ACREMONIUM ENDOPHYTES - OUR CURRENT STATE OF KNOWLEDGE AND FUTURE-DIRECTIONS FOR RESEARCH

Current knowledge of grass-Acremonium associations results from the di scovery that animals grazing on infected grasses show an array of debi litating symptoms which lead to severe economic losses. Acremonium end ophytes occur worldwide, infecting many cultivated and wild pooid gras ses. It is also apparent that parasitism of different grasses by these fungi is complex. The fungal symbiont may be completely or partially endophytic and expression of parasitism may range from agonistic (the pathogenic phase of Epichloe typhina (Pers.) Tul.) to mutualistic. Reg ardless of how symbiosis is expressed, the associations can often bene fit host grasses, improving their growth and survival. In addition, mu ch information has been gained on the biology, ecology and physiology of specific grass-endophyte associations, the effects of infected (E+) grasses on herbivores (vertebrates and invertebrates), the chemistry of alkaloids responsible for herbivore resistance, tolerance of E+ gra sses to drought, and the management of endophytes for the benefit of t urf and pasture grasses. Present information strongly suggests that mo st grass-endophyte symbioses must be maintained for optimum survival o f the host grasses. Future research efforts can be clearly defined, on a practical basis, as a continuation of studies that may lead to alle viation of toxicity to grazing animals, and the development of E+ gras ses suitable for turf and pasture use. These goals may be accomplished by manipulation of either livestock, endophyte or grass via genetic e ngineering, conventional breeding practices, or natural selection. Oth er approaches include improved plant and animal management and the use of chemical antidotes to reduce animal toxicoses. Specific research g oals include continuation of studies on the biology, ecology, and phys iology of symbiosis in cultivated and wild species of grasses. These s tudies should aid in elucidating the role of the symbionts in the host -fungus interactions (nutrition and metabolism) and mutualistic versus agonistic expression, as well as the origin and coevolution of the sy mbionts, mechanisms of biosynthesis of alkaloids, the bases for improv ed plant growth and resistance to biotic and abiotic stresses, and dev elopment of techniques for genetic manipulation of the symbionts. Path ophysiology studies using pure alkaloids, small animal bioassays, in v itro organs, tissue culture, and indicators of biochemical activity (e nzyme and hormones) will clarify the mechanisms of alkaloid toxicity, potentially leading to chemical antidotes and improved systems of anim al management to alleviate toxicoses. Through the interdisciplinary re search that has characterized this field, great strides have been made in understanding the role of Acremonium endophytes in animal toxicose s and the stress survival of E+ plants.