Improving Plants through Tissue Culture
More than micro-propagation, the field of controlled management and breeding of plant germplasm at the cellular level has received more impetus from this technology. Plant tissue culture techniques have greatly enhanced the ability of todayâ€™s industry to break, arrange and reorganize the constituents of higher plants. The commercial viability of this technique has been demonstrated in case of a number of model systems evolved today. However, a great deal of basic research has been already carried out on ornamental trees and shrubs with a view to develop new varieties of better landscape plants.
Selection of Plants with Better Capabilities of Stress and Pest Resistance
In fact, the most widely researched segment of tissue culture today is the idea of selecting advantageous varieties of plants that possess better capabilities of stress, disease and pest resistance. While the process of selecting and developing superior individuals has resulted in remarkable gains in the adaptability of a number of plant species, the search for superior individuals is accelerated, made easier and highly dependable by vitro systems. These systems endeavor to exploit the phenomenon of natural variability observed in plants. Alternatively, variability in plants can also be induced by chemical or physical agents that cause mutations in plants.
Plant tissues grown in vitro can be freed from the whole plant through the process of callus formation. If the resulting cells are exposed to a stress or susceptibility condition, only the tolerant ones survive while the susceptible ones are killed. This idea can be applied to a number of stress conditions as well as to achieve resistance to fungal and bacterial pathogens and phyto-toxic chemical agents. The process of selecting resistant cell lines help in reorganizing whole plants that can retain the resistance criteria selected. Some of the major achievements in this arena include selection of salt tolerant varieties of tomato, evolving tobacco plants that are resistant to freezing conditions and developing agronomic crops that are resistant to herbicides besides cultivating various plant species with improved resistance to pathogens.
Tissue Culture to Evolve Pathogen-free Plants
Plant tissue culture is the ideally suited technique to obtain, maintain and propagate pathogen-free plants in a commercial scale. The conventional system of labeling pest-free plants is akin to the idea of applying tissue culture as a selection process. Under this process, plants tested and reported free of pathogens like virus, bacteria and fungi are manually selected as explants for tissue culture. Most commonly, the apical domes of fast growing shoot tips are selected for this process and are grown under sterile conditions in vitro culture. The plantlets that result in the process are tested for the presence of pathogens and indexing is done. Those cultures indexed to be free of pathogens are maintained as explants stock.
Somatic Hybridization refers to the process of fusing plant cells gathered from different plant species that are incompatible for sexual crosses. Somatic Hybridization achieved through plant tissue culture makes it possible for plants to take in and incorporate in them foreign genetic codes in order to significantly extend the realms of plant modification. Somatic Hybridization employing plant tissue culture technique makes use of plant protoplasts. Protoplasts can be understood as single cells that are stripped of their cell walls by enzymatic treatment. A single leaf of a plant treated in this manner can yield several millions of single cells with each one of them capable of producing a whole plant eventually. The main concept underlying this technique is that plant cells stripped off their walls and brought into close contact tend to easily fuse with each other. Therefore, this method can overcome the limitations in plant breeding where it is rather impossible to hybridize species that are incompatible with each other. Though the concept is yet to be proved practically, the theory means that there is an infinite scope to evolve innumerable varieties of plants using this method.