Vegetative/asexual Propagation

 

Vegetative/Asexual Propagation

Vegetative propagation is a type of asexual reproduction of a plant. Only one plant is concerned and also the offspring is that the result of one parent. The new plant is genetically similar to the parent plant.

Importance of asexual propagation

• Multiplication of heterozygous material without alteration
• Easier and faster
• Juvenility is reduced
• Seed dormancy elimination
• Early bearing (Date palm)
• Multiplication of plants without viable seeds e.g. Washington navel orange, banana, seedless grapes, etc.
• Uniform produce quality
• Dwarfness
• Top working (Changing of the existing cultivar)

Disadvantages of asexual propagation

• Short-lived plants
• Lack of diversity
• Possibility of transmitting viruses in-stock plants to vegetatively propagated offspring.
• Evolving new variety is not possible
• Clonal plantations might not be adapted to sudden environmental changes, (e.g. pest attacks, drought).

Methods of vegetative propagation

1. Apomixis
2. Division
3. Layering
4. Cuttings
5. Budding
6. Grafting
7. Plant tissue culture

1. Apomixis

Apomixis was defined by Hans Winkler as a replacement of the normal sexual reproduction by asexual reproduction, without fertilization.

• Seed development without sexual process involvement
• The complete meiotic cycle may be eliminated
• The seed is directly formed from diploid cells
• Maybe non-reduced vegetative mother cell
• Cell from maternal ovule tissue.

2. Division

Utilization of specialized vegetative structures or stem modifications

• Runner            Strawberry
  
• Bulb                 Tulip, Onion
• Corm               Gladiolus
• Rhizome          Iris
• Off-shot            Daylily
• Tuber               Potato
• Tuberous root  Sweet potato

3. Layering

Layering is a means of plant propagation in which a portion of a stem above the ground grows roots while still attached to the parent plant and then detaches as a separate plant. Layering has developed as a typical methods of vegetative propagation of various species in natural environments.

Types of layering:

• Simple/Tip layerage
• Air/Gooti layerage or Marcottage
• Serpentine layerage
• Mound/Stool layerage

4. Cutting

A plant cutting is a piece of a plant that is utilized in horticulture for vegetative propagation. A piece of the stem or root of the source plant is placed during an appropriate medium like wet soil. In suitable conditions, the piece of the plant will start to develop as a new plant independent of the parent plant, this process called striking. A stem cutting makes new roots, and a root cutting makes new stems. A few plants can be developed from leaf pieces, also known as leaf cuttings, which produce both stems and roots. The scions utilized in grafting also known as cuttings.

5. Budding

It is the method of propagation where only a single bud with a small section of the bark of scion wood is used on rootstock.

Types of budding

• T- budding
• Ring budding
• Chip budding
• Patch budding

6. Grafting

It is the art of connecting two pieces of living plant tissue together in such a manner that these may unite, grow, and develop as one plant.

Types of grafting

• Inarching/Approach grafting
  
• Veneer grafting
• Cleft grafting
• Splice grafting
• Tongue grafting
• Cleft grafting
• Bridge grafting

7. Plant tissue culture

Plant tissue culture is a combination of techniques used to produce plant cells, tissues, or organs by sterilization on a nutrient culture medium of known composition. It is extensively used to produce clones of a plant in a method called micropropagation. Different strategies in plant tissue culture may offer certain advantages over conventional methods of propagation, including:

• The production of multiples of plants without seeds or essential pollinators to produce seeds.
• To quickly produce mature plants
• The production of the same copies of plants that produce especially good flowers, fruits, or have other desirable traits.
• Plant production in sterile containers that can be transplanted greatly reduces the chances of transmitting diseases, pests and pathogens.
• The regeneration of all plants from plant cells that have been genetically modified.
• The production of plants from seeds that in any other case have very low chances of germinating and growing, i.e. orchids and Nepenthes.
• To clean specific plants of viral and other infections and to rapid multiplication of these plants as 'cleaned stock' for horticulture and agriculture.