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Transcript
Chap 2. Biology of Propagation 1. 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 Tetraploid Hexaploid Octoploid 2x=24 4x=48 6x=72 8x=96 2n=24 2n=48 2n=72 2n=96 n=12=x n=24=2x n=36=3x n=48=4x ----------------------------------------------------------------------------------------- Haploid Triploid Pentaploid 1x=12 3x=36 5x=60 2n=12 2n=36 2n=60 n= 6 (?) n=18 (?) n=30 (?) ----------------------------------------------------------------------------------------Seedless watermelons are triploids Reproductive Biology • Cell Division – 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 - Somatic Cell Division - Ends up with same number ofchromosomes in divided cells - Divided cells are genetically identical to maternal cells 2N → 2N + 2N Meiosis • Reproductive cell division • Undergoes 2 separate divisions • Forms gametes • Divided cells have a half of the chromosome numbers • Ends up with genetic reassortment by chromosomal translocation (cross-over) 2N → → N + N + N + N An Example of Meiosis Fertility in Polyploid (Euploidy) Plants Ploidy Somatic Gametic Fertility Monoploid 2n=1x n=? Very low Diploid 2n=2x n=x High Triploid 2n=3x n=? Very low Tetraploid 2n=4x n = 2x Variable Pentaploid 2n=5x n=? Variable Hexaploid 2n=6x n = 3x Variable Heptaploid 2n=7x n=? Variable Octoploid 2n=8x n = 4x Variable Nonaploid 2n=9x n=? Variable Decaploid 2n=10x n = 5x Variable 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 6 Corn 2x 20 10 10 Potato 4x 48 24 12 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 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) 1. General Terminology (continued) a. 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 rr DD or Dd dd Red flower color Yellow flower color Solid color pattern 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) P1 P2 x Dilute Red (RRdd) Solid yellow (rrDD) F1 Solid Red (RrDd) F2 Solid red (R-D-) 9 Dilute red (R-dd) 3 Solid yellow (rrD-) Dilute yellow (rrdd) 3 1 2. Nomenclature 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 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 CloneAsexual propagation- cuttings, tubers, bulbs, grafts, rhizomes, cormels, stolon f. Apomictic Seeds Seed formed from maternal (ovule) tissues 4. Requirements for New Cultivar a. Distinctiveb. UniformHomogeneous (but, can be heterozygous as in F1) Homozygous (no segregation) c. Stable- d. Commercial-