Creation of Variations

The plants developing from callus have shown large variations in their characters. Such variations are called somaclonal variations. Such variations occur as a part of mutation or as a part of clonal development. As these variations are not due to heredity, their transmissions to next generations is not possible. However, such variations combined with action of mutagens could result into ideal breeding material for crop improvement programme. Such somaclonal variations have been reported in some crops such as

Potato - showing high protein content and resistance to late blight caused by Phytophthera

Rice - showing resistance to tungro rice virus and leaf hopper

Wheat - showing resistance to rust and resistance to high temperature.

They are utilised in breeding programmes to improve these crops.

The variations caused by such technique need not be always beneficial and may not remain permanent. They are not useful unless they are sustained over generations and are of some practical significance.

Somaclonal Variation

In plants genetic variation occur in plants at all levels of the tissue culture process. These variations have been termed as somaclonal variations. Somaclonal variations affects cytoplasmic genome as well as nuclear genome these variations, when heritable are useful for improvement of crops such as resistance to insect pests and diseases, tolerance to environmental stress, male sterility etc.

Examples of somaclonal variations observed in crop species are:

a) Rust resistance in wheat.

b) Resistance for late blight in potato.

c) Shortening of harvest duration in sugar cane.

d) Increased shelf life in tomato.

e) Tolerance to high temperature in wheat.

f) Resistance for leaf hopper in rice.

g) High protein content in potato.