Principles%20of%20Grafting%20and%20Budding

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Principles of Grafting and Budding

• Chapter 11

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Grafting Budding Terms
Graft Two living plants connected and growing
as one
Scion Dormant shoot, upper portion of graft
Stock Lower portion of graft, root system
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Grafting Budding Terms
Bud Similar to graft, but scion is reduced to a
single bud
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Grafting Budding Terms
Interstock A middle or intermediate stem piece
located between scion stock
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Grafting Budding Terms
Vascular Cambium Meristematic tissue between
xylem phloem
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Grafting and Budding

• Perpetuate clones
• Rootstock effects
• Changing cultivars
• Rapid maturity
• Shortens juvenility
• Used for breeding programs
• Special growth forms
• Damage repair
• Studying viruses

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Seedling Rootstocks

• Simple
• Cheap
• Disease free
• Better root systems
• Genetic variation

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Clonal Rootstocks

• Source
• Stool beds
• Cuttings
• Tissue Culture
• Characteristics
• Uniformity
• Disease Resistance
• Growth Habit
• Flowering Habit
• Scion rooting
• Disease potential

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Rootstock benefits

• Disease resistance
• Soil tolerance
• Size control
• Fruit quality

Interstock benefits

• Overcome incompatibility
• Add additional attributes
• Dwarfing

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Topworking

• Change cultivars
• Add pollinators

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Topworking

• Multiple varieties on one tree

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Formation of graft union

• Line up vascular cambium
• Wound healing response
• Necrotic plate
• Callus bridge formation
• Cambium formation
• Vascular tissue formation

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1. Close Vascular Contact

• 55-90F
• Active cambium
• High humidity
• Pathogen free
• Mechanical support
• Cambium matching

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2. Formation of Necrotic plate

• Cells killed when
• cut is made

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3. Callus Bridge Formation

• Production Interlocking of parenchyma
• Comes from phloem and immature xylem
• Stock produces most callus

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4. New Cambium Formation

• Adjacent callus differentiates to form cambium
• Cambium forms across bridge of callus tissue

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5. New Vascular Tissue (XP) From New Cambium

• Vascular system must be in place before bud break

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GRAFT FORMATION
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BUD FORMATION
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Factors of graft healing

• Incompatibility
• Species or variety (cultivar)
• Temperature
• Moisture
• Oxygen
• Growth status (active vs. dormant)
• Technique or type of graft
• Disease situation

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Polarity in grafting

• Distal and Proximal ends
• Reversed polarity works only for a limited time
  with grafts
• Nurse-root grafting
• Buds can be reversed
• Can cause a wide crotch angle as it grows - strong

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Limits of grafting

• Generally limited to dicots gymnosperms
• More closely related the better
• Permanent grafts in monocots are not successful
• Likely has a lot to do with cambium and vascular
  tissue production
• Common between same species
• Apple on apple
• Harder between different Genera in same family
• Tomato on potato (Solanaceae family, or
  Nightshade)
• Rare between families

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Symptoms of Incompatibility

• High failure rate
• Yellow foliage, early defoliation
• Premature death of scion
• Differences in growth rate
• Not always a sign of incompatibility
• Can be differences in genetic potential for
  growth rate
• Overgrowths
• Breaks at graft union

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Types of Incompatibility

• Localized
• At site of graft contact
• Translocated
• Substances moved from the scion to rootstock or
  vice-versa
• Virus present

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Incompatibility

• Cause Genetic
• Mechanism (example theories)
• Chemicals found in one partner may be toxic to
  the other (Cyanogenic glucoside)
• Lignification of cell walls may be inhibited

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Effects of Rootstocks on the Scion

• Size and growth habit
• Fruiting
• Size, quality, and maturity of fruit
• Winter hardiness
• Disease resistance
• Timing of fruit maturity

Effects of Scion on the Rootstock

• Vigor
• Cold-hardiness

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Effects of Interstock on Stock Scion

• Reduces stock and scion size
• Direct effect, not indirect

Mechanisms of effects (theory)

• Translocation (stem)
• Absorbing ability (root system)
• Interaction of all parts

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Factors influencing growth of grafted plants

• Nutrition
• Translocation
• Endogenous growth factors