Shortening of selection time of Rosa hybrida by in vitro culture of isolated embryos and immature seeds

Hybrid tea rose hips were harvested weekly from 7 to 35 days after pollination (DAP). Thereafter, the immature seeds were extracted and surface disinfected. One half of them were directly plated as immature seeds onto culture medium to induce germination under several different phytohormone concentrations and culture conditions; the other half were opened and the embryos were excised and also plated onto similar culture media and conditions to germinate. Results showed that in vitro germination was possible for both embryos and immature seeds commencing at 21 DAP. The optimum protocol (final germination percentage greater than 40%) used embryos at 28 DAP on a medium MS0 supplemented with 2.5 mg l-1 BAP and 0.5 mg l-1 GA3, which had been incubated for one week at 4°C in dark conditions and subsequently transferred under a 16 h photoperiod at either 23°C or 15°C. The protocols developed in this investigation might help breeders to improve and speed seed germination and to screen a wide morphological variability which would result in shortened selection time.