Week 12 - Increasing Yields, Selective Breeding, Controlling Pests and Environmental Management

Exercise 4.2

Lesson 4.2: New Plant Varieties are Developed by Selective Breeding

ACTIVITY A: Selective Breeding

Required Readings

Science in Action 7
pages 156 to 159
or
Science Focus 7
pages none

The world's first farmers learned many years ago that if they saved the seeds from their crops and planted them, they would get new crops similar to the old ones. They also realized that they could improve their domestic plants by choosing which ones to breed. For example, a farmer might choose to plant the seeds of only the largest carrots when planting his crop. When this process was repeated year after year, the farmer would gradually develop a carrot that on average grew larger than did the previous ones. Such deliberate alteration of particular traits is called selective breeding.

Selective breeding is as important for increasing yield as is modifying growing conditions. If human needs are to be sustained, selective breeding and genetically modified plants are necessary.

In western Canada in the 1800s, farmers had difficulty producing wheat, because the varieties that were available grew best in European conditions. Since the growing season in Canada is significantly shorter, these crops were frequently destroyed by frost before any grain had been produced. This problem was solved by Canadian Charles Saunders, by developing a variety suited to Canadian climates. Saunders' variety is called Marquis, which grows and ripens in as little as 100 days, reducing the crop loss due to frost. This variety was first available in 1909, and by 1920, 90% of wheat grown in western Canada was Marquis wheat.

Plants are selectively bred for a variety of reasons, depending on the characteristics which are desired. For example, if the plant is to be used for food, it could be bred for taste and appearance. If it's a rose or an ornamental flower, it could be bred for beauty and fragrance. Selective breeding means that people chose specific plants with particular characteristics, and encourage these plants to reproduce.

One of the most controversial topics currently in the news is that of genetically modified foods. Genetic modification is a type of biotechnology that focuses on particular genes in plants (genes are what give living organisms particular characteristics, located in cells). This technique allows plant producers to achieve the same goals as traditional selective breeders in much less time with greater selectivity. Some examples of genetically modified plants include fruits and grains that have been made resistant to viruses or pests. Genetic modification is controversial because of the potential effects on the food chain by altering characteristics within species.

ACTIVITY B: Apple Variety Investigation

Required Readings

Science in Action 7
pages 64 to 67

Science Focus 7
pages 116

There are many variety of apples produced around the world. Some are produced commercially and some are grown locally in our backyards. Different apples have different characteristics. What are the characteristic that you look for in an apple. This may depend on what you want to use the apple for. If you plan to bake with the apple, you may want a more tart apple. If you want it for fresh eating you probably want a sweet apple that does not bruise easily. In some other applications you may be looking for apples that last a long time in storage. In this activity, we will look at the characteristics of different apples that can be purchased locally.

QUESTION

Which characteristics are bred for in apples?

HYPOTHESIS

Form a hypothesis about which apple will perform the best. Remember to explain the reasons for your statement as well.

MATERIALS

Small Knife

Oven

Baking Pan

Aluminum Foil

Oven Mitts

Several varieties of apples (2 of each variety)

Small paper lunch bags (1 per apple variety)

PROCEDURE

1. Observe the general appearance of the apples. What is the colour of the exterior and the inner pulp. Are there any blemishes in or on the apple?

2. Cut one apple of each variety into 6-8 slices. Leave the other apple whole.

3. Taste one or two slices of each apple and rate their flavour and juiciness on a scale from 1 to 5 (5 is the best).

4. Wrap the remaining apple slices in some aluminum foil. Do not add butter, sugar, or spices. Put the packets on a baking tray and bake the apples at 350 degrees F for 30 minutes.

5. Remove from the oven with oven mitts and let them cool for 2 minutes.

6. Record their texture, appearance, and taste after being removed from the oven.

7. Take the remaining whole apples and place each one in its own paper bag. Label each bag with the apple type and leave them on the counter or in a cupboard for one week. Observe the characteristics of the apple after a week has gone by.

Exercise 4.2 - Apple Variety Investigation