Phylogenetics of Epichloe Species and Related Grass Mycosymbionts

9408018沙德尔博士。肯塔基大学的Schardl和Siegel与瑞士同事合作，正在研究一组令人着迷的子囊菌真菌，这些真菌侵入或感染禾草和莎草，这些真菌通常被称为Epichloe属。受感染的草包括具有重要商业价值的草坪草。真菌的分类和分类由于出现无性形式和普遍缺乏可靠的形态特征来区分物种而变得复杂。然而，众所周知，Epichloe菌株栖息在草的内部，在那里它们可能作为共生菌或病原体发挥作用。共生的内生真菌通过寄主的种子传播，它们提供保护免受昆虫、食草动物和干旱的侵害。致病性epiichloe抑制寄主产生种子，并能大量产生侵染孢子。研究人员正在研究真菌物种形成、交配系统和杂交的模式和机制，同时也试图确定真菌是否与它们的草宿主共同进化。主要目的是：(1)利用DNA序列分析作为工具来确定隐头鳞甲种及其近缘种，包括远形和变形类群的系统发育关系；(2)确定这些真菌的共生起源和致病性的数量和模式；(3)将这些模式与已知的草寄主系统发育联系起来。还将研究Epichloe菌株之间杂交导致无性“物种”形成的可能性。

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.