Plant Breeding

Question 1

What breakthroughs did Norman Borlaug do?

Answer 1

Developed high yield wheat varieties in Mexico
Fertiliser was used due to poor nutrient conditions, so wheat was mainly imported
If there was a heavy seed head, the stem would snap
Semi-dwarf spring wheat was made by crossbreeding and planted in north mexico
Variants insensitive to light for short daylight hours

Question 2

How is unintentional gene transfer prevented?

Answer 2

Maize has male and female parts so can self-fertilise, making hybrids difficult
Cmst line is male sterile and doesn’t produce viable pollen
Antners removed prior to crossing to emasculate the plant

Question 3

How has unintentional gene transfer affected plants?

Answer 3

Made crops in the US more susceptible to Southern Corn Blight

Question 4

What UN sustainable development goals are biotech crops meant to help with?

Answer 4

Zero hunger- population predicted to be 10 billion by 2050. 800 million people on earth without sufficient food
Good health and well being
Sustainable communities
Responsible consumption and production
Life on Land

Question 5

Explain marker assisted breeding

Answer 5

Traits from a donor line are put into an elite line
Markers are normally DNA in a known map position
Elite line and donor lines are crossed until undesirable genes are eliminated
By backcross 6, lines contain >99% DNA, so desired region of donor should integrate in DNA

Question 6

How has marker assisted breeding improved crops?

Answer 6

SUB1 rice is resistant to submergence
If they have time to adapt, they can survive. Otherwise flash floods kill it.
4 million tonnes lost to flooding in Bangladesh and India

Question 7

Describe mutational breeding

Answer 7

Make new alleles via mutagenesis
Not considered GM as no new genetic material introduced
Mutagens include gamma rays, thermal neurons, x rays and sodium azide (A-T -> G-C)

Question 8

What examples of mutational breeding are there

Answer 8

Semidwarf Rice Calrose 76’
Sd1 genes downregulated with gamma ray mutagenesis
Limited as it is not targetted and only affects genes in the pangenome

Question 9

What is introgression?

Answer 9

Artificial hybridisation
Crossing closely related species to create genetic variation
This can be done within species or between species.

Question 10

What is TILLING?

Answer 10

Switching out a homologue of a plant genome
Can identify mutants and new alleles in targets
No transgenic DNA, so not GM
Uses reverse genetics
Different mutagens favoured in different plants

Question 11

How is tilling done?

Answer 11

1. M1 plant is mutated
2. M2 seeds have DNA extracted on a 96-plate well and northern blot
3. Samples categorised with PCR