Enhancement of embryo yield from isolated microspores of Brassica napus by early iron starvation

Induction of embryogenesis in isolated microspores of Brassica napus requires stress conditions to trigger the developmental instead of the gametophytic pathway. To obtain further insight into the involvement of different ions in this process, a comparison has been made between embryo yields obtained with standard NLN-13 medium and the same medium without cobalt, copper or iron. It was confirmed that iron was essential to control embryo development, but not cobalt and copper. For the latter two ions, the concentration is probably too low to play a significant role in microspore embryogenesis. With the timing of iron application, as well as its chemical form, embryo yield could be improved or reduced. In media that exhibited iron deficiency, microspores initiated embryogenesis and the number of observed divided microspores increased 6 days after isolation. However, embryo development was not achieved. Addition of iron ions chelated with EDTA at day 3, leading to the doubling of embryo yield. Some of the putative role(s) of Fe-EDTA in the early events of embryogenesis is discussed.