L9- Plant Biotechnology

Question 1

What are the challenges faced by agriculture today?

Answer 1

• In the next 50 years we will need to produce more food than in the whole of human history & do it on the same amount of arable land
• Climate change

Solution:
- to produce food more efficiently (increase yield in a sustainable way)

Question 2

Discuss how traditional plant breeding and genetic engineering differ?

Answer 2

CONVENTIONAL SELECTIVE BREEDING (classical):

• Many genes are transferred with the desired gene (including genes responsible for unwanted characteristics)
• Goal: to meet food, feed, fuel and fibre needs of the world

GENETIC ENGINEERING (modern):
* Only the desired gene is transferred to a location in the recipient
Goal: to increase the effectiveness and efficiency of plant breeding

Question 3

Plant breeding: Conventional method

Answer 3

• Limited to exchanges between the same or very closely related species
• Little to no guarantee of any particular gene combination from the million of crosses generated
• Undesirable genes can be transferred along with desirable genes
• Takes a long time to achieve desired results

Question 4

Plant breeding: Genetic Engineering

Answer 4

• Allows the direct transfer of one or just a few genes, between either closely
• Crop improvement can be achieved in a shorter time compared to conventional breeding
• Allows plants to be modified by removing or switching off particular Genes

Question 5

Characteristics of an ideal herbicide

Answer 5

Herbicides affect biochemical functions specific to plants (such as photosynthesis or essential amino acid biosynthesis) which are common to all plants

• > Not kill animals
• > Be biodegradable
• > Kill weeds but not crops

Question 6

How plant biotechnology is used to engineer herbicide-resistant crops

Answer 6

Herbicide selective- making crop tolerant to herbicide
Two ways:
- Changing properties of target protein
- Introduction of detoxifying enzyme

Changing properties of target protein:

• Addition of a mutant gene that encodes the target protein but is not sensitive to herbicide
• > glyphosate inhibits enzyme EPSPS in the biosynthesis of essential aromatic amino acids
• mutated gene inserted in plant no longer binds, so does not get affected by herbicide

Question 7

Advantages of how plant biotechnology is used to engineer herbicide-resistant crops

Answer 7

• Improves weed control
• Improves farm efficiency ($)
• Reduce crop injury
• Encourages adoption of no-till

Question 8

How has biotechnology been used for pest resistance and what are the advantages of this approach?

Answer 8

Bt toxin

• Protein found in bacterium Bacillus thuringiensis (Bt) spores with potent insecticidal activity
• Took this gene from Bt toxin and inserted it in the cotton, potato and corn plants
• insect ingests portion of the plant and dies
• Bt cotton, corn and potato can protect itself from insects

Commercialisation of insect resistant crop

• Decrease in use of chemical insecticides
• Reduce the exposure of farmers
• Reduce chemical residues in the environment

Question 9

Example of plant biotechnology to improve food quality

Answer 9

Quality traits
- Texture, colour, flavour, ripening, shelf life, removal of unwanted characters

FLAVR SAVR tomatos

• Reduction of cell wall-degrading enzyme (polygalacturonase) activity with an antisense gene construct
• > more resistant to cracking and mechanical damage than normal varieties
• > FLAVR SAVR don’t need to be picked until a later stage of ripening when flavour is better
• > These tomatoes yield extracts with the commercially desirable characteristics of higher viscosity and high solid contents