Somaclonal Variation:A technique for Crop Improvement

Introduction- Plant tissue culture procedures give a substitute strategy for vegetative propagation of horticultural crops. Clonal propagation through tissue culture (popularly known as micro propagation) can be acknowledged generally quickly inside a little space. The consistency of individual plants inside a clone population is a significant bit of choice of clonal cultivars in business creation.

However, genetic variations do happen in undifferentiated cells, detached protoplasts, calli, tissues and morphological qualities of in vitro raised plants. In 1981, Larkin and Scowcroft Begat an overall term ”somaclonal variation” for plant variations got from any type of cell or tissue cultures. Somaclonal variation has been used in an enormous number of plant species such as potato, sugarcane, tobacco, tomato, wheat, rice, brassica and others for different agronomic qualities, for example, disease resistance, plant height, tiller number, maturity and for different physiological and biochemical characteristics. A few valuable somaclonal variations have been gotten and some of them have been released as cultivars. Somaclonal variation along these lines seems, by all accounts, to be a significant source of genetic fluctuation. Tissue culture-determined plants show variation which is similar to mutations in tissues and cultured cells. It has been discussed whether somaclonal variation is the consequence of previous genetic contrasts in physical cells or is initiated by explicit segments of the medium.

The main characteristic of somaclonal variation is variations for karyotype, isozyme characteristics and morphology in somaclones may also observe. Calliclone (clones of callus), mericlone (clones of meristem) and protoclone (clones of Protoplast) were produced. Generally heritable mutation and persist in plant population even after plantation into the field.

Cause of Somaclonal Variation:-There are main reasons for the somaclonal variation.
Physiological Causes:-
The somaclonal variation developed due to physiological activity such as plant hormone, plant growth regulators, and culture conditions of the media. This type of variation is caused when the sample exposes a longer time in a particular condition.

Genetic causes:-
Most of the somaclonal variations developed due to genetic reason. The genetic causes govern by changes in chromosomal number (Euploidy, Aneuploidy, polyploidy, monoploidy) chromosomal structure (Deletion, inversion, duplication, translocation), gene mutation (Transition, transversion, insertion, deletion), plasma gene mutation (self-replicating genetic particle postulated to be in the cytoplasm of a cell, as like in mitochondria) and DNA sequences (Changes in DNA, protein) etc.

Advantage of Somaclonal Variation :-
(1) It is less expensive than different techniques for genetic manipulation and doesn’t require ‘containment’ strategies.
(2) Tissue culture frameworks are accessible for more plant species than can be controlled by substantial hybridization and transformation right now.
(3) It isn’t important to have distinguished the genetic basis of the characteristic, or indeed, in the case of transformation, to have secluded and cloned it. It helps in crop improvement.
(4) This techniques important for creation of additional genetic variations. It Increased and improved production of secondary metabolites.
(5) Selection of plants resistant to various toxins, herbicides, high salt concentration and mineral toxicity. It is also suitable for breeding of tree species.

Disadvantage of Somaclonal Variation :-
The main disadvantages are:
(1) A serious disadvantage occurs in operations which require clonal uniformity, as in the horticulture and forestry industries where tissue culture is employed for rapid propagation of elite genotypes.
(2) Somaclonal Variations Sometime leads to undesirable results.
(3) Selected variants are random and genetically unstable. In this works require extensive and extended field trials
(4) It is Not suitable for complex agronomic traits like yield, quality etc. It may develop variants with pleiotropic effects which are not true.

Dr, Monika Karnawat, Associate Professor, School of Agriculture Sciences, Career Point University, Kota

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