Differences in viability between two Epichloë endophyte species ( E. uncinata and E. occultans ) in Italian ryegrass ( Lolium multiflorum Lam.) seeds during storage

Epichloë uncinata ( Eu ), which has a symbiotic relationship with meadow fescue in nature, can be cultured and artificially inoculated, raising expectations for its expanded use in the breeding of other grass species. However, its introduction into non‐native host species may increase the risk of unstable symbiosis. In this study, we aimed to compare the stability of Eu and E. occultans ( Eo ), a species naturally associated with Italian ryegrass (IR; Lolium multiflorum Lam.), in IR seeds. Endophyte viability tests under seed storage with accelerated aging conditions using genetically similar IR seeds revealed a significantly lower stability of the Eu Eto8 strain than that of the Eo strain. This suggests that the risk of reduced endophyte infection rates in the Eu –IR symbiotic system depends on the seed storage conditions. Factors other than endophyte density or localization may have contributed to the differences in viability between the Epichloë strains in the IR seeds.