PS 36-151
Genetic and geographic variation in Canada wildrye endophytes
Cool season grasses often have symbiotic relationship with epichloid endophytic fungi. Canada wildrye (Elymus canadensis), a grass native to North America, interacts with multiple endophyte species, including Epichloë canadensis, a hybrid species of Epichloe elymi and Epichloe amarillans. Canada wildrye’s and its endophyte’s life histories are tightly linked with the endophyte living it’s entire life within it’s host’s aboveground tissues and reproducing asexually by extending it’s hyphae into the developing seeds of its hosts. This intimate relationship between grass and endophyte creates a scenario where genetic correlations and coevolution would be expected to occur.
As part of a larger project assessing genetic variation in the interaction, Canada wildrye seeds were collected from populations ranging from Texas to Minnesota. The seeds were germinated on the Indiana University Kokomo campus and grown for 6-8 weeks before DNA was extracted from leaf tissue. Primers specific to E. canadensis were used to amplify ~200 bp regions of the genes transcription elongation factor-1-a (tefA) and beta-tubulin (tubB), both known to contain single nucleotide polymorphisms (SNPs). The resulting amplicons were analyzed with high-resolution melt analysis (HRM), a technique that can discriminate between DNA sequences differing by a single base. Representative samples of each group identified by HRM were sequenced to confirm results.
Results/Conclusions
HRM was able to accurately genotype E. canadensis individuals based on SNPs. As would be expected for an asexual species, there was significant linkage disequilibrium between the genetic markers. Genetic variation within populations is generally low with between population variation accounting for most of the observed differences. These results suggest that migration for the endophyte, and therefore movement of its host’s seeds, is limited, but also raises the possibility of local adaptations in the symbiosis between Canada Wildrye and its E. canadensis endophytes.