Symbiotic interactions of C₃ grasses with fungal endophytes, Epichlo species and their asexual relatives Neotyphodium, often provide the grass hosts with major fitness enhancements. The endophytes protect host plants from both biotic and abiotic environmental stresses. Documented enhancements to host fitness include greater resistance to mammalian herbivores and over 40 species of insects, pathogens and nematodes. Endophyte-infected plants exhibit several morphological and physiological responses to drought stress compared with E- plants. Drought-induced leaf rolling, leaf senescence, stomatal closure, and osmotic adjustment are more prevalent in E+ than in E- plants and may be mediated through endophyte enhancement of the production of phytohormones such as abscisic acid. Endophyte-infected plants have been shown to be more productive and competitive than E- plants through improvement of germiantion, tillering, and biomass production per tiller. The increase in tiller production associated with endophyte infection may be due to fungal secretion of indoleacetic acid. Our understanding of the mechanisms responsible for all of these effects on improved host fitness enhancements are largely attributable to the accumulation of four groups of alkaloids: lolines, peramine, ergot alkaloids and lolitrems. The type and concentrations of alkaloids in grass-endophyte symbiota are affected by several factors. (a) host related factors such as gene-type, population, species, tissue and growth stages of plant; (b) environmental factors, such as climate factors (e.g. temperature and precipitation), nutrients in soil, seasons changes; (c) other factors, such as fungal strains and field managements. The objective of this paper is to present the current status of knowledge on these alkaloids, focusing on their biological activities, the potential for genetically manipulating their expression in grass-endophyte symbiot, and the determining methods.
Future perspectives in endophyte research, including synthesis of specific alkaloids, which can kill pest insects and are safe to livestocks, genetic engineering to enhance the alkaloids productions and biocontrol applications of alkaloids in agricultural and natural ecosystems are also discussed.