PLSC 368: Chapter 2

    BIOLOGY OF PROPAGATION

I. GENERAL TERMINOLOGY

    A. Genotype- the genetic makeup of an organism

    B. Phenotype- Theexternal appeance of an organism expressed as the interaction of genotype and environment

    C. Ploidy- Variation in the genomic number (x) of chromosomes

    D. Homozygous- Having like alleles at corresponding loci on homologous chromosomes

    E. Heterozygous- Having unlike alleles at one or more loci on homologous chromosomes


    F. Meiosis- Reproductive cell division (Reduction division)
            1) Chromosome number is reduced to half
            2) Results in formation of gametes (pollen, egg cell)
            3) Allows genetic recomibination

    G. Mitosis- Somatic cell division
            1) Chromosome number same in daughter cells
            2) Results in somatic tissues genetically identical to parent cells
            3) Allows clonal duplication

II. NOMENCLATURE
        ICBN- International Code of Botanical Nomenclature

    A. Botanical Classification

    B. Cultivated Plants
           Genusspecies cultivar   (generally trinomial)
            Cultivar = Cultivated variety
            Cultigen = Cultivated variety that had been naturalized
                Syringa vulgaris cv. Mont Blanc
                Syringa vulgaris 'Mont Blanc'
                  Lilac 'Mont Blanc'

III. KINDS OF CULTIVARS

    A. Line- self pollinated seed propagated cultivar (homozygous)
                        i.e. inbred lines
                             synthetic lines
    B. Hybrids- (sexual)
            F1 hybrid- first generation progeny from a cross between 2 inbred lines (Single cross)

    C. F2 Cultivars (sexual)
            cultivars made from self-pollination of an F1


    D. Open Pollinated Cultivar (sexual)
            Cultivar made up of seeds formed by open pollination. (can be mixtures fo hybrids, selfs)

    E. Clonal Cultivars (asexual)
           Clone- plants propagated by asexual means (ex. cuttings, tuber, bulb, rhizomes, grafts, cormel, stolon)

    F. Apomictic Seeds (asexual)
            Seeds formed from maternal tissues (ovule)
 

IV. REQUIREMENTS FOR CULTIVAR

    A. Distinct- Morphologically, physiologically different characteristics

    B. Uniform- Homogeneity
                              variation should be minimal

                              Homogeneous- (but can be heterozygous as in F1 )
                            Homozygous

    C. Stable- A reasonable degree of reliability
                          Reproducible performance

    D. Commercial- Must have agronomic or horticultural value