Objectives of applied plant physiology:Increase productivity via:

– Enhanced efficiency or resistance

– Reduce losses to pests, stress, weeds

How do we increase yield despite marginal environments?– Traditional breeding; artificial selection

• Hybrids (2 species or cultivars crossed; generally close relatives)

• Induce mutations tissue culture mutations

• Find unique genotypes; propagate; use DNA markers that are tightly-linked to target loci (marker assisted selection)

Time intensive, but effective

F2

P2

F1

P1 x

large populations consisting of thousands of plants

PHENOTYPIC SELECTION

Field trialsGlasshouse trials

DonorRecipient

CONVENTIONAL PLANT BREEDING

Salinity screening in phytotron Bacterial blight screening Phosphorus deficiency plot

F2

P2

F1

P1 x

large populations consisting of thousands of plants

ResistantSusceptible

MARKER-ASSISTED SELECTION (MAS)

MARKER-ASSISTED BREEDING

Advantages - Selection at seedling stage, no environmental effects and can discriminate between homozygotes and heterozygotesDisadvantages – cost, technical expertise, marker must be tightly linked to trait of interest (<5cM of marker)

Objectives of applied plant physiology:Increase productivity via:

– Enhanced efficiency or resistance– Reduce losses to pests, stress, weeds

How do we increase yield despite marginal environments?– Traditional breeding; artificial selection

• Hybrids (2 species or cultivars crossed; generally close relatives)

• Induce mutations tissue culture mutations

• Find unique genotypes; propagate; use DNA markers that are tightly-linked to target loci (marker assisted selection)

Time intensive, but effective

– GMOs; transgenic plants• Recombinant DNA technology

• Tissue culture of transformed cells

– Time and $$ intensive

– Concerns by public (explore on T)

What traits could we modify?

What traits are we modifying?Herbicide resistance (so we can spray fields with herbicide and not kill the crop)

Insect resistance (so we don’t spray pesticides, the plants make the toxins)

Disease resistanceEnhanced shelf life, oil or nutritional content (golden rice)

– All of these are generally single gene traits

Hyperaccumulators – clean pollution

Stress tolerance to drought, heat, cold, salt, pollutionN fixation, C4 PSN

– Problem with these = multiple genes or they involve symbiotic interactions, which are harder to transform

Agrobacterium tumifaciensCrown gall disease – a bacterium

– Widespread

– enters plant via wounds– causes cancer-like tumors (crown gall disease)

– can reduce productivity

– Gall grows and divides (even if bacteria dies)

• Gall tissues have high [CK] and [IAA]

• Opines (unusual a.a.) made (C source)

– Agrobacterium transfers its plasmid into plant’s DNA

• Interkingdom horizontal DNA/gene transfer!

Lateral gene transfer by A. tumifaciensTumor inducing = (Ti) plasmid:

– Vir genes activated in response to plant wound signals

– T-DNA (endonuclease) cuts host DNA and then inserts its genes into host DNA!

– Bacterial DNA w/ eukaryotic gene promoters code for:

• IAA, CK synthesis; causes cell proliferation = home for bacterium

• Modified amino acids; unique C and N source for bacterium

Is this useful?

We can make transgenic plants:Remove aa and hormone synthesis genes; Keep endonuclease

Gene added from another species; new trait (e.g. herbicide, pest resistance)

Selectable marker added (usually antibiotic resistance gene or GFP)Plant cells (tissue discs) exposed to transformed Ti plasmidNew gene(s) integrated into plant DNA

– Transformed individuals selected on antibiotic plates

Whole plants regenerated w/ tissue culture

A. tumifaciens transformation:Only works well on dicots

Most of the world’s crop plants are monocots

How could we transform them?

Some approved commercial releases of transgenic plants

Crop /release date Name Company Novel properties

Tomato (1994) Flavr Savr Calgene Vine-ripened flavor, shelf life

Tomato (1995)   Zeneca Consistency of tomato paste

CottonPotatoMaize (1996-97)

BollgardNewLeafYieldGuard

Monsanto Bacillus thuringiensis toxin for insect feeding resistance

SoybeanCanola (rape)Cotton (1995-96)

Roundup Ready Monsanto Glyphosate herbicide resistance

Potato (2014)Simplot Reduced acrylamide when cooked

Maize (2011) DroughtGard Monsanto Drought resistance

Papaya, potato, squash

Viral resistance

How widespread (acreage) are transgenic crops in the world?

Benefits and costs/objectionsFind diversity of opinions that relate to benefits and costsFind data on:

– Benefits of transgenic crops. Include data.– Disadvantages/concerns about GM crops. Include data.– How transgenic organisms are regulated; who?– Effect on beneficial or non-target insects. Include data.– Crop to weed gene transfer– Selecting for resistant insects/pathogens– Consumer health– Impact on genetic diversity of crops– Is there is a reduction in herbicide or pesticide use w/ GMOs?– What are concerns among people in other nations, esp. developing

nations?

– Colorado State University has a good, but dated website with links. http://cls.casa.colostate.edu/transgeniccrops/index.html