Persistence of endophytic fungi in cultivars of Lolium perenne grown from seeds stored for 22 years.

PREMISE OF THE STUDY: Genetic resources for forage crops often consist of seeds of specific species and cultivars in cold storage for future use in breeding and selection programs. Temperate grasses such as Lolium perenne, used worldwide for forage and turf, produce seeds commonly infected by hyphae of an endophytic fungus (Epichloë festucae var. lolii). This research determined whether endophytes could persist and infect seedlings of L. perenne emerging from seeds stored for over two decades.

METHODS: Endophyte-infected seeds (>90% infected) of four cultivars were obtained in 1994 and stored dry in plastic bags at 4°C. Seed germination was tested after 12 yr (for two cultivars) and after 18 and 22 yr (for all cultivars). Seedling leaf sheaths were excised, stained, and examined at 400× for endophytic hyphae to quantify infection frequency (% plants infected) and intensity (mean number of endophytic hyphae per field of view).

KEY RESULTS: Seed germination after 22 yr depended on cultivar, ranging from 53 to 78%. Between 58 and 73% of plants grown from seeds stored for 22 yr still contained viable endophytic hyphae. Infection intensity remained at original levels for 18 yr in one cultivar; however, in all cultivars, infection intensity declined significantly between 18 and 22 yr.

CONCLUSIONS: Persistence of the grass seed-endophyte symbiosis for over 20 yr surpasses all prior records of endophyte longevity within stored seeds. Storage of germplasm of cool-season grass cultivars that contain potentially beneficial fungal endophytes should be possible for several decades under dry, cold conditions.