XVI International Botanical Congess

The non-grass fungal endophytes studied penetrated the plant hosts barley and bean using the same mechanisms utilized by pathogenic fungi: via the stomata, along the anticlinal epidermal cell walls and/or directly through the epidermal cell wall. Both the mechanisms of penetration and colonization were specific for the respective endophytes. Infections of the endophytes studied usually remained localized and were primarily intercellular. These infections may have remained localized due to the active plant defense reaction, which was elevated in simplified test systems. Additionally, both endophytes and hosts produced metabolites toxic to the respective partners. It is hypothesized that as long as a fungal infection remains endophytic, i.e. asymptomatic, the mutual antagonism between plant and fungal partner is balanced, permitting only limited colonization.