Impact of bag type on Epichloe endophyte survival and perennial ryegrass seed quality in three different storage environments

Abstract

The New Zealand seed industry uses woven polypropylene (WPP) bags for seed lots, unlike many other countries where multi-wall paper (MWP) bags are used. The continued use of WPP bags has been questioned from an environmental/sustainability perspective but the industry is reluctant to change from WPP because of concerns about the ability of alternatives to maintain the viability of Epichloe endophytes in perennial ryegrass seed lots from the first entry into storage until the sowing of the next crop. With industry support, the ability of six bag types, WPP, MWP, bi-axially orientated polypropylene (BOPP), low density polyethylene (LDPE), enviro-barrier paper (EPB) and moisture shield paper (MSP) to maintain both endophyte viability and perennial ryegrass seed quality (one seed lot each of two cultivars x endophyte) over one year of storage in three storage environments was evaluated. The three storage environments were ambient (15-25℃, 65%RH), cool (4℃, 30%RH) and warm (25℃, 80%RH). Seed moisture content (SMC), germination and vigour as well as endophyte viability were assessed at 1.5 month intervals (warm storage) and 3 month intervals (ambient and cool storage). After 6 months in warm storage, SMC for all bag types had increased by between 1- 3.5% from the initial SMC, but the increase was significantly lower for LDPE and BOPP. Seed germination had not changed but seed vigour (as measured by the accelerated ageing test) had declined for all bag types. Endophyte viability had collapsed from >85% before storage to > 40% irrespective of bag type. For ambient and cool storage, at 6 months no significant changes in endophyte viability or seed quality had occurred among all the bag types. Results following one year of storage will be presented.