Neotyphodium endophytes may increase tolerance to Ni in tall fescue

• Neotyphodium fungus increased growth and Ni tolerance in genotype 75B of Festuca.
• Endophyte infection reduced Ni accumulation in the shoots of genotype 75B of Festuca.
• Endophyte infection improved antioxidant systems and phenolic compounds content.
• Effects of endophyte in host tolerance to Ni depend on host–fungus combination.

Soil pollution with heavy metals is an important environmental problem which affects human and food health. Neotyphodium endophytes are a group of fungi which have their entire life cycle within the aerial parts of many cool-season grasses without any negative symptoms, and increase host tolerance to biotic and abiotic stresses. In this study, four groups of endophyte–host combinations including two genotypes of tall fescue either infected or non-infected by endophyte (75B E+, 75B E−, 75C E+ and 75C E−) were cultivated by using 10 equal sized tillers in each plastic pot containing Ni contaminated soil at concentrations of 30, 90 and 180 mg Ni per kg in 3 replicates. Growth parameters including root and shoot dry weight, tiller number of plants and chlorophyll and carotenoid content of shoots were measured at the end of the experiment. Antioxidant enzymes (CAT, SOD, APX, GPX, GR and GST) activities, total content of phenolic compounds and Ni accumulation in the roots and shoots after 10 weeks of growth was also determined. Results demonstrated that endophyte infection had a benefit to the plant growth and Ni tolerance in genotype 75B by improving the antioxidative system and by a reduction of Ni accumulation in the shoots. In genotype 75C, in contrast, the E− plants showed more tolerance to Ni stress compared to the E+ counterparts. It was revealed that the effect of endophyte infection on Festuca plants as the host may be dependent on the host genotype and endophyte*host interaction.