Grass endophyte in food chain – friend or foe?
Susanna Saari
University of North Carolina at Greensboro, NC, USA
Plants harbour many different microbes, fungi and bacteria that take advantage of their hosts. However, the host can also benefit from these organisms, which are known as endophytes. I have studied obligate endosymbiosis and the nature of the relationship between the symbiont and the host, using fungal Neotyphodium endophyte-grass symbiosis as a model system. According to my PhD thesis research, endophyte infections were found to be common in the meadow fescue cultivars in Finland, although the frequency varied considerably both between and within cultivars. European tall fescue cultivars were practically endophyte-free. Microfungi were common in natural meadow fescue populations found in the Åland Islands, Estonia, the coastal area of Södermanland in Sweden, and Gotland. The high level of infection indicates that endophytes are beneficial to their natural grass hosts at least in these areas. The reason behind the varying infection levels found in cultivars may be that where an endophyte affects one of the agriculturally important characteristics of its host grass, plant breeders may have inadvertently promoted or restricted the prevalence of the endophyte by favouring or rejecting individual plant characteristics. The toxins produced by endophytes affect the pest-resistance of grass in many ways. The study concluded that endophytes increased the resistance of meadow fescue to bird cherry-oat aphids, overriding the effects of seed lot and cultivar. Endophytes did not affect the body mass or population size of voles that consume endophyte-infected grass, but they did reduce the voles' mobility. In predation tests, immobility and calmness appeared to protect voles from weasels, as they were no longer able to detect voles among the grass. Fungal endophytes can also affect grass reproduction and growth. The fungi appeared to increase seed production in meadow fescue but to stunt growth after mowing in some circumstances. Endophytes appear to affect the competition between certain growth functions inside the plant. Endophytes have been found to benefit their hosts especially in fertile agricultural environments. In natural infertile environments, however, the fungus can be an enemy. The plant has to share the little resources that it collects from the soil with the fungus, which in turn may produce fewer toxins. This prevents the fungus from protecting its host effectively against pests. Endophytes have caused serious toxic symptoms in cattle fed on infected grass in the US and in New Zealand. Seed production companies in these countries now routinely examine animal feed for endophytes in order to prevent these problems from recurring. Endophytes affect many agriculturally important characteristics of the host grass, which is why they should be acknowledged in agricultural management in Europe as well.
Susanna Saari
University of North Carolina at Greensboro, NC, USA
Plants harbour many different microbes, fungi and bacteria that take advantage of their hosts. However, the host can also benefit from these organisms, which are known as endophytes. I have studied obligate endosymbiosis and the nature of the relationship between the symbiont and the host, using fungal Neotyphodium endophyte-grass symbiosis as a model system. According to my PhD thesis research, endophyte infections were found to be common in the meadow fescue cultivars in Finland, although the frequency varied considerably both between and within cultivars. European tall fescue cultivars were practically endophyte-free. Microfungi were common in natural meadow fescue populations found in the Åland Islands, Estonia, the coastal area of Södermanland in Sweden, and Gotland. The high level of infection indicates that endophytes are beneficial to their natural grass hosts at least in these areas. The reason behind the varying infection levels found in cultivars may be that where an endophyte affects one of the agriculturally important characteristics of its host grass, plant breeders may have inadvertently promoted or restricted the prevalence of the endophyte by favouring or rejecting individual plant characteristics. The toxins produced by endophytes affect the pest-resistance of grass in many ways. The study concluded that endophytes increased the resistance of meadow fescue to bird cherry-oat aphids, overriding the effects of seed lot and cultivar. Endophytes did not affect the body mass or population size of voles that consume endophyte-infected grass, but they did reduce the voles' mobility. In predation tests, immobility and calmness appeared to protect voles from weasels, as they were no longer able to detect voles among the grass. Fungal endophytes can also affect grass reproduction and growth. The fungi appeared to increase seed production in meadow fescue but to stunt growth after mowing in some circumstances. Endophytes appear to affect the competition between certain growth functions inside the plant. Endophytes have been found to benefit their hosts especially in fertile agricultural environments. In natural infertile environments, however, the fungus can be an enemy. The plant has to share the little resources that it collects from the soil with the fungus, which in turn may produce fewer toxins. This prevents the fungus from protecting its host effectively against pests. Endophytes have caused serious toxic symptoms in cattle fed on infected grass in the US and in New Zealand. Seed production companies in these countries now routinely examine animal feed for endophytes in order to prevent these problems from recurring. Endophytes affect many agriculturally important characteristics of the host grass, which is why they should be acknowledged in agricultural management in Europe as well.
