Epichloë endophyte enhances intraspecific competition of Achnatherum inebrians under nitrogen stress

Drunken horse grass (DHG, Achnatherum inebrians) is a perennial grass widely distributed in the grasslands of northwestern China, forming a symbiosis with the Epichloë endophyte, and has a strong growth advantage in the community. However, the mechanism of its competitive success remains unclear. Epichloë gansuensis-infected (EI) and endophyte-free (EF) DHG were employed in greenhouse experiments. EI plants served as competitive species, while EF plants were the target species. Aggressivity was employed to quantify the competitiveness. The effects of endophyte, plant density, and three different nitrogen levels in the pot on the competitiveness of plants were investigated. This study indicates that under 0.1 mM and 1 mM nitrogen stress, E. gansuensis enhances its competitiveness by improving the growth performance, light utilization capacity, and nitrogen absorption efficiency of the host plant, with a relative increase of 15.0