- Although the contribution of the conventional breeding methods to the ornamental crop improvement had been very significant in building up the floriculture industry so far, yet ornamentals are a group of plants where biotechnology has made tremendous impact both scientifically and economically.
- The three key areas in which plant cell and tissue culture has direct application in ornamental horticulture are large scale propagation of elite clones from a hybrid or specific parent lines through micro-propagation and somatic embryogenesis, production of disease free propagules and meaningful development of plant varieties through cellular and molecular techniques in conjunction with the whole plant breeding.
- Biotechnology has been applied to flower crops for producing new flower colours and flower forms.
- The value addition may be in the form of changed architecture, promoting in vivo or in vitro propagation of recalcitrant genotypes, resistance to biotic and abiotic stresses, improved vase life or modification in flower colour, shape and period of blooming.
- Biotechnology can play a vital role in modifying these in terms of varietal development and multiplication and popularization of newly bred varieties.
- Techniques of biotechnology have long been used by the floricultural industry, in both propagation and breeding. Meristem culture and micro-propagation are used to generate virus-free, high- quality propagation stock by plant propagators.
- Breeders commonly use other tissue culture techniques to supplement breeding programs such as anther culture and embryo rescue.
Biotechnological techniques used in ornamentals:
Micro-propagation:-
- One of the major aspects of plant biotechnology is the production of a large number of identical individuals via in vitro cloning. The plants produced through this technique are uniform and true to type with distinctive characteristics of increased vigour due to their higher health status.
- By the use of axillary shoot proliferation methods, micro-propagation can be carried out successfully in chimeras, which are very important in ornamentals. It has been particularly useful in clonal multiplication of a naturally occurring mutants under in vitro conditions for their further exploitation in breeding programmes.
- The techniques of meristem culture are now being used worldwide on commercial scale for micro-propagation of almost all important genera of orchids, thus placing orchids within the reach of an average person.
Production of specific pathogen free plants:-
- Tissue culture is being used to produce virus free propagules and facilitate their mass propagation. Generally, ornamental plants are vegetatively propagated and the viruses and virus like pathogen are transmitted mechanically.
- Currently, the technology for production of disease free propagule is available for alstroemeria, carnation, chrysanthemum, dahlia, lilium, iris, freesia, gladiolus, hyacinth, etc.
Use of cellular and molecular techniques in development of plant varieties:
- Successful creation of variation is of prime importance for breeding plants of desired traits. Techniques like protoplast culture, somaclonal variation, limited gene transfer; embryo rescue techniques, anther culture, gametoclonal variation, etc. speed up the process of introduction and induction of variation at cellular level.
In vitro pollination and embryo rescue:
- The techniques of in vitro pollination appears to be very promising for overcoming pre-fertilization barriers to incompatibility and raising new genotypes. The most critical step of in vitro pollination technique is the development of viable seeds from ovules and ovaries following fertilization.
- Ovule culture holds a great potential for raising hybrids which normally fail due to abortion of embryo at a rather early stage.
- Embryo culture or ovule culture has proven useful in reducing the breeding cycles of new varieties where long dormancy or slow growth of seedlings resulting long breeding cycles. It is also being used to test seed viability.
- In case of lilium, alstroemeria, impatiens, helianthus, new varieties have been produced using the technique of in vitro pollination and embryo rescue to overcome the pre-zygotic and post-zygotic compatibility, respectively.
Another culture:
- In haploids, mutations can be easily detected as they have only one set of genes. These haploids can be picked up and their chromosome duplicated to get fertile diploids with all desirable mutations in a single generation.
- Haploidy offers an easier and faster approach for raising an isogenic pureline. It has been successfully used in petunia, begonia and lilies.
Protoplast culture:
- In plants where fairly distant speces can be crossed, it has always not been possible to obtain full hybrids between desired individuals because of sexual incompatibility barriers. In this respect, cell fusion offers an entirely new and potential approach to distant hybridization.
- Plant protoplasts represent the finest single cell system and offers exciting possibilities in the field of somatic cell genetics and crop improvement.
Somaclonal variation:
- Regenerants from tissue culture often show much genetic variation. Such variation induced by culturing condition is called somaclonal variation. It may result in some advantageous trait by mutation of a single gene. Somaclonal variants have been obtained in chrysanthemum, begonia, lisianthus and day lily.
Somatic embryogenesis:
- Somatic embryogenesis is the formation of embryo from a cell other than a gamete or the product of gametic fusion.
- Somatic embryogenesis is a powerful tool for the improvement of ornamentals, not only with regard to clonal propagation but for other biotechnological applications as well. It has been successfully exploited in the improvement of crops like anthurium, alstroemeria, gladiolus, iris, lily etc.
Genetic engineering:
- Genetic engineering in ornamentals assumes greater utility, as conventional breeding success is limited due to high ploidy level, large nuclear genome and long generation time.
- The first genetically engineered crops were petunia and chrysanthemum, both with altered flower colour. Plant genetic engineering relies on two processes
- The insertion of genetic material into plant cells
- The regeneration of plants from these cells.
Gene transfer techniques:
a. Agrobacterium mediated gene transfer.
b. Electrophoresis
c. Electroporation
d. Laser cell perforation
e. Microinjection
f. Liposome mediated gene transfer
g. Silicon carbide technique
h. Ultra sonication
DNA fingerprinting:
- DNA finger printing has been standardized in rose, chrysanthemum and rhododendron. It can be used for the correct identification of the cultivar.
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