Synthetic Seeds - Student Notes

Introduction:

It is a technique of plant tissue culture where a single somatic embryo is entrapped inside a matrix, which has the ability to transform into a complete plant in the desired environment.

The matrix mainly used to entrap the somatic embryo is Polyoxyethylene and sodium alginate.

While performing encapsulation procedure, one should not damage the embryo, the coating should be mild and should carry all the nutrients and growth regulators to protect the somatic embryo from dying.

Synthetic seeds are defined as artificially encapsulated somatic embryos, shoot buds, cell aggregates, or any other tissue that can be used for sowing as a seed and that possess the ability to convert into a plant under in vitro or ex vitro conditions and that retain this potential also after storage.

In simple words, the synthetic seed contains an embryo produced by somatic embryogenesis enclosed within an artificial medium that supplies nutrients and is encased in an artificial seed covering.

The technology designed to combine the advantages of clonal propagation with those of seed propagation and storage. Also, be a channel for new plant lines produced through biotechnology advances.

The first synthetic seeds were produced by Kitto and Janick in 1982 using carrots.

Why Synthetic Seeds?

In some of the horticultural crops seeds propagation is not successful due to

• Heterozygosity of seeds particularly in cross-pollinated crops

• Minute seed size eg; orchids

• Presence of reduced endosperm

• Some seeds require mycorrhizal fungi association for germination for e.g. orchids

• No seeds are formed

• These crop species can be propagated by vegetative means like micro propagation and clonal propagation.

Characteristics Of Synthetic Seeds:

• High volume, Large scale propagation method

• Maintains genetic uniformity of plants

• Direct delivery of propagules to the field, thus eliminating transplants

• Lower cost per plantlet

• Rapid multiplication of plants

Procedure For Synthetic Seed Production:

The somatic embryos for synthetic seeds are produced in the lab through culturing of

somatic cells and treating them with different hormones to produce root and shoot. The

following are the different steps involved in artificial seeds production;

1. Establish somatic embryogenesis

2. Mature somatic embryos

3. Synchronize and singulate somatic embryos

4. Mass production of embryos

5. Encapsulation of matured somatic embryos

6. Desiccation

7. Field planting

Types of Synthetic Seeds:-

1) Desiccated Synthetic Seeds

• This involves the encapsulation of multiple somatic embryos followed by desiccation.

• The encapsulating material used in this case is polyoxyethylene (Polyox). This material doesn’t allow for the growth of the microorganisms and is non-toxic to embryos.

• In this case, a mixture is prepared by using equal volumes of embryo suspension and a 5% (w/v) solution of polyox to give a final concentration of 2.5% polyox.

• Then by using a pipette the suspension is dispensed as 0.2 ml drops onto Teflon sheets. Then the drops are dried till they themselves leave the Teflon sheet.

2) Hydrated Synthetic Seeds

• This involves the encapsulation of a single somatic embryo in hydrogel capsules.

• This technique is used in those plants which are recalcitrant for somatic embryogenesis and sensitivity to desiccation.

• The most popular method of forming hydrated synthetic seeds is using Ca-alginate encapsulation.

• The procedure followed to produce hydrated synthetic seed involves the mixing of somatic embryos with a 2% (w/v) solution of Na-alginate.

• Then, the embryo is dropped into a 100 mM solution of Ca(NO3)2 by using a plastic pipette.

• Of the two types of synthetic seeds, the desiccated synthetic seeds have greater potential to form synthetic seeds and are closure to the true seeds.

Advantages and Applications:

• Synthetic seeds can be transported easily without any contaminations

• We can produce sterile plants

• The synthetic seeds facilitate the growth of several plants that have low seed viability and poor germination rates.

• Some exotic plants can be preserved from extinction

• Mass propagation of elite plant varieties can be done

• Increased shelflife without losing viability

• GMOs can be propagated by synthetic seed technology

• Genetic uniformity can be maintained

• Synthetic seed can be directly used in the field

Limitations:

• Limited production of viable micro propagules that are useful in synthetic seed production

• Asynchronous development of somatic embryos

• Improper maturation of somatic embryos makes them inefficient for germination and conversion into normal plants

• Lack of dormancy and stress tolerance in somatic embryos that limit the storage of synthetic seeds

• Somaclonal variations which may alter the genetic constituent of the embryos

Factors That Affect a Synthetic Seed’s Production;

1. Selection of Plant Materials

• The synthetic seeds can be produced by using somatic embryos or other plant propagules, However, a specific plant species supports a specific plant material for the production of synthetic seeds.

• For example, somatic embryos have been successfully used to produce synthetic seeds in several plant species that include Oryza sativa, Dalbergia sissoo, Curcuma amada, Hemidesmus indicus, etc.

• Whereas, some plants support the production of synthetic seeds when nodal segments are used. It includes Eclipta alba, Cannabis sativa, Solanum tuberosum, Gossypium hirsutum, etc.

2. Selection of Encapsulation Matrix

The encapsulation of seeds is an essential factor that determines the production of synthetic seeds. So, there are some qualities that the encapsulating material should have if it’s going to be used for the production of synthetic seeds. It includes:

• It must not damage the embryo.

• The coating should be mild to protect the embryo.

• The coating should be durable for rough handling during manufacture, storage, transportation, and planting.

• The coat must contain all the essential growth materials such as nutrients and growth regulators.

• The formed synthetic seeds should be transplantable using the existing techniques.

REFERENCES

• https://www.plantcelltechnology.com/blog/an-overview-of-synthetic-seeds/

• https://www.biotecharticles.com/Agriculture-Article/Synthetic-Seed-Production-and-Application-104.html

• https://m.facebook.com/Biotechnologyandbiology/posts/282411698807661

• Faisal, M., & Alatar, A. A. (Eds.). (2019). Synthetic Seeds. DOI:10.1007/978-3-030-24631

• Bhojwani S. S. and Razdan M. K. (1983). Plant Tissue Culture: Theory and Practice. Elsevier publications.

• Rihan Z. Hail, Kareem Fakhriya, El-Mahrouk E. Mohammed, and Fuller P. Michael (2017).

• Artificial Seeds (Principle, Aspects, and Applications). Agronomy, 7(4), 71.

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