Molecular systematics of Clavicipitaceae supporting monophyly of genus Epichloë and form genus Ephelis

Abstract

The family Clavicipitaceae (Ascomycota) is comprised of fungi with perithecia borne on stromata, unitunicate asci, and filamentous, multiseptate ascospores. All are biotrophic symbionts, either mutualistic with plant hosts or pathogenic to plants, invertebrate animals or other fungi. Genera of plant- associated Clavicipitaceae (tribes Balansieae and Clavicipieae) are distinguished, in part, by stromal and ascus morphology, ascospore germination patterns, whether sclerotia are formed, and host interactions. Their anamorphs include enteroblastic microconidial states, classified in anamorphic genera Neotyphodium and Sphacelia (for teleomorphs Atkinsonella, Claviceps, Echinodothis, and Epichloë), and holoblastic macroconidia, classified in the anamorphic genus Ephelis (teleomorphs Atkinsonella, Balansia, and Myriogenospora). Epichloë species often are mutualistic with grass hosts, and are ancestral to asexual, seed transmitted endophytes symbiotic with many cool-season grasses. Partial 28S nuclear rDNA sequences were determined from isolates of five species and two undescribed mating populations of Epichloë, one asexual Epichloë hybrid (Neotyphodium coenophialum), and representatives of six other genera in the family. Results from phylogenetic analysis of the sequences supported monophyly of plant-associated Clavicipitaceae, with insect-pathogenic Cordyceps species more deeply rooted. Four clades were distinguished among plant-associated Clavicipitaceae: a monophyletic genus Epichloë (including N. coenophialum), a monophyletic genus Claviceps, a clade represented only by Echinodothis tuberiformis, and a clade including all sampled strains with Ephelis anamorphs. Morphological relationships of anamorphs and ascospore development better fit the molecular phylogenetic relationships than did host relationships or host tissue specificity.

Key Words:

• Ascomycetes
• ascospore germination
• molecular systematics
• phylogenetics
• ribosomal DNA