Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/1996
Publication Date: N/A
Interpretive Summary: Most grasses have fungi that live inside them and impart no harm. These fungi are referred to as endophytes and both fungus and grass benefit from the relationship. Endophyte infected grasses are also better suited for insect and pest resistance, drought tolerances and nitrogen efficiency than noninfected grasses. Tall fescue is one grass that is infected with an endophyte; this grass is also toxic to cattle and other livestock. In 1977, scientists at RRC and the University of Georgia discovered this infection and reported that the toxicity of tall fescue to cattle was due to the endophyte. In that paper the endophyte was referred to as the asexual state of the fungus Epichloe typhina. Shortly after this paper, the fungus was renamed Acremonium coenophialum Morgan-Jones and Gams by scientists using classical morphology. A scientist at RRC, his student, and other scientists from the University of Georgia reexamined this fungus and other endophytes using molecular techniques. The conclusion reached was that the endophyte of tall fescue is indeed, as Bacon et al., 1977, declared the asexual state of E. typhina. Thus, we have renamed the endophytic state Neotyphodium and the endophyte of tall fescue Neotyphodium coenophialum Glenn, Bacon and Hanlin. These molecular techniques indicate that grass endophytes have no close affinity to Acremonium and that most fungi placed in Acremonium are invalid. All grass endophytes are now Neotyphodium species. This and other data suggest that endophytes are hybrides of several different species, and explain why they do not produce reproductive structures in certain grasses such as tall fescue.
Technical Abstract: Acremonium is generally considered to be a highly polyphyletic form genus containing distantly related fungi. Sectional divisions within Acremonium distinguish the clavicipitaceous grass endophdytes of sect. Albo-lanosa from the generally saprobic species of sections Acremonium, Chaetomioides, Gliomastix, and Nectrioidae. In an effort to assess the possible number of lineages currently placed within Acremonium and to determine which groups of sexual ascomycetes are phylogenetically affiliated with Acremonium species, maximum parsimony and neighbor-joining analyses were performed using partial sequences of the nuclear small subunit ribosomal DNA (18S rDNA). Acremonium was shown to be a polyphyletic taxon with affiliations to at least three ascomyceteous orders: 1) most of the examined species from the sections Acremonium, Gliomastix, and Nectrioidae showed a relationship to the Hypocreales even though many of these species have never been associated with any teleomorph; 2) the grass endopytes of sect. Albolanosa and other taxa from the Clavicipitales formed a monophyletic clade derived from within the Hypocreales; 3) the thermophilic A. alabamense of sect. Chatomioides was affiliated with the Sordariales. Acremonium alternatum, the type species of the genus, was one of the species showing affiliation to the Hypocreales. In order to eliminate some of the heterogeneity within Acremonium while also emphasizing the unique biological, morphological, and ecological characteristics of grass endodphytes, we are proposing reclassification of the asexual grass endophytes into the new form genus Neotyphodium. Phylogenetic and taxonomic considerations are also presented for other taxa