Clonal Selection Flashcards

1
Q

Bud-Sport

(Bud Mutation)

A
  • when a mutant suddenly appears in the branch of a plant
  • Sports are generally unwanted, but have been the source of many new cultivars
  • a sudden change in a single branch due to a mutation apparently arising from a single bud
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2
Q

Chimera

A
  • A plant composed of a mixture of two genotypes, each expressed independently in separate layers of the shoot
  • the different genotypes originate within the meristematic tissue
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3
Q

Environment by Genotype Interactions

A
  • a source of phenotypic variation
  • clones gron in different environments may look different
  • plant size, shape, flower number and color may all be different in plants grown in the sun versus in the shade
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4
Q

Genetic Mosaics

A
  • a source of phenotypic variation
  • permanent genetic variation
  • 4 ways:
  1. variegation - the cellular-based cotrasting genetic expression in different parts of the same organ, usually caused by chimeras
  2. patterend genes - a differential gene expression that is not due to cell arrangement
  3. transposons - a unique kind of genetic element in cells of some organisms that have the capacity to change position within the chromosome
  4. somaclonal variation - pathogens that infect the cells of a plant and spread throughout the plant, where they remain infective
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5
Q

Genetic Variation

A
  • one type of clonal variation (phenotypic variation is the other)
  • Mutation - a permanent gentic change involving some part of the DNA molecule
  • Bud-Sport - a sudden change in a single branch due to a mutation apparently arising from a single bud
  • plants or seeds can be treated with chemicals or radiation to induce mutations
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6
Q

Graft Chimera

A
  • a chimera sometimes created when an adventitious shoot emerges from callus at a graft that has tissues of both the stock and scion
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7
Q

Mericlinal Chimeral

A
  • the mutant cells are only in a part of a single cell layer
  • unstable
  • thought of as a transition as cells divide to form a periclinal chimera or revert to a non-mutant form
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8
Q

Monoculture

A
  • the mass production of a single genotype within a singl planting
  • since all the plants of a nursery, field orchard, or plantationhave the same genotype, each is equally vulerable to specific environmental hazards and specific pests and diseases and may lead to an overall loss of genetic diversity
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9
Q

Patterned Genes for Variegation

A
  • a differential gene expression (as a color pattern) that is not due to cell arrangement
  • a genetic trait of the cultivar
  • an inherited trait
  • can be fixed by selection and seed propagation
  • the pattern is different due to different cells in a tissue expressing color genes
  • their typical pattern is displayed throughout the clone and expressed by each plant
  • not a chimera
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10
Q

Periclinal Chimera

A
  • all the cells in one layer different from the other layers
  • the most stable chimera
  • common cause of leaf veriegation
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11
Q

Phenotypic Variation

A
  • one type of clonal variation (genetic variation is the other)
  • involves a change in the way a plant’s genes are expressed
  • is not a mutation
  • sources of phenotypic variation:
  1. environment by genotypic interactions (phenological changes)
  2. ontogenetic aging (phase changes)
  3. permanent genetic variation
  4. infection by systemic pathogens (particularly viruses and similar organisms)
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12
Q

Reversion

A
  • a shoot which emerges from inner tissue of a chimera and shows the genotype of the inner tissue
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13
Q

Sectorial Chimera

A
  • the mutated tissue occupies a sector that encompasses all layers
  • not stable
  • would revert to a periclinal chimera or an all- mutant or non-mutant meristem
  • an unusual chimera
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14
Q

Systemic Pathogen Infection

A
  • usually infection of a plant with a pathogen causes sever symptoms and can lead to plant death
  • however, some viral infection cause only limited vigor loss
  • n some cases they cause a variegated leaf or flower cover and are prepuated during propagation
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15
Q

Transposon

A
  • a moveable genetic element
  • also called jumping genes
  • they randomly move about the chromosome creating genetic mosaics
  • A mobile genetic factor or jumping gene that turns on or off a gene resulting in a new phenotype
  • the variegation pattern is inherited from seed (chimera not inherited from seed)
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16
Q

Tunica-Corpus

A

.

17
Q

Advantage of Clones as Cultivars

A
  • genetic improvement and selections
  • uniformity of populations
  • control of phases of plant development (ex. earlier bearing of fruit trees)
  • combine more than one genotype into a single plant (grafting)
  • greater commercial value
  • facilitating propagation (sometimes only means to propagate)
18
Q

Disadvantages of Clones as Cultivars:

A
  • monoculture
  • slow reproductive rate
  • lack of genetic variation for breeding and selection
  • potential for propagating systemic pathogens from clonal sources
  • insufficient genetic diversity for resistance against unforeseen pests or pathogens
  • potential for latent genetic mutation
19
Q

Anticlinal Division

A
  • the direction of cell division in an end-to-end position to produce a continuous payer
  • (perpendicular to the surface)
  • divisions that eventually become the epidermis and outer layers of the plant
20
Q

Periclinal Division

A
  • the direction of cell division in a side-to-side position to increase numbers of cell layers
  • (parallel to the surface)
  • divisions to expand the shoot, particularly in the locations farther from the tip