In this article we will discuss about the process of cybrids production.
These are cytoplasmic hybrids. In cybrids, nucleus of one parent and cytoplasm of both the parents constitute cytoplasmic hybrids. More precisely, cybrids can be accomplished by fusing protoplast derived from one of the parent plants with enucleated protoplast of other.
Cybrids can also be obtained through various other means like chemical treatment of protoplast to induce metabolic inactivation or application of X-ray or gamma irradiation to one of the parental types of protoplast resulting in inactivation or non-dividing status of protoplast.
Percoll gradient technique is widely used for the production of enucleated protoplasts by high speed centrifugation upto 35,000 × g for 50-90 min using percoll (10-40%) density gradient.
The isolated enucleated protoplast is then used to fuse with other protoplast to accomplish cybrids (Fig. 10.3). In another approach, when protoplasts are fused, their nucleus may undergo fusion to produce true hybrid or remain separate without fusion. If elimination of one of the nuclei occurs with the retention of other in a mixed cytoplasm, the resulting product is a cybrid.
Cybrids can be used to transfer male sterility (through mitochondrial genome) or herbicides resistance (through chloroplast genome) characters via cytoplasmically inherited process.
For example, cytoplasm male sterile character (cms) has been successfully transferred from N. tobaccum to N. sylvestris and from N. campestris to Brassica napus. Similarly, from Lycopersicum esculentum to Solarium acaule after protoplast fusion.
