Plant Breeding Flashcards
(17 cards)
How big is a wheat hexaploid genome?
More than 5 times larger than humans
What is outcrossing?
- Plant with desirable trait is identified
- Plant combined with existing variety
- Improved progeny are identified
- Tested over multiple generations and environments
What are some desirable traits?
- High yield
- Taste
- High biomass
- Height
What is a hybrid development pipeline?
Potential products are bred, best phenotypes are chosen from the previous set and bred, each trait is scored on its performance
What was the green revolution?
Mid 1990s plant breeding
Norman Borlaug:
- Developed modern high-yield wheat varieties
- Semi-dwarf spring wheat insensitive to day length
- Yields doubled
- Seeds increased in size, not quantity (meant no need for more land)
How much land was saved from cultivation by the green revolution?
Saved 1.1 billion ha of land from cultivation
What is unintentional gene transfer?
Crossing could transfer many other traits not just desired ones
What is negative epistasis?
The combined effect of multiple mutations, resulting in lower fitness
E.g 1970s, Southern corn blight in maize, linked to a sterile parental line, maize could not self fertilise
What is marker assisted breeding?
Uses molecular markers to select plants with desirable traits (SNPs)
Targeted transfer of traits
Involves backcrossing: repeating the cross until an elite line
Relies on genetic variation
Useful for hard to identify traits
Speeds up conventional breeding
What is backcrossing?
Repeating the cross until an elite line
By BC6, >99 % will be elite DNA
What is SUB1 rice?
High yield rice, not tolerant to submergence
4 million tonnes lost to flooding in Bangladesh and India
SUB1A - has submergence tolerance, introduced into swarna by marker assisted breeding
Introduced into fields by 2004
What does marker assisted breeding require?
Requires desirable trait to exist in a related species that can be crossed with elite lines
What is mutational breeding?
Mutations deliberately introduced into plant genome using chemicals or radiation to generate a new genetic variation
Random mutations
Traits dependent on variation in genes
What is TILLING?
Targeted induced local lesions in genes
Identified mutations in a desired gene, gives random mutagenesis specificity
What is reverse genetics?
- Alter gene structure / activity
- Analyse change in phenotype
What are the steps of TILLING?
- Develop a mutagenized population of crop
- Self breed mutagenized M1 crops to M2 generation homozygous
- Extract DNA from M2
- PCR specific gene region and analyse
What are some previous crops made by TILLING?
- Potato: amylose-free tubors
- Wheat: reduced grain amylose
- Maize: kernel row number
- Melon: longer shelf life
