved complex biochemical or genetic systems to perceive stress, transmit stress-activated signals to different tissue and activate cellular responses to avoid detrimental effects. There are two major classes of fungal symbionts associated with plants which are fungal endophytes and mycorrhizal fungi. Fungal symbionts express a variety of symbiotic lifestyles including mutualism, commensalism and parasitism. The genetic and biochemical processes responsible for the expression of different fungal symbiotic lifestyle are unknown. Plants are known to initiate complex biosynthetic response to elevated temperature. However, there are few plants that are capable of thriving in geothermal soil that will impose temperature and drought stress. In this journal for example, plant species Dichanthelium lanuginosum that grows in the geothermal soils of Yellowstone (YNP) and Lassen Volcanic National Parks (LVNP). The filamentous fungal plant pathogens are responsible in tremendous annual crop and revenue losses throughout the world. The mechanism on how fungal endophytes confer disease resistance is unknown. The non-pathogenic mutants express either commensal or mutualistic lifestyles in cucurbit hosts. This will give benefits to hosts by mutualistic mutants that protected against virulent fungal pathogens. All plants have salt sensitive metabolisms. Plants that live in saline environments developed into several mechanism to tolerate salt stress. Mutualistic fungi include benefits to plants for example tolerance to drought, metals, disease, and temperature and growth enhancement. It is not known how endophytes activate host stress response system.