Asexual or vegetative propagation
This involves the use of parts of plant in multiplying the plant, parts of plant such as roots, stem and leaves can be used instead of seeds. For example, the root can be used to grow breadfruit and potato.
The leaf can be used to multiply the plant Bryophyllum. Crops such as cassava and sugar-cane can be grown from stem.
Methods of Asexual or Vegetative Propagation: There are several methods of asexual or vegetative propagation. These are:
1. Budding 4. Layering
2. Grafting 5. Marcotting
3. Cutting 6. Others.
Budding: This is the bringing together of the bud and stock. The bud is taken from a tree already producing or matured. This forms the bud stick or slip. The stock is a young plant of about a vear old.
During budding, a T-shaped cut or inverted T-shaped is made at about 45 cm from the ground on the stem of the stock plant. The cut shape is slightly raised to expose the cambium. The bud is carefully slipped into the raised bark and pressed firmly to ensure that the cambia of both bud and stock unite together.
It is tied with plastic material, or any device to hold it in place. This should be done quickly to prevent the bud from drying. Air and water should be prevented from the cut until the bud has taken\’ or heal together with the stock. This will show when the bud remains green.
The bud then shoots after some days. When it becomes well established, the part of the stock above the bud should be cut-off. The cut surface should be to avoid fungal or bacterial infection. It is commonly used in citrus.
2. Grafting: This is the union of the stock and scion. The part of the plant whose root is in the ground is called the stock while the part removed from other plant is called scion. The scion is normally attached to the stock for grafting to take place. The two plants must be of the same closely related species. The plant should be of the same age and size for grafting to be possible.
Both plants are cut in a slant or V-shape to provide good surfaces for contact. They are then tied together with plastic tape or any device to keep them in place. The junction is rubbed with grafting wax to prevent the entrance of air water and pathogens. It is advisable to water until when the wrapping may be removed after two weeks.
Advantages of budding and grafting:
1. They are used to bring good qualities in two crop species together. Examples are high yiejd, taste and resistance to diseases.
2. They are used in perpetuating clones.
3. Bdded plants mature very early. This is because the bud tends to assume the age of the parent plants.
4. They produce plants with uniform qualities.
5. They take the advantages of the roots of a more resistant stock to thrive.
6. Destroyed parts of a plant could be replaced by graft-tag.
3. Layering: This involves bending a shoot or branch of a plant to the ground so that the nodes can make contact with the soil. It is then pegged below the ground and covered with rich soil to provide good medium for root development.
4. Cutting: This involves the use of mature stem or branch stem to propagate plants. This is a very common method of many crops such as cassava, ixora. coton and sugar-cane. The plants produced, have the same characteristics as the original plant from which the cuttings were obtained. Cuttings can be obtained from soft wood as in sweet potato, semi hard wood as in cassava and hard wood as in hibiscus plant. they should be cut from stems that have started to harden. The cutting should be about 20 cm long or convenient length, with two to three nodes or buds. It should be put into the ground to enable it have contact with the soil.
It should be watered after planting or raised in shade during dry periods or planted during the rains.
5. Marcotting: Marcotting is a practical vegetative propagation method. In this practice, the bark of a branch is peeled off with a knife, up to a considerable length. This should not be more than 5 cm long.
Soil rich in organic manure is tied to the peeled portion by means of coconut husks or any suitable device. It is watered to keep moist always. After a time, roots will grow out of the peeled portion.
As the roots become strong enough, the branch is cut off the plant. The rooted branch is planted into the soil to give rise to a new plant.
It is used for plants whose cuttings do not produce roots easily. It is employed in fruit crops such as lemon and man no as well as shrubs.
6. Other methods: Some plants are grown or propagated means of suckers as in pineapple and plantain, tubers as in yam, under-ground stem (corms) in cocoyam, bulbs in onion. Vines (runners) in Irish potato. Some are grown from rhizomes as in grasses and ginger with horizontal underground stems, containing nodes and internodes. Also, the roots of plants can be used as is the case of breadfruit-and carrot and cut leaf as in the case of bryophyllum.
Advantages of vegetative propagation:
1. It enables crop to produce in very short time e.g. citrus.
2. Plants propagated vegetatively have uniform growth rate.
3. They can stand a more adverse environmental conditions e.g. poor soil.
4. Plants that do not produce viable seeds can be propagated by this method.
5. The offspring are identical to the parent plant always
6. It is easy to obtain planting materials.
7. Many flowers or ornamental plants are easily grown with the method.
Disadvantage of vegetative propagation:
1. It is sometimes very laborious because planting materials are bulky.
2. Diseases are easily transferred from parent to offspring.
3. Vegetative parts of plant cannot be stored for a long time for planting.
4. Genetic improvement of crop is impossible.
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1. Outline the various methods of crop propagation.
2. State Three advantages and disadvantages of seed or sexual propagation.
3. Enumerate Five types of vegetative propagation of crops.describe any Three of such methods.
4. State four advantages of budding and grafting as methods of vegetative propagation.
5. What are the advantages of vegetative propagation of crops?
6. Write short notes on the following:
i. Vegetative propagation
7. (a) Describe layering as a vegetative method of crop propagation.
(b) Mention some crops that can be propagated by layering.