Document: TER-3-99-152

Genetic variation of Neotyphodium in Arizona fescue.

SULLIVAN, T.J.* and S.H.FAETH

Arizona State University, Tempe, AZ 85287 USA ¹

Abstract:
Fungal endophytes occur in the vast majority of plant species with interactions ranging from parasitism to mutualism, making them useful systems for studying the ecology and evolution of symbiosis. One of the best studied genera of fungal endophytes, Neotyphodium, lives symbiotically with its pooid grass hosts. Neotyphodium endophytes are asexual, vertically transmitted, and may have strong mutualistic relationships with their hosts, at least in the agricultural grasses tall fescue, Festuca arundinacea, and perennial ryegrass, Lolium perenne. Despite these traits, they do not appear to show a strict pattern of coevolution with their plant hosts. For example, one strain of Neotyphodium in perennial ryegrass is the result of hybridization with the grass choke pathogen, Epichlok typhina. Arizona fescue, Festuca arizonica, is a grass native to the southwestern United States with most individuals harboring Neotyphodium. Unlike agricultural grasses, Arizona fescue is native to the United States and has not undergone any significant artificial selection or cultivation, making it ideal for examining natural patterns of genetic variation within Neotyphodium. Previous research, using DNA sequences from the internal transcribed spacer (ITS) of nuclear ribosomal DNA, described three distinct genetic types of Neotyphodium in Arizona fescue from a survey of 13 individuals in 9 populations in New Mexico. For this study, we isolated Neotyphodium from at least 20 individuals from 3 populations in Arizona to examine both broad geographic and within population variation. Based upon these ITS sequences, we found more distinct genetic types than the previous study, with substantial genetic distances between these types, and no clear pattern of coevolution.

Keywords: Neotyphodium

This abstract is being presented at: 9:15 AM in session:
Oral Session #5: Mutualisms.