Epichloë endophyte survival in rye (Secale cereale) and perennial ryegrass (Lolium perenne) seeds under different storage conditions

Abstract

Epichloë fungal endophytes are an important symbiont of some temperate forage grasses, providing the plant host with protection from biotic and abiotic stresses. Recent research has focussed on applying the potential benefits of the asexual form of this endophyte to cultivated cereal crops. Cereals are not known to naturally host Epichloë endophytes but can be artificially inoculated with selected fungal strains isolated from Elymus and Hordeum species. A critical aspect of a successful association is the ability of these obligate mutualistic endophytes to transmit through the seed and colonise the resulting offspring. Within agricultural and cropping systems, seed can be stored for varying lengths of time before being sown. The ability of these fungal endophytes to survive in stored seed and colonise the next generation of plants is an important consideration.

Optimal storage conditions required for Epichloë survival in seed of perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) are well documented, but little is known about endophyte survival within stored cereal grain, nor the conditions that are required for maximising its survival. Rye (Secale cereale L.) grain colonised with endophyte strain AR3002 and perennial ryegrass seed colonised with AR1 endophyte were stored under different temperature and humidity conditions, with the survival of both host and endophyte evaluated over a 2-year period.

Under controlled conditions of 0°C and a relative humidity of 24%, the endophyte and host maintained stable levels of viability for both species for the duration of the trial. In environments where both the temperature and relative humidity were not controlled and the seed was exposed to ambient conditions, the endophyte generally declined rapidly within 12-18 months, although in most cases the seed itself remained viable, for both rye and perennial ryegrass seed. The endophyte associated with rye responded in a similar way to endophyte associated with perennial ryegrass in these storage environments. This understanding provides guidance on seed storage conditions required to ensure sustained endophyte viability but also identifies timeframes in which endophytic grain will need to be resown if held at ambient conditions. Further work will be required to determine if similar limitations are applicable to Epichloë endophytes in wheat.