Genetics & Plant Breeding

J.G. Mexal

A/H 100 G

Spring 2006

Topics

• History

• Cell Division (mitosis)

• Reproduction (meiosis)

• Role of DNA

• Role of RNA

• Plant Breeding & Genetics

Gregor Mendel (1822-1864)

• Worked in monastery garden

• Time period = 1856-1863• Published: “Experiments

on Plant Hybrids” in obscure journal

• Worked ‘discovered’ in 1900

Gregor Mendel

S = smooths = wrinkled

• Dominant vs Recessive genes

Gregor Mendel

• Dominant vs Recessive genes (2)

F1

S = smooths = wrinkledY = yellowy = green

Gregor Mendel

• Incomplete dominance

Important Milestones

• 1866 Gregor Mendel• 1947 Barbara McClintock (jumping genes)

• 1953 Watson & Crick (structure of DNA)

• 1970s Foreign gene expressed in tobacco

• 1986 Transgenic plants field tested

• 1990s Bt gene inserted into crops

• 1994 Flavr-Savr tomato released

Sex in the Garden

Types of Propagation

#1 #2 #4 #5 #6 #7 #8 #9 #10

Sex in the Garden

Types of Propagation• Sexual

– Self-pollination -- Wind pollination– Cross-pollination -- Insect pollination

• Asexual– Cuttings -- Layering– Grafting -- Biotechnology

Sex in the Garden

Sexual Propagation• Terms

– DNA : Deoxyribonucleic Acid a polymeric molecule consisting of nucleotides (ribose, PO4, and adenine, cytosine, guanine, & thymine). Found in nucleus, chloroplasts, mitochondria. Makes RNA.

– RNA: Ribonucleic Acid a polymeric molecule consisting of nucleotides (ribose, PO4, and adenine, cytosine, guanine, & uracil). Found in nucleus, chloroplasts, mitochondria, ribosomes. Makes proteins.

Building Blocks

Sex in the Garden

Sexual PropagationTerms– Chromosome: genetic material of cell organized in

linear structures

– Gene: genetic material on a chromosone

determining a characteristic

– Genotype: the genetic makeup of an organism

– Phenotype: the physical manifestation of the genotype modified by the environment

Sex in the Garden

Sexual PropagationTerms– Diploid: a cell containing 2 sets (2n)of

chromosomes (vegetative cell)

– Haploid: a cell containing 1 (1n)set of chromosomes (pollen or ovule)

– Polyploid: a cell containing more than 2 sets of

chromosomes. Usually vegetatively reproduced.• Banana = 3n• Potato = 4n• Strawberry = 8n

Sex in the Garden

Sexual PropagationTerms– Mitosis: cell division where nuclear complement (1n

or 2n) is maintained

– Meiosis: cell division where nuclear complement (2n only) is reduced to 1n (gametes)

– Hybridization: controlled cross-fertilization

– Independent Assortment: each chromosome operates independently during mitosis & meiosis

– Mutation: a heritable change in a gene

Sex in the Garden

Sexual PropagationTerms

• Monoecious: Both sexes on same plant (e.g. corn, pecan)

• Dioecious: Sexes on different plants– Holly (female) Juniper (male or female)– Pistachio (female) Cottonwood (male)– Asparagus (male)]– Ash (male)

Cell Division-Mitosis

Cell Division-Meiosis

Sexual PropagationMeiosis

Flower

Pollen Ovule

microspores megaspores

#1 #2 #4 #5 #6 #7 #8 #9 #10

Sexual Propagation

Fertilization

Endosperm3n

Embryo

Pollen grain

Generative cellTube nucleus

Pollen tube

Sperm cells

Polar nuclei

Egg

Embryo sac4-nucleate

2-nucleate

Zygote 2n

Genetic Engineering

• The Tools– Agrobacterium – “Gene Gun”– Electroporation– Microinjection– Liposomes

• The Plan:– Find a gene of interest– Develop cell culture of crop– Insert the gene (tools)– Hope it gets incorporated in

plant DNA– Have gene product expressed– Regenerate plants from cells– Field test to see if it works!

Plant:People Interactions

• People to Plant– Moving plants

– Endangering plants– Chestnut, Echinacea

– Creating ‘new’ plants— Bt corn, RoundUp Ready Cotton

The Good The Bad and The UglyCorn Saltcedar Chestnut blightChile Tumbleweed Dutch Elm DiseasePeanut Kudzu Sudden Oak DeathApple Tree of Heaven White Pine Blister RustPotato Potato Karnal bunt

Biotechnology Advances

• Flavr-Savr Tomato• Ring spot virus-

resistant Papaya• Golden Rice (vitamin A)

• Round-up resistant crops (herbicide)

• BT crops (insecticide)

• ‘Designer’ plants

Genetic Engineering

• The Future:– Antibiotics in fruits– Salt tolerance??– Drought tolerance??– Freeze tolerance (INA)– Mexal’s botanical kindergarten??

#1 #2 #4 #5 #6 #7 #8 #9 #10

Plant:People Interactions

• Creating ‘new’ plants— for the future

• Sensitive Noses: Beano-Beans• Movie Goers:Glo-in-the-dark

Popcorn• Indecisive New Mexicans:

‘NuMex Red’nGreen’ Chile• Americans: Atkins-friendly Maple

Syrup• Christmas: Epiphany Poinsettia• Kinder-garden: Nile water lily X

Venus fly-trap

Plant:People Interactions

• People to Plant– Creating ‘new’ plants— for the

future• Sensitive Noses: Beano-Beans• Movie Goers:Glo-in-the-dark

Popcorn• Indecisive New Mexicans:

Red’nGreen Chile• Americans: Atkins-friendly Maple

Syrup• Christmas: Epiphany Poinsettia• Kinder-garden: Nile water lily X

Venus fly-trap

Sex in the Garden

Asexual Propagation• Terms

– Cutting– PGR (hormone)– Sport– Scion– Rootstock– Graft Union– Tissue Culture

Sex in the Garden

Asexual Propagation• Vegetative Propagation

– Timing (season) -- Age (branch)– PGR -- Leaf Area– Stem Wounding -- Cutting Size– RH -- T

Rooting of Blue Spruce/ Wagner1987

Rooting %

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Collection Month

IBA Treatment (ppm)

Rooting %

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Cutting Length (cm)

Genetics & Plant Breeding

• Things to Know– DNA– Gene– Chromosome– Ploidy

• Haploid (N)• Diploid (2N)• Polyploid (3N, 4N, 6N)

• Things to Know– RNA– Mitosis– Meiosis