Plant propagation is the process by which new plants grow from various sources, including seeds, cuttings and other plant parts.  Plant propagation may refer to both man-made and natural means.

Types of propagation

• Sexual propagation: occurs through the natural growth of viable seeds.
• Asexual propagation: allows for the creation of new plants using cuttings from vegetative parts, like the roots, leaves, and stems.

Treatment of planting materials

• Seed dressing –coating seeds with pesticides e.g. copper Sulphate.
• Chitting or encouraging sprouting e.g. in potato seeds.
• Inoculation, usually done legumes where seeds are coated with right bacterial for nodule formation.
• Hot water treatment against viral diseases e.g. in sugarcane and cassava.

 Selection of planting material

In order for a farmer to reduce the expenses the need to select the planting material that he is sure of.

Characteristics of a good planting material

1. Should be readily available within locality to reduce transport expenses and time wasted in looking for it.
2. It should be pest and disease free to reduce the transmission of such diseases and pest to the seedling.
3. It should be easy to transport i.e. should not be bulky.
4. In case, of seeds should be of uniform size and shape to allow easy mechanization during planting.
5. It should be easy to store so that it can used in future when needed.
6.   In case of seed, they should have passed the dormancy stage.
7. The planting material should be highly viable to reduce the costs involved in filling up the gaps where they did not germinate.
8. Seeds should be of uniform color to allow easy sorting and planting.
9. The planting material should be of high proven performance give high returns once planted.
10. Materials should be free from contamination by weeds.
11. Should be free from mechanical damage.
12. In case of seeds, should be large enough.

 Seed propagation

This is where seeds of mature plant having desirable qualities are used for planting.

Advantages of propagation from seeds

1. Seeds are not bulky and therefore are easy to handle and convenient to transport.
2. They can be stored for a long time while retaining viability
3. Seeds are easy to treat against pest and seed bone diseases
4. Seeds are easy to use during machine planting.
5. Seed planting is a quick method of increasing a crop population in a short period.
6. Some crops are difficult to plant from vegetative parts.
7. Plants raised from seeds have a longer life span than those raised by vegetative means .

Disadvantages of propagation from seeds

1. Some seeds are delicate hence difficult to handle during planting.
2. Seeds require special field preparation before planting more especially those with small seeds.
3. The method may introduce undesirable in the plant population.
4. Some seed may not breed true to type hence disappoint farmers
5. The formation of seeds requires special condition during pollination and fertilization.
6. Due to interference during pollination seeds may be formed but of a high degree of variability.
7. Crops raised from seeds take a longer time to mature.

Vegetative propagation

This is the reproduction of plants from plants part that are not associated with reproductive organs.

Advantages of vegetative propagation

1. The offspring is similar to the parent in all ways hence preserve good mother characters.
2. Offspring grows faster and mature early.
3. Offspring are strong and hardly compare with seedling obtain from seeds.
4. Vegetative propagation is the best way for propagating plants with no viable seeds.
5. Daughter plants obtain food from their parents until they are sufficiently strong hence increasing chances of survival.
6. Multiplication of the plant population is faster
7. Over comes the problem of prolonged dormancy in some seeds.
8. Offspring require less care.

Disadvantages of vegetative propagation

1. No genetic variation
2. It may cause overcrowding due to the ability to establish quickly and grow fast.
3. The planting materials are quite bulky and therefore difficult to handle store and transport.
4. Due to their high moisture content vegetative materials are difficult to store.
5. Some vegetative methods of propagation are complex and hence need a lot of skill to execute.
6. A small hectare can be covered during planting as compared to seed propagation.
7. Difficult to mechanize.

Methods of vegetative propagation

1. Layering –              Mainly used in passion fruits.
2. Grafting –              Used in most fruits like citrus, avocado, mangoes etc.
3. Budding –              Can be used in fruits also like citrus.
4. Tissue culture– group of cells are developed into a new plant or plants

5   Use of storage structures

1. Bulbs                    –     Used in onions and garlic.
2. Bulbils                 –      Used in sisal
3. Suckers               –      Used in banana and pineapple
4. Rhizomes.          –      Used in ginger
5. Runners              –      Used in strawberry
6. Corms                 –       Used in cocoyam
7. Splits                    –     Used in pyrethrums
8. Stem tubers       –     Used in Irish potatoes.
9.  Cutting                 –   Used in cassava sweet potato, clonal coffee.

 

GRAFTING

This is where two different stems are united in woody plants.  The upper part of the union is called a scion while the lower part is called a stock.

Principles of grafting/consideration for successful grafting

For successful grafting, there are about five principles which must be adhered to;

1. Compatibility – The scion and stock must be related or close to facilitate sexual hybridization.
2. Cambial alignment – The cambium of the scion and root stock should be aligned for the union form.
3. Timing of the grafting operation – Grafting must be done at a time when the root stock is in a proper physiological state.
4. Avoiding desiccation – After grafting operation make sure that all the surface is sealed off using wax or grafting tape around the joining
5. Pressure – Apply a pressure after aligning the cambium of the root stock and scion such that the xylem stays in contact.
6. Use sharp/suitable equipment
7. The scion and root stock should be disease free
8. The scion should have desirable ualities

Reasons for grafting plants

1. It changes the treetops from being undesirable to desirable
2. It makes it possible to grow more than one fruit or flower in the same plant.
3. Root stocks with desirable character like disease resistance, problem of water logging are used which may be beneficial to the scion and farmer.
4. It helps to propagate clones that cannot be propagated by any means.
5. It helps propagating special plants form e.g. seedless oranges.
6. Helps in change variety for more especially when the acid
7. Virus indexing – Plants having viral infection with no signs will show signs when grafted.

LIMITATION OF GRAFTING

1. Incompatibility – this failure of grafted material to survive due to a difference in genetic constitution.
2. Requires a lot of skills and experience for successful grafting to occur.
3. Requires a lot of time for tangible results to be got.
4. Encourage premature aging of a plant
5. No genetic variation

1. Top Wedge: a cut surface of the scion forms a wedge that is inserted into a vertical slit on the root stock that has been slash.
2. Cleft Grafting / Top working grafting: this involves grafting a scion into a canopy of a relatively large established tree.
3. Splice grafting: a long slanting cut is made in both scion and root stock which is later tied together.
4. Bark grafting: a bark grafting is a plant made by slitting the back of the stock and inserting the scion beneath it. It is often used to regenerate an adult tree that has stopped being productive and to replace its structural branches. The cambium of the scion must line up as closely as possible with the cambium of the stock for a good graft union
5. Whip and tongue grafting: this is done if the root stock and scion have the same dimensions. A stanty cut is made at the base of the scion top of the root stock.  The two are fitted together and waxed
6. Approach grafting: Here both the scion and stock remain attached to another plant until a secure union has been formed.
7. Bridge grafting: This is used in repairing damage free plant normally woody trunks of valuable established trees.

 Budding

This type of vegetative propagation the bud or scion is united with a seedling or a mature tree.

Types of budding

1. T-budding: a t-Shaped cut is made on the back of the root stock and a bud is made on the back of the root stock and the bud fitted in
2. Patch budding: a rectangular piece of bud is cut of the root stock. A matching piece of bark with a bud is cut from the bud wood and matched into the prepared root stock.
3. Top budding: buds from young plants are inserted at desired location on the stock and after setting the original branches are cut.

LAYERING

This involves inducing a part of plant usually a branch to produce roots while still attached to the mother plant.

Types of layering

1. Simple layering involves bending a stem and covering it with soil to produce roots.
2. Tip layering: the whole shoot is bent and covered in the soil
3. Compound layering (serpentine): this is achieved by bending a stem several times and sometimes at a point of covering.
4. Mount / stool layering: a stem is cut just above the ground and the under shoot starts
5. Trench layering: here a trench is dug near the plant and a branch is layered on the trench to facilitate root development.
6. AIR / MACOTTING LAYERING: the bark of a tree is open at a point and a wet mass is placed around the ring bar to keep it open. This stimulates root to develop at that point.

Tissue culture

Tissue culture is the growth of tissues or cells in an artificial medium separate from the parent organism. This technique is also called micro-propagation.

Advantages of tissue culture

• Plantlets are raised in a disease free conditions restricting disease dissemination.
• It overcomes seasonal restriction for seed germination
• Rapid multiplication of crops
• Requires small space
• Plantlets are not bulky
• Genetic engineering may be done on the tissue cells
• The method can produce useful chemicals from plants such as phermaceuticals.
• It can be employed on plants that do not produce viable seeds e.g. banana.

Disadvantages of tissue culture

• No genetic variation
• Plants obtained may undergo genetic change e.g. mutation
• Requires skill
• Expensive

Application of tissue culture technology

• Micro-propagation
• Embryo culture
• Haploid and diploid production
• In vitro hybridization protoplasm infusion
• Industrial products from the cell.

Crop breeding / improvement

This is a process of changing crops genetically to suit man’s needs of food, easy harvesting etc.

Or

It’s a directed adjustment of crop plants to fit specific environment and production practices.

Methods of crop improvement

1. Mass selection: here in breeding plants are selected basing on the individual character and these are used in the breeding program.
2. Bulk breeding: Products of F1 are grown in bulk before making a single plant selection depending on their performance.
3. Pedigree breeding: this is the most used method and it’s based on the performance of the ancestor and close relatives.
4. Single descent: here one seed from F2 or F₃ is used as a parent for the next generation.
5. Recurrent selection: this is whereby the best individual resulting from a first selection cycle are crossed to generate the materials for the next selection cycles.

Aims of crop breeding / improvement

1. To increase crop yields so as to save the problem of hunger and food shortage.
2. To increase the nutrient content of the crop product to solve nutrient deficiency in consumers.
3. Produce better size and colour of fruits / seeds that can attract consumers.
4. To reduce the gestation period of a crop so as to solve food shortage.
5. Conferring disease and pest resistance in crop.
6. Production of crops that can tolerate adverse environmental conditions like drought, low soil fertility, high temperature.
7. To change growth characteristics of a plant in order to suit harvesting spraying and weeding.
8. to improve on the short life of the sowed crop production
9. To improve on seed viability character in plants so that there is no wastage of seeds during planting.
10. Improving the taste and flavour of certain crop products.
11. To produce crop products that is easy to prepare as food for consumers.

Revision questions

1) Which of the following is true about plants that are produced by tissue culture? They

A. produce high quality fruits

B. are resistant to diseases

C. mature easily

D. are identical

2) The process by which a tissue causes another tissue to differentiate is

A. cleavage

B. metamorphosis

C. Induction

D. Gastrulation

3) Sets are planting materials used in propagation of

A. Irish potatoes

B. Banana

C. Sugar cane

D. cassava

4) Parthenogenesis is the process by which

A. isogametes fuse to form a zygote

B. anisogametes fuse to form a zygote

C. sperm and ova fuse to form a zygote

D. an ovum develops into a zygote without fusion with sperms

5) One advantage of using a vegetative material in crop production that the crop

A. gives a high yield

B. maintains mothers characteristics

C. matures uniformly

D. is pest resistant

6) the major disadvantage of asexual reproduction is

A. accumulation of deleterious genes by mutation

B. formation of new types due to environment

C. formation of new types due to recombination

D. inability to form new types by mutation

7) Which one of the following quickens rooting in cuttings?

A. Ethylene dibromide

B. Indole acetic acid

C. Phosphate fertilizer

D. auxins

8) Which of the following may be a result of in-breeding?

A. Improved fertility

B. Increased mutation rates

C. Accumulation of lethal genes

D. polyploidy

Answers to objective questions

1. A 2D 3C        4D        5D        6A        7B        8B

 

Thanks

Dr. Bbosa Science