Effect of seed soaking with Epichloë fermentation broth on germination characteristics in perennial ryegrass under drought stress

To explore the in vitro effect of Epichloë on the drought resistance in perennial ryegrass seeds during germination, the seeds were soaked in three species of Epichloë (E. gansuensis, E. bromicola, and Epichloë sp.) fermentation broth, to test the germination index of seeds under different concentrations of polyethylene glycol (PEG) through the paper germination test. The results showed that the seed germination rate, germination force, germination index, vigor index, seeding length, and seedling moisture content were decreased, the mildew rate was increased first and then decreased when the PEG concentration increased, and the root length of seedlings had a peak value at -0.6 MPa. The seeds inactivated and could not germinate when the concentration of PEG was -1.2 MPa. Compared to the control, soaking in Epichloë fermentation broth significantly (P<0.05) promoted seed germination, seedling growth, and root growth, and effectively reduced the mildew rate (P<0.05). Compared to seed soaking with Achnatherum inebrians Epichloë fermentation broth, the seed germination index, vigor index, seedling water content, seedling length, and root length of perennial ryegrass were greater than those in the Elymus dahuricus and Festuca sinensis experiments. In short, the fermentation broth of Epichloë had a certain effect on the germination of perennial ryegrass seeds under drought stress, and the effect of the A. inebrians fermentation broth was the strongest of the three different kinds of fermentation broth.