Plant Bio-Technology

Plant Bio-Technology, Biotechnology is a recent term that was coined for the first time around 1960s. It originated from Greek and French words (respectively);

“Bio” meaning life, and “Technology” meaning the “study of machines, tools and raw materials”.

The use of living organisms and their products for commercial purposes constitutes biotechnology. The first wine and bread makers could have been described as biotechnologists before the term “biotechnology” was coined (Bhojwani, 1990).

Plant Biotechnology (Plant Bio-Technology)

There are two possible definitions of the term plant biotechnology:

In sensu lato (or traditional)

This defines plant biotechnology as humans’ involvement in plant material by means of technological instruments in order to produce temporary effects (can’t be transferred to the next progeny).

In Sensu Stricto (or Modern)

This defines plant biotechnology as human involvement in plant material by means of technological instruments in order to produce permanent effects (which can be transferred to the next progeny). This includes gene manipulation and genetic engineering to obtain transgenic plants.

Plant genetic engineering is used to produce new inheritable traits by introducing external DNA to the plant material in an unnatural way. The outcomes are the transgenic plants or Genetically Modified Plants (GMPs).

The key instrument used in plant biotechnology is the Plant Tissue Culture (PTC) technique which refers to the in vitro culture of protoplasts, tissues, cells and organs. It consists of culturing cells or tissues in totally artificial conditions but unfortunately all the factors cannot be fully controlled often and it is not always possible to reproduce every in vitro procedure.

However, the PTC technique has the following main steps:

  1. The growth of microbe-free plant material in sterile (aseptic) conditions, such as in a closed test tube or container. This requires great care to maintain the aseptic conditions.
  2. The use of aseptic and known media, due to the involvement of many inorganic and organic components in the in vitro culture of plant material.
  3. The use of a growth room in which the environment (light and temperature) is controlled.

There has been unbelievable progress in the development of PTC technology over the past four decades. Nowadays PTC is the main protocol followed for plant biotechnology. It is used in:

  • Plant propagation or vegetative multiplication or cloning (Micro propagation), in addition to traditional grafting, cutting, layering and division methods.
  • Plant material and genotype conservation or plant material storage.
  • Improvement in plant health quality (plant recovery from virus).
  • Production of useful substances in pharmacology, agriculture and industry.
  • Plant breeding by somaclonal variation, selective pressure, the haploidy method, protoplast fusion and transfer of foreign DNA.
  • Research in plant biochemistry, plant physiology and plant morphology.

Initially the in vitro PTC technique was used to support the traditional or conventional breeding procedure in order to save time and/or to accelerate the evaluation of new genotypes. For some decades now, the use of this technique in breeding programmes has been increasing and it is actually considered more effective than the traditional ones.

Breeding Techniques

Breeding technique, in vitro culture can be divided into two groups (Taji, et al., 2002):

Traditional or conventional Breeding Technique

It induces variation or mutation in plant tissue by chemical and/or physical processes, by choosing the initial explant and the culture conditions (nutritive and environmental). Here there is no addition of external or new DNA to plant tissue and so variation is due to the new combination of DNA contained within the plant tissue. At present, three principal techniques are available to induce variation or mutation in plants, these are:

  1. Protoplast fusion,
  2. Haploidy methods,
  3. Somaclonal variation.

Nevertheless, two types of somaclonal variation are possible: heritable and epigenetic. The first is stable through the sexual cycle or repeated asexual (vegetative) propagation and may be defined as a mutation because it results in heritable alteration in the genotype due to a change in the structure of the genetic material of the involved plant tissue (i.e., DNA base sequence).

Epigenetic variation is unstable, even when asexually propagated, and disappears in the progeny or when the cause of variation stops.

In vitro breeding technique

It includes those techniques in which the new genetic combination is due to the deliberate and unnatural insertion of external DNA into the original plant genome with technological instruments. In other words, foreign DNA is inserted into plant material and so the plant becomes transgenic. To transport the DNA from donor biological material to host plant tissue, different biological vectors can be used (i.e., Agrobacterium, plasmids, virus) as well as chemical and physical methods (biolistic system, protoplast fusion, somatic hybridization, electroporation, electrofusion, microinjection). Regenerated plants from the new genome combination obtained by these innovative in vitro culture techniques are known as GMPs, which are included in the larger category of GMOs (Genetically Modified Organisms) and the techniques used are also called genetic engineering.

Without considering the vector used to transfer DNA between biological (plant) material, the general procedure for obtaining and using transgenic plants involves the following steps (Rosu,

1999):

  1. Gene location and isolation from donor,
  2. Gene cloning,
  3. Gene insertion into the host plant tissue,
  4. Transgenic plant regeneration,
  5. Genetic characterization and marker-assisted selection,
  6. Placing on the market procedure (including effects on the environment and on animal and human health),
  7. Commercial development.

Therefore it is necessary to have an effective procedure for plant regeneration from the modified callus of the species involved in the breeding programme.

Bio-tests and bioassays carried out using the PTC technique could be considered an efficient method for the evaluation of:

  • Agrochemical disturbance to crops (i.e., herbicides, growth regulators, pesticides),
  • Effects of the environment on plant growth and metabolism,
  • Response of plants to various stimuli.

References:

  • Bhojwani P. 1990. Plant tissue culture: applications and limitations. Amsterdam, Elsevier science publishers, 461p.
  • Rosu A. 1999. New trends in agrobiotechnology education. Temp us-phare cme 03066-97. Bucharest, International Conference, March 15-22nd 1999, 94p.
  • Taji A., Kumar P. P., Lakshmanan P. 2002. In vitro plant breeding. London, Hayworth press, 167p.

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