Symmetric & Asymmetric Hybrid and Cybrid

Symmetric & Asymmetric Hybrid and Cybrid

1. 1 WELCOME

2. Submitted to:- Dr. A. K. Singh Assistant Professor, Dept. of GPB S. D. A. U., S. K. Nagar Dr. N. N. Prajapati Assistant Research Scientist, C. C. I., S. D. A. U., S. K. Nagar Submitted by:- Vaghela Gauravrajsinh K M.Sc. (Agri.) Reg.no:-04-AGRMA-01840-2018 S. D. A. U., S. K. Nagar Symmetric & Asymmetric Hybrid and Cybrid Course Title : PLANT TISSUE CULTURE & GENETIC TRANSFORMATION

3. Somatic Hybridization Development of hybrid plants through the fusion of somatic protoplasts of two different plant species/varieties is called somatic hybridization. This is a non conventional genetic procedure involving fusion between isolated protoplast under in vitro condition and subsequent development of their product (heterokaryon) to a hybrid plant.

4. Symmetric hybrids: These contain the somatic chromosome of both the parental species. These are very significant as they show all the properties exhibited by parent species. Asymmetric hybrids: These are those hybrids which preserve the genetic material of one parent organism. The chromosome content of other parent species is lost.

5. Symmetric Hybrids Some somatic hybrid plants retain the full or nearly full somatic complements of the two parental species these are called symmetric hybrids. Such hybrids provide unique opportunities for synthesizing novel species, which may be of theoretical and/or practical interest. Frequently, somatic hybrids between distantly related sexually incompatible species are sterile, precluding their incorporation into a breeding programme. This may be circumvented by producing 3n somatic hybrids by fusing somatic (2n) cells of one species with haploid (n) cells of the other species; such 3n plants may be expected to be partially fertile.

6. Pomato :- Solanum tuberosum + Lycopersicum esculentum Other Example : Datura innoxia + Atropa belladonna Arabidopsis thaliana + Brassica campestris Atropa belladonna + Nicotiana chinensis

7. Asymmetric Hybrid Many somatic hybrids exhibit the full somatic complement of one parental species, while all or nearly all chromosomes of other parental species are lost during the preceding mitotic divisions; such hybrids are referred to as asymmetric hybrids. The available evidence suggests that such hybrids are likely to show a limited introgression of chromosome segments from the eliminated genome(s) due to drastically enhanced chromosomal aberrations and/or mitotic crossing over in vitro . Asymmetric hybrids can be obtained even from those combinations, which normally produce symmetric approach: Protoplast of one of the parental species are irradiated with a suitable dose of X-rays or gamma rays to induce extensive chromosome breakage.

8. Example :- Daucus carota + Aegopodium podagraria Daucus carota + Oryza sativa Daucus carota + Petroselinum Hortense Hyoscyamus muticus + Nicotiana tabacum D. Innoxia + Physalis minima Nicotiana tabacum + Daucus carota

9. CYBRID Cybrid – cytoplasmic hybrid. 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.

10. HISTORY In 1892 Klercker was the first to isolate protoplast from Stratiotes aloides using mechanical method. Cocking in 1960 was the first to report the isolation of protoplast from tomato root tips using concentrated solutions of cellulase from the fungus Myrothecium verrucosa. Enzymes for protoplast isolation was first employed by Takebe and his co workers in 1968. Kao and Michayluk in 1974 first proposed PEG for fusion of protoplast. Gleba 1979 fused tobacco protoplast which produced a cybrid.

11. 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.

12. NEED FOR CYBRIDS Production of full hybrids through protoplasts fusion of distantly related plants – unrealistic- wide spread instability of the two dissimilar genomes in common cytoplasm. Undesirable –exhibit structural and developmental abnormalities. Partial genome transfer – fusion of normal protoplasts of the recipient with enucleated protoplasts of the donor-cybridization.

13. ADVANTAGES 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.

14. Cybridization Possibility of injection of nucleus of A to B.

15. Aims of cybridization To obtain biological information on intra- and intergeneric transfer of organelles. To combine cytoplasm gene of one species to anther species which have nucleus with cytoplasm. This is also a way for those species which don’t perform to sexual reproduction with each other, so this way provided to facilitate to make a desire species with combination of both species.

16. Benefits Transfer of plasma genes of one species to nuclear background of another species. Production of wide range of genetic variations, sexually incompatible combinations. Useful for sterile plants. Mitochondrial gene also combined with chloroplast gens of another species. Plants like medicinal plant, crop plants, sterile pants, or many other valuable species also included in this.

17. Recent Examples of Cybrids

18. Production and molecular characterization of potential seedless cybrid plants between pollen sterile Satsuma mandarin and two seedy  Citrus  cultivars Cai, XD., Fu, J., Deng, XX. et al. Plant Cell Tissue Organ Culture (2007) 90: 275. https://doi.org/10.1007/s11240-007-9266-8 Cytoplasmic male sterility (CMS) is known to be controlled by mitochondrial genome in higher plants including Satsuma mandarin ( Citrus unshiu  Marc.). Citrus symmetric fusion experiments often produce diploid cybrids possessing nuclear DNA from the mesophyll parent and mitochondrial DNA ( mtDNA ) from the embryogenic callus parent. Therefore, it is possible to transfer CMS from Satsuma mandarin as callus parent to seedy citrus cultivars as leaf one by somatic cybridization.

19. Investigation of  Nicotiana tabacum  (+)  N. suaveolens cybrids with carpelloid stamens J ohn T.Fitter Mark, R.Thomas ChenNiu Ray, J.Rose (2005) Investigation of  Nicotiana tabacum  (+)  N. suaveolens cybrids with carpelloid stamens Journal of Plant Physiology Volume 162, Issue 2, Pages 225-235 To investigate cytoplasmic effects on homeotic floral morphology, Nioctiana tabacum and  N. suaveolens  protoplasts were fused and cybrids obtained to contrast with the sexual alloplasmic line Nta ( sua )S. Nta ( sua )S contains the nucleus of  N. tabacum  and cytoplasm of  N. suaveolens  while cybrids derive from fused cells where the cytoplasms can interact.

20. Introduction of transformed chloroplasts from tobacco into petunia by asymmetric cell fusion Sigeno , A., Hayashi, S., Terachi , T. et al. Plant Cell Rep (2009) 28: 1633. https://doi.org/10.1007/s00299-009-0763-6 An efficient regeneration system from the protoplasts of both the parents, and effectiveness of selection for the  aadA  gene with spectinomycin were established before the cell fusion. The results indicate the success in intergeneric transfer of transformed plastids of tobacco into petunia.

21. Production and molecular characterization of diploid and tetraploid somatic cybrid plants between male sterile Satsuma mandarin and seedy sweet orange cultivars Xiao, SX., Biswas, M.K., Li, MY. et al. Plant Cell Tiss Organ Cult (2014) 116: 81. https://doi.org/10.1007/s11240-013-0384-1 Symmetric somatic hybridization provides a new strategy for citrus seedless breeding by creating cybrids transferring mitochondrial DNA ( mtDNA ) controlled cytoplasmic male sterility (CMS) from the callus parent Satsuma mandarin ( C. unshiu  Marc.) to seedy cultivars.

22. PROTOPLAST ELECTROFUSION BETWEEN COMMON WHEAT ( Triticum aestivum  L.) AND ITALIAN RYEGRASS ( Lolium multiflorum  LAM.) AND REGENERATION OF MATURE CYBRIDS T. M. GE, X. H. LIN, F. L. QIN, S. W. YU, and Y. J. YU (2006) In Vitro Cellular & Developmental Biology - Plant 42(2):179-187. https://doi.org/10.1079/IVP2005742

23. Reference Singh. B. D. Biotechnology Expanding Horizons. Kalyani Publishers, New Delhi. p. p - 311-318.