In vitro culture of early globular-stage embryos of Brassica napus L.

Embryos of B. napus L. cl. Górczański from early globular to late globular stages (16-105 µm in length) were used for the culture. The embryo proper of the smallest ones consisted of 4-17 cells. A double-layer culture system was applied for culture of proembryos. The top layer contained 6% sucrose; the bottom was devoid of sugar. The osmotic pressure decreased gradually under culture due to the diffusion of osmotically active sucrose into the bottom layer. The medium used was based on ECM medium developed by Liu et al. (1993). The proembryos were placed on the surface of the bottom layer and then the top layer was placed over them, or else the proembryos were inoculated on the surface of the top layer. The percentage of embryo maturation was related to embryo length at the moment of inoculation. Among the embryos smaller than 50 µm, 3.7% matured, whereas 28.9% of the embryos larger than 50 µm produced seedlings. No embryo smaller than 30 µm grew in the culture. Coconut water (CW) had no significant influence on the effectiveness of culture, and an intact suspensor was not indispensable for the maturation of early globular embryos. Embedding proembryos in the top-layer medium was not necessary. The culture of proembryos inoculated on the surface yielded similar numbers of mature embryos.