Methods for stratification and storage of somatic embryos

1. A method for producing stratified cotyledonary conifer somatic embryos comprising:

(a) incubating a culture comprising immature conifer somatic embryos in a culture vessel comprising a development medium comprising PEG at a concentration of from 1% to 15% and having an osmolality in the range of from 300 mM/Kg to 450 mM/Kg at a temperature of from 22° C. to 25° C. for a first incubation period sufficient in length for at least a portion of the embryos to reach anatomical maturity; and

(b) subjecting the embryos in the culture vessel comprising the development medium comprisine PEG at a concentration of from 1% to 15% and having an osmolality in the range of from 300 mM/Kg to 450 mM/Kg, in accordance with step (a), to a temperature of from 0° C. to 10° C. for a second incubation period of at least one week to produce stratified cotyledonary somatic embryos.

2. The method of claim 1 , wherein. the development media comprises PEG at a concentration of from about 7% to about 15%.

3. The method of claim 1 , wherein the first incubation period is from 7 weeks to 12 weeks.

4. The method of claim 1 , wherein the second incubation period is from 1 week to 8 weeks.

5. The method of claim 1 , wherein the second incubation period is from 1 week to 6 months.

6. The method of claim 1 , further comprising culturing the embryos treated in accordance with step (b) in or on a germination medium to produce germinants.

7. The method of claim 1 , wherein the embryos in the first culture are singulated prior to the first incubation period.