Interactive Effects of Epichloë Endophyte, Dormancy-Breaking Treatments and Geographic Origin on Seed Germination of Achnatherum inebrians

Background: the cool-season grass Achnatherum inebrians (drunken horse grass) is an important species in the northwest grasslands of China. This grass engages in a symbiotic relationship with Epichloe endophytes, which affect host plants by increasing growth, repelling herbivores, and increasing tolerance to stressful environments. Methods: in this work, we evaluated the interaction effects of the endophyte on various dormancy-breaking treatments on A. inebrians seeds from six different locations. We used both endophyte-infected plants and noninfected plants and applied four dormancy-breaking methods to test germination. Results: our results showed that the germination rate of endophytic Achnatherum inebrians seeds from the Xiahe site (with highest altitude) was significantly higher than that from other sites when water soaking was applied (p < 0.05). Endophytic seeds had a greater germination rate, and soluble sugar, indole acetic acid (IAA), and gibberellin (GA) contents, under any condition. There was a significant interaction among the method, endophyte status, and origin regarding germination (p < 0.001); particularly, the effects of warm water soaking and endophyte infection on the germination of seeds from the Xiahe site was significant (p < 0.05). Conclusions: the infection of Epichloe endophyte is able to increase the content of soluble sugar, IAA, and GA, and stimulate the seed germination of A. inebrians.