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Somatic Hybridization in higher plants

Presented To: CoordinatorPresented By: Maryam RiazRoll No: M15-08Department of BotanyUniversity of The Punjab, Lahore

3Contents Hybridization Somatic Hybridization Need of somatic hybridization Somatic hybridization in higher plants Technique of somatic hybridization Brassicaceae Fabaceae Poaceae Solanaceae Citrus Family Importance of SH Limitations of SH Work in Pakistan Conclusion References

4Hybridization• Process of combining different varieties of organisms to create a hybrid• It may be

Interspecific Hybridizatio

n

Intraspecific

Hybridization

Intergeneric

Hybridization

Intrageneric

Hybridization

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Somatic HybridizationTechnique which allows the manipulation of cellular genomes by protoplast fusion.

6Need Of Somatic Hybridization

crossing barriers among plant species and in organelle genetics and breeding

Species barriers encountered in sexual hybridization

transfer of genes from wild species into the genes of crop plants

tool for the modification and improvement of polygenic traits

7Somatic Hybridization in Higher Plants

• Diploid protoplast have been used for somatic hybrids

• PEG is commonly used for inducing fusion• Somatic cells are produced only in early stages• Recently used in various crops within familyo Brassicaceaeo Fabaceaeo Poaceaeo Solanaceaeo Citrus family

8Technique of Somatic hybridization

Fusion of protoplast

Selection of Hybrid

cells

Identification of

hybrid cells

Regeneration of

hybrid plants

9Fusion of Protoplast• Also called somatic fusion• It is a fusion of two distinct forms of plant to form

a somatic hybrid• It may be achieved by

Spontaneous fusion

Mechenical fusion

Induced fusion

10Steps of Somatic Fusion

Formation of protoplast

Fusion of nucleus to

form heterokaryo

n

Formation of cell wall by hormones

Formation of somatic hybrids

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Enzyme treatment to dissolve cell wall

Chemical or electrical stimuli

Cell fusion

Cell nucleus fusion

Protoplasts

Plant leaf

Procedure for Protoplast Fusion

12Selection of Hybrids• Much time and effort is required• Based on visual identificationo Differentially stained protoplasts

Identification Of Hybrids• By observing morphology• By using PCR

Regeneration of Hybrid Plants• Fulfilment of all the conditions and

requirements for organogenesis

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Family Brassicaceae• Model family for somatic hybridization• Hybridization have been performed in Brassica genus• Resynthesis of Brassica napus, an intergeneric hybrid• Intertribal hybrid are also produced e.g., Raphanus x B.napus

Fig: Intertribal hybridization b/w Raphanus and Brassica

15Family Fabaceae

• Regeneration of plants was initially

troublesome• Now achieved in several genera

like Pisum,Trifolium,especially in Medicago• Flowering hybrids b/w Medicago

sativa & Medicago falcate• Intergeneric fusion b/w Onobrychis

viciifolia, Sanfoin & Alfalfa Fig: Flowering hybrids of Medicago spp.

16Family Poacae

• Somatic hybridization was initially difficult• Now several intergenric and intrageneric have been produced• e.g., Panicum maximum (+) Pennisetum americanum, Saccharum officinarum (+) P. americanum etc• Much work has been done on Saccharum spp.

Fig: Somatic plant regeneration of grass

17Family Solanaceae

• For disease & insect resistance in eggplant, Solanum melongena

• To restore the ploidy level and for viral resistance in potato

• In Tomato, several interspecific hybrid plants have been produced

• E.g., Tomato + Solanum etuberosum, Tomato + Nicotiana tabacum, Tomato + S. tuberosum etc

Tomato

Potato

Eggplant

18Citrus Family

• Somatic embryogenesis and plant regeneration are basic processes

• Production of allotetraploid somatic hybrids is most important

• For the recovery of cybrid plants

Fig: Citrus fruit varieties

19Importance of Somatic hybridization

• Introgression of traits from (wild) species into cultivars

• New combinations of nucleus and organelles for the creation of cytoplasmic male sterility (CMS)

• Provides an alternative approach to colchicine treatment

• Several interspecific and inter-generic hybrids with disease resistance

• Introduction of genes responsible for the tolerance of cold, frost and salt

20Limitations of somatic hybridization

• Does not always produce plants that give fertile and viable seeds

• Frequently associated with genetic instability• Production of viable somatic hybrids is not

possible in all instances• Limitations in the selection methods of hybrids• No certainty as regards the expression of any

specific character

21Work on Somatic Hybridization in Pakistan• Much work has been done in various research

institutes and labs• In Punjab University, much work on sugarcane• E.g., the protoplast cultures,• in vitro callus cultures of sugarcane, • electrofusion in sugarcane protoplasts • regeneration of sugarcane embryos

22Conclusion• Somatic Hybridization, a technique for the

manipulation of cellular genomes by protoplast fusuion

• Species barrier in sexual hybridization is encounterd

• Used in various crop production in higher plants• Produce genetic variability and disease

resistance in various crops

23References• http://www.yourarticlelibrary.com/biology/plants/hybridization-in-

plants-types-procedure-and-consequence-of-hybridization/23340/. 11/11/2016

• P. Aleza, A. Garcia-Lor, J. Juarez and L. Navarro. 2016. Recovery of citrus cybrid plants with diverse mitochondrial and chloroplastic genome combinations by protoplast fusion followed by in vitro shoot, root, or embryo micrografting. Plant Cell Tiss Organ Cult. [Vol.126]: 205–217

• Oluf L. Gamborg, F. Constabel, L. Fowke, K. N. Kao, K. Ohyama, K. Karthaa, and L. Pelcher. 1974. Protoplast and cell culture methods in Somatic hybridization in higher plants. Can. J. Genet. Cytol. [Vol.16]: 737-750

• Melchers. G and G. Labib. 1974. Somatic Hybridisation of Plants by Fusion of Protoplasts. Molec. Gen. Geneg. [Vol.135], 277-294

• Waara. S & K. Glimelius. 1995. The potential of somatic hybridization in crop breeding. Euphytica [vol.85]: 217-233, 1995

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