Symbiosis

Index:

• Grass endophytes: asexual life cycle
• Symbiosis: balanced symbiosis of grasses with Epichloe species
• Epichloe species and their hosts
• Mutualism and biological protection
• Taxonomy of grasses and symbionts

Seed transmissible fungal symbionts ("endophytes") protect grasses from insects, nematodes, and even drought.

Like their grass hosts, many of these symbionts are hybrids. Click to see the remarkable story of endophyte evolution.

Balanced symbiosis of grasses with Epichloe species.

Developing ears of the wild wheat relative, Elymus virginicus, symbiotic with the fungal endophyte, Epichloe elymi. The two inflorescences at right will develop normally and set seeds, all of which will inherit the symbiont.

The inflorescence at left shows profuse fungal growth. This is the first step of the symbiont's sexual development, resulting in meitoic spores (ascospores) that cause infections of developing seeds on neighboring plants.

The symbiotic continuum:

Our genetic model: red fescue with its mutualist, Epichloe festucae.

The tiller at left exhibits the sexual state of E. festucae, while the tiller at right will develop normally, set seed, and pass the symbiont on to the next generation of plants.Epichloe festucae protects red fescue from insects. We use the sexual stage to demonstrate the roles of specific fungal alkaloids in protecting the grass.