Origin, divergence, and phylogeny of epichloe endophytes of native Argentine grasses

The epichloe endophytes are systemic, constitutive, and often vertically transmitted fungal symbionts of grass species in subfamily Pooideae. Prior studies indicate that several asexual epichloe endophytes (Neotyphodium species) have evolved directly from sexual (Epichloe) species, whereas others evolved by hybridization between two or more endophyte species. In this paper, we investigate the phylogenies of 27 Neotyphodium spp. isolates from 10 native grass species (in 4 tribes) in 22 populations throughout Argentina. Relationships among these fungi and a worldwide collection of epichloe endophytes were estimated by phylogenetic analysis of sequences from variable portions (mainly introns) of genes for beta-tubulin (tub2) and translation elongation factor 1-alpha (tefl). Most of the Argentine endophyte isolates were interspecific hybrids of Epichloe festucae and E typhina. Only one isolate was a hybrid of a different ancestry, and three isolates were apparently non-hybrid endophytes. These results indicate that interspecific hybridization, which promotes genetic variation, was common during the evolution of the endophytes of Argentine grasses. (c) 2005 Elsevier Inc. All rights reserved.