: General seminar
Sandeeep Singh Deol
M.Sc. Biotechnology Contents: : Contents: Introduction
Types of somatic embryogenesis
Factors affecting somatic embryogenesis
Comparison between somatic embryos and shoot buds
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.
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
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
Plant Biotechnology: B.D. Singh