Seed packaging bag types - impact on endophyte viability and seed quality in perennial ryegrass during storage

Abstract

Using woven polypropylene (WPP) plastic bags for seed packaging challenges the New Zealand seed industry’s alignment with sustainability goals. The recycling scheme for farm plastic waste is still voluntary, especially for small seed bags (20-25 kg). The seed industry’s concerns are that alternative seed packaging may not maintain Epichloë endophyte viability in stored perennial ryegrass (Lolium perenne L.) seed lots. A storage experiment was conducted using two perennial ryegrass seed lots with different endophyte strains stored in six types of bags (woven polypropylene (WPP), bi-axially oriented polypropylene (BOPP), low density polyethylene (LDPE), multi-wall paper (MWP), enviro-barrier paper (EPB) and moisture shield paper (MSP)) for a year. The seeds were stored in cool/dry (4℃, 30%RH), ambient (15-25℃, 65%RH), and warm/moist conditions (25℃, 80%RH). Seed moisture content (SMC), germination, seed vigour, and endophyte viability were assessed every 1.5-months (warm storage) and every 3-months (ambient and cool storage). At 12 months, SMC had increased by 2-3.5% in ambient and warm storage, while it decreased by 1-2% in cool storage. LDPE and BOPP bags maintained stable SMC across storage conditions. Germination remained stable in ambient and cool storage but dropped significantly in warm conditions, from 92% to between 49-67% after a year. BOPP and LDPE bags resulted in less germination loss (about 10%). Seed vigour declined in all storage environments, with the highest vigour loss in warm storage and the lowest in cool storage. Endophyte viability fell significantly in ambient and warm conditions, but remained stable in cool storage, regardless of bag type. Overall, the storage environment had a greater impact on the endophyte survival than the bag type. While all bag types were suitable, their physical robustness and environmental footprints require evaluation before recommendations for change