Principles of Grafting and Budding

• grafting: the union of a root system (rootstock) with a shoot system (scion) in such a way that they subsequently grow and develop as one composite plant
• budding: a form of grafting; the scion is reduced in size, usually contains a single bud
• grafting is practiced on:

  • fruit trees
  • nut trees
  • grapevines
  • shade trees
  • flowering trees/shrubs
  • bonsai
  • herbaceous vegetables
  • cacti
• scion: composed of a short piece of detached shoot containing several dormant buds, which, when united with the rootstock, comprises the upper portion of the graft; becomes the new shoot system
• rootstock: the lower portion of the graft; develops into the root system
• interstock: a piece of stem inserted by means of two graft unions between the scion and the rootstock
• why we use interstock:

  • avoid incompatibility
  • for particular characteristics not possessed by rootstock or scion
  • may reduce vegetative growth and enhance reproductive growth
  • obtain special forms of plant growth
• types of rootstock:

  • seedling
  • clonal
• seedling rootstock:

  • propagated from seed
  • can be mass produced
  • may show genetic variation
• clonal rootstock:

  • clonally propagated by mound layering, rooted cuttings, or micropropagation
  • uniformity; preserve special characteristics
• Rootstock influence may be lost if scion rots
• reasons for grafting and budding:

  • propagate clones that cant be propagated by other vegetative methods
  • poor rooting
  • heterozygous
  • layering too slow/expensive
• reasons for grafting and budding:

  • propagate clones that can't be propagated by other vegetative methods
  • grafting can speed up plant growth rate
  • speed transition to adult phase in juvenile scions
  • obtain benefits of certain scions
  • take advantage of unique rootstock properties
  • nutrient deficiency resistance
  • obtain benefits of interstocks
  • change the cultivar
  • to repair damaged trees
  • to evaluate virus expression
• Grafting vegetables is common for managing soil-borne diseases, enhancing tolerance of low temperature and salinity, and increasing plant vigor and yield
• double-working: obtain the benefits of interstocks
• topworking: changes the cultivar of established plants; facilitates cross pollination of dioecious plants
• Scion or buds of infected plants are grafted onto an indicator plant for symptom development
• important things to know before grafting and budding:

  • graft union formation
  • factors affecting successful union formation
• vascular cambium: a thin tissue located between the phloem and the wood; cells are capable of dividing and forming new cells
• callus: tissue composed of parenchyma cells formed in response to wounding; important for graft union formation
• formation of graft union:

  1. lining up vascular cambiums
  2. formation of necrotic material from cells on the wound site
  3. callus bridge formation
  4. cambium formation
  5. vascular tissue formation
• Graft union formation in T- and chip budding:

  1. Laid against exposed xylem and cambium of rootstock
  2. Necrotic plate/layer develops from cut cells
  3. Callus starts to develop
  4. Continuous cambium is established between bud and rootstock
• graft compatibility: the ability of two different plants, grafted together, to produce a successful union and develop into a composite plant
• graft incompatibility: an interruption in cambial and vascular continuity leading to a smooth break at the point of the graft union, causing a graft failure
• graft failure: an unsuccessful graft caused by anatomical mismatching, poor craftsmanship, adverse environmental conditions, disease, or graft incompatibility
• most successful to least successful:

  • within a clone
  • within a species
  • within a genus
  • within a family
  • between families
• more distantly related plants = lower chances of compatibility
• factors influencing graft union success:

  • plant species and type of graft
  • environment
  • temperature
  • moisture
  • growth stage
  • virus
  • polarity
  • craftsmanship
  • plant growth regulators
  • post-graftage
• top grafting: proximal end of the scion is attached to the distal end of the rootstock
• root grafting: the proximal end of the scion is joined to the proximal end of the rootstock
• symptoms of incompatibility:

  • failure to form a successful union
  • yellowing
  • premature death
  • suckering of rootstock
  • graft components breaking apart cleanly
  • differences in growth rate of scion and rootstock
  • overgrowth around the graft union
• What is needed for successful grafting?

  • rootstock and scion are compatible
  • vascular cambium must be placed in close contact
  • rootstock and scion must be at the proper physiological stage
  • all cut surfaces must be protected from desiccation
  • post-graft care