The Biology of Grafting

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The Biology of Grafting

• Chapter 11

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The Biology of Grafting

• History
• Known by the Chinese by 1560 B.C.

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The Biology of Grafting

• History
• Aristotle (384 -322 B.C.)

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The Biology of Grafting

• History
• Theophrastus (371-287 B.C.) wrote about it

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The Biology of Grafting

• History
• -Romans grafted olive trees

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The Biology of Grafting
History Renaissance (1350-1600 AD) saw renewed
interest in grafting
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The Biology of Grafting
History 16-17th century grafting widely used
in England
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The Biology of Grafting
History 1800s grafting used in the U.S.
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The Biology of Grafting

• Terminology
• Grafting - Art of connecting two pieces of living
  plant tissue together so that they will unite,
  grow and develop as a composite plant

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The Biology of Grafting

• Terminology
• Budding - a form of grafting. The scion is
  small and typically one bud

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The Biology of Grafting

• Terminology
• Budding - a form of grafting. The scion is
  small and typically one bud

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The Biology of Grafting
Terminology Scion - short piece of detached
shoot containing several dormant buds. The upper
portion of the graft producing stems and branches
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The Biology of Grafting

• Rootstock (understock or stock) - lower portion
  of the graft. Produces the root system of the
  plant. Typically from seedlings, rooted
  cuttings, layered or micropropagated plants

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The Biology of Grafting

• Interstock (intermediate stock, interstem) - a
  piece of stem inserted by means of two graft
  unions between the scion and the rootstock.
  Often used to avoid incompatibility, to produce
  special forms, control disease or control growth

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The Biology of Grafting

• Vascular cambium - thin tissue located between
  the bark (phloem) and wood (xylem). Cells are
  meristematic and therefore capable of dividing.
  Cambium of scion must be in close contact wityh
  cambium of rootstock
• Callus - mass of parenchyma cells. Develop from
  wounded plant tissues. Occurs at the graft union.

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The Biology of Grafting

• Rootstock-
• Types
• Seedling
• () simple, economical, mass produced, often free
  of viruses, have better roots systems than
  cuttings
• (-) genetic variation, juvenile and can delay
  flowering and fruiting
• Clonal
• () uniform, can have disease resistance, can
  cause dwarfing
• (-) can harbor diseases (systemic),
  micropropagated shoots are juvenile and can delay
  flowering and fruiting

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The Biology of Grafting

• Propagation and use of clonal rootstock
• Produced vegetatively by layering, rooted
  cuttings or micropropagation
• An active area of research (esp. for nut trees
  like pecan and pistachio)

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The Biology of Grafting

• Reasons for grafting/budding
• Perpetuating clones that cannot be readily
  maintained or economically propagated by
  cuttings, layers, divisions or other asexual
  methods
• Obtain benefits of certain rootstocks
• Obtain benefits of certain interstocks
• Change cultivars of established plants
  (top-working)

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Topworking
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The Biology of Grafting

• Speed up reproductive maturity and induce earlier
  flower and fruit production
• Increase plant growth rate and reduce production
  time
• Obtain special forms of plant growth
• Repair damaged parts of trees
• Study or eliminate viruses
• Study plant development physiological processes

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Mango maturity excelled
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Camperdown elm
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The Biology of Grafting

• Perpetuating clones
• Because beech, eucalyptus, firs, oak and spruce
  root very poorly from cuttings, clones of these
  species are often maintained by grafting
• Pinus elliottii (slash pine) and Pseudotsuga
  menziesii (Douglas fir) are important to
  forestry/timber production. To get superior
  plants, you need to graft superior selections.
  This can then develop into a seed orchard
  stock-block with elite germplasm

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Slash pine
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The Biology of Grafting

• Benefits of rootstocks
• Can tolerate unfavorable conditions (heavy, wet
  soils)
• Can resist soil-borne insects, nematodes or
  disease better than the scions roots could
• (ex wine grapes in the U.S. are grafted onto
  native muscadine grapes to prevent problems from
  nematodes and phylloxera yellow aphid)
• Can produce larger size/better quality fruits

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Phylloxera
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The Biology of Grafting

• Benefits of rootstocks (continued)
• Can speed scion into early maturity (early
  fruiting) but must use dwarfing rootstock (not
  seedlings or rooted cuttings)
• Asiatic (Japanese maples) form poor root systems
  from cuttings and therefore must be grafted
• Special rootstocks (resistant to Fusarium and
  Verticillium wilts) for greenhouse vegetable
  production in Europe/Asia and the U.S.

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The Biology of Grafting

• Benefits of interstock (Double-working)
• Makes it possible to avoid certain kinds of
  incompatibilities
• May possess a special characteristic (disease
  resistance/cold-hardiness), not possessed by
  either rootstock or scion
• Can reduce vegetative growth and increase
  resproductive growth of the tree (ex East
  Malling 9 dwarfing)

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The Biology of Grafting

• Changing cultivars on established plants
  (topworking)
• Change unproductive cultivars or those no longer
  in demand
• Fix poor growth habit
• Change those susceptible to insects of disease
• In California, peaches, plums and nectarines are
  generally changed every 2 - 3 years!

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The Biology of Grafting

• Hastening reproductive maturity of seedlings
• Graft terminal shoots of seedlings onto
  established tree rootstock
• Takes advantage of the large root system of the
  rootstock and speeds up maturation of juvenile
  scion

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The Biology of Grafting

• Hastening plant growth rate/reducing nursery
  production time
• Some shade trees (like Acer platanoides Crimson
  King) can grow more quickly if budded/grafted
  than if grown as a rooted cutting (or sometimes
  even a seedling!)

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The Biology of Grafting

• Obtaining special forms of growth
• Ex tree roses, fuschia, mum or ivy standards,
  weeping cherries, weeping birches, weeping
  elms, weeping black gum!
• Generally you have an upright rootstock and a
  weeping scion
• Also unusual cacti are grafted

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The Biology of Grafting

• Repairing damaged trees
• From winter injury, rodents, machinery, disease
• Use a bridge graft or inarching

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The Biology of Grafting

• Study and Eliminate Viruses
• Graft suspect scion or bud onto a susceptible
  indicator plant indexing
• Prunus serrulata Shirofugen is an indicator
  plant for viruses in peach, plum, almond and
  apricot
• Treat scion/bud with thermotherapy
• Micrograft shoot meristem onto seedling rootstock
  to eliminate virus

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Healthy graft union
Black line disease in walnut
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