Explanation:

Somatic hybridization is a technique used in plant breeding to create hybrids by fusing the protoplasts (plant cells without cell walls) of two different plant species. This technique allows for the combination of desirable traits from different species, resulting in new varieties with improved characteristics.

In 1972, Carlson et al. achieved the first successful somatic hybridization between two species of tobacco (option A) plants. This breakthrough paved the way for further advancements in plant breeding and genetic engineering.

Importance of Somatic Hybridization:

Somatic hybridization has several advantages and applications in plant breeding:

1. Transfer of desirable traits: Somatic hybridization allows for the transfer of desirable traits from one species to another. For example, disease resistance, improved yield, and enhanced nutritional value can be introduced into crop plants through somatic hybridization.

2. Genetic diversity: By combining the genetic material of two different species, somatic hybrids can exhibit increased genetic diversity. This genetic diversity can lead to improved adaptability and resilience in plants.

3. Creation of novel varieties: Somatic hybridization enables the creation of novel plant varieties that possess unique combinations of traits. This can lead to the development of plants with improved agronomic characteristics, such as increased tolerance to environmental stress or enhanced quality.

Procedure of Somatic Hybridization:

The process of somatic hybridization involves the following steps:

1. Protoplast isolation: Protoplasts are isolated from the donor plants by enzymatic digestion, which removes the cell walls. This results in the formation of individual plant cells that can be fused together.

2. Protoplast fusion: The isolated protoplasts from two different plant species are mixed together and treated with chemicals or electric pulses to induce fusion. This fusion results in the formation of hybrid protoplasts.

3. Regeneration of hybrid plants: The hybrid protoplasts are cultured in a suitable growth medium that supports their division and development into plantlets. These plantlets are then transferred to soil for further growth and evaluation.

4. Selection and characterization: The regenerated plants are screened and selected based on the desired traits or markers. Molecular techniques, such as DNA sequencing or marker-assisted selection, can be used for the identification and verification of the somatic hybrids.

In conclusion, somatic hybrids in plants were first obtained between two species of tobacco by Carlson et al. in 1972. This pioneering work opened up new possibilities for plant breeding and genetic improvement, leading to the development of novel plant varieties with improved traits.