Information

Vine To Tree Root Grafting


I am experimenting with grafting multiple heartleaf philodendrons(philodendron cordatum) to the root of an oak tree(quercus). If the grafting is successful, the next step is to cut the root from the trunk, cap it, and place it in a long rectangular potter. The experiment to follow this will be to sustain the tree root with the philodendrons, and symbiotically use the philodendrons to sustain the tree root. Does anyone have experience in this type of experimental research and advice to provide?


I don't think this will work. Grafting will usually work between the same species and sometimes between the same genus. You're talking about grafting Philodendron cordatum to Quercus robur. The former is a tree from Europe, the latter a flowering plant from Brazil. They aren't compatible in the slightest. The graft will never take.

One possible route you might want to consider that may be more successful, but a lot more difficult, is using agrobacterium tumefaciens to infect a mix of cells from the two species. If you have a homogeneous mix of individual cells in culture, infect it with A. tumefaciens, the resulting gall will contain cells from both (incompatible) species. How they grow from there is unknown.


Can Grafted Trees Revert To Their Rootstock?

Tree grafting is an excellent way to bring the best of two varieties together into a single tree. Grafting trees is a practice that has been done by farmers and gardeners for hundreds of years, but the method is not fool proof. Sometimes grafted trees can revert to their original form.


Why Graft?

Reproduce vegetatively. Numerous selections of plants will not reproduce true from seeds or cannot be economically reproduced from vegetative cuttings (fruit varieties, flowering ornamentals, etc.).

Change variety. Established orchards of fruit trees may become obsolete as newer varieties are developed. Newer varieties may offer improved insect or disease resistance, better flavor, or higher yields. Rather than destroy the established root system, the older orchard may be top-worked using the new, improved variety.

Add pollinizer. Certain fruit trees are not self-fertile they require cross-pollination by a second fruit tree, usually of another variety. Some hollies are dioecious, meaning that a given plant has either male or female flowers but not both. To ensure good berry production on the female plant, a male plant must be growing nearby. Where this is not possible, the chances that cross-pollination will occur can be increased by grafting a scion from a male plant onto the female plant.

Change root system. Certain rootstocks have superior growth habits, disease and insect resistance, and better anchorage. For example, when used as rootstock for commercial apple varieties, some rootstocks can increase resistance to crown gall and root aphids. Some are also used as dwarfing rootstocks.

Produce certain plant forms. Plants with a weeping growth habit are often grafted or budded onto a standard rootstock. It may require staking for several years until the standard is large enough to support the weeping top.

Repair damaged plants. Large trees or specimen plants can be damaged easily at or slightly above the soil line. The damage may be caused by maintenance equipment or by disease, rodents, storms, or vandalism. This repair procedure is referred to as inarching, approach grafting, or bridge grafting.

Create designs. Advanced grafters may want to join plants to create designs such as hearts, chairs, or anything they can imagine.


Likely Grafted Plants

If your plant is a named variety of one of these, it is likely to be a graft or grown on a rootstock of a different species or variety from the one you bought. A named variety means a plant that has a name in quotes, such as Acer saccharum "Sugar Cone," the sugar cone sugar maple. If your plant is just a species, such as Acer saccharum, a sugar maple, it is probably not grafted, even if it is a genus on this list.

  • Apple especially types for fruit
  • Beech , many weeping and some other varieties
  • Camellia
  • Cedar varieties, such as weeping blue atlas cedar
  • Cherries, the oriental ornamental flowering types (Prunus serrulata)
  • Dogwood, weeping and red forms
  • Fir
  • Hawthorn
  • Hazelnut or filbert, especially nut crop varieties
  • Honey locust, the thornless and fruitless types
  • Horsechestnut, buckeye : Japanese, red, striped, and sugar varieties, as well as others
  • Redbud, especially "Oklahoma" , "Koster," "Moerheim," and "Hoosii" varieties

Grafting is a technique that vegetatively joins two plants into one. Instead of cross-pollinating two plants and producing hybrid seed, grafted plants use the roots and the bottom portion of one plant (rootstock) and attach it to a tender shoot (scion) from the top portion of another plant. This is often done with trees and shrubs, to combine the best characteristics of the two plants.

Most fruit trees today are grafted onto rootstock. Besides imparting specific characteristics to the resulting plant, it is a quick and reliable means of reproducing plants that do not grow true to type from seed. Unfortunately for the backyard gardener, that means we cannot save seed and grow more plants. Many grafted plants are patented.


Field Grafting Grape Vines

If you want to grow a new varietal, you have the option of grafting cuttings onto your existing rootstock, saving you the time of establishing a new root system. Also, if your original vines were planted on grafted rootstock designed to resist phyloxera, or if your current rootstock is designed to grow well in your type of soil and climate, you may wish to keep those already established roots and graft onto them.

Keep in mind that grafting does not heal sick vines. If your vineyard is unhealthy, attaching new cuttings to your old rootstocks most likely will not heal it. Diseases such as leaf roll, fan leaf and crown gall, for example, cannot be cured by grafting. Whatever made your vines sick in the first place is still in the vine, and it will just make your new grafts sick as well. Likewise, grafting does not make old vines young. If your rootstock and trunk is very old, grafting young healthy new wood will not make the vine young again — it is only as young as the root.

Any graft is traumatic to a vine, and grafting only works when you bind healthy cuttings to healthy trunks and rootstocks. Make sure your reasons for grafting are sound before proceeding.

Desirable Conditions for Field Grafting

You will want to check that your rootstock is compatible with what you will be grafting. For example, Vitis vinifera grapes are especially susceptible to phyloxera. If you are going to graft cuttings from vinifera onto your current roots, ensure the roots are resistant to phyloxera.

In addition, the row and vine spacing you have already established for your current vines should also be compatible with the new fruiting variety you have planned.

Three Stages of Field Grafting

Field grafting is performed in three stages: Pre-grafting, grafting and post-grafting. All three stages may span an entire season or more.

Pre-grafting operations fall into two parts: preparing the new wood and preparing the trunk. Grafting is surgery. A successful surgeon does not cut until his operation is well-planned.

After deciding what varietal you want to graft, you can either buy the scion or cut it yourself from other vines. First, calculate how much you need. Each scion that you graft to the trunk should have two buds and each vine trunk will receive two new scions.

If you are buying scions for the graft, the logistics of cutting and storage will be out of your control. Make sure your source is reliable and that your scions are disease free. They should be healthy, have been treated with a fungicide and properly kept in cold storage until you pick them up.

If you plan to take cuttings from other vines, note that from the moment the scion is removed from the vine it is vulnerable to infection, injury or drying if not treated and stored properly. The safest way to store new wood is to leave it on the vine until as late as possible in the dormant season. Make the cuts before the dormancy period ends and the buds begin to swell.

Cutting Canes and Preparing Scions

With clean, sharp pruning shears, cut the healthiest, most mature canes from the vine. These are canes that have been exposed to good sun, and are at least 3/8 to just over 1/2 inch (0.9–1.5 cm) in diameter. Make a cut at the base of the cane to remove it from the vine. Here’s a tip: When cutting canes or scions, always make the bottom cut flat and the top cut angled. This will help you to keep the cane or cutting oriented properly. The angled cut is always the top cut. After the entire cane has been removed it can be sectioned into scions.

Cut the cane into several 2-bud pieces. Avoid using the ends of the cane, where the diameter is under 3/8 inch (0.9 cm). Choose healthy buds separated by at least 2 inches (5 cm).

Although a scion should be a length of cane containing two buds, the actual piece will also include some internodal wood over the top bud to prevent the bud from drying out and at least 2 inches (5 cm) of wood below the bottom bud to shape and fit into your graft cut. See the sidebar on page 44 for how to store scions prior to grafting.

Preparing the Trunk

The next step is to prepare the receiving trunk. “Prepare” is a rather gentle word as you are actually going to cut the entire canopy off. This should be done in spring, just as the vines are getting ready to come out of dormancy. If the trunk is small (1–2 inches/2.5–5 cm in diameter), you can use large tree pruning sheers to make a clean cut. For larger trunk diameters, a chain saw is more suitable.

Heading the Vine

Before removing the canopy, determine where you want your vine to be headed. If your first trellis wire is at 39 inches (1 meter) and you want to head your vine there, cut the canopy off about 4 inches (10 cm) below that. This allows for space for the new grafted wood to grow shoots up to the trellis wire.

Since grafting is done as the vines are coming out of dormancy, the sap is running and they will “bleed” when cut. This can create quite a lot of internal pressure in the vine. The pressure can be great enough to push the new graft out of its union. This sap pressure needs to be relieved before making the graft.

At the base of the vine — a few inches off the ground, on each side of the trunk — make an incision into the cambium layer. This is the layer of living tissue underneath the bark. These cuts will reduce the sap pressure at the top of the trunk, allowing the graft union to heal.

Making the Graft

Now that the scions and trunks are cut, the actual graft cuts will be made where the scions will bond with the trunk. You will need to cut the scions to get them to fit into your graft cut. The type of graft you choose determines how you cut your scions.

In order to make a good graft, it is good to know a bit of basic vine biology.

Grafting Biology 101

In grafting, the injured tissue of one vine heals to the injured tissue of another. However, just putting two cut vines together does not guarantee a graft. The healing only takes place if the cambium layers of both the trunk and the scion are in permanent contact with each other. The cambium layer is the layer of green living tissue that lies between the bark and the wood. Therefore, the incision you make on your trunk, and the shape you cut your scion must be tailored to allow as much of the cambium tissue on both pieces to contact each other.

Grafting involves wounding your vines, and working with open wounds on both the trunk and scion. Open wounds are susceptible to infection. Therefore, the cutting tools you use should be clean and sharp for the most precision and least potential for contamination.

Types of Graft

I will describe the two easiest grafts to make, cleft grafts and whip grafts. There are other types of grafts used in vineyards, but they are just variations on the following themes. Cleft grafting is used for thick trunks, 1–1/2 inches (3.8 cm) or more in diameter. For small diameter trunks — 1 inch (2.5 cm) or less — whip grafting is used. The type of graft cut you make will determine how to prepare your scion for the union.

Cleft grafting is the easiest kind of graft. After removing the top of the vine, simply split the top of the trunk about 2 inches (5 cm) down with a cold chisel or small axe. Make sure the split line follows the direction of your trellis line. Hold the split open and fit two pre-shaped scions into the cut — one on each side, ensuring the cambium layer of both the trunk and the scions are in contact with each other. The natural tension of the split wood wanting to close again should grip the scions and hold them in place while you work.

The scions for cleft grafting are cut into a two-sided taper, about 2 inches (5 cm) long from below the lower bud, down the trailing length of the cutting. It will look like a little wedge extending from the bottom bud. When inserting the scion into the cleft, make the intersection of the two cambium layers as long as possible to increase tissue contact and the odds of bonding.

Now that both scions are placed into the cut, the open wound must be protected against drying and infection.

Even if the natural jaw pressure of the cleft is enough to hold the scions in place, wrap the grafting area with raffia or 1 inch (2.54 cm) wide grafting tape to clamp the scions in the cleft.

After the graft is completed, the entire wound area needs to be completely sealed with grafting compound to prevent infection, and drying of tissue. There are a number of grafting compounds, which look like black asphalt paint, on the market. Tree Seal or Tree Heal are two examples. Apply the compound with a disposable 1 1/2-inch (4-cm) bristle brush. After applying the compound, the brush should be disposed of at the end of the day. Use a fresh brush if you continue making grafts on another session. Coat every portion of the top of the cut stump, the inside of the cleft as well as the scions that are in place. Also, seal the upper green tips of the scions with compound. After the compound is dry, paint the entire graft union and scions with white interior latex paint. This will ensure the graft heats up less in the sun and the graft is sealed to hold moisture inside.

Whip Grafting

Whip grafting is used when a trunk’s diameter is so small that it will only hold one scion. Make an angled cut at least 2 inches (5 cm) long, just above the ground. Cut the scion at a complementary angle. If you can find a scion that is the same diameter of the trunk, this is best. If not, then the cambium layer of the trunk and the cambium layer of the scion can only be matched on one side of the cut.

Place the scion on the trunk and wrap it in place with raffia, or 1-inch (2.5-cm) compound tape. As with cleft grafting, coat the entire union with grafting compound then white latex paint.

Post Graft

Graft unions are fragile and should not be touched again during the healing process.

Although trunk incisions were made before the graft, pressure may build up again and push the graft union, or prevent it from healing. Avoid this by confirming the incisions you made in the trunk earlier. Make new incisions just above the old ones and repeat at least every week, if needed.

As the vine heals, suckers will emerge out of, and at the base of, the trunk. All but one sucker should be removed. The remaining sucker has a dual purpose — it may divert sap and help reduce vine pressure, and, if the graft union does not take, the sucker can be cultivated into new growth to make another graft later. When it appears that the graft is growing healthy shoots up to 10 inches (25 cm) long, remove the sucker.

As soon as the shoot is at the wire, tie it on. The graft union is still very fragile, and even strong wind could break it off. Since the graft is supporting the weight of a 12-inch (30-cm) shoot, it should be gently tied.

What to Expect

You will, of course, be anxious to see positive results — but remember that you just performed major surgery on your vine. It will take time to heal and not every graft is successful. Some of your buds may begin to show growth within weeks. You may even see them emerge and then die. This does not necessarily mean the graft was unsuccessful. The primary buds may push out naturally, but die due to the trauma of surgery. Allow the secondary buds to emerge. They may take several more weeks or even months. In the meantime, you can keep a sucker alive as a standby.

Within a season or two, you can begin to see fruit. It will take a few years for your vine to mature, but you are still a few years, and a lot of labor, ahead of replanting the entire vineyard. You have a healthy root system, and the fruiting varietal you always wanted.

Congratulations. You have a new vineyard!

Tips for Cold Storage of vine cuttings

If you need to cut your new wood into scions well before grafting time, they can be stored. Cuttings need to be kept cool and damp during cold storage. With proper care, cuttings can be stored for several months.

Cuttings should not be frozen. The ideal storage temperature is between 34–36 °F (1–2 °C).

Before storing, organize the cuttings in bundles of 10 or 20, held together with small gauge wire. Be gentle with the buds while handling. Keep the cuttings oriented so that the tops and bottom cuts are all in the same direction. If you are grafting more than one type of varietal, make sure they are labelled as separate bundles.

Cuttings can be stored in three ways:

Refrigeration

If you have space in your refrigerator, bundle the cuttings in groups, and wrap them in moistened newspaper, wood shavings or peat moss. (Make sure it is not dripping wet.) Store the cuttings in well-sealed plastic bags. This is the simplest method of storage.

Bin Storage

If the temperature where you live is cold, but remains above freezing, or if you have a cold cellar where the temperature remains consistently below 36 °F (2 °C) and above freezing, you can store the vines in a plastic lined bin full of moist wood shavings. Rubbermaid containers will work if the lid can be sealed to hold in the moisture. The bin needs to keep the cuttings cool without allowing them to dry out. Check frequently to make sure the cuttings and shavings are damp.

Burial

Cuttings can also be buried in a shallow pit or trench in the ground, if the temperature is right. Ground temperatures are the most unstable since they react to weather, sun, rain, and snow.

Prepare a well-drained trench at least a foot deep (30 cm), in a location shaded from daytime sun to maintain the least amount of temperature fluctuation. Ensure that the hole is not a water trap in case of rain. A sandy pit is ideal. Heavy clay is high risk as it traps water.

Wet the cuttings first to make them damp. Wrap and package the cuttings as you would if storing in a refrigerator. Cover them with soil. Remember to mark the burial place to find them again.

Some have found success by simply burying the bundled vines in sand or soil, unwrapped — as long as they do not become saturated or dry.

Preparing Cuttings for Grafting

Vines should be removed from cold storage 24 hours before grafting, to allow them to warm to the ambient temperature. Do not allow them to dry out as they warm up. Only warm up cuttings you expect to use that day.


Vine To Tree Root Grafting - Biology

A. Grafting for Clonal Selection and Propagation of Otherwise Difficult-to-Clone Plants

  • Norway Maple (e.g. Acer platanoides 'Crimson King')
  • Green Ash (e.g. Fraxinus pennsylvanica 'Marshall's Seedless')
  • Honeylocust (e.g. Gleditsia triacanthos inermis 'Moraine')
  • Littleleaf Linden (e.g. Tilia cordata 'Greenspire')
  • Dwarf Pine cultivars
  • Blue Spruce cultivars such as Picea pungens 'Pendens'

2. Economics - sometimes grafting is less expensive than cuttage

3. Budding for delayed self-rooting of slow-to-root species / nurse (root) grafting (NRG)

  • The root piece is typically whip and tongue grafted at the bench during winter, stored in a cool place where graft union formation occurs, and then lined out in the field in the spring, where scion rooting occurs.
  • Eventually the graft union fails due to delayed incompatibility, and the privet root piece dies. The likelihood, overall (for any kind of plant), of an intergeneric graft like this being a compatible scion/stock combination is low.
  • Alternatively lilacs may be nurse root grafted onto one year old root pieces of seedling Green Ash (Fraxinus pennsylvanica, also in the Oleaceae).
  • In recent years, most lilacs are propagated by tissue culture (micropropagation). Nurse root grafting has lost popularity because sometimes the graft union fails before the scion becomes self rooted, or it will not fail at all, or the rootsystem will sucker, eventually outgrowing the lilac scion. In the image shown here , this nurse root grafted lilac apparently did not self root, and after several years, the lilac/privet graft union broke apart (delayed incompatibility), killing the lilac.

B. Grafting for repair

1. Grafting to repair a girdled stem - Bridge Grafting

a. Young bridge graft
b. Older bridge graft
c. Bridge grafting described in a UConn bulletin on repairing mouse damage

/>How is bridge grafting like double working (described in the section on Concepts and Definitions)?
/>What time of year (season) is bridge grafting performed? (see Seasonal Considerations in the section on Required for Successful Grafting and Budding)

  • Inarching, an in-ground version of approach grafting, is described in the University of Georgia Extension Web site, Propagating Deciduous Fruit Plants Common to Georgia

3. To replace a damaged or diseased root system - inarching

  • The picture is from the cover of a 1933 extension bulletin by Thomas & MacDaniels, which described the use of inarching to repair damage caused by freezing.

4. To overcome a delayed incompatibility - bridge grafting or inarching

C. Grafting to create unusual growth forms - Highworking (see Grafting by Position)

1. To obtain a tree-like form high working of otherwise naturally shrubby plants several feet up on a tall straight trunk.

a. Tree (standard) Roses

  • Roses that typically grow as low shrubs or climbers can be given an arborescent (tree-like) appearance by grafting them at the top of a long straight interstock which is in turn grafted onto a suitable rose rootstock such as R. multiflora. This would be an example of both highworking /> and double working />.

c. Weeping Higan Cherry (a cultivar of Prunus subhirtella)

( Picture from Edgar Joyce Nurseries)

    Prunus subhirtella is normally an arborescent (tree) form, but the variety pendula "weeps," and would grow as a prostrate shrub. It is grafted

4 - 6' high on a P. subhirtella understock to give a "weeping tree."

Why are these suckers upright instead of weeping?

  • This ancient Chinese art is, perhaps, the ultimate in tree "engineering." If the grower wants a branch in a particular location where none exists, it can be grafted into place, as is described at the Bonsai Primer Web page

f. Living sculptures created by grafting

  • One of the most unusual applications of grafting is its use to create living sculptures such as chairs, tables, and a variety of strange abstractions.
  • The Arborsmith Studios has many examples of the work of its owner, Richard Reams, and images of other creative designs from the past.

D. Grafting to change fruit varieties

  1. Replacing an old variety on an established tree with an new one for economic or other reasons is known as Reworking, which is a form of topworking (see Grafting by Position spatial diagram)
  2. Seedling fruit trees can take 7 years or so to flower, and even grafted nursery stock can take several years. An alternative to waiting this long was, and still is, to a limited extent, to cleft graft a new variety up into the crown of an established tree. This could hasten production of the new fruit variety by several years.

E. Grafting to put multiple scion varieties on a single tree.

This is an example of Topworking (see Grafting by Position spatial diagram)

  • Apple with Macintosh, Granny Smith, & Red Delicious, etc. all on one tree
  • Citrus tree with orange, lemon, grapefruit all on one tree.
  • Hibiscus with several cultivars differing in flower color.

F. To provide a pollinizer branch for self-incompatible fruit tree species

    1. Apples, cherries and some other fruit tree species are self-incompatible within a clone.

    e.g. Macintosh apple will not self-pollinate, but it will cross-pollinate with another domestic apple or a crabapple.

G. Grafting to Influence Growth Phase

    (1) This is because the (adult) growth phase of the scion tends to be maintained whereas, a seedling is naturally rejuvenated by the process of embryogenesis (seed formation) compared to the seed-bearing parent tree.
    (2) Furthermore, dwarfing rootstocks tend to induce scion precocity, i.e. they cause a scion to come into flowering one or more years sooner than it would on its own roots or grafted onto a non-(or less) dwarfing rootstock.
  • e.g. Avocado would come acceptably true-to-type from seed, but several years of bearing would be lost. Hence top wedge grafting of a scion from a mature bearing tree onto a seedling understock is commonly practiced in the nursery production of this tropical crop.
    • See autotutorial slide set on Top Wedge grafting of avocado.
    • see autotutorial slide set on T-budding of citrus.

    2. Grafting for scion rejuvenation to facilitate subsequent rooting of cuttings ( Serial Grafting )

    a. Ease of rooting is a general property of juvenile compared to adult growth.

    b. Even though a scion from a mature tree tends to retain its adult growth phase.

    As pointed out in the previous section, an adult scion will be slightly rejuvenated by grafting onto a juvenile (seedling) understock. Because this rejuvenating effect is only slight a scion may have to be sequentially regrafted onto a series of juvenile rootstocks before a useful degree of rejuvenation has been achieved. Cuttings taken from this rejuvenated growth tend to root more easily than from mature growth.

    c. This rootstock-influenced gradual rejuvenation of the scion is called serial grafting.

    d. Serial grafting is an extreme (last resort) method for facilitating the rooting of cuttings from the mature wood of extremely difficult-to-root species such as 100 year-old Sequoia ( Tranvan, et al., 1991).

    H. Grafting for Virus Detection (Graft indexing)

    • Why is it important that the indicator is used as understock, not as the scion?
    • Note: for many viruses there are other newer, more specific and/or more sensitive virus indexing techniques such as ELISA (enzyme linked immuno sorbant assay). Hence, graft indexing tends to be used less frequently.

    I. Grafting to achieve independent optimization of component genotypes - Specific Rootstock / Interstock Benefits

    1. Grafted Plants are Compound Genetic Systems

    a. The rootsystem and the shoot system of a plant exist in different environments. Each has a different role in plant development and each makes a different contribution to agricultural productivity. Given the long generation time of trees (years), it could take a very long time, using standard plant breeding methods, to breed a tree to genetically optimize both the root and the shoot systems. Grafting, on the other hand, has allowed agriculturists to mix and match different genotypes in the root and shoot systems, resulting in a genetically compound plant that performs better overall than either genotype alone.

    b. Of course, in modern times, genetic engineering, is another way to "construct" a plant with genes from more than one organism. However promising, genetic engineering is still in its infancy with respect to "designer" trees.

    Do you think genetic engineering will ever make traditional grafting obsolete?

    2. What is the Difference Between "Specific" Rootstock Effects and Non-Specific Rootstock Effects?

    • Grafting Macintosh apple (scion) onto an M9 (dwarfing) rootstock, results in size control (dwarfing) of the scion because hormonal or other aspects of M9, under genetic control, are translated to the scion, affecting its vigor. Size control and other specific rootstock benefits in apples discussed in the section on Clonal Apple Rootstocks.
    • Grafting Arabica Coffee (Coffea arabica, higher quality but nematode susceptible) onto another species of coffee, C. robusta, which is nematode resistant .
    • Grafting onto a seedling rootstock merely to propagate a difficult-to-root clone.
    • Grafting onto a seedling rootstock to produce a plant with an unusual growth form, such as a weeping cherry.

    3. A List of Specific Rootstock Benefits

      Apple - the use of clonal rootstocks for size control (and other reasons) is a major part of modern apple production. The Malling and Malling-Merton apple rootstocks, introduced in the early 20th century, revolutionized apple production. Progress has been made since then by a number of other apple rootstock breeding programs around the world. Since apple is perhaps the best example of crop improvement through selection of clonal rootstocks, this topic is discussed at length in the section on Clonal Rootstocks.

      Pears are sometimes dwarfed by grafting them onto quince rootstocks

    • Flowering and fruiting of an adult phase scion occurs more rapidly (precociously) when grafted on some rootstock genotypes than on others. In particular, the more dwarfing caused by the rootstock, the sooner the scion will flower and "come into bearing" from the standpoint of fruit production.

      Many rootstocks have been selected for disease or pest resistance but in most cases the resistance is not transmitted to the scion (in contrast to dwarfing). For example:

      (1) Fungal pathogens

      • Fusarium sp.
        • Fusarium causes a wilting disease of many species, caused by fungal plugging of host xylem.
        • e.g. Passion fruit (Passiflora edulis), purple-fruited hybrid varieties that are Fusarium wilt-sensitive, are grafted onto resistant seedlings of P. edulis forma flavicarpa
        • Resistance to root rot is one of the major selection criteria for the apple rootstock breeding program at the NY Agriculture Experiment Station at Geneva, NY.
        • Fire blight (Erwinia amylovora)
          • A disease of pear, apple, etc. Rosaceous fruits (link to Geneva Experiment Station website)
          • Fireblight resistance is one of several selection criteria in modern apple rootstock breeding program at the NY Agriculture Experiment Station
          • Characteristics of Apple Rootstocks and Interstem Combinations by Paul Domoto (including resistance to fireblight) is part of the NC-140 Regional rootstock breeding program Web site .
          • Tristeza virus
            • Tristeza causes greening disease in citrus which is a serious problem in Africa and other parts of the world.
            • Resistance to tristeza is conferred by rough lemon rootstock. An article on citrus rootstock resistance to Tristeza and other diseases is presented on this Australian government website.
            • Wooly aphid (WA) (Eriosomalanigerum) is an insect pest of apple. The Malling-Merton series rootstocks were developed by crossing wooly aphid-susceptible East Malling selections with WA-resistant Northern Spy apple (Information sheet from UC Davis IPM Pest Management project ).
            • Phylloxera, described in an Information sheet from Univ. of California Integrated Pest Management project , is an aphid-like sucking insect pest of grape which parasitizes the root system. Phylloxera infestation in the wine regions of France in the 19th century virtually destroyed production of European (wines) grapes (Vitus vinifera) until they began grafting them onto resistant American grape rootstocks (Vitus lambrusca).
            • Nematodes are microscopic "eel worms" which parasitize the root systems of many agricultural crops
            • Almond (Prunus amygdala) scions are grafted on Mariana plum 2624 rootstocks which are nematode-resistant. ( Information sheet from University of California IPM Pest Management Project)
            • Arabian coffee (Coffea arabica) produces a higher grade of coffee than Canefera coffee (Coffea robusta, the kind used to make instant coffee), but the former is nematode-susceptible while the latter is resistant. Scions from seedlings of C. arabica are grafted onto seedling understocks of C. robusta for coffee plantations in Guatemala and other parts of Latin America.

            For what (other) reason is it surprising that Poncris trifoliata is used as a rootstock for Citrus sp. (hint, check the section on Requirements for Successful Grafting and Budding)?

            f. Tolerance of specific soil types

            (1) The apple rootstock M7 is tolerant of wet soil conditions conversely MM104 is tolerant of dry soil conditions. For a summary of apple rootstock soil adaptability consult Paul Domoto's Characteristics of Apple Rootstocks table.

            4. Specific Interstock Benefits

              Just as single working (scion/understock grafting) allows the grafter to combine the best possible scion genotype with the best possible rootstock genotype, double working (scion/interstock/understock grafting) allows for further optimization of each of the three components of a tree - root system (nutrition, anchorage, dwarfing, etc.), trunk (support), canopy (fruit). See Grafting by Position

              a. Size control

              (1) A genotype that causes dwarfing when used as a rootstock has a similar dwarfing effect (but to a lesser extent) when used as an interstock.

              (2) In addition, the degree of dwarfing by a given interstock genotype is proportional to the length of the interstock, i.e. a relatively long section of M9 used as an interstock has a greater dwarfing effect than a shorter section of the same genotype.

            Why use an interstock for size control of a double worked tree rather than using the same genotype as a rootstock in a single worked tree? (Hint: see Apple Grafting autotutorial slide set )

            b. To achieve an arborescent growth form of an otherwise shrubby scion variety (see Grafting to achieve special growth forms in this section, above)

            c. Avoid incompatibility of an otherwise incompatible stock / scion combination by inserting a mutually compatible interstock. (see discussion of Bradford pear/Quince incompatibility in the section on Compatibility)

            5. Summaries of Specific Rootstock Characteristics for Specific Crops


            Methods

            Plant material and grafting

            Avocado cv. ‘Hass’ and cv. ‘Velvick’ seeds and propagation material were provided by Anderson Horticulture Pty Ltd. and grown in Anderson nursery located in Duranbah, New South Wales, Australia. All avocado grafting experiments were generated at Anderson Horticulture Pty Ltd. nursery (appropriate permissions were obtained). Approx. 2 months old seedlings of cultivars ‘Velvick’ and ‘Hass’ were generated for seedling rootstocks and scions respectively. Clonal rootstocks of ‘Velvick’ were prepared using the Frolich method modified from Ernst, 1999 [36, 37], and ‘Hass’ mature scionwood (budwood) for mature scions was collected from adult trees as per commercial practise at Anderson Horticulture. Wedge grafts (Fig. 5a) were made in four possible combinations of 12 plants (scion/rootstock) (Fig. 5b-e): 1) budwood ‘Hass’/seedling ‘Velvick’, 2) budwood ‘Hass’/clonal ‘Velvick’, 3) seedling ‘Hass’/seedling ‘Velvick’, and 4) seedling ‘Hass’/clonal ‘Velvick’. Leaf samples were collected immediately pre-grafting and at 3 months and 6 months post-grafting. Another independent experiment was designed to determine the effect of clonal rootstock leaves on inter-graft signalling. Here budwood ‘Hass’ was grafted on ‘Velvick’ clonal rootstocks in two groups of 12 plants 1) ‘With Leaves (WL)’ - where leaves were left on the rootstock as per conventional practice, 2) ‘Without Leaves (WOL)’ - where leaves were removed from the rootstock (Fig. 5f, g). Leaves for expression analysis were sampled 3 months post-grafting. In all cases, the youngest fully expanded leaf was sampled and pooled into three biological replicates directly on dry ice and stored at -80 °C freezer.

            Grafting techniques and combinations used. Schematic diagrams of a Wedge grafting in avocado. Simplified graphical representations of avocado graft combinations 3 months post-grafting: b seedling scionwood grafted on seedling rootstock, c mature scionwood grafted on seedling rootstock, d seedling scionwood grafted on clonal rootstock and e mature scionwood grafted on clonal rootstock. Photographs of avocado defoliation experiment combinations on the day of grafting: f grafts without leaves on rootstock, g grafts with leaves on rootstock

            RNA extraction

            Leaf tissues were ground to fine powder under liquid nitrogen and total RNA was extracted using a MasterPure Plant RNA Purification kit (Epicentre, USA). RNA was quantified using a Nanodrop ND-1000 spectrophotometer and quality assessed on 1% TAE agarose gels. For miRNA quantification, 500 ng total RNA was utilized for low-molecular weight cDNA synthesis (to quantify mature miRNAs) with a miScript Plant RT Kit (Qiagen, Netherlands). For gene quantification, 600 ng of total RNA was used to synthesize high molecular weight cDNA using a SensiFAST™ cDNA Synthesis Kit (Bioline, Australia).

            Quantitative real time polymerase chain reaction

            MiRNA quantification

            qRT-PCR reactions were performed in duplicate for each biological replicate using a miScript SYBR® Green PCR Kit (cDNA prepared using a miScript Plant RT Kit was utilized) (QIAGEN, The Netherland). The primer sequences of miRNAs (miR156 and miR172) and housekeeping transcripts (U6 [38], 5.8S rRNA [39]) are shown in Additional file 1: Table S3. Reactions were performed on a Rotor-Gene Q 6000 (Qiagen, The Netherlands) and visualized using Rotor-Gene Q 2.3.1.49 software (QIAGEN, The Netherland).

            Gene quantification

            Primer sequences from our recent manuscript [17] were utilized for gene quantification (Additional file 1: Table S3) using a SensiFAST™ SYBR® No-ROX Kit (Bioline, Australia) in a BioRad CFX384 Touch™ Real-Time PCR Detection System (Bio-Rad, USA) in accordance with manufacturer instructions and visualized on CFX Manager™ Software (Bio-Rad, USA).

            For all qPCR runs, PCR efficiencies were computed using LinReg PCR version 7.5 (University of Amsterdam, Netherlands). This Data was then further analysed and evaluated to determine the relative abundance of miRNA and genes by employing the formula:

            where PE is primer efficiency and Ct is cycle threshold of each reaction. To check statistical significance of the data, a one-way analysis of variance (ANOVA) was done with Tukey correction (a post-hoc multiple comparison tests to compare means) using SPSS version 23 (IBM, USA). The averages of relative expression of miRNAs and genes were plotted with standard error using GraphPad Prism 6 (GraphPad Software Inc.).


            Graft Transformation

            Of all grafting issues, the least understood and most controversial is the ‘graft hybrid’ concept. According to this concept grafting may involve stock to scion transfer of genetic material (= graft transformation), leading to heritable changes in the scion. The scion which has acquired certain heritable traits from the rootstock is regarded as a ‘graft hybrid.’ However, graft transformations occur only under ‘Mentor grafting’ conditions, which presumably enforce the transfer of genetic material from stock to scion (Figure 2).

            FIGURE 2. Mentor grafting. (A) Non-graft normal plant as control. (B) Mentor graft scion leaves were removed in order to facilitate chromatin translocation from rootstock leaves and stems to the primordial organs of the scion. Arrows indicate the direction of chromatin translocation (reproduced from Ohta, 1991 with permission).

            In ‘Mentor grafting,’ young seedlings shoots serving as ‘scions’ are grafted onto mature, flowering plants used as ‘stocks.’ To make sure that the scions fully depend on the stock for the supply of nutrients, leaves of the scions (except for two or three leaves at the top) are removed throughout the experiment. Stock fruits are also removed in attempt to maximize flow of substances from the stock to the scion (Ohta, 1991). Interestingly, the ‘Mentor grafting’ technique is the same as that used in classical flowering research, where removal of leaves from the scion was expected to promote stock to scion movement of the floral stimulus (Lang, 1965).

            The graft hybrid concept, which was developed and demonstrated by the Soviet horticulturist Michurin (1949), appeared to be in contrast with Mendelian genetics and was rejected (and almost forgotten) by Western scientists who opposed and distrusted the Soviet biology led by Lysenko. Several published studies (and most probably many unpublished) could not confirm the appearance of graft hybrids (Stubbe, 1954 Bohme, 1957 Topoleski and Janick, 1963 Menda et al., 2006). Yet, reports supporting the occurrence of graft transformations appeared from time to time (Frankel, 1956), and increasingly so in recent years (Li et al., 2013 Tsaballa et al., 2013 Wu et al., 2013 Zhou et al., 2013). Proponents of the graft hybrid concept reviewed the supporting evidence and called for reassessment of the graft transformation hypothesis that has been neglected for several decades (Liu, 2006 Liu et al., 2010).

            Within the ‘graft hybrid’ supportive evidence some specific characteristics can be defined. (a) The frequency of the appearance of variant plants is highly variable, sometimes below 1% (Ohta, 1991). Thus, the argument that ‘no variants were found’ must be based on a very large number of replicate grafts. Indeed, some of the ‘negative’ reports used several thousands of grafts (Stubbe, 1954). (b) The graft hybrid experimental evidence rests almost exclusively on intra- and interspecific grafting of Solanaceae, in particular pepper (Ohta, 1991 Taller et al., 1998 Tsaballa et al., 2013), which is somehow more amenable than other plant species to rootstock-induced scion transformation. (c) The alleged rootstock to scion transmission of genetic material is the most mysterious part of it all. The initial belief of Michurin (1949) that genes can move between rootstock and scion has been refined by Ohta (1991) who presented histological evidence that masses of chromatin are moving via the vascular system from the older rootstock across the graft union to the apical primordia or flower buds of the younger, mentor-grafted scion. The model of amplified plasmodesmatal macromolecular transport toward apical meristems (Ueki and Citovski, 2005) has been cited in this context (Liu, 2006) but no further evidence in support of this mechanism has been presented.

            In their review, Mudge et al. (2009) indicated that the emerging concept of graft-transmissible gene silencing signals may hold the key for a new approach to the graft transformation riddle. Recent research further extends this view in conjunction with probable involvement of epigenetic inheritance mechanisms.

            Epigenetics refers to reversible heritable changes in genome function that occur without a change in the DNA sequence and may have morphological, physiological, and ecological consequences (Rapp and Wendel, 2005 Fossey, 2009). Changes in DNA methylation are presumably among the principal, ubiquitous epigenetic mechanisms (Rapp and Wendel, 2005) although their heritability requires further elucidation (Paszkowski and Grossniklaus, 2011). DNA methylation during plant gametogenesis, in particular, appears to involve epigenetic, heritable changes (Takeda and Paszkowski, 2006 Calcaro et al., 2012). Plant DNA methylation has been shown to be regulated by siRNAs ‘siRNA-mediated epigenetic modification’ is currently an acceptable term (Xu et al., 2013a).

            As already discussed, graft-transmissible RNA gene silencing signals have been demonstrated in both the upward (Brosnan et al., 2007) and the downward direction (Molnar et al., 2010). Changes in DNA methylation in the recipient organs have been detected these changes are regarded as epigenetic modifications (Molnar et al., 2010). Partially heritable, locus-specific alteration of DNA methylation patterns have recently been found in scions of interspecific grafts of Solanaceae (Wu et al., 2013). Wu et al. (2013) think that their research paves the way for resolution of the graft hybrid controversy. However, further, rigorous research is desperately needed, in order to unequivocally elucidate the graft hybrid – graft transformation issues.


            Grafting

            Grafting encompasses any process whereby a part (called the scion) taken from one plant, is made to unite with and grow upon another plant or part of a plant (called the stock). The scion may be a single bud, a small twig bearing a few to several buds, a piece of stem (as of a cactus), a terminal shoot (as of an evergreen), or a fragment of root of a desirable variety. The primary purpose of grafting is to either increase the chances of the scion's making successful growth by giving it a new foundation in the form of a more vigorous root system than it had originally, or to change over the form, character, fruit-bearing quality, etc. of the stock plant or tree by substituting some other variety for its original top.

            Grafting may also be used to create a tree or plant bearing two or more distinct varieties of flower or fruit. After the scion and stock have been cut and adjusted, they are tied into place after which the whole area of wounded surfaces is sealed with grafting wax, tape, or paraffin, which checks the evaporation of available moisture. As the two parts of a graft grow together they are said to form a "union".

            Many kinds of grafting are practiced by nursery growers for special purposes or with specific plants, but those best suited to the average gardener's needs are whip, cleft, side and bridge grafting.


            The function of grapevine roots

            • Provide a physical anchor of the vine
            • Absorb water and mineral nutrients
            • Store carbohydrates and nutrients in reserve for future use
            • Produce hormones that control plant functions

            The root system of a mature grapevine consists of a woody framework of older roots (Richards, 1983) from which permanent roots arise and grow either horizontally or vertically. These roots are typically multi-branching, producing lateral roots that can further branch into smaller lateral roots. Lateral roots produce many short, fine roots, which has the effect of increasing the area of soil exploited (Richards, 1983). Certain soil fungi, called mycorrhizae, live in a natural, mutually beneficial association with grape roots. Mycorrhizae influence grapevine nutrition and growth, and have been shown to increase the uptake of phosphorus.

            The majority of the grapevine root system is found within the top 3 feet (Richards, 1983 Winkler, et al., 1974) of the soil, although individual roots can grow much deeper in certain soil conditions and profiles. Distribution of roots is influenced by soil characteristics: the presence of hardpans or other impermeable layers, the rootstock variety, and cultural practices such as the type of irrigation system (Mullins et al., 1992). Grapevine roots require good internal soil drainage to function. Water-saturated soils do not have air spaces that allow roots to respire. High water tables and heavy textured soils (fine silty loams and clays) often restrict root growth, and thereby limit vine size and nutrient uptake from soils. Subsurface drainage tiles are often recommended in non-irrigated production areas to improve internal soil drainage.

            References:
            Mullins, M. G., A. Bouquet, and L. E. Williams. 1992. Biology of the Grapevine. Cambridge University Press.

            Richards, D. 1983. The Grape Root System. Horticultural Reviews 5:127-168.


            Watch the video: How to graft bougainvillea roots. Multigrafting bougainvillea (January 2022).