The following are the some of the examples of Somaclonal Variation: 1. Sugarcane 2. Potato 3. Tobacco 4. Rice 5. Barley.
Application of somaclonal variation in crop improvement programme was established in sugarcane. The Hawaian Sugar Planters Association Experimental Station recorded genetic variation among sugarcane plants regenerated from tissue culture. Variations were recorded based on cytogenetic, morphological and enzyme profiles.
After Hawaian success, work was initiated in Fiji in the development of resistant to Fiji disease virus and several somaclones resistant to Fiji disease and powdery mildew have been identified and established using tissue culture techniques. As many as 4000 independent series of somaclones have been produced in Hawai to screen for Fiji disease. Several of these variants are resistant to the toxin.
In Philippines, several somaclones from sugarcane exhibit significant characters which are different from parental variety in cane yield, staik length etc. Lieu and Chen (1976) in Taiwan have found significant genetic variations among sugarcane yield, staik number, length, percent fibre, etc.
Detailed studies in sugarcane revealed that it is easy to obtain variation in sugarcane which provides greater promise for the improvement of varieties.
The commercial potato is autotetraploid. Nearly 20% of the world potato production lost due to disease. Several popular varieties are subjected for improvement in North America in order to produce disease resistant somaclones.
Screening over few hundred somaclones exhibit different altered characters and particularly somaclones were obtained which were resistant to Alternaria solani toxin. About 2% somaclones screened were resistant to Phytophthera infestance causes late blight, some of which were resistant to multiple races of the pathogen.
Several reports established the occurrence of genetic variation among regenerated potato plants. Some of these variant characters are C02 adsorption and chlorophyll content. Improvement of 10% of the somaclones exhibit yield variability. The somaclones lines shows completes difference from itself as well as parental lines in several prominent characters. Anther derived dihaploids from heterozygous for each of three single genes controlled character showed more resistant to viral disease.
Plants regenerated from rice callus shows phenotypic characters. These somaclones exhibit variations such as number of tiller per plant, panicle size and frequency of fertile plant. About 800 somaclones were derived from seed callus. Among these variants chlorophyll content, plant height, fertility and morphology were considered normally in all these characters. In addition, wide variation in seed fertility and plant height were noticed.
The barley plants derived from pollen culture of homozygous sample show phenotypic variation. The reason for variation was drawn in favour of chromosomal breaks and reciprocal translocation instead from chromosome number alterations. In the media composition the concentration of 2, 4-D enhanced genetic variation.