RED-CLOVER VIGOR TESTING - EFFECTS OF 3 TEST VARIABLES

The conductivity, accelerated ageing and controlled deterioration tests have been used to detect vigour differences among high germinating seed lots of red clover (Trifolium pratense L.). A different aspect of the methodology for each of these tests was examined. Conductivity test results after a 6 and 8 h soak were strongly correlated with results after a 24 h soak period, but the ranking of seed lots differed among the soak times. A 24 h soak is recommended for red clover seed lots. Surface sterilising of seeds prior to accelerated ageing removed fungal contaminants during the subsequent germination test, but significantly reduced the germination of two lots considered to be of 'high' vigour after ageing at 40 degrees C for 72 h. However accelerated ageing test results for surface sterilised seeds were more strongly related to field emergence at the same site over eight sowings than those for non-surface sterilised seeds, possibly because of imbibition damage effects. This result requires further investigation. Assessment of controlled deterioration test results using the percentage of normal seedlings provided a more consistent relationship with field emergence than assessment of radicle emergence. The controlled deterioration test (18% seed moisture content for 24 h at 45 degrees C) was the best indicator of potential field performance, being significantly correlated with field emergence at the one site used for seven out of eight sowings during spring and autumn.