Neotyphodium endophytes trigger salt resistance in tall and meadow fescues

Infection with Neotyphodium spp. endophytes increases resistance to drought stress and soil mineral imbalances in tall fescue (Festuca arundinacea Schreb. = Lolium arundinaceum (Schreb.) S. J. Darbysh.) and meadow fescue (Festuca pratensis Huds. = Lolium pratense (Huds.) Darbysh.). We hypothesized that resistance of these grasses to salinity stress may also be attributed to endophyte infection. Two tall fescue genotypes, Fa75 and Fa83, and one meadow fescue genotype, Fp60, infected (E+) with their endophytic fungi, Neotyphodium coenophialum (Glenn, Bacon and Hanlin) and N. uncinatum (Glenn, Bacon and Hanlin), respectively, and their noninfected counterparts (E-) were cultured in nutrient solution at three salinity levels of 0, 85, and 170 mM NaCl. Except for genotype Fa75, E+ plants exhibited higher leaf survival rates than E-clones at a high salinity level (170 mM). Root dry matter was higher in E+ than in E-plants, but shoot dry matter was not affected by endophyte infection. This resulted in a lower shoot-to-root ratio in E+ plants (1.63) compared with E-plants (2.40). Sodium (Na+) and chloride (Cl-) concentrations were greater in roots of E-than in E+ clones. In shoots, Na+ and Cl- concentrations were not affected by the endophyte. In contrast, E+ plants accumulated more potassium (K+), which resulted in a greater K+ : Na+ ratio in shoots of E+ than in those of E-plants. Our results show that endophyte infection reduced Na+ and Cl- concentrations in tall fescue and meadow fescue roots but increased K+ concentrations in the shoots. Based on these results, we conclude that endophyte-infected grasses may thrive better in salinity-stress environments.