The formation of pomato is an example of:

Somatic hybridization

The correct answer is Option (4) → Somatic hybridization    

Somatic hybridisation: Isolated protoplasts from two different varieties of plants – each having a desirable character – can be fused to get hybrid protoplasts, which can be further grown to form a new plant. These hybrids are called somatic hybrids while the process is called somatic hybridisation. When a protoplast of tomato is fused with that of potato, and then they are grown – to form new hybrid plants combining tomato and potato characteristics – resulting in formation of pomato.