There is a complex relationship between endophytes and their host plants. Host-endophyte interactions can range from mutualism through commensalism to parasitism, as the phenotypes of the interactions are often plastic, depending on the genetic dispositions of the two partners, their developmental stage and nutritional status, but also on environmental factors (Johnson et al. 1997, Redman et al. 2001, Schulz & Boyle 2005). Commensalism provides benefit to the endophyte by enabling an undisturbed existen-ce and nutrient supply without affecting the host. The mutual relationship benefits the endophytic fungi through provision supply of energy, nutrients, shelter as well as protection from environmental stress. On the other hand fungal endophytes indirectly benefit plant growth by producing special substances mainly secondary metabolites and enzymes, which are responsible for the adaptation of plants to abiotic stresses such as light, drought and biotic stresses, such as herbivore, insect and nematode attack or invading pathogens (Barz et al. 1988, Kogel et al. 2006).