cybrids.pptx production_advanges_limitation

cybrids are the somatic hybrids.

1. CYBRIDS

2. CYBRID Cybri d ( c y t oplasmi c h yb r i d ) : Cybrids are cells or plants containing nucleus of one species but cytoplasm from both the parental species. Cybridization : production of somatic cybrid. The process of protoplast fusion resulting in the development of cybrid is known as cybridization.

3. Gleba 1979 fused tobacco protoplast which produced a cybrid. Melchers and Labib in 1974 fused protoplast of two haploid light sensitive lines of Nicotiana tabacum . Kao and Wetter in 1976 isolated cell cybrids of Glycine max and Nicotiana glauca . Pental and Cocking proposed that triploids could be produced by fusing protoplast isolated from microspores at the tetrad stage (n) of a species with protoplast isolated from the somatic cells of other species. Pirrie and Power synthesized triploids by fusing microspore protoplast of Nicotiana glutinosa with somatic cell protoplast of Nicotiana tabacum .

4. Cybrids are produced during fusion of protoplast from two phylogenetically distant species. Regeneration from phylogenetically distant species will have plastomes from both parental species but the functional genome of only one species through chromosomal elimination. The extranuclear genes which control agronomically important characters are of considerable interest.

5. Nuclear genome of one parent “donar” is inactivated chemically or with irradiation before protoplast fusion. Irradiation with x-rays or gamma rays ,in doses of 50 to 300 Gy, is effective in partial or complete inactivation of donar cells. Fusion of untreated “recipient” protoplast with “donar” and culturing result in cybrid plants possessing the nucleus of the “recipient” and the cytoplasm of both parental species. Phylogenetically distant species produce cybrids during protoplast fusion.

6. Fusion between protoplasts of potato ( Solanum tuberosum ) and tomato ( Lycopersicon esculentum ) has created pomato ( Solanopersicon , a new genus). 2. Interspecific fusion of four different species of rice ( Oryza brachyantha , O. eichngeri , O. officinalis and O. perrieri ) could be done to improve the crop. Cybrids are important for the transfer of cytoplasmic male sterility (CMS), antibiotic and herbicide resistance in agriculturally useful plants.

7. The cybrid produced by electrofusion between Citrus unshiu and C. sinensis . Restoration of male fertile Nicotiana by fusion of protoplast derived from two different cytoplasmic male sterile cybrids. Correct deficiencies of nitrate reductase and xanthium dehydrogenase activities in tobacco by fusing its normal protoplast with protoplast of Physalis and Datura inactivated by x-ray treatments. Streptomycin resistance has been transferred from Nicotiana tabacum to three other species of tobacco.

8. Two different parental genomes that cannot reproduce sexually (asexual or sterile) are recombined. Overcomes sexual incompatibility barriers. Used in study of cytoplasmic genes & their activities- plant breeding experiments. To transfer cytoplasmic male sterility (tomato,tobacco). To transfer antibiotic resistance character(tobacco) To transfer herbicide resistance (brassica) Used in mitochondrial research. Advantages

9. Biparental inheritance of cytoplasm during sexual reproduction occurs in only a few genera . Plant regeneration from protoplasts is often a difficult, or even impossible task. Instability of transferred genes in somatic hybrids. Recovering controlled asymmetric hybrids due to factors like cell fusion, nuclear fusion, nuclear genes segregation and recombination.