The relationship between three cold test temperatures, accelerated ageing test and field emergence of maize seed

The standard cold test temperature for maize of 10 degrees C may not be suitable for all genotypes because of variation in cold hardiness. The aim of the present work was to study the effect of three cold test temperatures on seed vigour of a large number of maize seed lots in comparison with the standard germination test and accelerated ageing (AA) test and to determine the relationship between all tests and field emergence. Thirty maize (Zea mays L.) seed lots with high germination but differing vigour were germinated in trays in sterile sand at 25 degrees C after 0 (standard germination test) or a 7-day cold treatment at 10, 7.5 and 5 degrees C and after AA at 45 degrees C for 72 hours. Field emergence after an early sowing was also evaluated. The three cold test temperatures significantly lowered the germination of almost all seed lots, with the magnitude of the decrease depending on the cold temperature used. The interaction treatments x seed lots was also significant owing to differences in vigour among seed lots. Despite the early sowing, the field environment was benign and almost all seed lots had a good emergence. However, standard germination still showed a poorer correlation (r = 0.51**) with field emergence than all the vigour tests (r = 0.75 to 0.79**). There were good correlations (r > 0.80) among all the laboratory vigour tests, while slightly lower correlations with standard germination were shown by the cold test at 10 degrees C and AA test (r = 0.71** and r = 0.63**, respectively). A low correlation with standard germination was shown by both the 7.5 and 5 degrees C cold tests (r = 0.42**). The AA test is likely to be as effective as the 10 degrees C cold test for assessing maize seed lot vigour. However, for cool tolerant varieties, a cold test at 7.5 or 5 degrees C may be necessary to detect vigour differences among seed lots.