Diversity of Epichloë in native grasses from Uruguay

Abstract

Studies on endophyte diversity have allowed to describe at least 43 taxa that belong to the genus Epichloë,including distinct species, subspecies, and varieties[1]. Screenings for grasses associated with Epichloë arecontinuously being done worldwide due to the agronomically important beneficial effects they provide to theirhosts. In spite of this, Epichloë presence and diversity in South America has been poorly studied, with most worksfocused in Argentina, although preliminary studies revealed the presence of Epichloë in grasses from Uruguay. Ourobjective was to assess the diversity of Epichloë associated with native grasses from Uruguay, South America.We sampled native grasses from Uruguay and inspected under microscope for typical Epichloë mycelia theparenchymal tissue from within the culm pith or sheaths stained with aniline blue[2]. Fragments of leaves and culmsof endophyte-infected plants were surface-sterilized and plated in Potatoe Dextrose Agar to isolate Epichloë.Subsequently, we obtained single spore cultures for morphological and molecular characterization by phylogeniesof calM gene and detection by PCR multiplex of alkaloid genes[3, 4].Specimens of Bromus auleticus, Bromus brachyanthera, Calamagrostis alba, Festuca fimbriata, Poalanigera and Polypogon elongatus were detected associated with Epichloë. Morphological differences in colony andmicroscopic characteristics were observed among isolates from different host species, but also among isolates fromthe same host species (B. auleticus and P. lanigera). Phylogenetic analyzes based on calmodulin gene (calM)sequences allowed us to infer at least 5 interspecific hybrid lineages. The E. typhina x E. festucae hybrid, Epichloëtembladerae, was detected in all of the studied hosts except in F. fimbriata. Some isolates from B. auleticus and F.fimbriata were also hybrids between E. typhina and E. festucae but clustered in different clades with endophytes ofthese hosts from Argentina, different from any previously described species. A hybrid isolate (E. baconii x E.typhina) was detected in B. auleticus. One isolate from Bromus auleticus presented three copies of calM indicatinga triple hybrid origin (E. festucae x E. typhina x E. elymi) and grouped in a clade that also included isolates fromArgentina. Alkaloid gene profiling indicated that all of the endophytes have perA gene. The endophytes from F.fimbriata and the triple hybrid were dmaW positive. LolC gene was only detected in some endophytes from B.auleticus. Indole di-terpene gene profiling allowed us to detect variability among isolates considered as E.tembladerae, and only some endophytes of B. auleticus were negative for the screened idt genes.These results suggest a great diversity of endophytes in Uruguay and, although most of the endophyteshave been also detected in Argentina, some lineages seem to be endemic to Uruguay. Taking into account thediversity of grasses in this country and that we only studied a small amount of isolates of each host, it is likely thatmore hosts and endophytes will be discovered in Uruguay.