chap 2. biology of propagation
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Chap 2. Biology of Propagation1. General Terminology
a. Genotype: the genetic make-up of an organismb. 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 chromosomesx =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=xTetraploid 4x=48 2n=48
n=24=2xHexaploid 6x=72 2n=72
n=36=3xOctoploid 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
– 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 re-assortment by chromosomal translocation (cross-over)
2N → → N + N + N + N
An Example of Meiosis
Fertility in Polyploid (Euploidy) Plants
Ploidy Somatic Gametic FertilityMonoploid 2n=1x n = ? Very low
Diploid 2n=2x n = x High
Triploid 2n=3x n = ? Very lowTetraploid 2n=4x n = 2x VariablePentaploid 2n=5x n = ? VariableHexaploid 2n=6x n = 3x VariableHeptaploid 2n=7x n = ? VariableOctoploid 2n=8x n = 4x VariableNonaploid 2n=9x n = ? VariableDecaploid 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 PloidySomatic
(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)
• EuploidyVariation between chromosome sets
• AneuploidyVariation within a chromosome set
• AutoploidyMultiplication 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
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
A diploid plant ( ) would contain the following chromosome numbers depending on aneuploidy conditions:
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 PatternSalpiglossis sinuata
RR or Rr Red flower colorrr Yellow flower colorDD or Dd Solid color patterndd 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)
Solid Red (RrDd)
F1
Solid red (R-D-) 9
Dilute red (R-dd) 3
Solid yellow (rrD-) 3
Dilute yellow (rrdd) 1
F2
2. NomenclatureBased on ICBN (International Code of Botanical Nomenclature)
a. Botanical ClassificationFamily-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 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-
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