Biotechnology in Horticulture – SS2 Horticulture and Crop Production Lesson Note (First Term)

Biotechnology in horticulture is the use of scientific tools to change or copy plants in ways that nature would take a long time to do alone. The two main methods are tissue culture, which grows many identical plants from a small piece of a plant in a sterile jar, and genetic modification, which changes a plant’s DNA.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Explain what biotechnology means in horticulture.
2. Describe tissue culture and state its four steps.
3. State the advantages of tissue culture.
4. Explain genetic modification and give examples of GM crops.
5. List the advantages and disadvantages of biotechnology in horticulture.

What is biotechnology in horticulture?

Biotechnology in horticulture is the use of living cells and scientific tools to change or copy plants so that they serve us better.

• Bio: means “life”.
• Technology: means “tools” or the practical use of science.
• Simple picture: it is like giving a plant a “software update” so that it works better for us.

What are the key terms?

• Explant: the small piece of plant (such as a bit of leaf or shoot tip) used to start tissue culture.
• Nutrient agar: a jelly that supplies sugar, water, minerals and vitamins to the explant.
• Sterile: free from germs such as bacteria and fungi.
• Plantlet: a very young plant with tiny roots and leaves, grown in the jar.
• DNA: the material in every cell that carries the instructions for how the plant grows.
• Gene: one section of DNA that controls one trait, such as pest resistance.

What are the main methods of biotechnology in horticulture?

• Tissue culture: makes many identical copies of a plant.
• Genetic modification: changes the plant’s DNA by adding or editing a gene.

What is tissue culture?

Tissue culture is the growing of new plants from a small piece of a parent plant on a sterile nutrient jelly in a laboratory.

• A few cells from one leaf can grow into hundreds or thousands of identical plants.
• Every new plant is a copy (clone) of the parent plant.

How does tissue culture work?

• No soil: the explant is placed in a glass jar, not planted in the ground.
• Nutrient agar: the jelly in the jar has everything a baby plant needs: sugar, water and vitamins.
• Clean conditions: the jar, the jelly and the explant must all be free from germs.

What are the steps of tissue culture?

1. Sterilisation: wash the explant so that no germs or fungi grow in the jar.
2. Incubation: place the explant on the nutrient agar and keep the jar in a warm, bright room.
3. Multiplication: the tiny piece grows into a clump of cells, which then sprout tiny roots and leaves.
4. Hardening: when the plantlets are strong enough, move them from the “lab” to a greenhouse, and finally to the soil.

Why do we use tissue culture?

• Mass production: thousands of orchids or pineapples can be grown in a very small room.
• Disease-free plants: the work is done in a sterile lab, so the new plants start out healthy.
• Saving rare plants: if a beautiful flower is almost extinct, it can be saved using just one leaf.
• Identical plants: every plantlet has the same good qualities as the parent.
• Year-round supply: plantlets can be produced in the lab at any time, whatever the weather.

Which plants are grown by tissue culture?

• Orchids: grown in large numbers for the flower trade.
• Pineapple: many uniform plantlets for planting.
• Banana and plantain: clean planting material free from many diseases.

What are genetically modified (GM) crops?

A genetically modified (GM) crop is a plant whose DNA has been changed by scientists to give it a useful trait.

• Tissue culture: makes copies of a plant.
• Genetic modification: changes the plant’s DNA.
• Recipe picture: a plant’s DNA is like a recipe book. If a tomato is too soft, scientists “edit” the recipe to make the skin tougher so that it does not bruise during transport.

How is a GM plant made?

1. Scientists find a gene that gives the useful trait, such as pest resistance.
2. The gene is put into the cells of the plant.
3. The changed cells are grown into whole plantlets, often by tissue culture.
4. The new plants are tested for the trait and for safety before farmers use them.

What are examples of GM in horticulture?

• Bt crops: plants given a gene from a soil bacterium (Bacillus thuringiensis) so that they make a protein that harms certain insect pests.
• Golden Rice: rice given genes so that the grain makes beta-carotene, which the body turns into vitamin A, helping to prevent eye problems.
• Slow-ripening fruits: tomatoes changed to ripen more slowly, so that they keep longer after harvest.

What is the difference between tissue culture and genetic modification?

Tissue culture copies a plant without changing its genes, while genetic modification changes the genes of the plant.

What are the advantages and disadvantages of biotechnology?

Biotechnology brings real benefits to growers, but people also have concerns about it.

Advantages

• Fewer chemicals: if a plant can resist its own pests (GM), the farmer needs fewer expensive, poisonous sprays.
• Better nutrition: fruits and crops can be made to carry more vitamins.
• Food security: more food can be grown on less land, which matters as the population grows.
• Healthy planting material: tissue culture gives clean, uniform plants.

Disadvantages and concerns

• Cost: tissue culture labs are very expensive to build and run.
• Skilled workers: trained staff and constant clean conditions are needed.
• Environmental fears: some people worry that “super weeds” might grow if GM genes escape into the wild.
• Taste and tradition: some people prefer “old-fashioned” crops and worry about long-term health effects, although GM foods are tested strictly.

Classroom discussion

If you could give a mango tree one “super power” using biotechnology (like making it grow in the desert or making it taste like chocolate), what would it be? Why?

Evaluation

1. What is biotechnology in horticulture?
2. What is an explant? Name the four steps of tissue culture in order.
3. State three reasons for using tissue culture.
4. Explain the difference between tissue culture and genetic modification.
5. Give two advantages and two disadvantages of biotechnology in horticulture.

Assignment

Write short notes on two examples of GM crops. For each one, state one advantage and one concern.