SYNTHETIC SEEDS

 

 Somatic embryogenesis results in the production of somatic embryos. These embryos can be propagated through clonal propagation or these embryos can be converted into synthetic seeds, synseeds, or artificial seeds.

 Synthetic Seeds are produced by encapsulating the somatic embryos in a protective layer.

 The synthetic seeds should have a coating layer that should be mildly protective.

This layer should protect the seeds from diseases and should be easily grown.

 It must contain nutrients growth hormones

 It is easy to handle and the seed must be protected from rough, handling.

 They can be grown using farm machinery.

TYPES OF SYNTHETIC SEEDS

 There are two types of synthetic seeds

The desiccated synthetic seed and hydrated synthetic seed

 Desiccated synthetic seeds

These were produced by Kitto and Janic in 1982 they used polyoxyethylene for encapsulating the somatic embryos.

Polyoxyethylene is non-toxic to somatic embryos and does not allow the growth of microorganisms. 

Somatic embryos were mixed with a 5% weight by volume solution of polyoxy Ethylene such that the final concentration becomes 2.5 percent of polyoxy.

This suspension was dispensed in 0.2 ml drops they were spread on a Teflon sheet the drops dry in 5 hours into wafers. 

For culture these Wafers were dissolved in a suspension medium, as a result, the survival of the somatic embryo was low.

 Hydrated synthetic seeds

 A number of methods have been started for the production of hydrated synthetic seed somatic embryos mixed into a 2 percent w/v  solution of sodium alginate and dropped using a plastic pipette in a 100 millimolar solution of calcium nitrate.

 Ion exchange results in the production of calcium alginate on the coats of seeds. Surface complexing is complete within 30 minutes the size of the capsule can be controlled by the size of the pipette.

Calcium alginate capsules are difficult to handle as they are sticky and are dried immediately once exposed to the atmosphere as they lose water.

 So, calcium alginate encapsulated somatic embryos are coated with Elvax 4260 (ethylene Vinyl Acetate acrylic acid terpolymer). 

SYNTHETIC SEED PRODUCTION

Hydrated synthetic seeds

 Large scale production of synthetic seed as described by Onishi et al. 1994 and Sakamoto et al. 1995.

PROMOTION OF EMBRYO DEVELOPMENT

 Promotion of embryo development by culturing somatic embryos in a suspension medium of high osmolarity with 10% Mannitol under 16 hours of light 300 Lx illumination.  It increased the size of somatic Andreas from 1-3 mm to 2 -8 mm.

DEHYDRATION OF EMBRYOS

 Dehydration of embryos to reduce their water content from 95 to 99% to 80 to 90% to keep them for 7 days on multiple layers of filter paper with 16 hours of photoperiod and 14μm²/s irradiance.

POST DEHYDRATION CULTURE OF SOMATIC EMBRYOS

Post dehydration culture of the somatic embryo on SH medium containing 2% Sorbitol, 0.01 milligram per liter BAP 0.0 1 mg/l GA3, and air enriched with oxygen in 16-hour photoperiod and 20ºC temperature for 14 days so that, somatic embryos acquired autotrophic nature.

 The storage of sugar and nutrients in the seeds is done with 3% sucrose. Microscopic capsules are formed with a mixture of 8% Elevax 4260, bee wax, and 0.1% Topsin M which is the fungicide.

 This microcapsule release sucrose slowly over a period of 3 to 21 days at 20ºC and at 4ºC, but it is not released. 

The gel is made self-breaking for its efficient germination. This involves rinsing the seeds thoroughly under tap water, followed by immersion in 200 mM solution of KNO₃ for 60min and finally desalting done by rinsing under tap water for 40 minutes. 

Encapsulating somatic embryos in calcium alginate has lowered the cost of artificial seed production.