Manual and automated counts of early radicle emergence assess differences in seed vigour and normal germination in four vegetable Brassicaceae species

The ability of early radicle emergence (RE) counts, evaluated manually and using image analysis, to assess differences in normal germination (NG) and vigour was investigated for four Brassicaceae species: cabbage, mustard, Chinese cabbage and radish. A manual RE count after germination for 48 hours at 20/30°C (RE 48h 20/30°C) correlated significantly with NG in all species ( P < 0.05). An automated count, at different times for each species, also correlated significantly with NG for three species although the coefficients of determination were lower than for the manual count. Both manual and automated counts also identified differences in vigour, giving significant correlations and coefficients of determination with early and/or final emergence in the field and in the glasshouse. A single automated count after 72 hours at 20°C was significantly correlated with at least two aspects of vigour in all four species. A significant relationship between germination after controlled deterioration and the manual and automated RE counts for cabbage and Chinese cabbage suggested that the differences in RE and vigour were attributable to ageing although differences due to variety could not be excluded. An early RE count can therefore provide a rapid and early assessment of differences in NG and vigour.