Abstract
Perennial ryegrass (Lolium perenne) infected by Epichloë endophytes contains alkaloids that are responsible for toxicosis in many countries. Drought may greatly affect the alkaloids contents of symbionts. The E+ perennial ryegrass was grown in pots with different soil moisture conditions (15%, 30%, 45% and 60% relative saturation moisture content, RSMC) for four months in a greenhouse of Lanzhou University, and then, the aboveground tissues were collected. The levels of peramine and lolitrem B in all plant samples were determined. The results showed that the drought stress significantly (p < 0.05) increased the peramine concentrations of perennial ryegrass but did not affect the lolitrem B concentrations. In addition, the drought stress significantly (p < 0.05) reduced the plant height and dry matter of perennial ryegrass. In conclusion, drought stress affects the peramine concentration in the perennial ryegrass−endophyte symbiont but may not affect the lolitrem B concentration.