The key to success with green pod propagation is to process the pod when the embryos have matured to the point at which they can carry on development in flasks but to not wait so long that the embryos have matured into seed which require more complex treatments, including vernalization, to break dormancy.
Timing of the collection of green pods is an empirical process and many tables exist with estimates. Green pods are optimally collected between weeks 5 and 8 following application of pollen. The exact time is affected by the weather during maturation, with warm temperatures speeding maturation and cool temperatures delaying maturation. If we harvest green pods 6 weeks following pollenation then we always have reasonable survival of the embryos. It should be kept in mind that this timing is appropriate for northwestern Connecticut and will be somewhat shorter in warmer areas and somewhat longer in cooler areas.
Check the pod carefully for insect holes or fungus or bacterial holes that may extend through the pod wall. If these exist the pod should be discarded as the embryos will be contaminated and sterilizing fluid will enter the pod and kill the embryos.
Prepare 200ml of Chlorox bleach (mixing 100ml of water into 100ml of Chlorox), in this bleach add 4 drops of tween 80 or Ivory dishwashing liquid. Place the green pod into the bleach solution and scrub lightly with a tooth brush. Before you scrub the green pod, remove any dried petals, long stem fragment using a scalpel or razor blade leaving only stumps. Do not cut too close to the pod cause the sterilization fluid may enter killing the embryos. Incubate the green pod in the bleach solution for 15 minutes.
Inside the hood place 2 sterile containers containing 100ml of sterile water and place one more sterile container containing 100ml of isopropyl alcohol(90%) along with a square of sterile glass, 4 to 6 inches on a side. Swirl the pod gently for 2 mins using forceps, into the first container of water to rinse off the bleach. Again swirl for 2 mins into the second container then swirl for another 2 mins into the alcohol. Place the pod onto the sterile glass to allow the alcohol to evaporate.
Using a sterile blade, remove both ends of the pod. Dip the blade into alcohol and allow to dry, then slice the pod lengthwise into 2 halves. Hold one half pod over an open flask using sterile forceps. Use a sterile needle to scrape about half the embryos into the flask. If the cut surface of the pod is glistening white rather than filled with fluffy embryos, use the needle to scrape about half of the placenta containing the immature embryos into a flask.
If the surface of the media is "dry" add about 0.5 ml sterile water, close the flask, and swirl it gently to disperse the seed. Seal the flask with Parafilm or plastic stretch sealer. Label the flask lid using a permanent marker. Include a description of the contents and the date this mother flask was made. Place the mother flasks into a dark cabinet at room temperature. If possible this should be 70 - 75 F to produce maximum growth rate.