EPICHLOE SPECIES - FUNGAL SYMBIONTS OF GRASSES

Epichloe species and their asexual descendants (Acremonium endophytes) are fungal symbionts of C3 grasses that span the symbiotic continuum from antagonism to mutualism depending on the relative importance, res pectively, of horizontal transmission of sexual spores versus vertical clonal transmission in healthy grass seeds. At least seven sexual Epi chloe species are identifiable by mating tests, and many asexual genot ypes are interspecific hybrids. Benefits conferred by the symbionts on host plants include protection from biotic factors and abiotic stress es such as drought. Four classes of beneficial alkaloids are associate d with the symbionts: ergot alkaloids, indolediterpenes (lolitrems), p eramine, and saturated aminopyrrolizidines (lolines). These alkaloids protect host plants from insect and vertebrate herbivores, including l ivestock. Genetic engineering of the fungal symbionts as more suitable biological protectants for forage grasses requires identification of fungal genes for alkaloid biosynthesis, and DNA-mediated transformatio n of the fungi.