Substantial evidence is available on the capacity of particular strains of Epichloë fungal endophyte to remove the barriers of self-pollination in host grasses. We hypothesized that this might open up new methods to obtain inbred lines for specific turf hybrids and genetic studies.• In the present study, we evaluated the first generation of self-pollination derived plants of endophyte infected clones (EIS 1 ) from putative genotypes 75B+ and 75C+ and those from the first generation of self-pollination in six commercial tall fescue clones plus their hybrids with 75B− and 75C− for growth, seed yield and polyphenolic content as an index for biosynthesis of defence compounds under field conditions.• The results showed that EIS 1 had high hyphal density within leaf sheaths and higher growth and seed-related traits in at least one genotype. There were higher amounts of flavonoid and phenolic compounds (up to twofold) in both genotypes than in their hybrid counterparts and endophyte-free progeny. Selected genotypes within EIS 1 contained significantly more chlorogenic acid, p-coumaric acid and rutin than the best non-infected genotypes.• We conclude that phenotypic selection of individuals from the S 1 population is feasible for improving fitness and stress resistance in novel inbred lines of tall fescue for development of new turf cultivars with the desired ecophysiological traits.