Temperature and time variables for accelerated ageing testing of perennial ryegrass (Lolium perenne L.) seed lots

The current recommendation for seed vigour testing in perennial ryegrass (Lolium perenne L.) of 40 degreesC for 48 h does not always give separation of high germinating seed lots, even though field performance indicates vigour differences. Five seed lots of perennial ryegrass cv. Grasslands Nui, all of which had a germination above 90%, were subjected to accelerated ageing (AA) at temperature/time combinations ranging from 41 degreesC for 48 to 96 h to 45 degreesC for 48 to 72 h. The combination of 43 degreesC for 72 h provided the best separation of post-AA germination. Results from a further experiment involving six seed lots of cv. Grasslands Nui, all with germinations greater than 98%, confirmed that AA at 43 degreesC for 72 h gave wider separation in post-AA seed performance than temperatures of 40-42 degreesC for 72 h.