somatic embryogenesis

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General seminar on “Somatic embryogenesis” Presented by: Sandeeep Singh Deol RP7906B47 M.Sc. Biotechnology

Contents: : 

Contents: Introduction Types of somatic embryogenesis Developmental stages Factors affecting somatic embryogenesis Comparison between somatic embryos and shoot buds Importance References

INTRODUCTION : 

INTRODUCTION In somatic embryogenesis, the embryos regenerate from somatic cells, tissue or organs either de novo directly from the tissues, opposite of zygotic or sexual embryogenesis. first recognized by Steward et al. (1958) and Reinert (1958, 1959) in culture of Daucus carota

Various terms for non-zygotic embryos : 

Various terms for non-zygotic embryos Adventious embryos – somatic embryos arising directly from other organs or embryos. Parthenogenetic embryos – formed by the unfertilized egg. Androgenetic embryos – formed by the male gametophyte.

Types : 

Types Direct embryogenesis The embryos initiate directly from explant in the absence of callus formation. Indirect embryogenesis Callus from explant takes place from which embryos are developed.

Indirect somatic embryogenesis in Carrot : 

Indirect somatic embryogenesis in Carrot

Development patterns : 

Development patterns

Somatic embryogenesis is influenced by several factors: : 

Somatic embryogenesis is influenced by several factors: Explant Genotype Growth regulators Nitrogen source Oxygen concentration Electrical stimulation

Explant : 

Explant Immature zygotic embryos : best explant for recalcitrant species Petiole section from youngest fully expanded leaves: establishment of embryonic cultures of Alfalfa

Genotype : 

Genotype Explant genotype has a marked influence on SE regeneration Strong genotypic effects have been shown in many species, e.g., alfalfa, wheat, maize, rice, chickpea, etc In case of wheat, chromosome 4B is important in regeneration a major gene affecting regeneration is located on the long arm of chromosome 2D a regulatory gene on the long arm of chromosome 2B

Growth regulators : 

Growth regulators Embryo initiation: auxin in the medium is generally essential 2, 4-D, 0.5 mg per l. : induces differentiation of localized groups of meristematic cells called embryogenic clumps. Embryo development: auxin free media

Nitrogen source : 

Nitrogen source The form of nitrogen has a marked effect on somatic embryogenesis. In carrot :NH+4 has a promotive effect on SE regeneration SE development : medium containing NO-3 as the sole nitrogen source

Comparison of Shoot Buds and Somatic Embryos : 

Comparison of Shoot Buds and Somatic Embryos Shoot bud Somatic embryo Origin:Many cells Unipolar; only the shoot pole present Vascular strands connected with those present in callus/explant Not easily separated from callus unless cut off Single cell, Bipolar; both shoot and root poles present There is no vascular connection with callus/explant Easily separated from callus since the radicular end is cutinized

Impotance of somatic embryogenesis: : 

Impotance of somatic embryogenesis: Raising somaclonal variants Synthesis of artificial seeds Synthesis of metabolites Clonal propagagation

Somatic embryogenesis as a means of propagation is seldom used: : 

Somatic embryogenesis as a means of propagation is seldom used: High probability of mutations The method is usually rather difficult. Losing regenerative capacity become greater with repeated subculture Induction of embryogenesis is very difficult with many plant species. A deep dormancy often occurs with somatic embryogenesis

References : 

References www.plant-molecularbiotechnology.com www.wikipedia.com/somaticembryos.html www.edu.books.com/somaticembryos.html www.wikipedia.com/somaticembryos importance.html www.springerlink.com/somaticembryos/developmentalstages.html Plant Biotechnology: B.D. Singh