Vegetative Propagation

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Vegetative Propagation

• Selection and Management of Clones

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Reasons for Using Clonal Cv.s

• Fixing superior genotypes
• uniformity of populations
• facilitate/ease of propagation
• shorten time to flower
• combine more than one genotype into a single
  plant
• control phases of development

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Fixing Genotypes

• Presently selected clones are heterozygous
• If propagated by seed, may lose characteristics
• Examples
• citrus
• fig
• grapes
• persimmons

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Uniformity of Populations

• Uniformity-major advantage
• Characteristics
• plant size
• growth rate
• time of flowering
• economic variables on production

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Facilitate Propagation

• Implies consistent and economically feasible
  production when possible.
• Examples
• hardwood cuttings of Pomegranate
• cuttings of Raphiolepis or Pittosporum

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Shorten Time to Flower

• Vegetatively propagated plants come into flower
  at an earlier age compared to those propagated by
  seed.
• Dependent on the maturation of plant tissue.

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Combine more than One Genotype into one plant

• Use of grafting or budding
• rootstock
• interstock
• Placement of multiple cultivars on one plant

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Control Phases of Development

• Phases
• juvenile
• transitional
• mature
• Vegetative propagation used to maintain, enhance
  of reverse specific phases.

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Origin of Clonal Cultivars

• Seedling selection
• Mutation
• point mutations
• deletions, duplications and transformations
• bud-sports or bud mutations
• Biotechnology
• recombinant DNA technology

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Kinds of Genetic Variation within Clones

• Chimeras
• Transposons
• Somaclones

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Chimeras

• Mutations producing an island of mutant cells
  within a growing point of a stem.
• Forms a mixture of two genotypes.
• Various kinds of variegation
• Bud sports
• Artificially induced

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Types of Chimeras

• Periclinal
• Mericlinal
• Sectorial

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Periclinal

• Mutated tissue completely surrounds an inner core
  of non mutated tissue.
• Red pigment in apples on outside, inner tissue
  have alleles for green and yellow.
• Thornless blackberry
• Stable chimera
• Not stable if cuttings used produce shoots from
  non mutated tissue.

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Mericlinal

• Cells carrying the mutant gene occupy only a part
  of the outer cell layer.
• Unstable-may revert to non-mutated form,
  periclinal chimera or remain a mericlinal
  chimera.
• May appear as red streaks in apple.

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Sectorial Chimera

• Mutated cells occupy an entire sector of the stem
  including all layers of the shoot apex.
• Formed if mutation occurs in roots and very early
  stages of embryos.
• Unstable-reverts to mericlinal and periclinal
  chimeras.

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Non-Genetic Variations within Clones

• Environmental
• Phase variation and change in maturation
• Phase variation and vegetative propagation
• Juvenile vs. adult phenotypes
• promoting shifts from juvenile to mature phase
• selection and maintenance of the juvenile phase
• reversions from mature to juvenile phase
• Topophysis
• orthotropic vs. plagiotropic

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Pathogens and Plant Propagation

• Plant pathogen complexes
• Systemic Pathogens and Clones
• viruses
• phytoplasma
• bacteria
• viroids

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Mgt. of Sources for Vegetative Propagation

• Characteristics of Source Material
• true to name
• true to type
• pathogen free
• detect pathogens
• visual inspection
• culture indexing
• virus indexing
• serology

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Mgt. of Sources for Vegetative Propagation

• Elimination of pathogens
• select uninfected parts
• shoot apex culturing and tip grafting
• heat treatments
• thermotherapy
• growing seedlings

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Management of Propagation Sources

• Commercial plantings
• Production material within nursery
• Stock blocks