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Summary Crop Improvement
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Detailed notes on Crop Improvement
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BLGY1211 Crop ImprovementEarly crops
Food; fruits, wheat, barley, potato
Non-food; silk, flax, wood
Constant expansion/modification of gene pool;
Natural radioactivity (space, volcanoes, soil…)
UV light
High temperature
Stress situations (i.e. pathogens, abiotic stress)
Sexual reproduction
The structure of genes
Most important region is the coding region
Single point mutations are often silent
Combination of 2 silent mutation by sexual reproduction can lead to a phenotype
Types of mutations;
Silent mutations; Non-essential amino acid substitution, Often the same
charge or hydrophobicity, Non-essential gene , Not in a gene, Degenerate
, codon usage reading frame unchanged as mutation doesn’t affect the
encoded protein
Loss of function mutations (recessive); Very frequent, Gene disrupted (stop-
codons, frame-shifts, deletions), Protein activity abolished, unlikely to
improve things proteins that are misfolded or truncated, Enzymes which
are inactive and don’t do their job, Promoters which don’t work (proteins not
made by the cell)
Gain of function mutations (dominant); Much less frequent, can be harmful
Receptors which are always activated, Enzymes which cannot be turned
off, Promoters which are constitutively active – it is almost impossible to
leave it to chance to create a novel trait which is beneficial
Improvement
Selection by humans based on natural variation = Mutations (genetic modifications);
Traits like yield, quality, appearance, taste Survival of the fittest, but for human
interests (biased evolution)
All current crops are GMOs in the true sense They would not exist without human
selection They have many unknown mutations that led to the desired traits
Those traits are not necessarily in the interest of the crop
“Big potato”- good for humans, bad for the plant;
Promotes pests due to excess of starch in the tuber
Tubers grow very close to the centre of the plant which promotes spreading
of diseases
Crop cannot proliferate well because it does not invade/explore other
territory
Commercial potato varieties cannot survive in nature
Easy harvesting and 50 tons/ha top yield (UK climate)
Cauliflower is a plant with a big meristem
Classical plant breeding;
1. Selection from natural variation within a species
2. Creating hybrids between selected ecotypes of that species
3. Repeat 1)-2) until you have an interesting trait
4. At all these steps, one has to test if the trait is stable and can be passed on to
the progeny
Generally accepted as safe
Accelerated seed mutagenesis; Artificial irradiation (g, a, b radiation),
Treatment with mutagenic chemicals (i.e. EMS), Heat shock,
Combinations
Production of hybrids; exploiting the natural genetic pool
Selection of traits; Yield, Stress resistance, Abiotic: Cold, heat, salinity,
drought, Biotic: Pathogens (fungi, bacteria, insects), Fruit quality,
appearance, taste…., Shelf-life, homogeneous appearance, Nutritional
value, Time to flowering
Extensive back-crossing with parent strain; Clearing out other
mutations, Maintaining desired trait, Re-establish general properties
Crossing with related variety to create hybrid seed; Heterosis effect
(hybrid vigor), Yield, quality, appearance
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