Comparison of three priming techniques for onion seed lots differing in initial seed quality

This study compared the effect of osmopriming (aerated PEG 8000 solution), hydropriming and drum priming on percentage and speed of germination, using six lots of onion (Allium cepa) seeds. For the osmopriming method, osmotic potentials of-0.5 MPa and-1.0 MPa and imbibition periods of 24 and 48 h were used. In the hydropriming method, seeds were moistened between 2, 4 or 6 layers of paper towel, for 48 or 96 h. In the drum priming technique, OF the optimal amount of water added and treatment period varied among seed lots, which exhibited a wide variation of germination and vigour. All treatments were carried out at 15 C; drum priming was also conducted at 25degreesC. The response to priming methods varied among seed lots and, in general, less vigorous onion seed lots did not respond well to priming treatments. The hydropriming technique was the most effective method for improving speed of germination for all six lots that were evaluated, especially when 96 h of priming was used. However, the most practical technique was drum priming, which allowed efficient seed hydration without the labour costs and disposal concerns associated with the hydropriming and osmopriming techniques, although this method promoted reductions in percentage and speed of germination in most of the lots.