Secondary embryogenesis and transient expression of the β-glucuronidase gene in hypocotyls of rapeseed microspore-derived embryos

Secondary embryogenesis from rapeseed microspore-derived embryos (MDEs) was studied in three Brassica napus L. cultivars Global, PF704 and Option. The best results in terms of secondary embryogenesis percentage obtained in cultures of Global and PF704 MDEs (75.88 and 65.97 %, respectively) and PF704 produced the highest number of secondary embryos per each primary embryo (14.91 ± 2.18). After optimization of physical parameters, rapeseed hypocotyls of MDEs were bombarded with microcarriers coated with a plasmid containing GUS reporter gene. The highest levels of transient GUS expression were obtained using bombardment with gold particles of 1.6 µm, at helium pressure of 9.3 MPa, a bombardment distance of 9 cm, chamber vacuum pressure of 7.1 × 10-6 kPa and single bombardment in bombardment medium containing 0.4 M mannitol.