24 pages on Global Change Biology module. definitions are highlighted throughout. Covers specifically the drought tolerance of rice, high temperature tolerance of wheat and blight tolerance of potato. Also goes over the GMO's of each crop, their herbicide tolerance. The impact of climate change on ...
Evidence for Climate change: higher summer temperatures, change in snowfall timing + amount,
change in flowering times, change in autumn leaf fall timing
Climate Change + Food:
• Decreasing water availability -> can’t irrigate crops
• Coral bleaching -. Decreases ecosystem product
• Increasing severity + frequency of costal flooding
Famines:
1. Great Famine 1315:
Volcanic eruption -> small ice age -> decreased seed return from planted crops
2. Irish Potato Famine 1840: fungal parasite -> potato blight -> crop losses
Overpopulation: food demand > food production
2 major approaches used to increase stress tolerance + productivity of crop plants = traditional
breeding techniques + genetic engineering
Sustaining Food Production:
• Plant breeding
• Genetic modification
• Agronomy
Threats to Food Production:
• Soil salinity, erosion, desertification,
• Lack of incentive for rural careers
• Climate change
Components of Anthropogenic climate change:
1. Increased atmospheric CO2 – multiple trajectory lines
2. Increased global temperatures
3. Changing rainfall patterns
Evidence proving climate change decreases food production:
1. Experimental trials:
a. Implementing climate change treatments:
370 -> 740 ppm CO2 concentration
20/18 -> 28/24 day/night temperatures
Well-watered -> drought
➔ Lower temp, higher CO2 = increased plant growth
b. Limitations:
Strict + unrealistic environments
Rainfall poorly simulated in small pots
Some climate change factors absent e.g. UV-B light, O3 greenhouse gas
CO2 increases atmospheric ozone layer -> increases UV radiation
2. Historical Yield: environmental analysis
a. Evidence:
Crop yields increased
Rainfall had no effect
Yields decreased with increased temperature
, b. Limitations:
Small proportion of yield variation (30%)
Retrospective analysis – back in time
3. Predictive yield modelling:
a. Structure:
Use crop simulation models
Train a statistical model
Projected yield increases
b. Limitations:
Expansion into new cropping areas
Adoption of new varieties
Changes in farmer practice (agronomy)
Principles of Plant Breeding:
1. Select wild relative showing trait of interest
2. Cross 2 parental lines to produce offspring
Stress tolerant plant x exile cultivator (high yield/quality)
3. Select offspring that shows both traits
4. Multiple generations of backcrossing to recover most of genetic material of original elite line
over time
Displayed traits different to parents/not complete mix
5. Most of genetic material of original elite line over time
Backcrossing: breed hybrid with parent
Backyard Breeding: Gregor Mendel
1. Assemble variability in traits of interest
2. Evaluate + select parents of interest
3. Backcross within parental line -> ensure self-pollination -> Create pure/homozygous lines
4. Hybridise pure parental lines -> F1
5. Evaluate F1 hybrids
6. Backcrossing across multiple generations
= breed, seed, select, repeat
Genetically related parental lines -> F1 hybrid may be sterile
Commercial seed producers Breeding:
Male flower = tassel
Detasseling: remove flower tassels
1. TMA gene more susceptible to plant pathogens
2. Male tassels Anthesis shed pollen before female silks receptive
3. Pollen spreads to other females -> ensures genetic variation
4. F1 Hybrid maize more vigorous than self-pollinated
5. Detasseling F1 hybrid seed
6. TMS gene introduced -> produce hybrid seed -> reduce physical labour = less susceptible to
plant pathogens
Commercial Breeding:
Wild mustard plant = Brassaca oleracea = split into multiple crops due to commercial breeding
= Kohlrabi, Kale, Broccoli, Brussel sprouts, Cabbage, Cauliflower
, Advantages: free, limited tech required, socially acceptable
Disadvantages: time consuming, labour intensive, some characteristics from many genes -> difficult
to modify multi-genetic traits, high genetic uniformity -> vulnerability
Green Revolution in 1960s: can plant breeding keep up with climate change:
• Semi-dwarf cereal varieties (high harvest index)
• Fertilisers
• Irrigation
• Pesticides
• Mechanisation
➔ 2% gain in cereal yields per year
➔ Supports rapid human population growth
➔ Green revolution still occurring in some countries
Thermal cameras, molecular markers -> speed up plant breeding
Molecular markers assisted breeding = checks genome to see whether it will breed
Old Principles + New Tools:
New genes combat climate change
Constraints of Plant Breeding:
➔ Genes available
➔ Their random recombination -> backcrossing
➔ Lack of genetic diversity for key traits
➔ Labour-intensive screening of phenotypic variation in progeny
Examples of Plant Breeding approaches to protect food production under specific climate related
stresses;
Drought, high temperature, potato blight
1. Drought Tolerance of Rice:
• Rice grown in a range of cropping systems = Flooded Lowland + droughted upland
o Oryza Savita adapted to flood -. Produce higher yield in lowland
• Flood-tolerant rice bred to tolerate sustained inundation = sub1 gene
Inundation: flooding
• Changing monsoon patterns means fields often exposed to drying soil
Plant Breeders: to increase drought tolerance
a. Introduce wild rice relatives:
i. Introduce genes for greater root growth from rice relative
ii. Rice has larger roots -> greater water capture
iii. Survive droughts
▪ Use molecular genetics to identify wild rice with gene for large root
b. Grow African rice species:
African rice species = already resistant to drought
Select for yield in dry target environment
- Selection rice root phenotypes takes time due to roots being underground
c. IRRI Breeding Drought tolerant upland rice variety:
➔ Enhance food security
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