Stromal Development and Mating System of Balansia epichloë, a Leaf-Colonizing Endophyte of Warm-Season Grasses

Studies of the stromal development and mating system of Balansia epichloë were conducted. Early development of the stroma consists of both endophytic and epiphytic phases of growth. As development progresses, the epiphytic stromal subiculum on the upper surface of leaves is linked with endophytic mycelium within leaves by hyphal bridges, which may provide carbohydrates for stromal development. Sugar utilization studies suggest that Balansia epichloë is excluded from growth within inflorescence primordia of grasses by the presence of high levels of sugars that are inhibitory to growth of the endophyte. Studies of the mating system of B. epichloë were conducted, and the fungus was shown to be heterothallic, with ephelidial conidia functioning as spermatia. Insect vectoring of ephelidial spermatia is suggested to account for the irregular pattern of perithecial development on stromata.