What is the Difference Between Somaclonal and Gametoclonal Variation

The main difference between somaclonal and gametoclonal variation is that somaclonal variation occurs during the fusion of somatic cells whereas gametoclonal variation occurs during the fusion of two gametes.

Somaclonal and gametoclonal variations are two types of genetic variations that occur during reproduction. Generally, both methods bring variation to the DNA sequence of the individual.

Key Areas Covered

1. What is Somaclonal Variation
– Definition, Characteristics, Importance
2. What is Gametoclonal Variation
– Definition, Characteristics, Importance
3. Similarities Between Somaclonal and Gametoclonal Variation
– Outline of Common Features
4. Difference Between Somaclonal and Gametoclonal Variation
– Comparison of Key Differences

Key Terms

Gametoclonal Variation, Somaclonal Variation

What is Somaclonal Variation

Somaclonal variation is a type of variation that occurs in the fusion of two somatic cells. Generally, this type of variation occurs when the plant cells are in a tissue culture medium. Chromosomal rearrangements are the source of somaclonal variation. The main feature of somaclonal variation is that it produces plants in different ploidy levels. The characters of somaclonal variation affect both qualitative and quantitative traits.

Figure 1: Callus Culture

Furthermore, somaclonal variation is more common in plants that regenerate from calli. Normally, these variations can be either genotypic or phenotypic. They can also be genetic or epigenetic. In general, the changes in chromosome number, chromosome structure, and DNA sequence are the genetic changes in somaclonal variation. DNA methylation is the epigenetic changes in the somaclonal variation.

What is Gametoclonal Variation

Gametoclonal variation is the type of variation that occurs in the fusion of gametes. Generally, it occurs in pollen and microspore cultures. The significant feature of gametoclonal variation is that it undergoes chromosomal segregation. Therefore, diploid plants occur in the gametoclonal variation. The variation occurs in gametes and gametophytes in gametoclonal variation. There are four types of distinct variation types that occur in gametoclonal variation. They include new genetic variation, variations resulting from segregation and independent assortment, new variation in the haploid level resulting from chromosomal budding, and new variation at the diploid level resulting in heterozygosity.

Figure 2: Alteration of Generations in Plants

Similarities Between Somaclonal and Gametoclonal Variation

• Somaclonal and gametoclonal variations are two types of genetic or epigenetic variations that can occur during reproduction in plants.
• Both bring changes to the DNA sequence of an individual.
• Both pass to the next generation.
• They occur during plant tissue culture.

Difference Between Somaclonal and Gametoclonal Variation

Definition

Somaclonal variation refers to genetic or epigenetic changes that arise in vitro between clonal regenerants and their corresponding donor plants, while gametoclonal variation refers to the variation among plants regenerated from gametic cells in culture.

Occurrence

Usually, somaclonal variation occurs during the fusion of somatic cells while gametoclonal variation occurs during the fusion of gametes.

Ploidy

Allotetrapolid plants occur in the somaclonal variation while diploid plants occur in the gametoclonal variation.

Cytoplasm Contribution

Both cells have equal contribution to the cytoplasm in somaclonal variation while the female gamete contributes more cytoplasm in gametoclonal variation.

Segregation

Segregation of chromosomes does not occur in the somaclonal variation while segregation of chromosomes occurs in the gametoclonal variation.

Occurrence of the Variation

Somaclonal variation occurs in the parts of the plant such as the leaves, stem, root, tuber, and propagule, while gametoclonal variation occurs in gametes and gametophytes.

Conclusion

In brief, somaclonal and gametoclonal variations are two types of genetic variations that occur in plants in cell cultures. Somaclonal variation occurs after the fusion of somatic cells, producing allotetraploid plants. Therefore, there is no chromosomal segregation during the fusion of two somatic cells. In general, somaclonal variation occurs in the leaves, stem, root, and tubers. In comparison, gametoclonal variation occurs during the fusion of gametes and chromosomal segregation occurs in the gametoclonal variation. Gametoclonal variation occurs in gametes and gametophytes. Therefore, the main difference between somaclonal and gametoclonal variation is a type of fusion of cells and the segregation of chromosomes.  

References:

1. “Somaclonal Variation.” Wikipedia, Wikimedia Foundation, 26 May 2022.

Image Courtesy:

1. “Callus1” By Igge – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Alternation of generations simpler still” By Peter coxhead – Own Work (CC BY-SA 4.0) via Commons Wikimedia