What is tissue culture ?
In essence, tissue culture is just a more sophisticated way of taking cuttings and growing them. The difference is in the size of the cuttings , that are much smaller and the speed at which they grow. This allows the commercial grower, starting from the same amount of base material, to get a lot more plants in a shorter time span.
Are OS-plants superior to TC-plants ?
OS (Original Stock): plants, obtained by manual division of the original plant.
TC (Tissue Culture): plants obtained by division of the original plant through tissue culture.
The answer is NO
If and when the process of tissue culture is carried out like it
should be, (starting from the correct base material, culling of plants
that show signs of mutation (sports), a TC plant is genetically
identical to the OS-plant.
Likewise, an OS division can show differences to the base material, because every hosta can produce mutations, even OS plants.
Tissue culture is basically the same as the manual division of a plant. Both are vegetative cloning techniques.
The OS hype seems to me nothing more than a marketing trick (How do I sell the same plant for 2 to ? times its actual value ?).
Hoe does tissue culture work ?
Tissue culture is carried out in 2 stages.
The propagation stage
First, the base material for the propagation is collected from the desired cultivar: the hosta buds, with a little piece of the crown still attached to it (preferably just before the leaves start to unfurl).
All leaves are removed, until all that's left is the centre of the bud, which contains the growing point. The harvested growing points are cleaned as thoroughly as possible, to reduce the chances on diseases, fungi and other infections. Afterwards, they are placed in a sterile breeding cell, in a jelly like growing medium, that contains a cocktail of hormones, that induces rapid growth and sprouting. The process of photosynthesis is kept going and speeded up by artificial light.
It takes the original growing tip about 7 weeks to become a bundle of mini buds. bundle is divided again, and every mini bud is placed in a breeding cell, to grow into another small bundle. This process is repeated until the desired number of plants is reached.
The rooting stage
When coming out of the propagation stage, the little plants barely have roots. They are placed in a growing medium that induces the rapid growth of a root system. This takes another 7 weeks, after which the process of tissue culture is ended.
The young plants still are very tiny and fragile; they are placed in a real soil (or peat) based potting mixture for the first time, and get the chance to slowly harden off. After one, two are three years they are ready for sale as liners. All plants from the same base materials together form one production line, hence the name liner.
Advantages of tissue culture
- fast propagation on a large scale of new cultivars, resulting in lower prices for the hosta enthusiast;
- because the base material is healthy and almost free of pathogens, and the complete process is carried out as sterile as possible, the end product will be al healthy
- because hostas tend to produce mutations quite regularly, and because of the speeded up propagation process, tissue culture will quite frequently produce new sports. These can be the start of yet another exciting new cultivar.
Disadvantages of tissue culture
- with the old method of manual division, a plant had to be grown for a long period of time before there were enough of them for commercial purposes. This gave the opportunity to destroy poorly growing and inferior plants. Before a plant is propagated through tissue culture, it should be kept under evaluation for a couple of years. When this stage is left out, inferior plants can make it to the market.
- when a TC line is started from base material that carries diseases, viruses, etc. the market can be flooded with contaminated plants.
- before, during and after the TC process, all the plants of a line should be checked regularly and thoroughly on aberrant plants. If there are any plants that are nor 100 % like the mother plant, they should be removed without mercy. If this culling isn't carried out with the necessary rigidity, aberrant plants will turn up in collections, plants that are not true to their name.