plant genetic improvement methods
TRANSCRIPT
Plant Genetic ImprovementWhat it is and what it isn’t
Kevin M. FoltaProfessor and Chairman
Horticultural Sciences Department
kfolta.blogspot.com@kevinfolta
Everyone Loves New Technology
What Plant Genetic Improvement Is
More varieties
Grow better under given conditions
Improved yields
What Plant Genetic Improvement Is
People Think
Improved yields
Plant Genetic Improvement
Breseghello and Coelho, J Ag Food Chem 2013
Methods of Plant Genetic Improvement
What are the major ways we genetically improve varieties?Major methodsSome common examplesStrengths / limitations
How do they compare to each other?
The future of plant genetic improvement
How to talk to the public about genetic improvement methods
Dispelling the Naturalistic Fallacy– This is Nothing New!
Remind audiences that genetic improvement of food is a continuum.
Almost none of the plants we regularly consume originated in North America. Almost all were brought here by humans.
None of the food you eat is like its “natural” form
GM technology is simply the most precise version of an age-old practice of breeding and selection.
Humans have always manipulated crop genetics
Inbreeding
Decreases useful production traits
Lower heterozygousity
Non-specific crosses
Combining the desirable traits from two genetic backgrounds into one.
Problem: Linkage drag
Requires many backcosses to “clean up” genetics
Can require a long time
No regulatory issues
X =
IRRI Images
Non-specific crossesBackcrossing removes undesirable genes/alleles.
Wide genetic crosses
Integrating traits from wild relatives into elite varieties
Problem: Linkage drag
Solution (+/-) marker-assisted breeding
Marker-Assisted Breeding
Association between the likelihood of inheriting a trait and a certain sequence of DNA
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Marker-Assisted Breeding
Association between the likelihood of inheriting a trait and a certain sequence of DNA
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Wide genetic crosses
North America
Chile
Crossing the Impossible
Bridging Crosses- when the desired cross is not possible, finding a sexually-compatible plant, creating the interspecific hybrid, and then crossing the progeny to the other parental genotype.
Embryo Rescue
Fertilization takes place, but embryo is not viable for normal germination.
If given the proper conditions, the embryo can germinate and mature into a plant.
Hybrids between inbreds
B73 Mo17
Iowa Sate Univ photo
Produce plants from inbreeding that are highly homozygous
Cross two inbreds together and get tremendous heterozygousity
Hybrids between inbreds
Polyploids
Increased numbers of genomes in a cell
Can be natural or induced
Examples:
Beans, potato, strawberry, wheat, brassicas, many others
Polyploids
Increased numbers of genomes in a cell
Seedlessness
Wheat breeding
Mutation Breeding
All genetic variation begins with mutation
Mutations can be induced with ionizing radiation or chemicals
May require backcrossing
High lycopene
Seedlessness
Regeneration from single cells
Plant cells can “re-program”
Somatic Fusions
Transgenics
What people usually think of as “GMO”
Addition of a gene, or small number of genes
Transgenics
Can add traits from across species (like the Bt gene for insect resistance)
Can suppress traits or viruses using RNAi (as in the papaya and potato)
GM Crops Available Now
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potato
Keep it Simple– What are the Three Main Traits?
Virus Resistance
Insect Resistance
Herbicide Resistance
(how the traits work lecture online – (google “ UF biotechnology literacy day”)
Strengths Limitations
Virus resistance Works great, no foreign material
Has cut insecticide use by 10-70%
Saves time, labor, fuel. Allows conservation tillage
Can spread to nonGM populations
Pockets of developing resistance
Resistant weeds are a problem in areas.
Insect resistance
Herbicide resistance
Distill Into Digestible Units - Keep it simple. Discuss strengths and limitations (don’t create false equivalence)
Transgenic Traits May be Stacked into a Single Background
Cisgenics/Intragenics
Transfer of specific genes from the same species
Cis-genic = as-is
Intra-genic = all ‘native’ sequence with some re-arrangement
Cisgenics/Intragenics
Apple Scab
Traditional breeding introduced resistance gene from M. floribunda over 50 years.
Same sequence added by Dutch researchers in <5.
Gene Editing
CRISPR (clustered regularly interspaced short pallindromic repeats)
Targeted, few collateral effects
Allows production of custom mutations
Reasonably fast and efficient
No foreign genes present
GE vs. Traditional Breeding
Wide crosses exchange hundreds or thousands of genes and gene variants; GE moves only one/few.
Traditional breeding frequently uses plants that could never normally cross, GE uses genes from self or any other organism
GE can monitor the effect of a specific change; breeding seeks to judge the effect on plant productivity and does not address possible effects on individual genes.
Talking to public audiences
Plant genetic improvement techniques are safe.
All methods involve some small risk– but all are about the same risk as traditional breeding.
Techniques that breed in traits can take a long time
Directed changes are more precise and more rapidly available, but frequently require regulatory hurdles
Farmers
The Needy
Environment
Consumers
Talking to public audiences
We need to celebrate that we have the safest and most abundant food supply in human history- and expand plant genetic improvement techniques to serve the farmer, the needy, the environment and the consumer.
