I.  WHY VEGETATIVE PROPAGATION

    A. Convenient and Economical

            -Easy to start plants
                Rooting cuttings by sticking into ground (i.e. grape, fig, willow)
                Separation of roots, tubers, bulbs (i.e. banana, yam, potato)
            -Grafting and budding substituted cutting methods
                Apple, pear, cherry, etc. --------grafting, budding easier than rooting cuttings
                 (use seedling rootstock)
            -Availability of Controlled Environment
                misting facility with heating system   Fogging (1000 psi)
                use of rooting hormones (IBA)
            In general veg. propagation is economical (i.e. woody plants)

    B. Clonal Selection and Maintenance

            -Plants of a clone are identical genetically
                No genetic segregation
            -Most woody and perennials are highly heterozygous
                Asexual propagation immediately fixes genetic variation
                    anologous to the use of F₁

    C. Combining Some Traits
            -Grafting
                desirable traits in rootstock, scion combined

    D. Faster Maturity
            -Shortens time required from planting to maturity

            -Herbacious Perennials require 5-10 yrs from seeding to flowering
                i.e. Orchid (Cattleya)
                                seed to flowering --------  6 yrs
                                protocorm to flowering--- 4 yrs
                     Tulip, Bulbs, etc
                                seed to flowering--------- 3-8 yrs
                                protocorm to flowering--- < 1 yr

    E. Control of Growth Phases
            -Cuttings taken from juvenile and mature phases carry different morphological traits
                i.e. Citrus--- thorny in juvenile phase
                      Conifers--better lumber yield if juvenility is extended

II. VARIABILITY WITHIN CLONES

    B. Phenotypic Variation (Developmental, Environmental)
            -Variation due to environment
            -Non-genetic variation

                i.e. 'Bartlett' pear --- good fruit shape in WA, OR

    C. Phase Variation (Cyclophysis)
             -Variation from juvenile phase to mature phase
            1) The seedling cycle
                    Homoblastic- phase change gradually
                    Heteroblastic- phase change occurs abruptly
                                                                                                                                     Young shoots

 

                                    Juvenility =  A>B>C>D>E

              Classification of within-clone variation
                    a. Phenotypic variation
                            periphysis- developmental, environmental
                    b. Epigenetic variation
                            topophsis - position
                            cyclophysis- ontogenic age in apical meristem
                    c. Genetic changes including Chimeras*
                            nuclear mutations -nuclear genes, chromosomes
                            cytoplasmic mutations (maternal effect)- mitochondria, chloroplasts
                    d. Pathogenic variations
                            systemic - virus, viroids, mycoplasma (phytoplasma)
                            nonsystemic- bacteria, fungi

            2) The clonal life cycle

    D. Topophysis

            Effect of the position on the propagule stock plant on the type of vegetative growth in the vegetatively propageted plants

III. GENETIC VARIATION IN ASECUALLY PROPAGATED PLANTS

    A. Mutations
            -point mutations (genetic)
            -chromosomal deletions, duplications, translocations, inversions
            -ploidy changes (aneuploidy (2x-1, 4x+1), polyploidy (2x, 4x, 6x)
            -plastid mutations (cytoplasmic)- maternal inheritance
                -results in albino, variegated plants
            -sports (mutation on bud resulting in mutant branches)

    B. Chimeras
                A plant that is composed of tissure of more than one genotype
              chimera (GK) - a mythological monster having a lion's head, a goat's body, and a serpent's tail

           1) Origin - apical meristems

            2) Types of Chimeras
                 Periclinal chimera- mutated tissues in external layers
                 Mericlinal chimera- mutant tissues in segments of external layers
                 Sectoral chimera- a section of stem (plant) is mutant type

            3) Histogenic layers

    C. Nonchimeral Variations
            -color breaks in tulips caused by viruses
            -leaf colors in coleus due to hormonal distribution
            -some varigation is due to trasposible elements "jumping gene"

    D. Graft Chimeras
            -Chimeral buds of adventitious shoots formed on graft union

IV. PATHOGEN ELIMINATION

    A. Bacterial and Fungal Diseases

            -culture a stem section of the cutting on an agar medium to detect if the tissue carries pathogen
            -discard infected cuttings and propagate clean cuttings only

    B. Viruses
            -Indexing for virus transmission by grafting onto sensitive indicator plants (now use ELISA)
            -'clean' the infected plants by meristem cultures
                use of heat treatment
                plant generation from meristems

V. SOURCE SELECTION IN CLONAL CULTIVARS

    - Single plant selection
    - Pedegree selection
    - Nuclear stock selection
 

    Plant Quarantines
    -applied to vegetatively propagated plants
     -exchange of materials between countries
     -post-entry inspection and observations

VI.  THE PLANT PATENT LAW

    A. Amendment to the U.S. Patent Law (1930)

            Allows monetary rewards to breeders and originators of new plant forms
                -any distinct and new variety
                    sports, mutants, hybrids, newly found seedlings
                -excluded from patenting
                    tuber crops, plants naturally growing
                -obtain a patent from the U.S. patent office
                    some may require genetic 'fingerprinting'

    B. The U.S. Plant Variety Protection Act (1970)

            Patents extended to sexually propagated cultivars which can be maintained as lines
                i.e cotton, soybean, alfalfa, bluegrass, flowers