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The following points highlight the top eight practical applications of protoplast culture.
Application # 1. Production of Somatic Hybrids:
To overcome the sexual incompatibility barriers the protoplast fusion programme may be taken to obtain the interspecific and inter-generic hybrids. For example, the fusion between Lycopersicon esculentum (tomato) and Solanum tuberosum (potato) have been possible to obtain the somatic hybrid ‘Pomato’, at inter-generic level.
Similarly attempts to overcome the conventional breeding barrier between many species of Oryza have been possible through this process. The interspecific somatic hybrids have been obtained through fusion with many wild species of Oryza like O. brachyantha, O. eichingeri, O. officinales, etc.
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Many asymmetric hybrid have also been developed when there is partial fusion, i.e., these somatic hybrids do not contain the total complete set of chromosomes of both the parents, rather there are variation in chromosome number of different somatic hybrids obtained.
Application # 2. Somatic Hybrids with Specific Alien Gene:
(a) Gene for Disease Resistance:
There are many disease resistance genes available among the wild varieties of Solanaceae and Brassicaceae. So many of the protoplast fusion programmes have been done among the wild and cultivated varieties of Brassicaceae and Solanaceae successfully.
For example, the disease resistance gene has been successfully transferred to Lycopersicon esculcmtum from a wild relative Solarium orchranthum, a woody vine yielding tomato like fruit.
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Resistance to blackleg disease (Phoma lingam) has been found in Brassica nigra, B. juncea and B. carinata, the symmetric and asymmetric hybrids between these gene donors and B. napus, the resistant somatic hybrids have been developed.
(b) Abiotic Stress Resistance:
The fusion programme for transfer of abiotic stress resistance property has been mainly done on families like Fabaceae, Brassicaceae, Poaceae and Solanaceae. The somatic hybrids between Solanum lycopersicoides and Lycopersicon esculentum showed cold tolerance, the somatic hybrid between Solanum tuberosum and S. acaule developed disease resistant characters.
(c) Quality Characters:
Somatic hybrids between Brassica sp. and Eruca sativa i.e. Erucobrassica showed low erucic acid content which has been used further to transfer the low erucic acid gene into the cultivar variety by conventional breeding programme. The high nicotine content has been obtained in Nicotiana tabacum from N. rustica by this fusion programme.
Application # 3. Production of CMS Line:
Cybrid production programme has become very much useful to transfer the agronomic traits which are encoded by cytoplasmic genome such as cytoplasmic male sterility character or the herbicide resistance property, etc. Cybridisation has been successfully used to transfer the CMS in rice, Brassica and Chicory. Resistance to herbicides (atrazine) and antibiotics as well as CMS has been successfully introduced in many cultivated species of Brassica.
Application # 4. Production of Unique Nuclear-Cytoplasmic Combination:
Though the protoplast fusion programme results into the mixing of both nuclear and cytoplasm of both the parents initially but during developmental process sometimes some nuclear material may get eliminated as also the cytoplasm of one parent may predominate.
In such cases the newer combination of nucleus and cytoplasm may develop some novel and unique germplasm which is not possible through conventional breeding programme.
Application # 5. Production of Autotetraploid or Allotetraploid:
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Somatic hybridisation can be used as an alternative way to obtain the tetraploid without the use of colchicine, i.e., fusion within the same species yield autotetraploid and between different species easily result into allotetraploid.
Application # 6. Production of Heterozygous Line:
In case of vegetatively reproducing crop the protoplast fusion programme may be an useful way to produce heterozygous line, as there the general sexual breeding cannot yield potential result.
Application # 7. Production of Fertile Diploid and Polyploid from Sterile Line:
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When sterile line is obtained through some conventional breeding programme then either by partial fusion or by cybrid production the fertile diploid or by total fusion the polyploid line can be raised.
Application # 8. Production of Hybrid at the Juvenile Phase:
Even before reaching the reproductive stage the protoplasts from the parental plants can be used to obtain the somatic hybrid or cybrid.
