Organogenesis & somatic hybridrization

ORGANOGENESIS&

SOMATIC EMBRYO HYBRIDIZATION

Presented by:Neha Agrawalm.sc. 3rd sem

Introduction (organogenesis) Factor affecting organogenesis Advantages of organogenesis Application of organogenesis Somatic hybridization Somatic hybridization technique

Mechanical enzymatic

Isolation of protoplast Advantages of somatic hybridization Limitation of hybridization Difference between organogenesis and somatic hybridization

CONTENT

Introduction

Organogenesis is a process of differentiation by which plant organ viz. roots, shoots, bud flower, stem, etc. are formed while adventitious refers to the development of organ or embryo from unusual points of origin of an organized explant where a preformed meristem is lacking.

This process is much more common than somatic embryogenesis and has far more potential for mass clonal propagation of plants.

INTRODUCTION

FACTORS AFFECTING ORGANOGENESIS-

Physical factor

Chemical factor

PHYSICAL FACTOR

Intensity of light-the blue region of spectrum promotes shoot formation and red light induce rooting.

The treatment of blue light followed by treatment of red light also stimulates the organogenesis phenomenon.

Temperature-increase in temp. up to 33°c may be associated with rise in the growth of tobacco callus but for shoot-bud differentiation a lower temp. 18°c may be optimal.

Electric stimulation- Bagga et.al 1985 suggested the role of phytochrome in shoot induction.

CHEMICAL FACTOR

Cytokinin or auxin - cytokinin in the medium leads to the promotion of bud differentiation and development.

Kinetin is 30,000 times more potent than adenine. Phosphate-increase level of the phosphate in the

medium is reported to counteract the inhibitory effect of auxin.

Casein hydrolysate – casein hydrolysate or tyrosine also induces kinetin type bud formation even in the presence of higher level of IAA in the medium.

Advantages of organogenesis-

Cheap.Fast process.No variables. Less space.Easily scale.

APPLICATION OF ORGANOGENESIS

Scale up easily.Variation is not produce. Use as a bioreactor.Protoplast culture.Gene transfer.

SOMATIC EMBRYOGENESIS

Somatic hybridization

SOMATIC HYBRIDIZATION

Development of hybrid plants through the fusion of somatic

protoplasts of two different plant species/varieties is called somatic

hybridization.

Somatic hybridization technique

1. isolation of protoplast

2. Fusion of the protoplasts of desired species/varieties

3. Identification and Selection of somatic hybrid cells

4. Culture of the hybrid cells

5. Regeneration of hybrid plants

SOMATIC HYBRIDIZATION

The technique of hybrid production through the fusion of isolated somatic protoplast under in vitro conditions and subsequent development of their product (heterokaryon) to a hybrid plant is known as somatic hybridization.

In somatic hybridization the nucleus and cytoplasm of both parents are fused in the hybrid cell.

Sometimes; nuclear genome of only one parent but cytoplasmic genes (plastome) from both the parents are present in the fused hybrid, which known as cybrid or cytoplasmic hybrid.

Somatic hybridization involves the following aspects:1) Fusion of protoplasts .2) Selection of hybrid cells . 3) Identification of hybrid plants.

Protoplast fusion

It involves mixing of two different genomes and can be achieved by spontaneous or induced fusion method.

Spontaneous fusion : -I. cell fusion is natural process as is observed in case of egg fertilization.II. During the course of enzymatic degradation of cell walls, adjoining

protoplasts may fuse to form homokaryocytes (homocaryons). III. These fused cells may sometimes contain high number of nuclei (2-40).IV. The frequency of homocaryon formation was found to be high in protoplasts

isolated from dividing cultured cells.

Induced fusion method :-

I. Isolated protoplasts can be fused by induction. II. There are several fusion inducing agents which are

collectively referred to as fusogen.III. example: sodium nitrate ,high glycol, polyvinyl

alcohol, lysozyme, concavalina, electro fusion dextran and dextran sulphate , fatty acid and esters.

Advantages of somatic hybridization

Production of novel interspecific and intergenic hybrid. Pomato (Hybrid of potato and tomato).

Production of fertile diploids and polyploids from sexually sterile haploids, triploids and aneuploids.

Transfer gene for disease resistance, abiotic stress resistance, herbicide resistance and many other quality characters.

Limitations of Somatic hybridization

Poor regeneration of hybrid plants. Non-viability of fused products. Not successful in all plants. Production of unfavorable hybrids. Lack of an efficient method for selection of

hybrids. No confirmation of expression of particular trait in

somatic hybrids.

Difference between organogenesis and somatic embryogenesis-

organogenesis Somatic embryogenesis

Production of unipolar structure ( shoot or root primordium ).

Vascular system connected to parent tissue.

Organogenesis is a property of the somatic tissue.

Organogenesis is a popular process.

Production of bipolar structure ( shoot or root axes).

Vascular system not connected to parent tissue.

Somatic embryogenesis pertains to the reproductive tissue

Somatic embryogenesis is a relatively less popular.

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