Phylogenetics of Epichloe Species and Related Grass Mycosymbionts

点击翻译按钮获取中文摘要

9408018 Schardl Drs. Schardl and Siegel at the University of Kentucky in collaboration with Swiss colleagues are studying a fascinating group of ascomycetous fungi that invade or infect grasses and sedges, fungi usually treated in the genus Epichloe. The grasses infected include commercially important turf grasses. The taxonomy and classification of the fungi is complicated by the occurrence of asexual forms and by a general paucity of reliable morphological characters for distinguishing species. Yet Epichloe strains are known to inhabit grass plants internally, where they may function either as mutualists or as pathogens. The mutualistic endophyte fungi are transmitted through the hosts' seeds and they provide protection from insect herbivores and drought. The pathogenic Epichloe inhibit seed production by the host and are able to produce infecting spores in large quantities. The investigators are studying patterns and mechanisms of fungal speciation, mating systems, and hybridization, while also seeking to determine whether the fungi coevolve with their grass hosts. Primary objectives are (1) to use DNA sequence analysis as a tool for determining phylogenetic relationships of Epichloe species and relatives, both teleomorph and anamorph taxa; (2) to determine the number and pattern of origins of mutualism and pathogenicity in these fungi; and (3) to correlate these patterns with the known phylogeny of the grass hosts. The possibility of hybridization between Epichloe strains leading to the formation of asexual "species" will also be examined.