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List types of abiotic stress
- Drought
- Heat
- Cold
- Salinity
- Mineral Toxicity
- Water-logging
- Mineral Deficiency
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Describe Stress and Yield Potential
- Yield is the product of genotype by
- environment interactions
- Any stress can impact plant growth and
- development
- Stress resistance is inherent to all
- breeding programs
- Genotypes must be evaluated at different
- locations and over years
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Screening for Stress Resistance
- Genetic variation must occur
- Heritability of trait should be greater than
- heritability of yield per se
- The trait should be correlated with yield
- Screening should be easy, rapid, and
- economical
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Describe Drought Stress
- Focus on water use efficiency
- Yield = Transpiration X WUE X HI
- Characterization of drought environment
- Indirect selection on traits affecting
- drought response
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Mechanism of Drought Stress
- Escape
- Early maturing to miss drought conditions
- Avoidance
- Efficient WUE or epicuticular waxes
- Tolerance
- Continual photosynthesis and partitioning
- Recovery
- Rebound after drought stress
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Traits Affecting Drought
- Phenology
- Leaf area index, flowering time, maturity time
- Plant development and size
- Root characteristics
- Plant surface
- Non-senescence (stay-green)
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Canopy temperature
- an indirect measure of Water Use (WU)
- Transpiration of water cools the plant.
- Cooler canopies suggest that roots are reaching deeper water allowing them to transpire
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Indirect Breeding approach
- Genotypes exposed to environmental stresses
- for selection, but not in the location where
- stress conditions occur
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direct Breeding approach
- Selection for stress under environments
- where the conditions are conducive
- Field Selection
- Managed stress environments
- Select on yield per se
- Select on developmental traits
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what is Cold Stress
- Multiple classifications for cold stress
- Frost-resistant, cold hardy, cold-hardened
- Depends on a highly integrated system of
- structural, regulatory, and developmental
- genes
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Mechanisms for Cold Stress
- Chilling resistance
- Freezing resistance
- Escape
- Avoidance
- Tolerance
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Salinity Stress
- Occurs from natural weathering of parent
- materials
- Human-aided salinity occurs from
- agricultural practices, irrigation, and rising
- water tables
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Breeding Approaches
- Tolerance is the best approach
- Field screening is effective but a long
- process
- Marker technology is advancing
- Resistance more beneficial than tolerance
- Field screening under high temperature
- environments
- Control all factors except heat
- Controlled environments (growth
- chambers
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Heat Stress
- High daytime/high nighttime temperatures
- High nighttime temperatures more detrimental
- Rice: 4°C increase above threshold = 18% fertility
- Warm and cool season plants affected
- differently
- High temperatures tend to accelerate
- reproductive development
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Flood Stress
- Most plants need well-drained soils
- Breeding is usually done to fit into a
- specific cropping system
- Rice was developed to be flooding
- resistant
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End use quality traits
- High protein content (and its quality)
- High nutrient content
- Lysine, Vitamin A, etc
- Oil composition
- Low phytate (animals produce less methane)
- Extended shelf life
- Cooking and processing
- qualities
- Seedlessness
- Pharmaceuticals
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Transgenic Approaches
- Golden Rice
- Gene inserted from daffodil to produce
- beta-carotene
- Agrobacterium used for transformation
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