Generating more and better food Flashcards
How did ancient Mesoamerican farmers transform teosinte into modern maize?
- 6,000-10,000 years ago, ancient Meso-American farmers changed the teosinte through selection.
Name 3 agronomical characteristics selected for in crops.
- Higher yields
- Improved morphology of fruits and seeds (e.g., seedless grapes)
- Easier cultivation (e.g., easier harvest)
Name 3 food quality/processing characteristics selected for in crops.
- Improved nutrients and flavor (e.g., purple tomatoes, improvement of protein and Omega-3 Fatty Acid in soybean)
- Reduced toxicity (e.g., potatoes which produce less acrylamide)
- Extended shelf life (e.g., blueberries with longer shelf life)
Name an environmental trait selected for in crops.
- Adaptation to environment (e.g., drought, temperature, and resistance to pests = less pesticides = safer foods)
Has been neglected in the past, but is becoming more important.
Natural selection
Historically performed by humans based on what available in nature
Historically performed by humans based on what available in nature
Natural selection
What is modern plant breeding?
- Based on the principles of heredity
- Darwin’s theory of evolution and natural selection (mid 1800s) and Mendel’s basic principles of heredity (mid 1800s) allow us to apply the principles of heredity and the knowledge of genetics and chromosomes to use the genetic variation (biodiversity) available in a species
- Molecular techniques for the selection of the best plants
Traditional breeding (does not include genetic modification, but may involve things like biomarkers)
Mutation breeding
Induction of mutations on the genomes to generate new plants from existing plants
Induction of mutations on the genomes to generate new plants from existing plants
Mutation breeding
Transfer of genes from a species to another using lab techniques.
Genetic engineering
- Transfer of genes from a species to another using lab techniques. In 1970, Agrobacterium was modified to be non harmful for plants.
- In 1988 first GE crop was tested in the field (Tomato FLAVR SAVR, late ripening).
- In 1994 it was in the commercial market.
Genetic engineering
Transfer of genes from a species to another using lab techniques.
- Transfer of genes from a species to another using lab techniques. In 1970, Agrobacterium was modified to be non harmful for plants.
- In 1988 first GE crop was tested in the field (Tomato FLAVR SAVR, late ripening).
- In 1994 it was in the commercial market.
What is crucial for improving crops?
Genetic variation
What does genetic variation arise from? [3]
- Hybridization: Recombination of alleles (variants of a gene) through sexual reproduction, introgression of genes from another species
- Mutation (changes in the DNA sequence)
- Genetic engineering.
How is hybridization used to breed new plant varieties?
- Hybridisation between a donor (parent 1) and a recipient (parent 2), can be within or among species
-
Selection of the desired progeny
Eventually… - Backcross (cross of the new plant) to the recipient line (recurrent/good parent) for restoring the genome content and the phenotype of the recipient
What does this photo show?
- Two siblings from the same crossing
(hybridization between a commercial
variety of grape and a variety that is
resistant to a pathogen [downy
mildew].) - One sibling is susceptible (left
picture), one sibling is resistant
(bottom)
Name 3 common phenotyping agronomical traits in grapes.
- Vigour
- Yield
- Cluster architecture
How are enological phenotype traits selected for in wine grapes?
- Microvinification (a winemaking technique used often for experimental batches of wine where the wine is fermented in small, specialized vats)
- HPLC & GC-MS analyses
- Wine tasting
Take home message: breeding a new grape variety requires 10-15 years of work if we are lucky!
How can recombination of alleles through sexual reproduction create a new variety with desirable traits?
- Recombination of alleles (variants of a gene) through sexual reproduction within a species
Meiosis generates […]
Meiosis generates new allele combinations in the gametes
Describe the formation of gametes in the paternal line (Cabernet franc).
Not all the gametes (i.e., pollen genes) have the colour gene due to recombination.
Describe the formation of gametes in the maternal line (Formation of gametes in the maternal line (Sauvignon blanc).
Not all gametes have the aroma gene.
Describe the breeding of the maternal and paternal lines and selection of progeny.
- Lots of variation
- The ‘problem’ of hybridization - what you obtain might be very different from the original plant.
- But when we find a plant we like we can clone it infinitely (i.e., take a branch and put it in dirt and it will grow; much easier than cloning an animal)
Describe the effect of crossing over on two genes located in the same chromosome
Not all gametes have the alleles we are looking for; gametes produced will have new combinations of alleles.
Describe why not all the gametes have the alleles we are looking for.
Crossing over and recombination (i.e., independent assortment)
How do crossing over and recombination affect the chances of obtaining the desired combination of alleles?
Shuffling of alleles due to crossing over and recombination, imply lower chances to obtain the “wanted” combination of alleles.
What are the problems of traditional breeding?
- We have thousands of genes that recombine in a random fashion
- Wide hybridization introduces many potentially negative genes combinations in order to obtain one desirable gene trait
- We have to eliminate undesired traits introduced by recombination
- Backcrossing of the new selection with the recurrent (good) parent
What is traditional breeding?
Crossing individuals with desirable characteristics and selecting
among the progeny
Concerns with how long traditional breeding takes, and how much space & resources are required.
What challenges arise when recombining alleles through sexual reproduction between interfertile species?
- Lots of unwanted traits may be inherited along with desired traits.
- Wide hybridization introduces many potentially negative gene combinations to obtain one desirable gene trait.
Why is backcrossing of the new selection with the recurrent (good) parent necessary?
- We have to eliminate undesired traits introduced by recombination
- Back-crossing of the new selection with the recurrent (good) parent
What are the pros of hybridization (traditional breeding)? [2]
- It applies to all traits, provided that the source of improved trait and the recipient are interfertile
- No knowledge is required on the genetic control of the trait.
What are the cons of hybridization (traditional breeding)?
- Meiosis and crossing over cause a random assortment of parental chromosomes and alleles, the parental genotype (and phenotype) cannot be recovered in filial generations
- The donor transmits half of its genome to the progeny (in addition to the gene/s that control the trait under improvement)
- Backcrossing may be required for recovering most of the recipient genome, if long seed to seed cycle, the backcrossing process is long
What is a molecular marker? [2]
- A molecular marker is a molecule (normally a specific DNA sequence/feature) of an organism that can be used to reveal certain characteristics about the organism.
- A fragment of DNA that is associated with a certain location within the genome.
What are the advantages of molecular breeding using Marker Assisted Selection (MAS)? [4]
- Using molecular biology (the genotype) to help select the progeny
- Improve efficiency and speed up screening methods
- Simultaneous selection for multiple traits
- Screening not based on the phenotype and hence not affected by environmental factors
Requires knowledge on the control of traits.
What is a nontransgenic approach to increase genetic variation?
Mutagenesis - creation of genetic variants by introducing mutations
Mutation is the permanent alteration of the nucleotide sequence of the genome of an organism.
Define: mutation.
The permanent alteration of the nucleotide sequence of the genome of an organism.
A change in the genome sequence of an organism.
Describe the approach.
Mutagenesis - creation of genetic variants by introducing mutations
Mutation is the permanent alteration of the nucleotide sequence of the genome of an organism.
A nontransgenic approach to increase genetic variation
The permanent alteration of the nucleotide sequence of the genome of an organism.
Define: mutation.
What is a transgenic approach to increase genetic variation?
Genetic engineering - introduction of one (or a few) foreign ‘good’ genes into the best accepted cultivar using horizontal gene transfer
Agrobacterium transformation; biolistic
1970s to present day
Genetic engineering - introduction of one (or a few) foreign ‘good’ genes into the best accepted cultivar using horizontal gene transfer
Transgenic approach to increase genetic variation
1970s to present day
Define: horizontal gene transfer
Movement of genetic material between unicellular and/or multicellular organisms rather than transmission of DNA from parent to offspring (Vertical Gene transfer).
Movement of genetic material between unicellular and/or multicellular organisms rather than transmission of DNA from parent to offspring (Vertical Gene transfer).
Define: horizontal gene transfer
Define: spontaneous mutation
Occurs without treatment of the organism with an exogenous mutagen.
These mutations are rare.
Define: induced mutation
Occurs due to the treatment of a plant or plant parts such as seed, stem, cuttings, pollen, and ovules with the mutagens.
This treatment increases the frequency of mutations.
Induced mutation or mutagenesis is the sudden heritable change in the genome of an organism (not caused by genetic recombination or segregation) but induced by physical, chemical, or biological agents.
Occurs without treatment of the organism with an exogenous mutagen.
These mutations are rare.
Define: spontaneous mutation
Occurs due to the treatment of a plant or plant parts such as seed, stem, cuttings, pollen, and ovules with the mutagens.
This treatment increases the frequency of mutations.
Define: induced mutation
Induced mutation or mutagenesis is the sudden heritable change in the genome of an organism (not caused by genetic recombination or segregation) but induced by physical, chemical, or biological agents.