Biotechnology application in Agriculture

The three options that can be thought of increasing food production are,

• Agro-chemical based agriculture
• Organic agriculture; and
• Genetically engineered crop-based agriculture.

The Green Revolution has succeeded in tripling the food supply but yet it was not enough to feed the growing human population. Scientists have decided that use of genetically modified crops is a possible solution.

Plants, bacteria, fungi, and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO).  Genetic modification has;

• Made crops more tolerant to abiotic stresses
• Reduced reliance on chemical pesticides
• Helped to reduce post-harvest losses
• Increased efficiency of mineral usage by plants
• Enhanced nutritional value of food, eg., Vitamin ‘A’ enriched rice.

Bt Cotton:

Some strains of Bacillus thuringiensis produce a toxic insecticidal protein.  The Bt toxin protein exists as inactive protoxins but once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilizes the crystals.  The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and eventually cause the death of the insect.

Bt toxin genes were isolated from B. thuringiensis and incorporated into the several crop plants such as cotton.  The toxin is coded by a gene named ‘cry’.  There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control bollworms and cryIAb controls corn borer.

Pest Resistant Plants: A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield.  A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi).  This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).

Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant.  The introduction of DNA was such that it produced both sense and antisense RNA in the host cells.  These two RNA’s being complementary to each other formed a double-stranded (ds DNA) that initiated RNAi and thus, silenced the specific mRNA of the nematode.  The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA.  The transgenic plant, therefore, got itself protected from the parasite