Epichloë spp. and Serendipita indica endophytic fungi: Functions in plant-soil relations

Abstract Fungal endophytes, by living entire or part of their life inside a plant, are potentially useful in natural ecosystems and agroecosystems to confer multiple benefits to their hosts. These include improvement of water and nutrientional status, higher tolerance against biotic/abiotic stresses. In this review, the consequences of infection by Epichloe spp., as an obligative symbiont, and Serendipita indica, as a facultative one, on plant-soil relations have been discussed. Colonization and infection by both Epichloe and S. indica results in better plant growth and productivity, including enhanced root proliferation by indole-3-acetic acid production which in turn leads to a better nutrient acquisition. Moreover, the symbionts can confer both local and systemic resistances to pathogens/diseases through signal transduction. Up-regulation of antioxidant defense system components and reprogramming of stress-related genes in the presence of endophytic fungus can enhance plant resistance against biotic/abiotic stresses. Individual mechanical or drought stresses may impair plant growth and functioning; however, under combined mechanical and drought stresses, drought has little impact on the plant responses and mechanical stress mainly controls physiological attributes including water status and leaf proline. Endophyte-infected hosts usually have higher ability to do osmotic adjustment due to higher proline content. The physical, chemical and biological properties of rhizosphere soil might be changed by the endophyte infection too, presumably resulted in improving soil quality. Altering microbial communication structure and diversity, higher organic carbon storage, enhanced soil fertility and increased aggregate stability due to induced sub-critical hydrophobicity are some important influences of endophyte-host symbiotic relations on soil environment.