Creating new plant varieties

In a nutshell

Plants can be bred for desirable characteristics such as disease resistance. This can increase yield and therefore the amount of available crop. Traditional breeding methods involve selecting desirable characteristics and transferring pollen. Newer techniques involve DNA analysis.

Selective breeding

Definition

Selective breeding is when plants are bred for certain beneficial characteristics that increase yield and improve the quality of food crops.

Examples

Some of the beneficial characteristics include:

Disease resistance.
The ability to grow and mature quickly.
Having a distinctive taste, aroma or colour.
Having a long shelf life or being able to be stored well/frozen.

Selective breeding allows crop growers to plant large areas with identical plants to give maximum yields. This means the crops are genetically identical. This can be an issue if there is an environmental change as the whole crop could be lost. Selective breeding has had a huge impact on the world's food production.

Traditional plant breeding

During traditional plant breeding, a plant with a desirable trait is crossed with another plant that has the same or another desirable trait. These plants would be from a mixed population or existing varieties.

Pollen is transferred from the flowers of one plant to the other, the plant is then prevented from self-fertilising or being cross-pollinated by another plant. This process is repeated over several generations until the plants breed true for the selected desirable trait. Plants in horticulture (the care of gardens and plants) are bred for the size and colour of their flowers.

Example

Clematis is a wildflower that grows in hedgerows and up trees. In the $19^{th}$ -century plant breeders across Europe raced to breed varieties with the largest, most colourful flowers.

Producing a new plant variety

It can be very difficult to combine multiple desirable characteristics into a plant as well as very expensive. A traditional plant breeding programme will take $12-15\ years$ . It involves the selection and crossing of suitable individual plants, various selection processes and a series of trials.

Biology; Global challenges; KS4 Year 10; Creating new plant varieties

1.	A male flower.
2.	Pollen.
3.	A female flower.
4.	A fertilised female flower (hop cone) whose seeds are collected and grown (A).
5.	$20,000$ hop plants.
6.	The plants are then exposed to a fungal disease called downy mildew (B) and the $4000$ most resistant hop plants are selected.
7.	The plants are then exposed to powdery mildew (C) and the $2000$ most resistant hop plants are selected. They are then grown in field trials (D).
8.	$200$ hop plants that are selected for best growth.
9.	$20$ hop plants are selected for bitterness (E).
10.	The plants are tested for hop yield.
11.	The plants are tested for tolerance to a fungal disease known as wilt disease.
12.	The hop plant is tested on farms on a large scale.
13.	The hop plant is tested for brewing.
14.	The potential variety is checked to ensure it is new (F) and then the new hop variety is registered.

New techniques

Many plant scientists now use marker-assisted techniques to breed plants. This involves identifying genetic markers in a plant's DNA that are associated with important characteristics such as nutritional qualities, disease resistance and yield.