Interspecific and intraspecific hybrid Epichloë species symbiotic with the North American native grass Poa alsodes

ABSTRACT

The endophyte presence and diversity in natural populations of Poa alsodes were evaluated along a latitudinal transect from the southern distribution range in North Carolina to New York. Two distinct Epichloë hybrid taxa were identified from 23 populations. Each taxon could easily be distinguished by polymerase chain reaction (PCR) genotyping with primers designed to mating type genes and alkaloid biosynthesis genes that encode key pathway steps for ergot alkaloids, indole-diterpenes, lolines, and peramine. The most commonly found Epichloë taxon, Poa alsodes Taxonomic Group-1 (PalTG-1), was detected in 22 populations at high infection frequencies (72–100%), with the exception of one population at high elevation (26% infection). The second taxon, PalTG-2, was observed only in five populations in Pennsylvania constituting 12% of infected samples. Phylogenetic analyses placed PalTG-1 as an interspecific hybrid of E. amarillans and E. typhina subsp. poae ancestors, and it is considered a new hybrid species, which the authors name Epichloë alsodes. PalTG-2 is an intraspecific hybrid of two E. typhina subsp. poae ancestors, similar to E. schardlii from the host Cinna arundinacea, which the authors propose as a new variety, Epichloë schardlii var. pennsylvanica. Epichloë alsodes isolates were all mating type MTA MTB and tested positive for dmaW, easC, perA, and some LOL genes, but only the alkaloid N-acetylnorloline was detected in E. alsodes–infected plant material. Epichloë schardlii var. pennsylvanica isolates were all mating type MTB MTB and tested positive for perA, but peramine was not produced. Both E. alsodes and E. schardlii var. pennsylvanica appeared to have complete perA genes, but point mutations were identified in E. alsodes that would render the encoded perA gene nonfunctional.

KEYWORDS:

• Alkaloid genotype
• Epichloë alsodes
• Epichloë schardlii var. pennsylvanica
• latitudinal transect
• N-acetylnorloline
• peramine

ACKNOWLEDGMENTS

We gratefully thank the Great Smoky National Park, Allegheny National Forest, Pisgah National Forest, and state parks in South Carolina, Virginia, West Virginia, Pennsylvania, and New York for assistance with collections; University of North Carolina at Greensboro Department of Biology; Faeth’s lab members Dr. Susanna Saari, Dr. Martina Oberhofer, and Danielle Heyes; Shymanovich family for help with collections; Noble Research Institute Genomic Core Facility and Forage Analysis Core Facility; Ginger Swoboda and Mihwa Yi (Noble Research Institute) for research support; and Wade Mace (AgResearch, New Zealand) for analysis of samples for peramine.

FUNDING

C.A.Y. is supported by the Noble Research Institute, LLC. S.H.F. and N.B.C. are supported by NSF grant DEB 0917741.

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Additional information

Funding

C.A.Y. is supported by the Noble Research Institute, LLC. S.H.F. and N.B.C. are supported by NSF grant DEB 0917741.