Somaclonal Variation

Somaclonal Variation:

Term first coined by Larkin and Scowcroft (1981)

Genetic variability regenerated during tissue culture

This occurs as a result of genetic heterogeneity in plant tissue culture, changes can pass from one generation to another.

Types of Somaclonal Variation:

1.?? Genetic (Heritable) Variations:

Pre-existing variation in explants

These cause by mutations and other changes

These occurs at high frequency

2.?? Epigenetic (Non-Heritable) Variations:

Variations generated during tissue culture

It caused by temporary phenotypic changes

These occurs at low frequency

(Satyanarayana, 2015)

Types of Variations:

1.?? Gametoclonal Variation: Clones of gametes

2.?? Protoclonal Variation: Clones of protoplast

3.?? Calliclonal Variation: Clones of callus

4.?? Mericlonal Variation: Clones of mericlone

Causes of Somaclonal Variation:

1. Physiological race

2. Genetic cause

·???? Change in chromosome number

·???? Change in chromosome structure

·???? Gene mutation

·???? Plasma gene mutation

·???? Transposable element activation

·???? DNA sequence

3. Biochemical cause

Factors affecting Somaclonal variation:

·???? Selection agent

·???? Selection propagules

·???? Duration of cell culture

·???? Growth hormone effects

·???? Technique used for selection

·???? Stability of resistance substance

·???? In-vivo testing procedure

·???? Genotype and explants source

·???? Ability for regeneration of plants

Eg. Rice, Wheat, Maize, Sugarcane, Barley, Soybean, Tomato

Detection and Isolation of Somaclonal Variant:

Analysis of qualitative and quantitative characters

Variants detection by cytological studies

Variants detection by DNA contents

Variants detection by gel electrophoresis

Detection of disease resistance variants

Detection of herbicide resistant variants

Detection of environmental stress tolerant variant