Rate of physiological germination compared with the cold test and accelerated ageing as a repeatable vigour test for maize

Daily counts were made of the physiological germination (2mm radicle emerged) of 6 lots of F₁ hybrid maize during two runs of germination in rolled towels at 13°C in each of four laboratories. The mean germination time (MGT) was calculated for the data in each run, lot and laboratory. An overall mean for each lot was calculated for both MGT and the physiological germination at 6d. Both measurements of rate of germination (MGT and 6d count) were significantly related to the cold test germination (10°C for 4d and 3d at 25°C) determined in one of the laboratories. The relationship was particularly close for the 6d counts (R² = 0.96, p < 0.001). Cold test germination was significantly correlated with MGT for most experimental runs. The single count at 6d consistently gave the same ranking of the seed lots as the cold test. Counts of normal germination after accelerated ageing (AA) at 43°C for 72h were significantly correlated with the cold test in only one experimental run. A single early count indicative of rate of germination could be readily standardised and is suggested as an alternative to the cold test. Evidence is presented to explain the close association between rate of germination and cold test germination in terms of seed ageing and the repair of deterioration in the lag period between the start of imbibition and the emergence of the radicle.