Cytoplasmic Hybrids for Cybrids,Sexual Hybrids,Protoplasts,Cybrid Production,Ogura Cytoplasm

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	Cytoplasmic Hybrids for Cybrids - In sexual hybrids, the cytoplasm is derived from the maternal parent and in somatic hybrids, it is derived from both the parents. However, hybrids can be obtained, where nucleus is derived from one parent and cytoplasm is derived from both, thus producing cytoplasmic hybrids, which are also called cybrids. These cybrids can be obtained using anyone of the following methods: (i) fusion of normal protoplasts from one parent with enucleated protoplasts from the other parent; enucleated centrifugation, protoplasts can be obtained by high speed centrifugation (20,000 - 40,000g for 45-90 min) of protoplasts or by irradiation treatment,
(ii) fusion of normal protoplasts from one parent and protoplasts containing non viable nuclei from the other; (iii) selective elimination of one of the nuclei from the heterokaryon or (iv) selective elimination of chromosomes of one parent at a later stage after fusion of the nuclei. The technique of cybrid production has been utilized for transfer of cytoplasmic male sterility as has been successfully done in Nicotiana, Brassica and Petunia. Other characters like streptomycin resistance have also been transferred from N. tabacum to N. sylvestris, using this technique. CMS lines with 'Ogura cytoplasm', a herbicide (atrazine) resistant line and lines with increased nectar production have also been obtained using cybrids in crop brassicas.