PROMOTION OF VIGOUR IN CABBAGE SEED BY OSMOTIC PRIMING PRETREATMENT AT BOTH VERNALISATION AND NON-VERNALISATION TEMPERATURES

Abstract

Osmotic priming of cabbage seeds with polyethylene glycol (PEG 6000), to prevent germination during a vernalising treatment, was investigated as part of a study into potential seed production in the tropics.A preliminary attempt to vernalise cabbage seeds had resulted in weak stemmed seedlings, with fungal infections, as a consequence of the nonprimed seeds having germinated while still in the fridge at the low temperatures used for vernalisation (0° – 5°C).Two experiments to determine the effect of PEG 6000 on the viability and vigour of cabbage seed at non-vernalisation and vernalisation temperatures were carried out. In the first experiment, seeds of ten varieties of cabbage were imbibed separately in 302.44 g l–1 PEG 6000 in Petri dishes lined with filter papers moistened with PEG solution, or with distilled water as controls.The primed seeds were kept for 2 weeks at 25°C (non-vernalisation temperature) under an 8 h photoperiod, washed in distilled water and sown immediately into 4 cm-square plastic modular trays filled with Levington F2S compost. Priming did not have any significant effect on the proportion of seeds that germinated (P > 0.05), but significantly enhanced the coefficient of velocity (CV) at 25°C. In the second experiment, seeds of four varieties of cabbage were primed at 0° – 5°C for 8 weeks prior to sowing in compost. Controls were seeds primed in the same concentration of PEG 6000 and kept at 25°C for 11 d, and seeds sown without priming or vernalisation. Again, priming of cabbage seed with PEG 6000 had no adverse effect on the proportion of seeds that germinated, but promoted the CV (vigour) of seeds kept at vernalisation temperatures (0° – 5°C).