Chap 2. Biology of Propagation General Terminology a. Genotype: the genetic make-up of an organism b. Phenotype: the external appearance of an organism (usually the outcome of interaction between a genotype and environment) c. Ploidy: Variation in the genomic number (x) of chromosomes x = n = 2n = “wholeness” n = “halfness”

Variation in Euploidy (for Organisms with x=12) Ploidy No. Chromosomes Somatic Gametic ----------------------------------------------------------------------------------------- Diploid 2x=24 2n=24 n=12=x Tetraploid 4x=48 2n=48 n=24=2x Hexaploid 6x=72 2n=72 n=36=3x Octoploid 8x=96 2n=96 n=48=4x Haploid 1x=12 2n=12 n= 6 (?) Triploid 3x=36 2n=36 n=18 (?) Pentaploid 5x=60 2n=60 n=30 (?) Seedless watermelons are triploids

Reproductive Biology Cell Division Flowering and Anthesis Somatic cell division (Mitosis) Reproductive cell division (Meiosis) Flowering and Anthesis Megagametogenesis (EMC to Egg Cells) Microgametogenesis (PMC to Pollen Grains) Pollination and Fertilization Pollen germination on stigma Pollen tube growth through style tissue Double fertilization

Mitosis 2N → 2N + 2N - Somatic Cell Division Ends up with same number of chromosomes in divided cells Divided cells are genetically identical to maternal cells 2N → 2N + 2N

Meiosis 2N → → N + N + N + N Reproductive cell division Undergoes 2 separate divisions Forms gametes Divided cells have a half of the chromosome numbers Ends up with genetic re- assortment by chromosomal translocation (cross-over) 2N → → N + N + N + N

An Example of Meiosis

Fertility in Polyploid (Euploidy) Plants Somatic Gametic Fertility Monoploid 2n=1x n = ? Very low Diploid 2n=2x n = x High Triploid 2n=3x Tetraploid 2n=4x n = 2x Variable Pentaploid 2n=5x Hexaploid 2n=6x n = 3x Heptaploid 2n=7x Octoploid 2n=8x n = 4x Nonaploid 2n=9x Decaploid 2n=10x n = 5x

Polyploidization Use of Cholchicine to induce polyploids Colchicine interferes with spindle fiber function during metaphase of meiosis

Production of Seedless Watermelon www.parkseed.com

Example of Ploidy Variation Chromosome Number Species Ploidy Somatic (2n) Gametic (n) Genomic (x) Spinach 2x 12 6 Corn 20 10 Potato 4x 48 24 Strawberry 8x 56 28 7

Polyploidy Terminology (continued) Euploidy Variation between chromosome sets Aneuploidy Variation within a chromosome set Autoploidy Multiplication of the complete set of genomes of a species Alloploidy Polyploid containing genetically different sets of chromosomes derived from 2 or more species

Aneuploidy Variation within a chromosome set A diploid plant ( ) would contain the following chromosome numbers depending on aneuploidy conditions:   Aneuploidy Somatic chromosome number  Examples  Trisomic  2n + 1 (extra) 11  22  33  44  55  66 777  Monosomic   2n - 1 (deficient) 11 22 3_ 44 55 66 77  Double-trisomic 2n + 1 + 1 (2 extra) 11  22  33  44  555  66  777 4 of one chromosome 2n + 2 (2 extra) 11  22  33  44  5555  66  77

- One tube nucleus - Two sperm nuclei Pollen Tetrad and Microgametophyte   - One tube nucleus    - Two sperm nuclei 

Megagametophyte

Pollination and Fertilization, Angiosperms

Double Fertilization A process of fertilization in which one male gamete (sperm nucleus, n) unites the egg nucleus (n) to form embryo (zygote, 2n) and the other sperm nucleus (n) unites polar nuclei (2n) to form endosperm (3n)

General Terminology (continued) Homozygous- b. Heterozygous- Having unlike alleles at one or more corresponding loci on homologous c. Meiosis- - Chromosome number is reduced to one half - Results in formation of gametes - Allows genetic recombination d. Mitosis- - Chromosome number same in daughter cells - Results in somatic tissues genetically identical - Allows clonal duplication

Fruit Flesh Color and Skin Texture Inheritance - Peach

Inheritance of Flower Color and Color Pattern Salpiglossis sinuata RR or Rr Red flower color rr Yellow flower color DD or Dd Solid color pattern dd Dilute color pattern

Gene Symbols RR DD or R_R_ (red, solid) RR dd or R_ dd (red, dilute) rr DD or rrD_ (yellow, solid) rr dd (yellow, dilute)

x P1 P2 F1 F2 9 Dilute Red (RRdd) Solid yellow (rrDD) Solid Red (RrDd) 3 Solid yellow (rrD-) 3 Dilute yellow (rrdd) 1

2. Nomenclature Family-Genus-Species-Variety-Form-Individual Based on ICBN (International Code of Botanical Nomenclature) a. Botanical Classification Family-Genus-Species-Variety-Form-Individual - Subspecies - Clines- - Ecotypes- b. Cultivated Plants Genus, species, cultivar Cultivar = Cultivated variety (cv.) Cultigen = Cultivated variety that has been naturalized Examples:

3. Kinds of Cultivars Cultivars made up of self-pollination of an F-1 a. Line- Self pollinated seed-propagated cultivar (homozygous) - Inbred lines - Synthetic lines (composite lines) b. Hybrids (sexual) F-1 hybrid- first generation progeny from a cross between 2 inbred lines (single cross) c. F-2 Cultivars (sexual) Cultivars made up of self-pollination of an F-1

3. Kinds of Cultivars (continued) d. Open Pollinated Cultivar - Cultivar made up of seeds formed by open pollination - Can be mixtures of hybrids, selfs) - Inbred lines - Synthetic lines (composite lines) e. Clonal Cultivars Clone- Asexual propagation- cuttings, tubers, bulbs, grafts, rhizomes, cormels, stolon f. Apomictic Seeds Seed formed from maternal (ovule) tissues

4. Requirements for New Cultivar a. Distinctive- b. Uniform- Homogeneous (but, can be heterozygous as in F1) Homozygous (no segregation) c. Stable- d. Commercial-