Induction of viable 2n pollen in sterile Oriental × Trumpet Lilium hybrids

In order to induce viable 2n pollen from highly sterile diploid Oriental × Trumpet (OT) (Lilium), N2O was used to treat flower buds of four sterile diploid OT cultivars (‘Nymph’, ‘Gluhwein’, ‘Yelloween’, and ‘Shocking’) at different stages of meiosis. There was no pollen germination in the controls. However, after N2O treatment at 600 kPa, three of the OT hybrids (‘Nymph’, ‘Gluhwein’, and ‘Yelloween’) not only exhibited fertile flower percentages (4.3-16%), but also higher rates of pollen germination (18.8-72.5%). In addition, both the fertile flower percentages and rates of pollen germination were higher following 48 h N2O treatment at 600 kPa than the 24 h treatment. Following 72 h N2O treatment at 600 kPa, most flower buds or plants were damaged and any undamaged flowers showed abnormal anthers at the time of flowering. This indicated that 48 h of N2O treatment at 600 kPa was optimal to induce viable 2n pollen in three out of four sterile hybrid OT lily cultivars. These results also showed that prophase I - metaphase I was the optimum stage of meiosis at which to induce 2n pollen by N2O treatment in lily hybrids.