Asexual Propagation Techniques in Horticultural Crops

Group Members

Muhammad Ozair 09-arid-345

Adnan Saleem 05-arid-23

Syed Ali Ameer 09-arid-344

Why is plant propagation important?

Plant propagation- reproduction of new plants from seeds and vegetative parts, such as leaves, stems, or roots

Produce new and better breeds of plants faster

Can reproduce exact duplicates of desirable plants

Can increase quality of plants

Asexual propagation?

Asexual propagation Reproduction of new plants from existing

stem, leaf or root of parent plant No seed is formed Produces an exact duplicate of the parent

plant called a clone Can produce new plants from plants that

are difficult to produce from seed

What are types of Asexual propagation?

Stem cuttings Leaf cuttings Leaf-bud cuttings Budding Layering Separation and division Tissue culture Grafting

What are stem cuttings?

Stem cuttings: A portion of the stem that contains a

terminal bud or lateral buds is cut and placed in growing media to produce roots.

Stem Cutting with terminal growing area.

Stem Cutting

Leaf cuttings

Consists of a leaf blade or leaf blade with petiole attached

Leaf cutting with petiole.

Leaf cutting without petiole.

Leaf cutting that has rooted. Used leaf with petiole.

Leaf Cuttings

Leaf-bud cuttings

Consists of a leaf blade, petiole and a short piece of stem with the lateral bud

Leaf-bud cutting

Budding

Budding is a grafting technique in which a single bud from the desired scion is used rather than an entire scion containing many buds.

Preparation of Scion Bud

Insertion of Scion bud in T-shape Cut

Rapping of Inserted bud

Bud sprouting

Pruning of Rootstock

Layering

Layering is a mean of plant propagation in which a portion of an aerial stem grow roots while still attached to the parent plant and then detaches as an independent plant

Removing epidermis for layering.

Air Layering

Packing moss around area to provide moisture.

Wrap in saran wrap to keep moisture in.

Removing saran wrap to see new roots and bud.

New bud with roots.

Layering – taking a branch and placing it on the soil.

Layering – Simple or mound

Separation Method

Separation Take mature plants that were

stolons or offspring from a parent plant and separate.

Stolons – Parent plant puts out runners and each node a new plant forms along with roots.

Runners or Stolons

Separation of runner from parent.

Separation Method

Tissue culture (often called micropropagation) is a

special type of asexual propagation where a very small

piece of tissue (shoot apex, leaf section, or even an

individual cell) is excised (cut-out) and placed in sterile

(aseptic) culture in a test tube, Petri dish or tissue

culture container containing a special culture medium. 

Tissue culture

Areas of Tissue Culture Collection

Overview of the Tissue Culture Process

1.    It can create a large number of clones from a single explant.

2.    It is easy to select desirable traits directly from the culture setup (in vitro), thereby decreasing the amount of space required for field trials.

3.    The time required is much shortened, no need to wait for the whole life cycle of seed development.

4.    For species that have long generation time, low levels of seed production, or seeds that do not readily germinate, rapid propagation is possible.

The advantages of plant tissue culture

5. It overcomes seasonal restrictions for seed germination.

6.    It enables the preservation of pollen and cell collections form which plants may be propagated.

7.   It helps to eliminate plant diseases through careful stock selection and sterile techniques.

The advantages of plant tissue culture

Grafting is a method of asexual plant propagation

widely used in agriculture and horticulture where the

tissues of one plant are encouraged to fuse with those

of another in such a way so that maximum cambial

contact takes place.

Grafting

Rootstock:

That part of a tree which becomes the root system

of a grafted or budded tree.

Scion:

A piece of last year's growth with three or four buds;

the part inserted on the understock.

To understand Grafting

Cambium:

The growing part of the tree; located between the

wood and bark.

Types of Grafting

Cleft Graft Bark Graft Side-Veneer Graft Splice Graft Whip and Tongue Graft Saddle Graft Bridge Graft Inarch Graft Approach Graft

One of the simplest and most popular forms of grafting, cleft

grafting is a method for top working both flowering and fruiting trees

(apples, cherries, pears, and peaches) in order to change varieties.

Cleft Graft

The rootstock used for cleft grafting should range from 1 to 4

inches in diameter and should be straight.

The scion should be about 1/4 inch in diameter, straight, and long

enough to have at least three buds.

Cleft Graft

Bark Graft

This technique can be applied to rootstock of larger diameter (4 to 12 inches). Cut surface of the rootstock and make a vertical slit through the bark where each scion can be inserted (2 inches long and spaced 1 inch apart).

Prepare several scions for each graft. Cut the base of each scion to a 1 ½- to 2-inch tapered wedge on one side only.

Bark Graft

Side-Veneer Graft

Side-veneer grafting is usually done on potted rootstock.

Make a shallow downward cut about 3/4 inch to 1 inch long at

the base of the stem on the potted rootstock to expose a flap of

bark with some wood still attached.

Make an inward cut at the base so that the flap of bark and wood

can be removed from the rootstock.

Choose a scion with a diameter the same as or slightly smaller

than the rootstock. Make a sloping cut 3/4 to 1 inch long at the base

of the scion.

Side-Veneer Graft

Splice Graft

In splice grafting, both the stock and scion must be of the same

diameter.

Cut off the rootstock using a diagonal cut 3/4 to 1 inch long.

Make the same type of cut at the base of the scion. Fit the scion

to the stock.

Wrap this junction securely with a rubber grafting strip or twine.

Splice Graft

Whip and Tongue Graft

Both the rootstock and scion should be of equal size and

preferably no more than 1/2 inch in diameter.

Cut off the stock using a diagonal cut. The cut should be four to

five times longer than the diameter of the stock to be grafted.

Make the same kind of cut at the base of the scion.

Whip and Tongue Graft

Saddle Graft

Both rootstock and scion should be the same diameter.

Stock should not be more than 1 inch in diameter.

Using two opposing upward strokes of the grafting knife, sever

the top from the rootstock. The resulting cut should resemble an

inverted V, with the surface of the cuts ranging from 1/2 to 1 inch

long.

Now reverse the technique to prepare the base of the scion

Saddle Graft

Bridge Graft

Bridge grafting is used to "bridge" a diseased or damaged area

of a plant, usually at or near the base of the trunk.

Select scions that are straight and about twice as long as the

damaged area to be bridged. Make a 1 1/2- to 2-inch-long tapered

cut on the same plane at each end of the scion.

Cut a flap in the bark on the rootstock the same width as the

scion and below the injury to be repaired.

Bridge Graft

Inarch Graft

Inarching, like bridge grafting, is used to bypass or support a

damaged or weakened area of a plant stem.

Unlike bridge grafting, the scion can be an existing shoot,

sucker, or watersprout that is already growing below and

extending above the injury.

The scion may also be a shoot of the same species as the

injured plant growing on its own root system next to the main

trunk of the damaged tree.

Inarch Graft

Approach grafting is a method used to propagate plants in which one independent plant is fused with another independent plant. It is usually done when the two plants grow close to each other.

At the point where the two plants will join, a 1- 2 inch long slice of bark is cut on each stem.

The two stems are bound together, with the cut areas touching, using any wrapping material.

Approach Graft

Approach Graft

Dwarfing: To induce dwarfing or cold tolerance or other characteristics to the scion

Ease of propagation: Because the scion is difficult to propagate vegetatively by other means, such as by cuttings.

Hybrid breeding: To speed maturity of hybrids in fruit tree breeding programs. Hybrid seedlings may take ten or more years to flower and fruit on their own roots. Grafting can reduce the time to flowering and shorten the breeding program.

Hardiness: Because the scion has weak roots or the roots of the stock plants have roots tolerant of difficult conditions.

Sturdiness: To provide a strong, tall trunk for certain ornamental shrubs and trees.

Advantages of Grafting

Repair: To repair damage to the trunk of a tree that would prohibit nutrient flow, such as stripping of the bark by rodents that completely girdles the trunk.

Changing cultivars: To change the cultivar in a fruit orchard to a more profitable cultivar, called topworking. It may be faster to graft a new cultivar onto existing limbs of established trees than to replant an entire orchard.

Maintain consistency: Apples are notorious for their genetic variability, even differing in multiple characteristics, such as, size, color, and flavor, of fruits located on the same tree.

Pollen source: To provide pollenizers. For example, in tightly planted or badly planned apple orchards of a single variety, limbs of crab apple may be grafted at regularly spaced intervals onto trees down rows, say every fourth tree.

Advantages of Grafting