The Effect of Endophyte on Salinity Tolerance in Perennial Ryegrass

Perennial ryegrass (Lolium perenne L.) is an important cool-season turfgrass species that germinates quickly and is the main species used for overseeding on golf courses in the United States. It will be important to improve salinity tolerance in perennial ryegrass as the use of alternative water sources (with increased salinity levels) increases. The natural Epichloë festucae var. lolii endophyte in perennial ryegrass has been shown to convey resistance to various abiotic and biotic stresses but the role of endophytes in salinity tolerance has not been well studied. The objective of this study was to determine whether endophytes have an overall effect on salinity tolerance in perennial ryegrass or whether salinity tolerance is specific to the genotype–endophyte combination. Four perennial ryegrass clones (two salt susceptible [Brightstar SLT clone 5 and Paragon GLR clone 4], and two salt tolerant [4501-7 and 4540-9])), with (E+) and without (E–) their natural endophytes were grown in control (1 dS m^-1) and saline water conditions (15 dS m^-1) for 10 wk. Treatments were applied using an overhead irrigation chamber in the greenhouse. Visual percent green, digital image analysis, clipping yields, shoot weight, and root weights were collected. In the Paragon GLR clone, the E– clone performed better than the E+ clone for all measurements when averaged across rating dates. For most of the clones, E–clones tended to be more tolerant than E+ clones except for 4540-9 which exhibited the opposite effect. The natural endophytes in these grasses did not provide a strong positive effect on salinity tolerance among these ryegrass clones, however, there is some evidence for an endophyte–host genotype dependent response in salinity tolerance among specific perennial ryegrass clones.