cybrids are the somatic hybrids.

1. z
CYBRIDS

2. z 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.

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 .

5. • 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.

6. • 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.

7. • 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.

8.  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.

9. • 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

10. • 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.