Biotechnology in agriculture:

Biotechnology can be used in:

• Agro-chemical-based agriculture.
•  Organic agriculture.
• Genetically modified crop-based agriculture.

Green revolution has increased food supply because of:

• Improved crop variety.
• Use of agro-chemicals.
• Use of better management practices.

Genetic modifications of crop have resulted in;

• Made crops more tolerant to a-biotic stresses (cold, drought, salt, heat).
• Reduced reliance on chemical pesticides (pest-resistant crops).
• Helped to reduce post harvest losses.
• Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
• Enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice.

 

1. BT cotton:

• Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
• B. thuringiensis forms protein crystals which contain a toxic insecticidal protein.
• But it does not  kill the Bacillus itself because Bt toxin protein exist as inactive pro-toxins but
  once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals.
• The activated toxin bind with the epithelial cells of mid-gut and create pores that cause cell swelling and lysis (breaking down of membrane of cell by enzyme action or any other phenomenon) and eventually cause death of the insect.
• 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 the cotton bollworms, and cryIAb controls corn borer.

 

2. Pest resistant plants:

• A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. It is prevented by a process of RNA interference (RNAi).
• This method involves silencing of a specific mRNA due to a complementary dsRNA (double stranded RNA) molecule that binds and prevents translation of the mRNA called silencing of mRNA.
•  The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate through an RNA intermediate.
• Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant.
• The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells.
• These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA.