XVI International Botanical Congess

Grass endophytes form systemic and often mutualistic associations with their hosts. Sexually reproducing species produce ascospores which can cause infections via stigmata or meristems of new hosts (horizontal transmission). Alternatively, endophytes may be vertically transmitted through seeds. Seed-transmitted Epichloë species which mostly have coevolved with their hosts tend to have narrow host ranges, whereas species with strictly horizontal transmission have wider ranges. Presumed host shifts are most likely in the latter group and may have involved hybridization between endophytes with different transmission modes. Mechanisms for genetic isolation and specific adaptation of host races include selective ecological niches, live cycle variations of host and fungus, and selectivity of insect vectors.